Spatial Variability of Yield and Nitrogen Indicators—A Crop Rotation Approach

Abstract

The division of an arable field into zones of different productivity requires a reliable, discriminatory tool. This hypothesis was validated by analyzing the spatial variability of yield and N indicators in the crop rotation of winter oilseed rape (WOSR)/winter triticale (WTR) during 2016/2017 and 2017/2018 in a field of 30 ha (Przebędowo, Poland). The direct, measurable variables were: yield, N accumulated in—seeds/grain and crop residues, mineral N in spring, and harvest. The basic N indicators were total N uptake (TN), N-partial factor productivity, and N balance (Nb). The attainable yields of WOSR and WTR were 4.93 and 6.51 t ha−1, and a yield gap of −2.04 and −2.10 t ha−1. The management of 50 kg of the non-used N by crops, i.e. nitrogen gap (NG) could cover 36% and 65% of the yield gap (YG), respectively. The Nb, based on N input (Nin = Nmin + Nf) and TN, was the key field indicator, defining both yield and NG. Geostatic parameters, i.e., the nugget to sill ratio, spatial dependence range, and mean correlation distance, were very stable (≤0.2–0.17; 94–100 m; 28 m for WOSR and WTR). The spatial stability of Nb, irrespective of the crop and growing conditions, corroborates its suitability for discriminating high and low-productivity field zones.