Inter-row crop competition for band-injected ammonium nitrate

Abstract

Inter-species competition for applied nutrients may be managed by weed control in cultivated communities. However, intra-crop competition may still occur. Thus, regarding a fertilizer band as a finite nutrient source, individual rows of a cereal crop may compete for the applied nitrogen. The aim was to explore the partition of applied N between crop rows affected by the displacement of the fertilizer band relative to the rows. In a micro-plot experiment, a 15N-ammonium−15N-nitrate solution was injected in four positions parallel to two rows of spring wheat (Triticum aestivum ssp. vulgare). The course of 15N crop uptake in each row was estimated by a sigmoid growth function using eight samplings during the elongation phase. The estimated parameters were used for calculating the asymptotic value (a), the time until a/2 was reached (T0.5a), and the uptake rate at this time (MaxRate), and related to the distance between the crop row and fertilizer band. The a-value decreased by 5.1%-point recovery cm−1, T0.5a increased by 0.5 day cm−1 and the MaxRate decreased by 0.3%-point recovery day−1 cm−1. Placement of the fertilizer band centred between two crop rows caused an even access to the applied nitrogen, but a parallel displacement from the centre by a few centimetres significantly affected the parameters. The proliferation of the roots in the soil and thus the time until the roots reached the fertilizer zone is assumed to cause the inter-row competition for the band-injected N source. The access to the fertilizer band was clearly reflected in the dry matter production causing an uneven crop stand. The consequences of inter-row crop competition for a band-injected N source with respect to grain yield and grain quality were not explored, but attention on these parameters are required, particularly in the production of high quality wheat grains.