MALHEUR EXPERIMENT STATIONPage, Gary Malheur County Weed Supervisor, Vale, OR . Penning, Tom Irrometer Co., Inc., Riverside, CA . Riley, Kay Snake River Produce, Nyssa, OR

MALHEUR EXPERIMENT STATION ANNUAL REPORT 2019, Ext/CrS 163

Oregon State University, Malheur Experiment Station Annual Report 2019, Department of Crop and Soil Science Ext/CrS 163, July 2020

For additional copies of this publication, please contact Malheur Experiment Station 595 Onion Avenue Ontario, OR 97914 For additional information, please check our website https://agsci.oregonstate.edu/mes

On the Cover: Kyle Wieland is the Farm Supervisor at the Malheur Experiment Station.

Agricultural Experiment Station Oregon State University Department of Crop and Soil Science Ext/CrS 163, July 2020

Malheur Experiment Station Annual Report 2019 These projects were supported by Formula Grant nos. 2019-31100-06041 and 2019-31200-06041 from the USDA National Institute of Food and Agriculture. The information in this report is for the purpose of informing cooperators in industry, colleagues at other universities, and others of the results of research in field crops. Reference to products and companies in this publication is for specific information only and does not endorse or recommend that product or company to the exclusion of others that may be suitable. Nor should information and interpretation thereof be considered as a recommendation for application of any pesticide. Pesticide labels should always be consulted and followed before any pesticide use. We are thankful for the broad support of the work of the Oregon State University, Malheur Experiment Station.

CONTRIBUTORS AND COOPERATORS MALHEUR EXPERIMENT STATION ANNUAL REPORT

2019 RESEARCH MALHEUR EXPERIMENT STATION Feibert, Erik Senior Faculty Research Assistant Felix, Joel Associate Professor of Weed Science Ishida, Joey Bioscience Research Technician III Jones, Janet Office Specialist II Rivera, Alicia Bioscience Research Technician I Reitz, Stuart Professor, Director Shock, Clinton Professor Emeritus Wieland, Kyle Farm Supervisor MALHEUR COUNTY OFFICE, OREGON STATE UNIVERSITY EXTENSION SERVICE Arispe, Sergio Assistant Professor Brody, Barbara Assistant Professor of Practice Howell, Bobbi Office Manager Tanner, Christy Assistant Professor of Practice MALHEUR EXPERIMENT STATION SEASONAL STAFF AND STUDENTS Alexander, Kelsey Student Technical Assistant Bezona, Brooke Seasonal Technical Assistant Bourasa, Bo Student Technical Assistant Chew, Alan Student Technical Assistant

Fisher, Shandee Student Technical Assistant Rose, Hannah Seasonal Technical Assistant Simmons, Allison Seasonal Technical Assistant

Trenkel, Ian Seasonal Technical Assistant OREGON STATE UNIVERSITY, CORVALLIS, AND OTHER STATIONS Charlton, Brian Potato Faculty Scholar, Klamath Falls Graebner, Ryan Assistant Professor of Practice, Pendleton

Jeliazkov, Valtcho Associate Professor, Dept. Crop and Soil Science Noller, Jay Director, Global Hemp Innovation Research Center Rondon, Silvia Professor, Hermiston Sathuvalli, Sagar Assistant Professor, Hermiston

Yilma, Solomon Senior Faculty Research Assistant, Dept. of Crop and Soil Science

OTHER UNIVERSITIES Hutchinson, Pamela Associate Professor, University of Idaho, Aberdeen, ID Neufeld, Jerry Associate Professor, University of Idaho, Caldwell, ID Pavek, Mark Associate Professor, Washington State University, Pullman, WA

Schroeder, Brenda Associate Professor, University of Idaho, Moscow, ID Thornton, Mike Professor, University of Idaho, Parma, ID Waters, Tim County Director, Washington State University, Pasco, WA

Wenninger, Erik Associate Professor, University of Idaho, Kimberly, ID Woodhall, James Assistant Professor, University of Idaho, Parma, ID OTHER PERSONNEL COOPERATING ON SPECIAL PROJECTS Bentz, Andy Malheur Watershed Council, Ontario, OR Breidenbach, John Ontario Chamber of Commerce, Ontario, OR Bushman, Shaun USDA-ARS Forage and Range Research Lab, Logan, UT

Buhrig, Bill J. R. Simplot Company Cane, Jim UDSA-ARS, Bee Lab, Logan, UT

Carpenter, Mark Owyhee Irrigation District, Nyssa, OR Chamberlin, Jay Owyhee Irrigation District, Nyssa, OR

Cooper, Rodney USDA-ARS, Wapato, WA Corn, Dan Cooperating Grower, Ontario, OR Cruickshank, Scott Cooperating Grower, Ontario, OR

Diebel, Ken Malheur Watershed Council, Ontario, OR Donar, Larry Fresno Valves and Castings, Inc., Kennewick, WA

Doron, Lior Netafim, Tel Aviv, Israel Faw, Gary Malheur County Soil and Water Conservation District, Ontario, OR Gets, Yechiam Netafim, Tel Aviv, Israel Gips, Ami Netafim, Tel Aviv, Israel Halford, Anne U.S. Bureau of Land Management, Boise, ID Halperin, Ofer Netafim, Tel Aviv, Israel Hill, Carl Owyhee Watershed Council, Ontario, OR Jensen, Scott USDA Forest Service Shrub Science Lab, Provo, UT Johnson, Douglas USDA-ARS Forage and Range Research Lab, Logan, UT Kameshige & Sons Cooperating Grower, Ontario, OR

Kilkenny, Francis USDA Forest Service, Boise, ID Kitamura Farms Cooperating Grower, Ontario, OR Klauzer, Jim Irrigation Consultant, Ontario, OR Kreeft, Harry Western Laboratories, Inc., Parma, ID Larsen, Lynn USDA Natural Resources Conservation Service, Ontario, OR Manser, Harvey Owyhee Irrigation District, Nyssa, OR Novy, Rich Research Geneticist/Potato Breeder, USDA, Aberdeen, ID

OTHER PERSONNEL COOPERATING ON SPECIAL PROJECTS (continued) Page, Gary Malheur County Weed Supervisor, Vale, OR

Penning, Tom Irrometer Co., Inc., Riverside, CA Riley, Kay Snake River Produce, Nyssa, OR

Rowe, Linda Malheur County Soil and Water Conservation District, Ontario, OR Saito, Jeff Cooperating Landowner, Ontario, OR

Shaw, Nancy USDA Forest Service, Boise, ID Simerly, Bob McCain Foods, Fruitland, ID

Skeen, Paul Skeen Farms, Nyssa, OR Swisher, Kylie USDA-ARS, Prosser, WA Taberna, John Western Laboratories, Inc., Parma, ID Tolmie, Don Treasure Valley Seed Co., Inc., Wilder, ID Weidemann, Kelly Malheur Watershed Council, Ontario, OR Wettstein, Lou Owyhee Watershed Council, Ontario, OR Winegar, Dell Winegar Farms, Fruitland, ID GROWERS’ ASSOCIATIONS SUPPORTING RESEARCH Idaho-Eastern Oregon Onion Committee Idaho Onion Growers’ Association Malheur County Potato Growers Malheur County Onion Growers’ Association Northwest Potato Research Consortium Nyssa-Nampa Beet Growers’ Association Oregon Potato Commission Oregon Wheat Commission PUBLIC AGENCIES SUPPORTING RESEARCH Agricultural Research Foundation U.S. Bureau of Land Management Lower Willow Creek Working Group Malheur County Soil and Water Conservation District Malheur Watershed Council Oregon Department of Agriculture Oregon Watershed Enhancement Board Owyhee Watershed Council USDA Forest Service USDA National Institute of Food and Agriculture

MALHEUR EXPERIMENT STATION ADVISORY BOARD Beck, Deron Phillips, Tom (Chair) Fitch, Candi Price, Vikki

Kitamura, Grant Saito, Reid Klauzer, Jim Simerly, Bob Komoto, Bob Skeen, Paul Maag, Doug Svaty, Randi

COMPANY CONTRIBUTORS ADAMA USA

Allied Seed, LLC Amalgamated Sugar Co.

American Takii, Inc. Andrews Seed, Inc. BASF Corp. Bayer CropScience Bejo Seeds, Inc. Certis

Corteva Agriscience Crookham Seed Co. D. Palmer Seeds DuPont Enza Zaden FMC Corp. Gowan Co. Irrometer Co., Inc. J.R. Simplot Co. McCain Foods Netafim New Zealand Onion PGG

Saddle Butte Ag, Inc. Sakata Seed America

SePRO Syngenta Crop Protection

TKI NovaSource Treasure Valley Seed Co., Inc. Valent BioSciences Corp. Winfield Solutions

TABLE OF CONTENTS WEATHER

2019 Weather Report --------------------------------------------------------------------------- 1

COVER CROPS

Brassica Cover Crop Variety Trial ------------------------------------------------------------ 12 Controlling Yellow Nutsedge (Cyperus esculentus L.) with Competition from Cover Crops — Preliminary Results --------------------------------------------------------- 17

ONION

2019 Onion Variety Trials ---------------------------------------------------------------------- 21

Onion Production from Transplants in 2019 ----------------------------------------------- 50

Onion Response to Dual Magnum® Application Rate and Timing ------------------- 63

Control of Yellow Nutsedge with Effective Crop Rotations ---------------------------- 69

Weed Control in Direct-Seeded Onion with Various Post-emergence Herbicide Combinations -------------------------------------------------------------------------------------- 77

Onion Response to Delayed Pre-emergence Application of Sonalan® ------------- 83

Evaluation of Mastercop® for Disease Management—2019 -------------------------- 89

Monitoring Onion Pests across the Treasure Valley—2019 --------------------------- 92

Thrips and Iris Yellow Spot Virus Management in the Treasure Valley—2019 --- 97

NATIVE PLANT AND WILDFLOWER SEED PRODUCTION

Irrigation Response for Seed Production of Several Native Wildflower Species - 121

Irrigation Requirements for Native Buckwheat Seed Production in a Semi-arid Environment --------------------------------------------------------------------------------------- 135

Prairie Clover and Basalt Milkvetch Seed Production in Response to Irrigation - 143 Irrigation Requirements for Lomatium Seed Production ------------------------------- 150 Irrigation Requirements for Seed Production of Five Native Penstemon Species 165

TABLE OF CONTENTS (continued) POTATO

2019 Potato Variety Trials ---------------------------------------------------------------------- 179

Evaluation of Two Automated Irrigation Scheduling Methods and Two Fertigation Strategies for Drip Irrigated Potato ------------------------------------------- 202

Drip Irrigation to Activate Herbicides in Season-long, Drip-Irrigated Potato Production Systems ----------------------------------------------------------------------------- 230

Insecticide Effects on Pest and Beneficial Arthropods in Potato --------------------- 238

Malheur County Potato Pest Monitoring Program—2019 ------------------------------ 249

SOYBEAN

Soybean Performance—2019 ----------------------------------------------------------------- 255

WHEAT

2018–2019 Oregon Winter Wheat Elite Yield Trials ------------------------------------- 261

2019 Weather Report 1

2019 WEATHER REPORT Erik B. G. Feibert and Clinton C. Shock, Malheur Experiment Station, Oregon State University, Ontario, OR

Introduction Air temperature and precipitation have been recorded daily at the Malheur Experiment Station since July 20, 1942. Installation of additional equipment in 1948 allowed for evaporation and wind measurements. A soil thermometer at 4-inch depth was added in 1967. Since 1962, the Malheur Experiment Station has participated in the national cooperative weather station system of the National Weather Service. The daily readings from the station are reported to the National Weather Service forecast office in Boise, Idaho. Starting in June 1997, the daily weather data and the monthly weather summaries have been posted on the Malheur Experiment Station website at: https://agsci.oregonstate.edu/mes/malheur-experiment-station. On June 1, 1992, in cooperation with the U.S. Department of the Interior, Bureau of Reclamation, a fully automated weather station, linked by satellite to the Pacific Northwest Cooperative Agricultural Weather Network (AgriMet) computer in Boise, Idaho, began transmitting data from Malheur Experiment Station. The automated AgriMet station continually monitors air temperature, relative humidity, dew point temperature, precipitation, wind run, wind speed, wind direction, solar radiation, and soil temperature at 8-inch and 20-inch depths. Data are transmitted via satellite to a computer in Boise every 4 hours and are used to calculate daily Malheur County crop water-use estimates. The ground under and around the weather stations was bare until October 17, 1997, when it was covered with turf grass. The AgriMet database can be accessed at https://www.usbr.gov/pn/agrimet/ and from links on the Malheur Experiment Station web page at https://agsci.oregonstate.edu/mes.

