Advances in Nitrogen Handling Strategies to Increase the Productivity of Wheat

Abstract

Nitrogen Use Efficiency (NUE) currently averages 33% for wheat, and corn production around the world. Precision Sensing Technologies have the potential to increase NUE’s in wheat and corn to levels exceeding 50%. This has primarily been developed via the application of two very fundamental approaches. 1. Similar to the use of yield goals, established prior to planting, predicting grain yields mid-season can be accomplished by collecting NDVI readings (V8 in corn, Feekes 5 in wheat), and then dividing by the number of days from planting to sensing. The index (INSEY or In Season Estimated Yield or YP0) essentially reflects biomass produced per day, since NDVI is an excellent indicator of plant biomass. 2. Predicting whether or not a year will be responsive to applied N is accomplished by establishing N Rich Strips in farmer fields (N applied at a rate where it will not be limiting throughout the growth cycle), but where the remaining land receives modest amounts of preplant N, but where severe N stress is not encountered. The Response Index (RI) is then computed by dividing the NDVI from the N Rich Strip by the NDVI from the farmer practice. Estimated yield is then multiplied times the RI to obtain the yield achievable with added N (YPN). The mid-season fertilizer N is determined by subtracting grain N uptake at YP0 from grain N uptake at YPN, divided by an expected efficiency factor (between 0.5 and 0.7 for topdress N). This method has proven to be very reliable in wheat and corn for obtaining maximum yields, increased NUE, and maximum farmer profit from N fertilization. Averaged over years, and locations, OSU work has shown that this methodology will on average net farmers in excess of 30 ha^-1. Current work is ongoing with INTA and AAPRESID (Ing. Ricardo Melchiori, and Ing. Agustin Bianchini) to further refine algorithms tailored toward Argentinean production environments (http://www.soiltesting.okstate.edu/SBNRC/SBNRC.php)