Exploratory Research in Corn and Wheat - Virginia

Previous Virginia Research NDVI Tiller Density 0.3 0.4 0.5 0.6 0.7 0.8 0.9 500 1000 1500 2000 0.1 0.2 Predicted Yield Index Yield, Mg ha-1 1 2 3 4 5 6 7 0.001 0.002 0.003 0.004 0.005 0.006 0.007 Spring N rates for VA wheat production can be determined using spectral reflectance sensors and applied at a 4-ft2 resolution using commercial equipment

Standard VA Rotation (3 crops in 2 years) No-till Corn Conv.-till Wheat No-till DC Soybean

Objectives Refine current methods of determining variable topdress N rates and incorporate foliar P recommendations into fertilization algorithms for wheat using sensor-based technology Develop a sensor-based N and P fertilization strategy for Virginia corn production Evaluate the benefits of foliar P applications for wheat and corn production

------- lb N / acre ------- Experimental Procedures - Obj. 1 6 site years (2 in each of 3 yr) RCBD; 3 replications TREATMENT STRUCTURE Trt GS 25 N GS 30 N Resolution ------- lb N / acre ------- 1 NONE 2 30 60 FLAT RATE 3 120 4 5 6 NFOA 1 m 7 TILLER 8 TISSUE 13 NFOA3 14 15 NFOA3+PFOA2 16 9 NFOA2 10 11 NFOA2+PFOA1 12 Year 2 Year 3

Experimental Procedures - Obj. 2 12 site years (4 sites in each of 3 yr) Irrigated and non-irrigated Conventional and no till RCBD; 3 replications Preplant N (0 to 240 lb N/acre) Starter N (0 to 70 lb N/acre) Sidedress N (0 to 150 lb N/acre) Plots will be fertilized and harvested using conventional plot equipment

Experimental Procedures - Obj. 2 Spectral measurements collected from canopy at V4, V6, V8, and V10 Chlorophyll and tissue N and P will be measured at same growth stages A PSNT will be conducted for each treatment prior to sidedress N applications at V6

Preliminary Results - Obj. 2 30 60 90 120 150 180 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 NDVI, V8 Yield, bu/acre Dryland, No N Irrigated, No N Dryland, Added N Irrigated, Added N

Foliar P Applications in Virginia Determine from soil test Residual P can carry over from starter application to previous crops P can be banded with wheat crop

PHOSPHORUS RESPONSE Foliar P Application Foliar P No preplant P 90 lb P2O5 -- lb P2O5/acre -- -- bu/acre -- -- bu/acre -- 0 77 90 4 84 90 8 84 93 12 87 98 Preplant P2O5 Tiller Density Grain Yield -- lb/acre -- -- tillers/ft2 -- -- bu/acre -- 0 50 83 30 70 85 60 80 96 90 95 93 120 95 95

Experimental Procedures - Obj. 3 12 site years (4 sites in each of 3 yr) 2 corn and 2 wheat No till Preplant P STP 1/3 STP 2/3 STP Foliar P rates 0, 4, 8, and 12 lb P2O5/acre for wheat (double for corn) Applied at GS30 or V6

Expected Results Virginia producers will have the knowledge required to implement existing variable-rate fertilizer technology into standard cash grain production systems Grain yields will increase by applying nutrients at the resolution where variability exists Nitrogen use efficiency will increase 30 to 50% while soil-applied P fertilizer will be reduced 50 to 100%