Materials and Methods The manually observed weather data are recorded each day at 8:00 a.m. Consequently, the data in the tables of daily observations refer to the previous 24 hours. Evaporation is measured from April through October as inches of water evaporated from a standard class A pan (10 inches deep by 4-ft diameter) over 24 hours. Crop evapotranspiration (ETc) for each crop is calculated by AgriMet using data from the AgriMet weather station and the Kimberly-Penman equation (Wright 1982). AgriMet calculates reference evapotranspiration (ETr) for a theoretical 12- to 20-inch-tall crop of alfalfa assuming full cover for the whole season. Crop evapotranspiration is calculated for each crop using ETr and crop coefficients specifically developed for that crop. The crop coefficients for each crop vary throughout the growing season based on the plant growth stage (crop cover and maturity). The crop coefficients are tied to the plant growth stage by three dates: start, full cover, and termination dates. Start dates are the beginning of vegetative growth in the spring for perennial crops or the seedling emergence date for row crops. Termination dates are defined by maturity, expected harvest, frost, or dormancy. Alfalfa mean ETc is calculated using ETr and assuming a 15% reduction to account for cuttings.


Wind run is measured by the AgriMet weather station as total wind movement in miles over 24 hours at 9.8 ft above the ground. Weather data averages in the tables, except evapotranspiration, refer to the years preceding and up to, but not including, the current year.

2019 Weather The total precipitation for 2019 (13.5 inches) was higher than the 10-year (10.4 inches) and 76-year averages (10.1 inches) (Table 1). Precipitation for February, April, May, and September, was at least twice as high as the average. Total snowfall for 2019 (11.3 inches) was lower than the 76-year average (17.4 inches) (Table 2). The highest air temperature for 2019 was 100°F on July 23 and August 5 (Table 3). The lowest air temperature for 2019 was 10°F on October 31. The month of January had average maximum and minimum air temperatures substantially higher than average. The month of October had average maximum and minimum air temperatures substantially lower than average. The average maximum and minimum 4-inch soil temperatures in January were higher than average (Table 4). The average maximum and minimum 4-inch soil temperatures in October were lower than average. Total monthly wind runs in 2019 were close to the 26-year average (Table 5). Total pan evaporation in 2019 was close to the 21-year average (Table 6). Total accumulated ETr in 2019 was lower than the 27-year average (Table 7). The year 2019 had 3227 growing degree-days (50 to 86°F), lower than the 26-year average of 3317 (Table 8, Figure 1). October had substantially fewer growing degree-days than average. The year 2019 had a lower than average frost-free period (154 days) (Table 9). The last spring frost (≤32°F) occurred on May 1, two days later than the 43-year-average date of April 29; the first fall frost occurred on October 2, five days earlier than the 43-year-average date of October 7. Since 1943, the lowest average maximum and minimum air temperatures for October occurred in 2019 (Table 10). Also since 1943, October of 2019 had the lowest minimum air temperature in October (10°F on October 31).

Acknowledgements This work was supported by the National Oceanic and Atmospheric Administration, U.S. Bureau of Reclamation, Oregon State University, the Malheur County Education Service District and Formula Grant nos. 2019-31100-06041 and 2019-31200-06041 from the USDA National Institute of Food and Agriculture.

References Wright, J.L. 1982. New evapotranspiration crop coefficients. Journal of Irrigation and Drainage

Division, American Society of Civil Engineers 108:57–74.


Table 1. Monthly precipitation at the Malheur Experiment Station, Oregon State University, Ontario, OR, 1990–2019.

Year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Total -------------------------------------------------- inches ----------------------------------------------------

1990 0.44 0.35 0.72 1.52 1.70 0.36 0.04 0.61 0.00 0.49 0.69 0.29 7.2 1991 0.59 0.44 0.88 0.81 1.89 1.09 0.01 0.04 0.35 1.01 1.71 0.43 9.3 1992 0.58 1.36 0.25 0.74 0.21 1.43 0.36 0.01 0.09 0.95 1.15 1.51 8.6 1993 2.35 1.02 2.41 2.55 0.70 1.55 0.18 0.50 0.00 0.80 0.64 0.60 13.3 1994 1.20 0.57 0.05 1.02 1.62 0.07 0.19 0.00 0.15 1.23 2.46 1.49 10.1 1995 2.67 0.28 1.58 1.16 1.41 1.60 1.10 0.13 0.07 0.57 0.88 2.56 14.0 1996 0.97 0.86 1.03 1.19 2.39 0.12 0.32 0.31 0.59 0.97 1.18 2.76 12.7 1997 2.13 0.17 0.25 0.66 0.67 0.86 1.40 0.28 0.40 0.43 1.02 0.94 9.2 1998 2.26 1.45 0.95 1.43 4.55 0.36 1.06 0.00 1.00 0.04 1.07 1.11 15.3 1999 1.64 2.50 0.59 0.23 0.28 1.02 0.00 0.09 0.00 0.40 0.49 0.73 8.0 2000 2.01 2.14 0.97 0.72 0.28 0.26 0.03 0.06 0.39 1.74 0.38 0.66 9.6 2001 1.15 0.41 1.11 0.70 0.37 0.64 0.32 0.00 0.10 0.68 1.33 1.00 7.8 2002 0.77 0.27 0.49 0.77 0.09 0.60 0.14 0.10 0.36 0.29 0.44 1.86 6.2 2003 1.46 0.48 0.99 1.12 1.52 0.24 0.36 0.11 0.15 0.02 0.86 1.47 8.8 2004 1.82 1.54 0.25 0.98 1.70 0.43 0.13 0.64 0.56 2.03 0.93 0.97 12.0 2005 0.41 0.12 1.66 0.80 2.94 1.02 0.22 0.06 0.14 1.38 1.58 3.92 14.3 2006 1.91 0.67 3.33 2.00 0.62 0.45 0.00 0.08 0.55 0.28 1.14 1.76 12.8 2007 0.07 0.95 0.12 0.82 0.47 0.63 0.03 0.15 0.92 0.68 1.07 1.56 7.5 2008 0.50 0.43 0.79 0.14 0.74 0.27 0.43 0.03 1.26 0.44 1.12 1.47 7.6 2009 0.65 0.43 0.86 0.13 1.47 2.27 0.09 1.39 0.02 1.24 0.63 1.82 11.0 2010 2.13 1.19 0.59 1.21 1.18 1.95 0.02 0.86 0.19 1.16 1.09 4.19 15.8 2011 1.05 0.42 2.97 0.44 2.61 0.81 0.19 0.02 0.08 1.59 0.57 0.45 11.2 2012 1.65 0.49 1.36 1.03 0.77 0.45 0.00 0.04 0.1 0.83 1.13 1.25 9.1 2013 0.58 0.34 0.32 0.19 0.37 0.80 0.00 0.11 2.39 0.44 0.90 0.59 7.0 2014 0.69 1.58 1.22 0.92 0.45 0.24 0.02 0.28 0.62 0.52 1.46 3.04 11.0 2015 0.64 0.74 0.77 0.67 1.80 0.18 0.51 0.05 0.50 1.13 1.29 3.21 11.5 2016 0.98 0.38 0.98 0.88 0.95 0.25 0.98 0.01 0.13 0.75 0.58 2.11 9.0 2017 3.02 1.61 1.61 1.27 1.02 0.62 0.00 0.00 0.49 0.45 0.00 0.84 10.9 2018 1.41 0.26 1.12 0.62 0.56 0.47 0.00 0.00 0.01 1.23 0.51 1.13 7.3 2019 1.48 3.38 1.17 1.53 2.27 0.18 0.00 0.09 1.36 0.71 0.14 1.22 13.5

10-yr avg 1.28 0.74 1.18 0.74 1.12 0.80 0.18 0.28 0.45 0.93 0.82 1.86 10.4 76-yr avg 1.27 0.92 0.96 0.79 1.05 0.79 0.22 0.33 0.46 0.74 1.12 1.41 10.1


Table 2. Annual total snowfall (inches) at the Malheur Experiment Station, Oregon State University, Ontario, OR, 1943–2019. Average annual snowfall (1943–2018) is 17.4 inches.

1943 1944 1945 1946 1947 1948 1949 24.7 10.3 19.0 8.2 9.1 14.6 9.6

1950 1951 1952 1953 1954 1955 1956 1957 1958 1959 23.9 32.4 22.3 7.5 10.4 40.3 15.6 26.4 9.8 12.1 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 21.2 9.7 14.8 13.3 32.6 19.6 6.3 11.9 14.9 24.8 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 13.5 17.1 23.7 19.2 20.3 27.3 21.3 21.3 9.3 31.0 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 11.5 14.5 32.7 35.4 21.0 33.4 13.0 15.5 34.8 25.1 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 5.7 7.5 15.5 36.0 32.0 15.0 14.5 5.8 14.6 13.2

2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 13.8 15.5 11.5 4.5 24.0 13.5 12.3 3.8 26.0 13.8 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 28.0 1.0 4.0 14.0 22.5 14.0 24.5 31.5 3.8 11.3


Table 3. Maximum and minimum air temperatures by month, Malheur Experiment Station, Oregon State University, Ontario, OR, 2019.

Month Highest Lowest 2019 avg 76-yr avg

----------------------- °F -----------------------

Jan Max 50 31 41 35 Min 36 17 25 19

Feb Max 55 32 42 43 Min 37 16 28 25

Mar Max 69 40 54 55 Min 42 23 29 31

Apr Max 80 53 64 64 Min 51 30 40 37

May Max 87 57 72 74 Min 58 31 48 45

Jun Max 92 63 82 82 Min 65 40 54 52

Jul Max 100 81 91 92 Min 69 52 60 58

Aug Max 100 76 91 90 Min 68 48 60 56

Sep Max 97 55 79 80 Min 64 33 51 46

Oct Max 71 40 58 65 Min 42 10 29 37

Nov Max 34 34 51 48 Min 18 18 25 28

Dec Max 50 31 40 37 Min 35 17 28 22 Table 4. Monthly maximum and minimum soil temperatures at 4-inch depth, Malheur Experiment Station, Oregon State University, Ontario, OR, 2019.

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Max Min Max Min Max Min Max Min Max Min Max Min Max Min Max Min Max Min Max Min Max Min Max Min

-------------------------------------------------------------------- °F --------------------------------------------------------------- 2019 avg 35 34 36 35 42 40 52 50 60 57 69 65 72 69 72 69 66 64 51 49 42 41 38 37 Highest 38 36 39 37 48 46 57 54 67 63 74 69 75 72 75 72 72 69 57 55 46 45 42 41 Lowest 32 31 33 32 37 36 48 46 53 49 63 59 70 67 70 67 58 56 41 40 39 37 34 34

21-yr avg 33 32 36 35 43 41 50 46 60 55 68 62 74 68 72 68 65 61 55 52 44 42 35 34 52-yr avg 33 32 37 34 48 41 58 47 69 57 77 65 85 72 83 72 73 63 59 51 44 40 35 33


Table 5. Daily and monthly wind run, Malheur Experiment Station, Oregon State University, Ontario, OR, 2019.

