Morteza MozaffariSoil Testing and Research Laboratory, Marianna

Efforts to Improve N Use Efficiency of Corn in Arkansas

Highlights of Research in Progress

Acknowledgement

Research was funded by Arkansas Corn and

Grain Sorghum Promotion Board

Presentation outline

• Backgrounds Information

• Presidedress soil nitrate test (PSNT)

• Using chlorophyll meters

Mississippi Delta Region of Arkansas (MDRA)

MS River Delta Region of Arkansas

• Soils: predominantly alluvial

• Topography: relatively flat land

• One of the oldest row crop production regions

Corn Production in Arkansas

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Urea Price

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Current AR corn N fertility recommendations

Yield Goal Silt and sandy loams

Clay loam and clay soil

- bu/acre - ---------------- lb N /acre ---------------------

125 150 230

150 185 280

175 220 330

> 200 255 330

Long-term sustainability of corn production

Protect water quality

Profit margin

Presentation outline

• Backgrounds Information

• Presidedress soil nitrate test (PSNT)

• Using a chlorophyll meter

The PSNT idea

• Apply a small amount of N (30-40 lb/acre) at planting

• Collect a soil sample from 0-12” depth at 6-8-leaf stage

• Use the PSNT result as a guide to identify and apply the optimum N rate

Objectives

For irrigated corn production in MRDRA

• Evaluate the effect of sidedress N-fertilizer rate on corn grain yield

• Assess the suitability of PSNT for improving corn N fertility management

Research Approach • 21 replicated field experiments– Production fields and AES sites across the MRDRA – 04-07

• Experimental Design: – Randomized complete block with 4-5 replications – Five or six N rates

• Total N rates: 0-300 lb N/acre – Year 1 and 2: 0, 50, 100, 150, 200, and 300 lb N/acre

– Year 3: 0, 60, 120, 180, 240 300 lb N/acre

• Cultural Practices:– AES Sites: Cooperative Extension Service recommendations– Commercial sites: Growers’ Practices

Nitrogen fertilizer application schedule

Total N rate Pre-plant At 6-8 leaf

-------------------------- lb N /acre -----------------------

0 0 0

60 30 30

120 30 90

180 30 150

240 30 210

300 30 270

• Important dates:– planted: 17 March to 4 June– sidedress N date: 4 May to 6 June (6-8 leaf stage)– harvest: 10 Aug to Sep 18

• Soil sampling and analysis:– pre plant, top 6”, six cores/replication

– measured NO3-N, pH, texture, Mehlich-3 nutrients

– PSNT samples 6-8 leaf (before 2nd N application)– zero to 12’’, six cores, 0 N plots

– measured NO3-N by ISE

Research Approach

• Analysis of Variance:– to evaluate the effect of N rate on grain yield– sites were analyzed separately

• Calculated Relative Yield as:– (check plot yield/highest plot yield) X 100

Data Analysis

Results and Discussion

Properties of soil samples collected from the 0-6” depth before planting

Range Soil pH NO3-N SOM Sand Silt Clay Soil texture

-- ppm ----------------------- % ---------------------

Min. 5.6 3 1.2 2 21 13 sandy loam

Max. 7.5 85 3.2 57 74 57 clay

Summary of the Results • PSNT (mg/kg):

• 4-36: all sites • 4-10: 12 sites • 10-20: 5 sites• > 20: 4 sites

• Grain yield:– Significant N response: 20 sites, P≤0.0003

– Zero N treatments: 9-192 (bu/acre)– Highest N rate: 140-223 (bu/acre)– State average: 131-146 (bu/acre)

• Agronomic Optimum N rate: – 150-250 (lb/acre)

Correlation between PSNT and relative yield of the check plot (All 21 sites)

y = 1.95x + 20.2

R2 = 0.53, P=0.0003

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PSNT (ppm)

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Correlation between PSNT and relative yield of the check plot (sandy loam and silt loam sites, 16 sites)

PSNT (ppm)

Rel

ativ

e yi

eld

(%)

y = 2.06x + 21.4

R2 = 0.62, P=0.0003

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Conclusions of PSNT Study In irrigated corn production in MRDRA

• Sidedress application of N significantly increased corn grain yield in 20 of the 21 sites

• Agronomic Optimum N rate was 150-250 lb/acre

• Presidedress soil nitrate test shows great promise for improving corn N fertility management

Presentation outline

• Backgrounds Information

• Presidedress soil nitrate test

• Using a chlorophyll meter

Basic Idea• Establish a well fertilized N reference strip in your field

• Collect chlorophyll meter reading from plants in area you may want to fertilize

• Collect chlorophyll meter reading from your reference strip

• Calculate relative chlorophyll meter value (RCM)

CM reading from are you want to fertilize RCM = CM reading from the reference area

34.6 RCM =

58.0 = 0.59

Research Approach

• 5 replicated field experiments– Production fields and AES sites across the MRDRA – 07

• Experimental Design: – Randomized complete block with 4-5 replications

• N fertilizer management:– Five N rates 0, 60, 120, 180, 240 300 lb N/acre

– Split N application: preplant and four leaf stage

• Cultural Practices:– AES Sites: Cooperative Extension Service recommendations– Commercial sites: Growers’ Practices

•

• Important dates:– planted: 4 April to May 5– harvest: 15 Aug to Sep 17

• Soil sampling and analysis:– pre plant, top 6”, six cores/replication

– measured NO3-N, pH, texture, Mehlich-3 nutrients

• Leaf and CM data collection:– 9-12 leaf stage

Research Approach

• Analysis of Variance:– to evaluate the effect of N rate on grain yield, leaf N,

and CM– sites were analyzed separately

• Calculated Relative Yield and Relative CM

Data Analysis

Results and Discussion

Properties of soil samples collected from the 0-6” depth before planting

Range Soil pH NO3-N SOM Sand Silt Clay Soil texture

-- ppm ----------------------- % ---------------------

Min. 5.6 10 1.1 2 12 11 sandy loam

Max. 7.5 53 2.9 75 72 39silty clay

loam

Summary of the Results • Grain yield:

– Significant N response: all sites, P≤0.0044

– Zero N treatments: 31-178 (bu/acre)

– Highest N rate: 131-233 (bu/acre)

– State average: 148 (bu/acre)

Correlation between RCM and relative yield at five sites

PSNT (ppm)

Rel

ativ

e yi

eld

(%)

y = 2.01x - 1.07

r2 = 0.77, P=0.001

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1.20

0.5 0.6 0.7 0.8 0.9 1.0 1.1

Concluding Remarks• PSNT and CM are promising tools for Improving N

use efficiency in Arkansas

• Additional work is underway