Nitrogen Substitution Values and Sidedress Nitrogen for Organic Materials Fields Guided by Corn Canopy Reflectanc

After an organic material (OMat) is land applied, the nitrogen (N) mineralization has low predictability causing farmers to apply more pre-plant N fertilizer than is needed, resulting in low N use efficiency. Crop-canopy-sensor (CCS) technology estimates the corn (Zea mays) N status and determine the complementary in-season N-rate (ISN) to maximize organic-N recovery and improving the agronomic efficiency of fertilizer N. Five irrigated and three rainfed continuous-corn no-till fields were land applied with eight OMat. These included four types of animal manure, three municipal biosolid-products and one industrial by-product. Two sets of trials were conducted. The first set was on two irrigated-fields with five pre-plant inorganic N rates from 0 to 200 kg-ha-1 combined with three beef cattle feedlot manure rates. The second set was on six fields where eight OMat were applied using a similar expected organic-N release rate. A complementary ISN was applied between V12 and V14 and was calculated according with a previous algorithm based on CCS using the Normalized-Difference-Red-Edge as a vegetative index. Grain yield increased with OMat application but was not affected by the type of OMat. Grain yield increased with ISN across locations and OMat. The OMat-N mineralization was greater with sandy compared with medium texture soil and with low compared with high lignin and cellulose content of OMat. The apparent mean OMat-N-recovery for the first crop after application was 30% for livestock manures, 22% for the industrial by-product, and 12% for municipal biosolids which had relatively high lignin and cellulose contents. Using a rate of 150 kg-ha-1 as reference, the fertilizer-N substitution value of applied organic N in the OMat was 0.35, 0.26, and 0.13 kg-kg-1 for livestock manures, industrial by-product and biosolids, respectively, for the first crop following application. The availability of OMat-N was considered in determination of ISN adding to the agronomic efficiency of OMat-N use. The AE of the fertilizer ISN was not affected by OMat and was similar to a pre-plant N rate of 90 kg-ha -1. The adoption of CCS on manured fields increased grain yield, accounted for OMat-N availability, and had similar AE of fertilizer ISN as pre-plant-N.