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Daily ------------------------------------------- miles/day -----------------------------------------------

Mean 85 153 109 150 128 142 123 106 113 109 92 59 Max 355 375 291 380 298 274 231 237 280 338 326 142 Min 36 36 51 45 54 61 71 54 47 39 40 8

Monthly total -------------------------------------------- miles/month ------------------------------------------------ 2019 2631 4275 3370 4502 3959 4271 3805 3291 3401 3392 2752 1824 26-yr avg 2802 3282 4180 4624 4179 3697 3378 3283 3174 3265 2997 3234

Table 6. Daily and monthly pan evaporation, Malheur Experiment Station, Oregon State University, Ontario, OR, 2019.

April May Jun Jul Aug Sep Oct Total Daily ---------------------- inches/day -------------------------

Mean 0.18 0.26 0.37 0.38 0.33 0.21 0.12

Max. 0.37 0.48 0.59 0.50 0.47 0.36 0.29

Min. 0.03 0.03 0.18 0.18 0.11 0.05 0.03

Monthly ---------------------- inches/month ------------------------- 2019 5.46 8.05 11.11 11.88 10.34 6.40 3.42 56.7 21-yr avg 6.37 8.64 10.16 12.39 10.49 7.03 4.10 59.2


Table 7. Total accumulated reference evapotranspiration (ETr) and estimated crop evapotranspiration (ETc) (acre-inches/acre) for various crops over the past 28 years, Malheur Experiment Station, Oregon State University, Ontario, OR, 1992–2019.

Alfalfa (Mean)

Winter grain

Spring grain

Field corn

Poplar

Year ETr Sugar beet Onion Potato

Dry bean Yr. 1 Yr. 2 Yr. 3 +

1992 53.7 44.4 26.9 27.9 36.1 30.3 28.8 21.3 29.8 1993 51.9 36.4 21.3 22.7 29.3 24.1 22.8 17.9 23.7 1994 57.6 40.6 21.3 22.6 34.5 29.5 28.2 21.1 27.7 1995 49.6 37.1 18.9 22.2 29.0 26.7 23.6 16.7 23.7 1996 52.8 39.8 22.3 24.1 32.9 27.2 26.3 19.5 25.7 1997 55.2 41.5 23.8 25.3 33.4 28.0 26.6 19.7 25.1 1998 55.0 40.7 21.3 23.9 32.4 28.2 26.2 21.0 27.9 23.9 37.1 44.0 1999 58.6 43.9 25.0 26.4 33.7 28.9 26.5 21.7 28.5 24.3 37.8 45.5 2000 58.7 45.5 26.0 25.7 38.3 32.0 29.5 24.1 30.6 24.9 38.9 47.1 2001 57.9 43.8 25.5 27.2 34.8 30.3 27.4 21.4 29.1 23.7 37.0 44.7 2002 58.8 41.7 25.9 28.7 35.2 30.4 27.7 21.9 27.8 23.6 36.7 44.4 2003 54.2 44.1 27.5 31.7 39.1 31.6 31.9 22.4 29.3 24.3 37.9 45.9 2004 52.8 43.5 27.8 30.6 34.3 30.2 27.9 22.1 28.4 23.3 36.3 44.1 2005 53.8 44.5 26.5 27.0 36.0 32.8 30.2 20.0 29.2 24.3 37.8 45.3 2006 57.7 47.9 24.4 31.4 38.5 33.8 29.4 23.9 29.6 26.3 41.0 49.3 2007 59.0 47.2 27.6 26.7 38.9 33.7 29.7 24.5 31.9 25.7 40.1 48.6 2008 58.0 46.4 28.1 30.4 36.4 32.7 30.0 24.0 30.4 23.3 36.5 44.5 2009 58.1 42.5 26.3 28.4 34.7 28.4 27.6 20.3 26.7 22.6 35.2 42.7 2010 51.5 41.9 21.0 26.8 33.4 28.9 27.7 21.1 26.7 22.2 34.5 41.4 2011 51.0 41.9 23.3 25.8 34.4 29.2 27.5 22.8 28.0 23.6 36.8 44.5 2012 57.3 45.3 23.6 27.6 36.4 31.5 31.6 24.0 31.2 25.3 39.4 47.4 2013 59.3 47.8 28.9 30.9 39.2 34.9 32.5 25.9 33.4 25.8 40.2 48.7 2014 59.2 49.0 29.7 32.6 37.5 35.0 34.5 26.6 35.1 26.1 40.8 49.6 2015 61.6 50.3 27.1 29.8 36.2 33.8 32.9 24.7 34.0 25.4 39.5 47.6 2016 60.0 49.7 28.0 31.3 37.0 34.0 31.5 23.4 34.6 26.3 41.1 49.9 2017 53.8 51.7 25.6 27.9 36.2 30.6 29.5 23.9 31.2 23.8 37.1 44.8 2018 59.6 48.9 27.4 29.3 38.8 36.3 31.5 24.8 32.7 25.3 39.5 47.5 2019 53.8 42.8 27.5 34.0 34.8 29.8 28.8 23.1 29.0 22.3 34.9 42.4

Avg inch 56.2 44.4 25.2 27.6 35.4 30.8 28.9 22.2 29.3 24.5 38.1 46.1 mm 1427 1127 641 701 900 783 733 565 745 622 969 1170


Table 8. Monthly total growing degree-days (50–86°F), Malheur Experiment Station, Oregon State University, Ontario, OR, 1992–2019.

Year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Total 1992 480 538 647 697 456 273 12 0 1993 0 0 58 139 451 371 473 556 459 239 17 4 2768 1994 0 5 172 242 398 507 712 695 523 195 7 0 3456 1995 2 60 77 155 330 443 646 566 469 170 16 12 2945 1996 0 19 103 188 286 490 662 614 377 216 37 11 3004 1997 3 10 122 167 447 508 632 665 489 215 35 0 3293 1998 0 4 95 175 268 436 737 690 529 220 40 5 3198 1999 0 9 81 175 320 467 629 651 458 268 69 1 3127 2000 1 13 79 277 380 541 702 684 421 202 8 0 3309 2001 0 0 122 176 433 502 680 712 507 231 62 0 3424 2002 0 4 76 202 375 564 749 620 457 230 37 11 3325 2003 1 11 134 164 370 580 782 714 479 338 27 8 3610 2004 0 0 189 264 322 535 727 657 410 238 7 1 3349 2005 0 19 126 193 342 446 692 685 435 215 6 0 3158 2006 0 18 48 204 406 597 791 647 446 219 60 4 3441 2007 0 20 183 220 441 543 796 644 442 184 50 6 3528 2008 0 2 39 144 389 512 713 665 452 228 36 6 3186 2009 1 7 66 209 415 509 702 644 523 130 34 0 3239 2010 1 5 92 159 248 467 671 605 470 271 50 0 3037 2011 0 11 46 106 272 423 676 699 531 221 11 4 2999 2012 1 8 129 253 353 484 751 694 512 222 56 12 3475 2013 0 8 130 226 407 549 745 717 491 201 18 7 3498 2014 0 22 116 227 424 544 779 685 503 293 36 17 3647 2015 7 71 190 241 427 674 716 700 461 347 33 9 3876 2016 0 42 129 305 405 576 680 683 443 227 78 0 3570 2017 0 0 114 169 380 533 766 706 461 189 19 0 3337 2018 1 28 101 225 471 516 733 683 443 210 36 0 3446 2019 0 4 95 213 372 530 698 691 435 135 53 1 3227

Avg 1993-2018 1 15 108 200 375 512 705 665 469 228 34 4 3317


Table 9. Last and first frost (32°F) dates and number of frost-free days, Malheur Experiment Station, Oregon State University, Ontario, OR, 1990–2019.

Year Date of last frost Date of first frost

Total frost-free days Spring Fall 1990 8-May 7-Oct 152 1991 30-Apr 4-Oct 157 1992 24-Apr 14-Sep 143 1993 20-Apr 11-Oct 174 1994 15-Apr 6-Oct 174 1995 16-Apr 22-Sep 159 1996 6-May 23-Sep 140 1997 3-May 8-Oct 158 1998 18-Apr 17-Oct 182 1999 11-May 28-Sep 140 2000 12-May 24-Sep 135 2001 29-Apr 10-Oct 164 2002 8-May 12-Oct 157 2003 19-May 11-Oct 145 2004 16-Apr 24-Oct 191 2005 15-Apr 6-Oct 174 2006 19-Apr 22-Oct 186 2007 4-May 11-Oct 160 2008 2-May 13-Oct 164 2009 13-May 1-Oct 141 2010 7-May 12-Oct 158 2011 4-May 25-Oct 174 2012 29-Apr 4-Oct 158 2013 23-May 5-Oct 135 2014 29-Apr 22-Oct 176 2015 15-Apr 27-Oct 195 2016 28-Mar 12-Oct 198 2017 13-May 10-Oct 150 2018 19-Apr 14-Oct 178 2019 1-May 2-Oct 154

avg 1976-2018 29-Apr 7-Oct 162


Table 10. Record weather events at the Malheur Experiment Station, Oregon State University, Ontario, OR.

Record event Measurement Date

------------------------------------------ Since 1943 ------------------------------------------------

Highest annual precipitation 16.87 inches 1983

Lowest annual precipitation 5.16 inches 1949

Highest monthly precipitation 4.55 inches May 1998

Highest June precipitation 2.27 inches June 2009

Highest December precipitation 4.19 inches December 2010

Highest 24-hour precipitation 1.52 inches September 14, 1959

Highest annual snowfall 40 inches 1955

Greatest snow depth 28 inches January 17, 2017

Highest 24-hour snowfall 10 inches November 30, 1975

Earliest snowfall 1 inch October 25, 1970

Highest air temperature 110°F July 22, 2003

Total days with maximum air temp. ≥100°F 18 days 2013

Lowest air temperature -26°F Jan 21 and 22, 1962

Total days with minimum air temp. ≤0°F 35 days 1985

Lowest average maximum air temperature for October 58°F 2019

Lowest average minimum air temperature for October 29°F 2019

Lowest minimum air temperature in October 10°F October 31, 2019

Longest frost-free period 198 days 2016

------------------------------------------ Since 1967 ------------------------------------------------

Lowest soil temperature at 4-inch depth 12°F Dec 24, 25, and 26, 1990

------------------------------------------ Since 1993 -----------------------------------------------

Most yearly growing degree-days 3876 2015

Fewest yearly growing degree-days 2768 1993

Fewest growing degree-days in March 39 2008

Fewest growing degree-days in April 106 2011

Most growing degree-days in April 305 2016

------------------------------------------ Since 1992 -----------------------------------------------

Highest reference evapotranspiration 61.6 inches 2015


Figure 1. Cumulative growing degree-days (50–86°F) over time for 2019 compared to the years with lowest (1993) and highest (2015) totals since 1993 and to the 26-year average (1993–2018), Malheur Experiment Station, Oregon State University, Ontario, OR. Lines for 2019 and the average overlap.

Brassica Cover Crop Variety Trial 12

BRASSICA COVER CROP VARIETY TRIAL Christy Tanner, Malheur County Extension Service, Oregon State University, Ontario, OR

Introduction Cover crops can directly benefit farmers by improving soil health and water holding capacity; suppressing weeds, pests, and diseases; preventing erosion and nutrient losses; fixing nitrogen; and providing additional forage for livestock. In Malheur County, Oregon, there is growing interest in cover crops, but little work has been done to identify which cover crops are best suited to this area. This trial evaluated the performance of brassica cover crop species and varieties planted in August 2019 following wheat harvest. Varieties were evaluated for biomass production, weed suppression, and forage quality.

