Phosphorus Fertilizer Placement and Tillage in a Wheat‐Fallow Cropping Sequence

Abstract

AbstractSince water and wind erosion are serious problems during fallow in most western winter wheat (Triticum aestivum L.) growing areas and available soil P is often low, field studies were conducted at three locations in western Nebraska on a Keith silt loam (fine‐silty, mixed, mesic, Aridic Argiustoll). These studies compared the performance of broadcast, knife and seed placement of fertilizer P with and without a residue treatment of 13.5 Mg ha−1 in a plow, no‐till, and stubble mulch tillage system. Plowing generally tended towards the highest and no‐till the lowest grain yield and P uptake. Delayed maturity resulting from abnormally cool spring temperatures was believed to be a contributing factor to lower yields in no‐till. Without applied residue, grain yields were increased by P placement methods in the order of seed = knife > broadcast similar to other reported research. When residue was applied, knife placement was less effective and broadcast more effective compared to seed placement at the low P rate (8.4 kg ha−1). At the high P rate (16.8 kg ha−1) seed placement produced the highest yield of all treatments. Seed placement showed higher P uptake in no‐till than other tillage treatments at one location while broadcast P resulted in higher P uptake with plowing than with stubble mulch or no‐till at another location. The colder soil temperatures associated with surface residues apparently favored seed placement of P. There was a trend for grain yield and P uptake to be lower when P was knifed in the presence of surface residues.