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Efforts to Improve N Use Efficiency of Corn in Arkansas Highlights of Research in Progress Morteza Mozaffari Soil Testing and Research Laboratory, Marianna 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 800 600 400 200 0 99 00 01 02 03 YEAR 04 05 06 07 Urea Price 800 $670 600 400 $395 $295 200 0 03 07 YEAR 08 Current AR corn N fertility recommendations Yield Goal Silt and sandy loams - bu/acre - ---------------- lb N /acre --------------------- Clay loam and clay soil 125 150 230 150 185 280 175 220 330 > 200 255 330 Long-term sustainability of corn production Profit margin Protect water quality 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 • 21 replicated field experiments Research Approach – 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 Research Approach • 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 Data Analysis • 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 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) Relative yield (%) 100 80 60 40 y = 1.95x + 20.2 R2 = 0.53, P =0.0003 20 0 0 10 20 PSNT (ppm) 30 40 Correlation between PSNT and relative yield of the check plot (sandy loam and silt loam sites, 16 sites) Relative yield (%) 100 80 60 40 y = 2.06x + 21.4 R2 = 0.62, P =0.0003 20 0 0 10 20 PSNT (ppm) 30 40 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 = = 0.59 58.0 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 Research Approach • 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 Data Analysis • 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 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 39 silty 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) Relative yield (%) Correlation between RCM and relative yield at five sites 1.20 y = 2.01x - 1.07 r2 = 0.77, P =0.001 0.80 0.40 0.00 0.5 0.6 0.7 0.8 0.9 PSNT (ppm) 1.0 1.1 Concluding Remarks • PSNT and CM are promising tools for Improving N use efficiency in Arkansas • Additional work is underway