Materials and Methods Brassica cover crops were grown on an Owyhee silt loam soil in the fall following wheat harvest in 2019. Wheat stubble was shredded, and the field was disked and irrigated. A soil analysis showed a pH of 8.1, 2.94% organic matter, 3 ppm nitrate-nitrogen (N), 3 ppm ammonium-N, 31 ppm phosphorus (P), 331 ppm potassium, 29 ppm sulfate, 3577 ppm calcium, 345 ppm magnesium, 99 ppm sodium, 7.9 ppm zinc, 1.7 ppm copper, 2 ppm manganese (Mn), 14 ppm iron, and 0.04 ppm boron (B). Fertilizers were broadcast applied based on this soil analysis at rates of 120 lb N/acre, 200 lb elemental sulfur/acre, 6 lb Mn/acre, and 1 lb B/acre. The field was then disked and rototilled, then bedded at 30-inch spacing. A total of 11 varieties of 6 species of brassica were planted on August 28, 2019. Three of the tested varieties are marketed for pest control (biofumigation and nematode control), while the other eight varieties are forage types. The experiment was a randomized complete block design with four replicates. Seeding rates were determined based on dealer recommendations (Table 1). Plots were 15 ft wide (6 beds) by 40 ft long. A 7-row small plot planter with 7.5-inch row spacing was used for planting. The middle row of the planter was plugged to avoid planting in the furrow, resulting in three rows per bed. Seed was planted at ½-inch depth and drag chains were used to ensure good seed-to-soil contact. The trial was furrow irrigated for 24 hours the day after planting. No additional irrigation was applied, and no herbicides or pesticides were used. By not controlling volunteer wheat and weeds, we were able to evaluate weed suppression. Biomass samples were collected on October 15, 2019, (blocks 1 and 2) and October 16 (blocks 3 and 4). A quadrat measuring 10 ft2 in area was sampled by cutting all biomass at soil level from a 48-inch-long section of a single bed (30-inch width) within each plot. Four quadrats were sampled in the area surrounding the study to measure weed biomass when no cover crop was present. The fresh weights of the samples were recorded. Two representative subsamples were taken from the original sample. Weeds were removed from the first subsample and the cover crop was sent to Western Laboratories (Parma, ID) for forage quality analysis including percent protein, acid detergent fiber (ADF), and neutral detergent fiber (NDF). The second subsample


was weighed, separated to weed biomass and cover crop biomass, dried, and the dry weights of cover crop and weeds were recorded. Differences between varieties were evaluated using analysis of variance (ANOVA) and means separation was determined using Tukey’s honestly significant difference with a family-wise error rate of P < 0.05.

Results and Discussion All varieties emerged by September 3, 2019. The pest control varieties (Master mustard, Control radish, and Caliente 199) were planted at much higher seeding rates than the forage varieties. Unsurprisingly, the pest control varieties reached canopy closure more quickly than the forage types. By September 24, 2019, pest control varieties had fully covered the beds and were largely shading the furrows. Of the forage varieties, Shield mustard had the fullest canopy, fully covering the beds and partially shading the furrows, and Enricher radish, African cabbage and Bayou kale had full coverage of the beds in most plots, followed by Ethiopian cabbage. Winfred forage brassica, purple top rutabaga, and Graza radish had poor stands. It is possible that the 2 lb/acre seeding rates were too low for Winfred and the rutabaga. Local producers have reported good results with Winfred when planted earlier, so it may perform better in warmer parts of the season. Graza was planted from 2-year-old seed which was found to have poor germination, so the results of this trial are likely not representative of this variety. Cover crop dry biomass ranged from 0.34 ± 0.15 to 1.4 ± 0.23 ton/acre, with biomass production generally following the same pattern as canopy closure (Table 2). The highest yielding varieties were the three pest control varieties and the forage varieties Shield mustard and Bayou kale, and there were no statistically significant differences in yield among these varieties. Ethiopian cabbage and African cabbage had intermediate biomass yields (0.82 ± 0.12 and 0.93 ± 0.10 ton/acre, respectively) that were statistically different from both the highest and lowest yielding varieties. Enricher radish, Graza radish, Winfred forage brassica, and Purpletop rutabaga had average yields of 0.71 ton/acre or less. Weed and volunteer wheat biomass ranged from 0.05 ± 0.05 ton/acre to 0.61 ± 0.32 ton/acre in cover-crop-planted plots, and averaged 0.80 ton/acre in no-cover-crop check plots. Weed biomass was negatively correlated with cover crop biomass (P < 0.05) on a plot-by-plot basis (Figure 1). All varieties except for Purpletop rutabaga had significantly lower weed biomass than the check plots, and most of the varieties had significantly lower weed biomass than Purpletop rutabaga. There was relatively high variability in weed biomass measurements, so sampling methods designed to reduce variability and increased replication would be needed to detect varietal differences in weed suppression. Many of the cover crop varieties are intended for forage production, often in mixtures with wheat or other cereals. Since volunteer wheat made up the majority of the weed biomass, its contribution to the amount of forage produced should also be considered. The amount of biomass produced by volunteer wheat and weeds in the check plots exceeds the amount of cover crop biomass produced by several of the cover crop varieties. When the total biomass is considered (cover crop biomass + weed biomass), only Control radish, Master mustard, Caliente 199, Shield mustard, Bayou kale, and Ethiopian cabbage produced significantly more biomass than was produced by volunteer wheat.


The cover crops had high forage quality with lower fiber than supreme quality alfalfa and protein content of good quality alfalfa and higher. The protein content of the cover crops ranged from 18.3 ± 1.2% (Enricher radish) to 25.7 ± 2.7% (Winfred forage brassica). Acid detergent fiber ranged from 16.8 ± 1.2 to 21.3 ± 1.3%, and NDF ranged from 29.4 ± 1.7 to 34.3 ± 1.9%, with the exception of Master mustard, which had significantly higher fiber content (26.7 ± 3.6% ADF and 39.7 ± 2.6% NDF).

Conclusions Brassica cover crops were able to produce up to 1.4 dry ton/acre of high quality forage when planted the last week of August. There is likely room to increase production by optimizing seeding rates, establishment, and planting timing. During an average year, 1070 growing degree units (base 41F) accumulate between August 28 and October 15. Planting 3 weeks earlier would provide the cover crop an additional 650 growing degree units. The late planting date of this study likely limited yield.

Acknowledgements A special thanks to Saddle Butte Ag, PGG, Allied Seed and Simplot for donating seed used in this project.

Table 1. Brassica varieties included in the cover crop trial and seeding rates used, Malheur Experiment Station, Oregon State University, Ontario, OR 2019. Seeding rates were chosen based on recommendations indicated on suppliers’ websites or verbal recommendations from suppliers.

Variety Seed donor Seeding rate (lb/acre) Forage

Winfred forage brassica PGG 2 Purpletop rutabaga Allied Seed 2 Ethiopian cabbage PGG 4 African cabbage Saddle Butte Ag 4 Graza radish PGG 6 Enricher radish Saddle Butte Ag 6 Shield mustard Saddle Butte Ag 6 Bayou kale Saddle Butte Ag 6

Pest control Master mustard Allied Seed 20 Caliente 199 Simplot 20 Control radish Allied Seed 25


Table 2. Forage quality and dry biomass production of brassica cover crop varieties at the Malheur Experiment Station, Oregon State University, Ontario, OR. 2019. Values are mean ± standard deviation (n = 4). Within each column, values with the same letter did not differ significantly according to Tukey’s honestly significant difference.

Variety Protein (%) Acid detergent

fiber (%)

Neutral detergent fiber

(%)

Cover crop biomass (ton/acre)

Weed biomass (ton/acre)

Total biomass (ton/acre)

African cabbage 22.4 ± 5.3 ab 20.3 ± 2.2 bc 34.3 ± 1.3 b 0.93 ± 0.10 bc 0.15 ± 0.04 c 1.08 ± 1.08 bcd Bayou kale 23.8 ± 1.7 ab 18.0 ± 1.1 bc 31.0 ± 1.2 bc 1.03 ± 0.04 ac 0.22 ± 0.09 c 1.25 ± 1.25 ac Caliente 199 20.4 ± 2.0 ab 21.3 ± 1.3 b 34.3 ± 1.9 b 1.21 ± 0.19 ab 0.05 ± 0.05 c 1.26 ± 1.26 ac Control radish 19.3 ± 1.4 ab 19.9 ± 1.4 bc 32.8 ± 1.6 bc 1.39 ± 0.10 a 0.15 ± 0.09 c 1.53 ± 1.53 a Enricher radish 18.3 ± 1.2 b 19.0 ± 0.9 bc 31.5 ± 1.6 bc 0.71 ± 0.07 ce 0.21 ± 0.11 c 0.92 ± 0.92 cd Ethiopian cabbage 23.3 ± 4.1 ab 20.5 ± 1.3 bc 33.4 ± 2.5 bc 0.82 ± 0.12 cd 0.33 ± 0.21 bc 1.15 ± 1.15 ad Graza radish 25.5 ± 2.4 ab 18.6 ± 1.0 bc 30.6 ± 1.2 bc 0.52 ± 0.26 de 0.34 ± 0.08 bc 0.86 ± 0.86 cd Master mustard 19.3 ± 3.5 ab 26.7 ± 3.6 a 39.7 ± 2.6 a 1.40 ± 0.23 a 0.07 ± 0.06 c 1.47 ± 1.47 ab Purpletop rutabaga 22.8 ± 3.7 ab 16.8 ± 1.2 c 30.8 ± 1.0 bc 0.34 ± 0.15 e 0.61 ± 0.32 ab 0.96 ± 0.96 cd Shield mustard 19.5 ± 2.7 ab 19.1 ± 1.1 bc 31.7 ± 1.3 bc 1.19 ± 0.18 ab 0.19 ± 0.12 c 1.38 ± 1.38 ab Winfred forage brassica 25.7 ± 2.7 a 17.0 ± 0.8 c 29.4 ± 1.7 c 0.47 ± 0.05 de 0.35 ± 0.12 bc 0.82 ± 0.82 d Weedy check 0.80 ± 0.27 a 0.80 ± 0.27 d


Figure 1. Weed biomass vs. biomass of brassica cover crops for each plot, by cover crop variety, Malheur Experiment Station, Oregon State University, Ontario, OR, 2019. Linear regression analysis (after Box-Cox transformation to meet model assumptions) showed a statistically significant relationship (P < 0.05, r2 = 0.68).

Controlling Yellow Nutsedge (Cyperus esculentus L.) with Competition from Cover Crops — Preliminary Results 17

CONTROLLING YELLOW NUTSEDGE (CYPERUS ESCULENTUS L.) WITH COMPETITION FROM COVER CROPS — PRELIMINARY RESULTS Christy Tanner, Malheur County Extension Service, Oregon State University, Ontario, OR Joel Felix, Malheur Experiment Station, Oregon State University, Ontario, OR

Introduction Yellow nutsedge (YNS) is a problematic weed in onion production systems in eastern Oregon. The high-moisture, high-light conditions found in onion fields allow YNS to thrive (Ransom et al., 2009). Few herbicides are available for the selective control of YNS in onion fields, so cultural practices that limit its growth will be valuable to growers. The goal of this project is to evaluate the YNS suppression potential of planting a cover crop in the fall before onions are grown, both with and without herbicide application. Cover crops are expected to help suppress YNS through competition (Sturm et al., 2018) and will hopefully complement existing weed control practices such as herbicides. Thus far in our current project, YNS has been established in experimental enclosures, and 1 year of cover crop and herbicide treatments has been applied. The effects of the treatments will be measured during spring 2020 when YNS emerges. Treatments will be applied again during fall 2020 to collect a second year of data.

Materials and Methods The experiment was conducted on an Owyhee silt loam soil. A soil analysis on August 15, 2019, showed a pH of 8.5, 3.1% organic matter, 5 ppm nitrate-nitrogen (N), 3 ppm ammonium-N, 16 ppm phosphorus, 321 ppm potassium, 51 ppm sulfate, 3794 ppm calcium, 366 ppm magnesium, 163 ppm sodium, 2.6 ppm zinc, 1.3 ppm copper, 4 ppm manganese, 12 ppm iron, and 0.3 ppm boron.

