Morteza Mozaffari Soil 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 YEAR Acres Planted X 1000

Urea Price YEAR $ / Ton

Current AR corn N fertility recommendations Yield Goal Silt and sandy loams Clay loam and clay soil - bu/acre lb N /acre >

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 – Experimental Design: – Randomized complete block with 4-5 replications – Five or six N rates Total N rates: lb N/acre – Year 1 and 2: 0, 50, 100, 150, 200, and 300 lb N/acre – Year 3: 0, 60, 120, 180, lb N/acre Cultural Practices: – AES Sites: Cooperative Extension Service recommendations – Commercial sites: Growers’ Practices

Nitrogen fertilizer application schedule Total N ratePre-plantAt 6-8 leaf lb N /acre

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 NO 3 -N, pH, texture, Mehlich-3 nutrients – PSNT samples 6-8 leaf (before 2 nd N application) – zero to 12’’, six cores, 0 N plots – measured NO 3 -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 RangeSoil pHNO 3 -NSOMSandSiltClaySoil texture -- ppm % Min sandy loam Max 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≤ – Zero N treatments: (bu/acre) –Highest N rate: (bu/acre) –State average: (bu/acre) Agronomic Optimum N rate: – (lb/acre)

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

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

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 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, 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 NO 3 -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 RangeSoil pHNO 3 -NSOMSandSiltClaySoil texture -- ppm % Min sandy loam Max silty clay loam

Summary of the Results Grain yield: – Significant N response: all sites, P≤ – Zero N treatments: (bu/acre) –Highest N rate: (bu/acre) –State average: 148 (bu/acre)

Correlation between RCM and relative yield at five sites PSNT (ppm) Relative yield (%)

Concluding Remarks PSNT and CM are promising tools for Improving N use efficiency in Arkansas Additional work is underway