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Applied organic nitrogen: Pre-plant and in-season estimation of corn nitrogen uptake

Juan Pablo Garcia Montealegre,C. Wortmann,J. Schepers,R. Little

Published 2019 in Field crops research (Print)

ABSTRACT

Abstract Nitrogen availability from land-applied organic materials (OrgMat) is not well-predicted and often under-credited in fertilizer-N decisions. Pre-plant estimation of fertilizer N equivalence (FNE, kg kg−1) may be improved with better consideration of OrgMat and field properties. Canopy sensors to direct in-season N application (ISN) may account for corn (Zea mays L.) uptake of OrgMat-N. The objectives of this 3-yr field study of N availability from eight OrgMat were to determine factors affecting FNE and to validate or calibrate sensor directed ISN for fields with OrgMat applied. Research was conducted over 17 site-years in eastern Nebraska. The ISN was at growth stage V12 or V14. The FNE, ISN, grain yield, yield response to ISN, and agronomic efficiency (kg grain increase kg−1 ISN-N) were not affected by OrgMat type but varied by site-year. The mean total FNE of OrgMat-N over the three years following application was 0.76. Corn response to ISN allowed for partial recovery from N deficiency stress by tasseling. The mean OrgMat with ISN yield was 88% for rainfed sites and 98% for irrigated sites compared to yield with split-application of 200 kg ha−1 fertilizer-N without OrgMat. The mean agronomic efficiency was 31.9 kg kg−1 of ISN-N but 37 kg kg−1 for the application of a minimum of 33.4 kg ha−1 ISN when canopy sensing indicated that less ISN was needed. The relatively low yield with OrgMat and ISN compared with fertilizer-N alone and the high agronomic efficiency for ISN indicated a need to revise the algorithm for calculating ISN for OrgMat fields. The results do not provide a basis for a pre-plant differentiation of FNE for OrgMat as environmental conditions, including soil organic matter level, prevail over OrgMat properties. The low predictability of FNE can be overcome by the use of sensor directed ISN for manured fields as it considers crop N uptake from OrgN and gives a high efficiency of ISN use.

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