Compatibility of Cover Crops and Herbicide To test whether or not the cover crop and herbicide treatments were compatible, a separate small plot study was established to evaluate the emergence of four cover crop varieties when treated with Dual Magnum® herbicide. Four cover crop varieties (Master mustard, Control radish, Purpletop rutabaga, and Ethiopian cabbage) were planted on July 9, 2020 in a randomized complete block design with four replicates. Immediately before planting cover crops, Dual Magnum herbicide was applied at 1.33 pt/acre to the eastern half of each plot. This arrangement ensured that herbicide-treated soil was not moved into untreated areas. The herbicide was incorporated by lightly rototilling and the cover crops were planted at ½-inch depth and 6-inch row spacing. Seeding rates were based on seed dealer recommendations: Master mustard, 20 lb/acre; Control radish 25 lb/acre; Purpletop rutabaga and Ethiopian cabbage, 7 lb/acre. The


herbicide treatment at planting reduced the emergence of the cover crops. Based on the results of this test, we selected the two most vigorous cover crops for planting in enclosures and waited to apply the herbicide treatments until after cover crop emergence.

Enclosures In October 2018, 36 enclosures were made from 14-inch-wide by 19-ft-long galvanized metal flashing with the ends riveted together to create circular enclosures 6 ft in diameter. The rings were buried to a depth of 12 inches in an area of tilled soil known to be free of YNS. Wheat was grown to simulate the common practice of farmers who typically plant onions in the spring the year after wheat harvest. Wheat (cultivar: Ovation) was planted by hand in rows spaced 6 inches apart on October 25 and 26, 2018, at 120 lb/acre and 1 inch deep. The plots were irrigated with sprinklers, and Watermark sensors were used to determine irrigation timing. On April 2, 2019, 217 lb N/acre was applied as urea to the plots.

Yellow Nutsedge Establishment Establishing YNS with competition from wheat proved difficult. Tubers were collected from a local heavily infested area on March 22, 2019, rinsed, and stored in the refrigerator at 4 °C for 14 days to promote even germination. On April 5, 2019, tubers were placed in gallon Ziploc bags in a single layer on moist paper towels and moved to a germinator set to 20 °C at night and 25 °C during the day. Germinated tubers were separated by size, and medium-sized mature tubers were selected for planting. On April 11, 2019, four tubers were planted in each plot (circular ring) 1 inch deep. Tuber placement was halfway between the center and edge of the plot and equally spaced around the center. The first tubers did not establish, so additional tubers were planted on May 8, 2019 and irrigation was increased. The wheat was cut at soil level in a 1-foot radius around the developing YNS plants on May 31, 2019 to reduce competition and promote YNS growth. YNS plants were still small when wheat was harvested, so additional tubers were collected, and 10.1 g of tubers (about 50 tubers) were spread in each plot when cover crops were planted on August 22, 2019.

Treatments In August 2019, the wheat was harvested and cover crop and herbicide treatments were applied to the enclosures. The experiment was a three by two factorial design with three cover crop treatments (Control radish, Master mustard and no cover crop) and two herbicide treatments (Dual Magnum and no herbicide), resulting in a total of six unique treatments. The treatments were assigned to the plots in a randomized complete block design with six replicates.

Cover Crop Establishment Wheat was harvested on August 12, 2019, and the plots were rototilled on August 20, 2019. On August 22, fertilizers were broadcast applied based on soil analysis. Elemental sulfur at 200 lb/acre and phosphate at 50 lb/acre were applied to all plots. Plots where cover crops were planted also received N at 110 lb/acre. YNS tubers were seeded to all plots as described above. Master mustard and Control radish cover crops were broadcast seeded at 20 and 25 lb/acre respectively and lightly incorporated with a hand cultivator. The plots were irrigated after planting and again on August 25, to ensure germination. After the cover crops had emerged, Dual Magnum (1.33 pt/acre) was applied to respective treated plots on 28 August, and ½ inch of irrigation was applied with sprinklers to incorporate the herbicide in the soil.


Cover Crop Termination and Biomass Measurement On October 24, 2019, samples were taken to measure cover crop biomass and cover crops were terminated. A pie-slice-shaped area measuring one-sixteenth of the plot was cut at ground level and removed from the plot to measure biomass of the cover crop. The biomass sample from each plot was divided into cover crop and weeds, dried to constant weight at 106°F and the dry weights were recorded. The biomass sampling procedure was designed to accurately measure the amount of cover crop biomass that was incorporated into each plot at termination, but it is likely not representative of field-scale cover crop production due to edge effects common in small plots. The remaining standing cover crop biomass was cut into short (~3 inch) pieces using a hedge trimmer. A small garden rototiller was used to incorporate the cover crop biomass into each plot. Soil within each plot was smoothed and packed with a shovel, then irrigated to promote the biofumigation process.

Statistical Analysis A two-way analysis of variance (ANOVA) was used to test for the effects of variety and herbicide treatment on both cover crop and weed biomass.

Next Steps When YNS begins to emerge in the spring of 2020, shoots will be counted in all plots to evaluate the effectiveness of the treatments. Due to the difficulty of establishing YNS during the first year of this study, YNS will be allowed to grow without competition during the spring and summer of 2020 to ensure establishment. Cover crop treatments will be repeated in the fall.

Results and Discussion Cover crops were successfully established in the plots, and biomass production is shown in Table 1. Herbicide injury (curled leaves) was visible in one plot that received extra irrigation from a neighboring experiment. However, herbicide-treated plots had slightly, but not significantly, higher cover crop biomass than untreated plots, which suggests that the herbicide treatment did not negatively impact cover crop growth. Master mustard had significantly higher biomass production than Control radish (P < 0.05). It was not practical to measure belowground biomass, but observations of cover crop roots suggest that Control radish had higher belowground biomass production than Master mustard. No statistically significant differences were detected in weed biomass production between treatments.

Conclusions This study was based on the idea that YNS can be suppressed through competition with another crop. The poor establishment of YNS when wheat was present demonstrates that competition with a cover crop has potential to be a successful YNS control strategy.


Acknowledgements This project was funded by the Agricultural Research Foundation and the College of Agricultural Sciences at Oregon State University. A special thanks to Allied Seed for the donation of the cover crop seed, and to Cody Kramer for technical advice.

References Ransom, C. V., Rice, C. A. & Shock, C. C. (2009). Yellow nutsedge (Cyperus esculentus)

growth and reproduction in response to nitrogen and irrigation. Weed Science, 57, 21–25. Sturm, D. J., Peteinatos, G. & Gerhards, R. (2009). Contribution of allelopathic effects to the

overall weed suppression by different cover crops. Weed Research, 58, 331–337.

Table 1. Mean ± standard deviation (n = 6) cover crop and weed biomass (reported on a dry matter basis) incorporated into plots in the cover crop–yellow nutsedge control study, Malheur Experiment Station, Oregon State University, Ontario, OR, 2019.

Cover crop Herbicide Cover crop biomass (g/plot) Weed biomass (g/plot) Master mustard no 1788 ± 263 61 ± 48 Control radish no 1248 ± 407 201 ± 3471 Master mustard yes 1834 ± 368 60 ± 71 Control radish yes 1395 ± 337 36 ± 34 ANOVA2

Cover crop * NS Herbicide NS NS Cover crop x Herbicide NS NS

1 Includes one outlier that had more than five times higher weed biomass than the second highest biomass measurement in the study. When this outlier is removed, the weed biomass of this treatment is similar to other treatments. 2 Significance codes: * = P < 0.05, NS = P > 0.05

2019 Onion Variety Trials 21

2019 ONION VARIETY TRIALS Erik B. G. Feibert, Stuart Reitz, Alicia Rivera, and Kyle D. Wieland, Malheur Experiment Station, Oregon State University, Ontario, OR

Introduction Direct-seeded yellow, white, and red onion varieties were evaluated in the field in 2019 for plant disease, thrips damage, maturity, bolting, and bulb single centers. Out of storage, the varieties were evaluated for yield, grade, and bulb decomposition. Three early-season yellow varieties and one early-season red variety were planted in March and harvested and graded in mid-August. Fifty-four full-season varieties (35 yellow, 11 red, and 8 white) were planted in March, harvested in September, and graded out of storage in January 2020. Each year, growers and seed industry representatives have the opportunity to examine the varieties at our annual Onion Variety Day in late August and during bulb evaluations in January. Onion varieties were evaluated objectively for bolting, yield, grade, single centers, and storability. Varieties were evaluated subjectively for maturity, thrips leaf damage, Iris Yellow Spot Virus (IYSV), bulb shape, bulb shape uniformity, flesh brightness, and skin color and retention.

Materials and Methods Onions were grown in 2019 on an Owyhee silt loam previously planted to wheat. After the wheat was harvested in 2018, the stubble was shredded and the field was irrigated to sprout unharvested wheat kernels and then the field was disked. A soil analysis taken in the fall of 2018 showed a pH of 7.7, 2.5% organic matter, 6 ppm nitrogen (N) as nitrate, 2 ppm N as ammonium, 41 ppm phosphorus (P), 323 ppm potassium (K), 9 ppm sulfur (S), 2751 ppm calcium, 500 ppm magnesium, 186 ppm sodium, 2.9 ppm zinc (Zn), 2 ppm manganese (Mn), 1.7 ppm copper (Cu), 11 ppm iron, and 1.1 ppm boron (B). Based on the soil analysis, 50 lb N/acre, 22 lb P/acre, 42 lb K/acre, 80 lb S/acre, 12 lb Mn/acre, and 1 lb B/acre were broadcast before plowing. In addition to the chemical fertilizer, 10 ton/acre of composted cattle feedlot manure was broadcast before plowing. Based on an analysis of the manure, 186 lb N/acre, 107 lb P/acre, and 375 lb K/acre were added from the manure. After plowing and groundhogging, the field was fumigated with Vapam® at 15 gal/acre and bedded at 22 inches. The varieties were planted in three adjacent trials based on bulb color (yellow, white, red). The experimental designs for each full-season trial and the early-maturing trial were randomized complete blocks with five replicates. A sixth nonrandomized replicate was planted for demonstrating onion variety performance to growers and seed company representatives at the Onion Variety Day. All trials were planted on March 21 in plots 4 double rows wide and 27 ft long. The early-maturing trial had 4 varieties from 2 seed companies, the full-season yellow trial had 35 varieties from 9 seed companies, the full-season white trial had 8 varieties from 6 seed companies, and the full-season red trial had 11 varieties from 7 seed companies. An additional trial with onion transplants is not reported here. Seed was planted in double rows spaced 3 inches apart at 9 seeds/ft of single row. Each double row was planted on beds spaced 22 inches apart. Planting was done with customized John Deere


