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This slide set includes preliminary data that demonstrates that the nitrogen source during bedding plant production impacts plant water use.
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An-Chueh ChouMaster of Science Graduate Student
John A. Ray, M.S.Research Associate
Steven E. Newman, Ph.D., A.A.F.Greenhouse Crops Extension Specialist and
Professor of Floriculture
Nitrogen Source on Bedding Nitrogen Source on Bedding Plant Growth and Water UsePlant Growth and Water Use
ProGreen EXPO – 2009
What form of N is in the bag?What form of N is in the bag?
Three forms of nitrogen– Ammonium-N NH4
+
– Nitrate-N NO3-
– Urea-N CO(NH2)2
Maximum of 40% ammonium-N and urea-N to avoid ammonium toxicity– Low pH (<5.5)– Low medium temperatures– Overly wet medium
Ammonium vs. NitrateAmmonium vs. Nitrate
Urea is considered to be the same as NH4, since urea needs to be converted to NH4 to be assimilated by plants
The NO3 form is readily taken up by the roots, is very mobile within the plant, and can be stored within the plant at high levels with no toxicity
Some NH4 can be taken up directly by roots, but most of it needs to be changed to NO3 by bacteria in the soil before root uptake can occur
Ammonium vs. NitrateAmmonium vs. Nitrate
Bacterial conversion of NH4 to NO3 is dependent on soil temperature and soil pH
Cool temperatures (less than 60°F) and low soil pH (<5.5) reduce the conversion, and NH4 toxicity can occur
Most of the NH4 taken up directly by roots has to be incorporated into organic compounds in the roots
Plants can store NH4 only at low levels without suffering from toxicity
Ammonium ToxicityAmmonium Toxicity
Lower leaves– Rolled margins– Chlorosis– Necrosis
Roots– burning
Dr. Douglas A. Cox,University of Massachusetts
Nitrate Nitrogen UptakeNitrate Nitrogen Uptake
NO3- OH-
pH goes up
Ammonium Nitrogen UptakeAmmonium Nitrogen Uptake
NH4+
H+
pH goes down
Ion Uptake and pHIon Uptake and pH
Uptake of cations (positive charge) – lowers medium pH
Uptake of anions (negative charge) – raises medium pH
True for any cation or anion uptake process More N ions are taken up than all others
combined– so N has the greatest pH effect
Common FertilizersCommon Fertilizers
Fertilizer NH4 (%) Ca (%) Mg (%)
21-7-7 100 0 0
20-20-20 69 0 0
20-10-20 40 0 0
15-5-15 22 5 2
Nitrate NitrogenNitrate Nitrogen
100% NO3-
– leaves and stems small
– plants are “hard”– may be useful for
plugs
15-40% N should be in the NH4
+ form
Older FertilizersOlder Fertilizers
20-20-20 Soil-based media Optimum pH > 7.0
– NH4+ NO3
-
– pH 6.0-7.0 had enough bacterial activity
pH < 6.0 leads to toxicities
Modern FertilizersModern Fertilizers
15-5-15 Cal Mag Soilless media
28% NH4+
5% Ca
2% Mg
How does the N-sourceHow does the N-sourceimpact plant growth?impact plant growth?
Study included two bedding plant species– Pansy– Petunia
Standard 200 ppm N– 20-10-20
Five rates or NO3:NH4– 0% NH4
– 25% NH4
– 50% NH4
– 75% NH4
– 100% NH4
Pansy, NOPansy, NO33--:NH:NH44
++=100:0=100:0
Pansy, NOPansy, NO33--:NH:NH44
++=75:25=75:25
Pansy, NOPansy, NO33--:NH:NH44
++=50:50=50:50
Pansy, NOPansy, NO33--:NH:NH44
++=25:75=25:75
Pansy, NOPansy, NO33--:NH:NH44
++=0:100=0:100
Petunia, NOPetunia, NO33--:NH:NH44
++=100:0=100:0
Petunia, NOPetunia, NO33--:NH:NH44
++=75:25=75:25
Petunia, NOPetunia, NO33--:NH:NH44
++=50:50=50:50
Petunia, NOPetunia, NO33--:NH:NH44
++=25:75=25:75
Petunia, NOPetunia, NO33--:NH:NH44
++=0:100=0:100
Pansy – Plant GrowthPansy – Plant Growth
Petunia – Plant GrowthPetunia – Plant Growth
ChlorophyllChlorophyll
Pansy - EvapotranspirationPansy - Evapotranspiration
Daily EvapotranspirationDaily Evapotranspiration
SummarySummary
Nitrogen source impacts plant growth– Species dependent
– High NH4 is detrimental
– No NH4 is detrimental
Nitrogen source impacts water use– Higher levels of NH4 increases water use of petunias– Increasing levels of NH4 increases water use of
pansies until 50% then water use decreases
ThanksThanks
Colorado State University – Horticulture and
Landscape Architecture– Agricultural Experiment
Station– Extension
Welby Gardens– Plant donations
For more information:http://ghex.colostate.edu
http://ghadvisor.blogspot.com
Find us out on Facebookhttp://tinyurl.com/a436tk
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