Flexi Planter units equipped with disc openers. Immediately after planting, the field received a narrow band of Lorsban® 15G at 3.7 oz/1000 ft (0.82 lb ai/acre) over the seed rows and the soil surface was cultipacked. Onion emergence started on April 9. On May 13, alleys 4 ft wide were cut between plots, leaving plots 23 ft long. The seedling were hand thinned on May 15 and 16, and then, due to rainfall, thinning was finished on May 23 and 24. The seedlings were hand thinned to a target spacing of 4.75 inches between individual onion plants in each single row, or 120,000 plants/acre. The field had drip tape laid at 4-inch depth between pairs of beds during planting. The drip tape had emitters spaced 12 inches apart and an emitter flow rate of 0.22 gal/min/100 ft (Toro Aqua-Traxx, Toro Co., El Cajon, CA). The distance between the tape and the center of each double row of onions was 11 inches. The onions were managed to minimize yield reductions from weeds, pests, diseases, water stress, and nutrient deficiencies. For weed control, the following herbicides were broadcast: oxyfluorfen at 0.13 lb ai/acre (GoalTender® at 4 oz/acre), bromoxynil at 0.25 lb ai/acre (Brox® 2EC at 16 oz/acre), pendimethalin at 0.95 lb ai/acre (Prowl® H2O at 2 pt/acre), and clethodim at 0.12 lb ai/acre (Shadow® 3EC at 5.3 oz/acre) on May 7 and pendimethalin at 0.48 lb ai/acre on May 30. For thrips control, the following insecticides were applied by ground: azadirachtin at 0.0093 lb ai/acre (Aza-Direct® at 12 oz/acre) and potassium salts of fatty acids at 2% v/v (M-Pede®) on May 30; spirotetramat at 0.078 lb ai/acre (Movento® at 5 oz/acre) and azadirachtin at 0.0093 lb ai/acre on June 5; spirotetramat at 0.078 lb ai/acre and spinetoram at 0.078 lb ai/acre (Radiant® at 10 oz/acre) on June 12; abamectin at 0.019 lb ai/acre (Agri-Mek® SC at 3.5 oz/acre) on June 21; cyantraniliprole at 0.13 lb ai/acre (Exirel® at 20.5 oz/acre) on July 12 and 22; spinetoram at 0.078 lb ai/acre on July 30. The following insecticides were applied by air: abamectin at 0.019 lb ai/acre and spinetoram at 0.078 lb ai/acre on July 3. Starting on June 11, root tissue and soil samples were taken every week from field borders (variety ‘Vaquero’) and analyzed for nutrients by Western Laboratories, Inc., Parma, Idaho (Tables 1 and 2). Nutrients were applied through the drip tape based on the root tissue and soil solution recommendations from Western Labs (Table 3). In 2019, both the soil solution N and the root nitrate levels went above the critical level only in late July. Urea ammonium nitrate solution (URAN) was applied through the drip tape seven times from May 30 to July 18, supplying a total of 152 lb N/acre. A total of 127 lb K/acre as potassium chloride was also injected through the drip tape based on the root tissue analyses during the season.


Table 1. Onion root tissue nutrient content in the onion variety trial, Malheur Experiment Station, Oregon State University, Ontario, OR, 2019.

Nutrient 11-Jun 18-Jun 25-Jun 2-Jul 9-Jul 16-Jul 23-Jul 30-Jul 6-Aug 13-Aug

NO3-N (ppm) Sufficiency range 8500 7667 6833 6000 5168 4338 3508 2678 1834 1000 NO3-N (ppm) 4155 3724 4158 4211 3864 4279 4349 3361 2523 4387 P (%) 0.32 - 0.7 0.58 0.49 0.65 0.48 0.51 0.45 0.38 0.36 0.32 0.37 K (%) 2.7 - 6.0 2.47 2.42 2.90 2.53 2.79 2.13 1.76 2.15 1.86 1.46 S (%) 0.24 - 0.85 0.69 0.82 0.80 0.96 0.97 0.49 0.64 0.40 0.50 0.55 Ca (%) 0.4 - 1.2 0.52 0.62 0.53 0.38 0.45 0.37 0.34 0.43 0.52 0.64 Mg (%) 0.3 - 0.6 0.28 0.32 0.33 0.25 0.30 0.25 0.26 0.22 0.27 0.29 Zn (ppm) 25 - 50 48 57 52 40 34 36 37 35 45 39 Mn (ppm) 35 - 100 120 101 73 94 82 95 72 55 52 61 Cu (ppm) 6 - 20 20 18 15 13 10 9 8 7 7 8 B (ppm) 19 - 60 35 34 28 20 26 30 23 29 26 29 Table 2. Weekly soil solution analyses in the onion variety trial. Data represent the amount of each plant nutrient per day that the soil can potentially supply to the crop. Malheur Experiment Station, Oregon State University, Ontario, OR, 2019. Critical level Nutrient lb/ac or g/ac 11-Jun 18-Jun 25-Jun 2-Jul 9-Jul 16-Jul 23-Jul 30-Jul 6-Aug 13-Aug N Critical levels 8.6 7 6.2 5 4 4 3.8 2.8 2 1.5 N 1.7 1.7 1.7 2.0 2.3 2.6 2.9 3.1 3.4 6.6 P 0.7 lb/acre 2.0 2.5 3.0 2.3 3.2 2.8 3.5 3.8 3.2 2.9 K 5 lb/acre 6.0 5.3 5.6 4.7 4.3 4.0 4.4 3.4 4.2 4.5 S 1 lb/acre 1.6 1.8 2.0 2.6 2.3 3.1 2.0 1.8 2.2 2.1 Ca 3 lb/acre 5.4 5.9 5.0 4.9 4.4 5.2 4.8 5.4 5.4 4.9 Mg 2 lb/acre 0.7 0.8 0.9 1.1 0.9 0.8 0.9 1.1 1.2 1.0 Zn 28 g/acre 90 84 63 63 72 60 57 48 57 60 Mn 28 g/acre 30 24 18 21 27 27 33 36 39 33 Cu 12 g/acre 75 78 84 78 57 57 63 72 66 54 B 21 g/acre 36 26 20 21 24 20 23 29 23 27


Table 3. Nutrients applied through the drip irrigation system in the onion variety trial, Malheur Experiment Station, Oregon State University, Ontario, OR, 2019.

Date N K Mg Ca

---------------- lb/acre ---------------- 30-May 20 3-Jun 25

12-Jun 20 14-Jun 10 19-Jun 20 21-Jun 10 28-Jun 23 3-Jul 24 2 5-Jul 9 8-Jul 9 17-Jul 10 2 18-Jul 20 19-Jul 10 24-Jul 10 2 4 2-Aug 15 2 5-Aug 15 8-Aug 10 2

15-Aug 19 2 Total 152 127 12 4

Table 4. Soil-available N (as NO3 + NH4) in lb/acre in the top foot of soil in the onion variety trial from 2014 through 2019, Malheur Experiment Station, Oregon State University, Ontario, OR, 2019.

2014 2015 2016 2017 2018 2019 29-May 42 26-May 38 8-Jun 48 12-Jun 32 8-Jun 14 11-Jun 12 12-Jun 51 14-Jun 207 19-Jun 28 15-Jun 16 18-Jun 12

17-Jun 48 19-Jun 123 23-Jun 147 27-Jun 46 22-Jun 68 25-Jun 12 24-Jun 102 26-Jun 87 29-Jun 168 4-Jul 76 29-Jun 60 2-Jul 14 1-Jul 90 6-Jul 165 6-Jul 150 11-Jul 90 9-Jul 68 9-Jul 16 8-Jul 33 10-Jul 81 13-Jul 144 17-Jul 92 23-Jul 60 16-Jul 18 15-Jul 219 20-Jul 99 20-Jul 129 24-Jul 112 27-Jul 70 23-Jul 20 22-Jul 141 24-Jul 99 27-Jul 120 31-Jul 112 3-Aug 88 30-Jul 22 29-Jul 255 31-Jul 90 3-Aug 99 7-Aug 102 10-Aug 70 6-Aug 24 5-Aug 174 7-Aug 87 13-Aug 46 14-Aug 225 17-Aug 147


Onions were irrigated automatically to maintain the soil water tension (SWT) at 8-inch depth in the onion root zone below 20 cb (Shock et al. 2000). Soil water tension was measured with eight granular matrix sensors (GMS, Watermark soil moisture sensor model 200SS, Irrometer Co. Inc., Riverside, CA) installed at 8-inch depth in the center of the double row of onions. Sensors had been calibrated to SWT (Shock et al. 1998). The GMS were connected to the datalogger via multiplexers (AM16/32, Campbell Scientific, Logan, UT). The datalogger (CR1000, Campbell Scientific) read the sensors and recorded the SWT every hour. The datalogger automatically made irrigation decisions every 12 hours. The field was irrigated if the average of the eight sensors was at a SWT of 20 cb or higher. The irrigations were controlled by the datalogger using a controller (SDM-CD16AC, Campbell Scientific) connected to a solenoid valve. Irrigation durations were 8 hours, 19 min, to apply 0.48 inch of water. The water was supplied from a well and pump that maintained a continuous and constant water pressure of 35 psi. The pressure in the drip lines was maintained at 10 psi by a pressure-regulating valve. The automated irrigation system was started on April 22 and irrigations ended on September 3. Onions in the early-maturing trial were evaluated for maturity, severity of symptoms of IYSV, and bolting on August 1. Onions in the full-season trial were evaluated for maturity on August 1, August 13, and August 29. On August 29, onions in the full-season trial were also evaluated for IYSV, thrips damage severity, and bolting. Onions in each plot were evaluated subjectively for maturity by visually rating the percentage of onions with the tops down and percent dry leaves. For the IYSV evaluations, onions in each plot were given a subjective rating on a scale of 0 to 5 for severity of IYSV symptoms. The rating was 0 if there were no symptoms, 1 if 1 to 25% of foliage was diseased, 2 if 26 to 50% of foliage was diseased, 3 if 51 to75% of foliage was diseased, 4 if 76 to 99% of foliage was diseased, and 5 if 100% of foliage was diseased. For thrips leaf-feeding damage, each plot was given a subjective severity rating on a scale of 0 to 10. The number of bolted onion plants was counted in each plot and compared to the plant population. Onions from the middle two double rows in each plot in the early-maturity trial were topped by hand, bagged, and graded on August 14. After grading, onions were stored in a shed at ambient air temperature for 2 weeks, after which the onions were evaluated for decomposition and sprouting. In the full-season trial, the red onion varieties matured before the yellow and white varieties. About half of the red varieties were harvested on August 21 and the other half on August 27. At harvest, onions from the middle two rows in each plot of the red onion varieties were topped and bagged to cure in the field for a week, when they were put in storage. The remaining yellow and white onions were lifted on September 10 to field cure. Onions from the middle two rows in each plot of the yellow and white varieties were topped by hand and bagged on September 16. The bags of white varieties were moved into storage on September 16. The bags of yellow varieties were moved into storage on September 23. The storage shed was ventilated, and the temperature was slowly decreased to maintain air temperature as close to 34°F as possible. Onions from the full-season trial were graded out of storage in early January 2020. After harvest, bulbs from one of the border rows in each plot of both trials were rated for single centers. Twenty-five consecutive onions ranging in diameter from 3½ to 4¼ inches were rated. The onions were cut equatorially through the bulb middle and separated into single-centered (bullet) and multiple-centered bulbs. The multiple-centered bulbs had the long axis of the inside diameter of the first single ring measured. These multiple-centered onions were ranked


according to the inside diameter of the first entire single ring: small had diameters less than 1½ inches, medium had diameters from 1½ to 2¼ inches, and large had diameters greater than 2¼ inches. Onions were considered "functionally single centered" for processing if they were single centered (bullet) or had a small multiple center. During grading, bulbs were separated according to external quality: bulbs without blemishes (No. 1s), split bulbs (No. 2s), bulbs infected with the fungus Botrytis allii in the neck or side, bulbs infected with the fungus Fusarium oxysporum (plate rot), bulbs infected with the fungus Aspergillus niger (black mold), and bulbs infected with unidentified bacteria in the external scales. The No. 1 bulbs were graded according to diameter: small (4¼ inches). Bulb counts per 50 lb of super colossal onions were determined for each plot of every variety by weighing and counting all super colossal bulbs during grading. Marketable yield consisted of No.1 bulbs larger than 2¼ inches. After grading, 50 No. 1 bulbs from each plot were cut longitudinally and evaluated for the presence of incomplete scales, dry scales, internal bacterial rot, and internal rot caused by Fusarium proliferatum or other fungi. Incomplete scales were defined as scales that had more than 0.25 inch from the center of the neck missing or any part missing lower down on the scale. Dry scales were defined as scales that had either more than 0.25 inch from the center of the neck dry or any part dry lower down on the scale. On January 14, 2020, two replicates of each variety were evaluated for bulb shape, bulb shape uniformity, firmness, skin color, skin retention, and flesh brightness (Tables 5 and 6, Figure 1). The quality characteristics were evaluated by a group of 10 people who did not know the variety identities. Evaluators included OSU personnel, seed company employees, and others. The varieties from each of the early-maturity and full-season trials were compared for yield, grade, internal quality, and disease expression. Varietal differences were determined using analysis of variance. Means separation was determined using a protected Fisher’s least significant difference test at the 5% probability level, LSD (0.05). The least significant difference LSD (0.05) values in each table should be considered when comparisons are made between varieties for significant differences in their performance characteristics. Differences between varieties equal to or greater than the LSD value for a characteristic should exist before any variety is considered different from any other variety in that characteristic. Because variety performance varies by year, growers are encouraged to review variety performance data over a number of years before choosing a variety to plant.


Figure 1. Onion bulb shape rating system. Malheur Experiment Station, Oregon State University, Ontario, OR.

Table 5. Bulb shapes. For a description of bulb shapes, see Fig. 1.

Scale Shape A Flat B Granex C Flattened globe D Globe E Blocky globe F Tall globe G Top H Torpedo

Table 6. Onion variety subjective quality evaluation rating system. Characteristic Scale Description

Bulb shape A-H see Fig. 1 Skin color 1-5 1 = light, 5 = dark, white varieties: 1=dark, 5=white Bulb shape uniformity 1-5 1 = nonuniform shape, 5 = uniform shape Firmness 1-5 1 = soft, 5 = hard Skin retention 1-5 1 = bald, 5 = no cracks Flesh brightness 1-5 yellow varieties: 1 = yellow, 5 = white

red varieties: 1 = pale red, 5 = dark red white varieties: 1 = less white, 5 = very white


Results The rate of accumulation and total number of growing degree-days (50–86°F) in 2019 were close to the 26-year average (Figures 2, 3). Precipitation for the months of February, April, May, and September was substantially higher than average. Precipitation in February, April, May, and September was 3.4, 1.5, 2.3, and 1.4 inches in 2019 compared to the 75-year average of 0.9, 0.8, 1.1, and 0.5 inches, respectively. The high spring precipitation could have been the cause of the unusually low amounts of soil N during the season in 2019 compared to previous years (Table 4). The onions were subject to higher than average precipitation in September after irrigations were terminated and during curing. The red varieties were placed into storage in early September, before precipitation events occurred. The yellow and white varieties were subject to 4 days of precipitation totaling 0.39 inches in early September after irrigations were terminated and before lifting. The yellow varieties were later subject to another 3 days of precipitation totaling 0.86 inches in mid-September during curing. With regards to irrigation management, the SWT at 8-inch depth frequently exceeded the target of 20 cb by 5 to 10 cb during the season (Figure 4).

Early-maturing Trial On August 13, all varieties had at least 85% tops down (Table 7). After 2 weeks of storage, bulb sprouting or decomposition was low, averaging 1.2%. The percentage of onions that were functionally single centered averaged 28% and ranged from 19% for ‘Yosemite’ to 39% for ‘Ovation’ (Table 8). Total yield averaged 1031 cwt/acre, ranging from 730 cwt/acre for ‘Redstone’ to 1192 cwt/acre for ‘Spanish Medallion’ (Table 9).

Full-season Trials Yellow varieties. On August 1, the percentage of tops down averaged 8% and ranged from 0% for ‘Joaquin’ to 81% for ‘Elsye’ (Table 10). By August 13, the percentage of tops down averaged 45% and ranged from 11% for ‘Caliber’ to 94% for Elsye. The severity of thrips leaf damage, on a scale from 0 to 10, averaged 2.7 and ranged from 2 for ‘Oracle’, Joaquin, ‘SV6672’, ‘Aruba’, and ‘Dulce Reina’ to 3.8 for ‘Traverse’. Bolting averaged 0.1% and ranged from 0% for many varieties to 0.3% for Dulce Reina. Iris Yellow Spot Virus Severity was low in this trial, with all varieties showing low intensity of symptoms with a rating of 1 (0–25% of foliage diseased), except for Caliber, which had a rating of 2 (25–50% of foliage diseased). The percentage of functionally single-centered bulbs averaged 71% and ranged from 23% for ‘Ridge Line’ to 98% for ‘Oloroso’ (Table 11). Marketable yield out of storage in January 2020, averaged 1052 cwt/acre and ranged from 841 cwt/acre for ‘Saffron’ to 1348 cwt/acre for ‘Ranchero’ (Table 12). Ranchero, Joaquin, and ‘Vaquero’ were among the varieties with the highest marketable yield. Storage decomposition averaged 5% and ranged from 0.5% for ‘Sedona’ to 48% for Elsye. Elsye had the highest storage decomposition followed by ‘Avalon’, ‘Scout’, and Oracle. In January 2020, the percentage of bulbs with incomplete scales, regardless of dry scale or disease, averaged 39% and ranged from 11% for ‘Grand Perfection’ to 84% for Traverse (Table 13). The percentage of bulbs with internal decomposition, regardless of incomplete or dry scales, averaged 0.4% and ranged from 0% for many varieties to 2% for ‘Tucannon’. In 2019, the percentage of bulbs with internal decomposition was low and was almost exclusively caused by neck rot (Table 14). Internal decomposition caused by bacterial rot was observed only in


‘Mondella’ at 4%. Internal decomposition caused by Fusarium proliferatum and black mold was not observed in 2019. Subjective bulb quality ratings can be found in Table 15. Significant variations were found among varieties in all the subjective characteristics except flesh brightness. White varieties. On August 1, the percentage of tops down averaged 4% and ranged from 1% for ‘Bridewhite’ to 5% for several varieties (Table 16). On August 13, the percentage of tops down averaged 24% and ranged from 14% for ‘37-127’ to 36% for ‘Rhea’. The severity of thrips leaf damage, on a scale from 0 to10, averaged 2.3 and ranged from 2 for Rhea to 2.6% for ‘SV4058’ and ‘Diamond Swan’. Bolting averaged 0.03% and was less than 0.1% for all varieties. Iris Yellow Spot Virus Severity was low in this trial, with all varieties showing low intensity of symptoms, with a rating of 1 (0–25% of foliage diseased). The percentage of functionally single-centered bulbs averaged 80% and ranged from 42% for Bridewhite to 98% for ‘White Cap’ (Table 17). Marketable yield in January 2020 averaged 970 cwt/acre and ranged from 813 cwt/acre for Diamond Swan to 1114 cwt/acre for 37-127 (Table 18). Varieties 37-127, ‘Cometa’, and Rhea were among those with the highest marketable yield. Storage decomposition averaged 14% and ranged from 9% for Rhea to 21% for ‘DPS-2056’. In January 2020, the percentage of bulbs with incomplete scales, regardless of dry scale or disease, averaged 27% and ranged from 10% for Cometa to 42% for Diamond Swan (Table 19). The percentage of bulbs with internal decomposition, regardless of incomplete or dry scales, averaged 5% and ranged from 2% for White Cap to 12% for SV4058. In 2019, the internal decomposition was caused by neck rot (Table 20). Internal decomposition caused by bacteria, Fusarium proliferatum, and black mold were not observed in white onion varieties in the 2019 trial. Subjective bulb quality ratings can be found in Table 21. There were no statistically significant variations among varieties in any of the subjective characteristics. Red varieties. On August 1, the percentage of tops down averaged 17% and ranged from 3% for ‘RW011’ to 86% for ‘Monastrell’ (Table 22). On August 13, the percentage of tops down averaged 51% and ranged from 19% for ‘Purple Haze’ and RW011 to 95% for Monastrell. Bolting averaged 0.03% and was less than 0.1% for all varieties. The percentage of functionally single-centered bulbs averaged 45% and ranged from 16% for ‘TAS040’ to 82% for Purple Haze (Table 23). Marketable yield in January 2020 averaged 530 cwt/acre and ranged from 396 cwt/acre for TAS040 to 590 cwt/acre for ‘SV4643NT’ (Table 24). SV4643NT, Purple Haze, and ‘Marenge’ were among the varieties with the highest marketable yield. Storage decomposition averaged 9% and ranged from 1% for RW011 to 19% for Monastrell. In January 2020, the percentage of bulbs with incomplete scales, regardless of dry scale or disease, averaged 69% and ranged from 57% for TAS040 to 84% for ‘TAS042’ (Table 25). The percentage of bulbs with internal decomposition, regardless of incomplete or dry scales, averaged 1.6% and ranged from 0% for Monastrell to 5% for Marenge. In 2019, the percentage of bulbs with internal decomposition was low and was caused by neck rot (Table 26). Internal


decomposition caused by bacteria, Fusarium proliferatum, and black mold was not observed in red onion varieties in the 2019 trial. Subjective bulb quality ratings can be found in Table 27. Significant variations were found among varieties in all the subjective characteristics except bulb shape, bulb shape uniformity, and flesh brightness.

Acknowledgements This project was funded by the Idaho-Eastern Oregon Onion Committee, cooperating onion seed companies, Oregon State University, the Malheur County Education Service District, and supported by Formula Grant nos. 2019-31100-06041 and 2019-31200-06041 from the USDA National Institute of Food and Agriculture.

References Shock, C.C., J. Barnum, and M. Seddigh. 1998. Calibration of Watermark soil moisture sensors

for irrigation management. Irrigation Association. Proceedings of the International Irrigation Show. Pages 139-146. San Diego, CA.

Shock, C.C., E.B.G. Feibert, and L.D. Saunders. 2000. Irrigation criteria for drip-irrigated onions. HortScience 35:63-66.

Sullivan, D.M., B.D. Brown, C.C. Shock, D.A. Horneck, R.G. Stevens, G.Q. Pelter, and E.B.G. Feibert. 2001. Nutrient management for sweet spanish onions in the Pacific Northwest. Pacific Northwest Extension Publication PNW 546:1-26.


Figure 2. Cumulative growing degree-days (50–86°F) for selected years and 26-year average, Malheur Experiment Station, Oregon State University, Ontario, OR, 2019. Lines for 2019 and the average overlap.


Figure 3. Monthly growing degree-days (50–86°F) for 2016–2019 and 26-year average, Malheur Experiment Station, Oregon State University, Ontario, OR, 2019.

Figure 4. Soil water tension at 8-inch depth below the onion row, Malheur Experiment Station, Oregon State University, Ontario, OR, 2019.

0

5

10

15

20

25

30

Soil

wat

er te

nsio

n, c

b

April 22 - September 8


Table 7. Maturity ratings and bulb quality for early-maturing onion varieties lifted and harvested August 14, 2019, Malheur Experiment Station, Oregon State University, Ontario, OR. Maturity Aug. 1 Maturity Aug. 13 Bulb quality 2 weeks after harvest Seed company Variety

Bulb color Tops down Leaf dryness Tops down Leaf dryness Sprouted Decomposed

Sprouted and decomposed

Sprouted or decomposed

----------------------------------------------------------- % ----------------------------------------------------------------------- Hazera Redstone R 50 6 100 10 0.0 0.8 0.0 0.8 Sakata Ovation Y 22 2 85 5 1.6 0.0 0.0 1.6

Spanish Medallion Y 22 1 87 5 0.8 0.8 0.0 1.6 Yosemite Y 48 3 92 5 0.0 0.8 0.0 0.8

Average 35.5 3.0

91.0 6.3 0.6 0.6 0.0 1.2 LSD (0.05) 19.0 3.3 5.7 NS NS NS NS NS Table 8. Single- and multiple-center bulb ratings for early-maturing onion varieties lifted and harvested August 14, 2019, Malheur Experiment Station, Oregon State University, Ontario, OR. Multiple center Single center Seed company Variety large medium small functionala bullet

--------------------------- % ---------------------------- Hazera Redstone 37.6 43.2 16.0 19.2 3.2 Sakata Ovation 26.6 34.7 22.6 38.7 16.1

Spanish Medallion 23.2 40.0 8.8 36.8 28.0 Yosemite 50.9 30.6 4.9 18.5 13.7

Average 34.6 37.1 13.1

28.3 15.3 LSD (0.05) 16.0 NS 11.7 16.6 NS

aFunctional single-centered bulbs are the small multiple-centered plus the bullet-centered onions.


Table 9. Yield and grade performance of early-maturing onion varieties lifted and harvested August 14, 2019, Malheur Experiment Station, Oregon State University, Ontario, OR. Marketable yield by grade Bulb

counts >4¼ in

Seed company Variety

Total yield Total >4¼ in 4-4¼ in 3-4 in 2¼-3 in Small No. 2s

Split root

Total rot

Black mold

Slime rot

----------------------------------- cwt/acre ---------------------------------- -------------- % -------------- #/50 lb Hazera Redstone 729.7 659.5 10.6 70.3 500.9 77.7 14.6 27.1 0.2 2.4 2.4 0.0 34.2 Sakata Ovation 1174.0 1107.1 213.0 482.6 397.7 13.8 8.3 23.0 0.6 2.4 1.9 0.5 30.6

Spanish Medallion 1192.2 1116.0 179.7 465.0 451.1 20.2 6.6 31.0 0.3 3.0 2.6 0.4 30.7 Yosemite 1026.8 877.6 81.9 327.1 434.4 34.3 11.0 62.1 1.2 5.6 5.6 0.0 31.5

Average 1030.7 940.1 121.3 336.3 446.0 36.5 10.1 35.8 0.6 3.3 3.1 0.2 31.8 LSD (0.05) 288.0 211.3 59.1 199.8 NS 33.1 NS NS NS NS NS NS 1.0


Table 10. Maturity, bolting, thrips leaf damage, and Iris Yellow Spot Virus symptoms ratings of full-season yellow onion varieties, Malheur Experiment Station, Oregon State University, Ontario, OR, 2019.

1-Aug 13-Aug 29-Aug 29-Aug

Seed company Variety

Tops down

Leaf dryness

Tops down

Leaf dryness

Tops down

Leaf dryness Bolting

Thrips leaf

damagea IYSVb

-------------------------------- % -------------------------------- 0-10 0-5 A. Takii Grand Perfection 4 0 31 5 87 20 0.00 2.2 1.0

Ridge Line 16 3 86 15 100 42 0.00 3.6 1.0 Traverse 10 2 84 16 100 40 0.00 3.8 1.0

Bejo Mondella 5 0 25 8 82 25 0.04 3.4 1.0 Hamilton 6 0 15 5 52 16 0.09 2.8 1.0 Legend 7 0 42 6 96 19 0.00 2.4 1.0 Sedona 5 0 18 7 78 24 0.17 3.2 1.0 Gunnison 7 1 76 10 96 35 0.00 3.4 1.0 Crockett 5 0 14 5 50 18 0.00 2.8 1.0

Crookham Avalon 7 0 72 8 94 25 0.09 2.2 1.0 Scorpion 11 0 64 13 94 32 0.00 3.6 1.0 Scout 8 0 64 9 88 24 0.04 2.6 1.0 Oracle 1 0 18 5 68 19 0.09 2.0 1.0 Trident 7 0 48 8 86 30 0.00 3.2 1.0 OLYX08-640 11 0 82 9 94 30 0.00 3.2 1.0 Caliber 1 0 11 5 52 28 0.00 3.0 2.0

Enza Zaden Elsye 81 3 94 13 100 29 0.00 2.6 1.0 Hazera Rhino 6 0 70 8 90 23 0.00 2.6 1.0

37-120 8 0 82 7 93 26 0.22 2.8 1.0 Nunhems Arcero 5 0 20 10 74 28 0.04 2.8 1.0

Granero 5 0 32 5 90 24 0.04 2.6 1.0 Ranchero 5 0 46 5 90 22 0.00 2.6 1.0 Joaquin 0 0 12 5 62 16

0.13 2.0 1.0 Montero 9 0 70 12 98 35

0.04 3.4 1.0 Oloroso 4 0 18 5 72 22

0.00 3.0 1.0 Pandero 3 0 19 5 70 18 0.09 2.2 1.0 Vaquero 4 0 31 6 86 22 0.00 2.8 1.0

Sakata Aruba 9 0 72 6 94 26 0.17 2.0 1.0 Dulce Reina 1 0 34 5 84 21 0.30 2.0 1.0 Yukon 7 0 50 7 90 26 0.00 2.2 1.0

Seminis Tucannon 4 0 44 6 90 26 0.00 2.6 1.0 16000 5 0 70 5 96 22 0.04 2.2 1.0 SV6646 3 0 20 5 82 21 0.00 2.2 1.0 SV6672 4 0 26 5 82 23 0.04 2.0 1.0

D. Palmer Saffron 6 0 23 6 78 25 0.00 2.6 1.0 Average 8 0 45 7 84 25 0.05 2.7 1.0 LSD (0.05) 4 1 11 3 8 5 0.13 0.6 NS aThrips leaf damage: 0 = no damage, 10 = most damage. bIYSV: 0 = no symptoms, 5 = 100% foliage diseased.


Table 11. Single- and multiple-center ratings for full-season yellow onion varieties, Malheur Experiment Station, Oregon State University, Ontario, OR, 2019.

Multiple center Single center Seed company Variety large medium small functionala bullet

--------------------------- % -------------------------- A. Takii Grand Perfection 20.8 24.0 23.2 55.2 32.0

Ridge Line 36.1 41.2 16.2 22.7 6.5 Traverse 20.0 47.2 24.0 32.8 8.8

Bejo Mondella 10.4 10.4 29.6 79.2 49.6 Hamilton 27.2 7.2 19.2 65.6 46.4 Legend 41.6 26.4 26.4 32.0 5.6 Sedona 29.4 15.1 23.0 55.5 32.5 Gunnison 11.2 27.0 25.2 61.8 36.6 Crockett 24.0 24.0 26.4 52.0 25.6

Crookham Avalon 23.3 16.8 22.7 59.9 37.2 Scorpion 2.4 2.4 17.6 95.2 77.6 Scout 19.2 27.2 16.0 53.6 37.6 Oracle 2.4 7.3 18.0 90.3 72.3 Trident 3.2 3.2 7.2 93.6 86.4 OLYX08-640 1.6 7.2 9.6 91.2 81.6 Caliber 1.6 4.0 8.8 94.4 85.6

Enza Zaden Elsye 42.4 34.4 17.6 23.2 5.6 Hazera Rhino 8.7 17.4 11.1 73.9 62.8

37-120 20.8 7.2 26.4 72.0 45.6 Nunhems Arcero 2.4 3.2 8.7 94.5 85.8

Granero 7.2 11.2 13.6 81.6 68.0 Ranchero 9.1 8.8 20.3 82.1 61.8 Joaquin 2.4 4.0 11.2 93.6 82.4 Montero 4.0 6.3 21.9 89.7 67.8 Oloroso 1.6 0.0 1.6 98.4 96.8 Pandero 7.2 10.4 28.8 82.4 53.6 Vaquero 4.0 5.6 15.2 90.4 75.2

Sakata Aruba 12.0 10.4 8.8 77.6 68.8 Dulce Reina 8.7 15.8 15.0 75.5 60.5 Yukon 30.4 17.6 17.6 52.0 34.4

Seminis Tucannon 6.3 1.6 10.9 92.1 81.1 16000 16.0 11.2 11.2 72.8 61.6 SV6646 8.8 3.2 15.2 88.0 72.8 SV6672 25.8 12.9 13.8 61.3 47.5

D. Palmer Saffron 32.5 25.4 28.3 42.1 13.7 Average 15.0 14.2 17.4 70.8 53.4

LSD (0.05) 10.3 9.1 11.7 11.9 12.3 aFunctional single-centered bulbs are the small multiple-centered plus the bullet-centered onions.


Table 12. Yield and grade of full-season experimental and commercial yellow onion varieties graded out of storage in January 2020, Malheur Experiment Station, Oregon State University, Ontario, OR. (Continued on next page)

Total yield

Marketable yield by grade Bulb counts >4¼ in

Split basal plate

Seed company Variety Total >4¼ in 4-4¼ in 3-4 in 2¼-3 in Small

No. 2s

Total rot

Neck rot

Plate rot

Black mold

------------------------------ cwt/acre ------------------------------ #/50 lb --- % of total yield --- A. Takii Grand Perfection 1254.8 1111.2 276.4 451.6 363.5 19.6 5.5 33.1 31.0 8.0 6.1 0.7 1.2 0.1

Ridge Line 943.9 901.5 19.5 254.9 597.3 29.8 8.8 17.3 32.1 1.4 0.4 0.9 0.0 0.4 Traverse 889.9 852.5 22.5 217.3 588.3 24.4 5.2 6.7 32.1 2.8 0.3 1.2 1.3 0.0

Bejo Mondella 962.4 909.9 51.4 327.9 514.9 15.7 5.9 21.4 32.3 2.4 0.6 1.8 0.0 0.2

Hamilton 1094.7 998.7 89.3 388.3 494.6 26.5 7.6 60.1 32.9 2.6 1.1 0.5 1.0 0.0

Legend 1115.7 1021.1 84.5 420.0 496.2 20.3 5.8 57.5 31.8 2.7 1.1 1.2 0.4 0.2

Sedona 1159.8 1054.7 112.3 398.0 522.1 22.4 8.1 91.5 32.0 0.5 0.1 0.4 0.0 0.0

Gunnison 901.0 844.3 1.3 143.4 670.1 29.5 6.2 18.7 41.0 3.5 1.2 1.4 0.8 0.0 Crockett 1034.7 916.4 59.3 315.3 512.0 29.8 9.3 100.2 34.6 0.8 0.2 0.6 0.0 0.1

Crookham Avalon 1404.4 1150.4 300.6 483.4 348.3 18.3 5.8 5.7 28.4 17.2 14.3 0.1 2.9 0.0

Scorpion 872.4 848.5 22.5 137.8 654.4 33.9 9.4 0.0 31.7 1.6 0.8 0.7 0.2 0.0

Scout 1400.9 1197.9 363.3 490.4 331.9 12.4 3.7 23.3 28.3 12.6 4.3 0.4 8.0 0.1

Oracle 1306.1 1159.6 317.0 465.1 365.0 12.4 5.2 2.1 31.2 10.1 8.4 0.7 1.0 0.1

Trident 974.2 943.9 46.0 277.1 589.2 31.7 9.4 2.4 33.7 1.9 0.2 0.8 0.9 0.0

OLYX08-640 936.3 900.9 30.2 224.9 623.1 22.8 8.8 4.8 32.3 2.3 1.3 0.4 0.6 0.0 Caliber 1214.8 1164.4 336.3 476.4 334.6 17.1 4.5 5.1 31.3 3.4 1.9 0.6 0.9 0.0

Enza Zaden Elsye 1298.0 670.4 132.5 243.5 278.8 15.6 4.7 0.0 27.5 47.8 43.0 0.0 4.8 0.0


Table 12. (continued) Yield and grade of full-season experimental and commercial yellow onion varieties graded out of storage in January 2020, Malheur Experiment Station, Oregon State University, Ontario, OR.

Total yield

Marketable yield by grade Bulb counts >4¼ in

Split basal plate

Seed company Variety Total >4¼ in 4-4¼ in 3-4 in 2¼-3 in Small

No. 2s

Total rot

Neck rot

Plate rot

Black mold

----------------------------------- cwt/acre ----------------------------------- #/50 lb ------------ % of total yield ------------ H

Documents

MALHEUR EXPERIMENT STATIONPage, Gary Malheur County Weed Supervisor, Vale, OR . Penning, Tom Irrometer Co., Inc., Riverside, CA . Riley, Kay Snake River Produce, Nyssa, OR