Tillage and Compost Effects on Corn Growth, Nutrient Accumulation, and Grain Yield

Applying organic amendments to cropland affects corn (Zea mays L.) response to tillage systems differently. Identifying causes of the tillage by amendment interaction could match amendment inputs to responsive tillage systems. The objectives of this research were to determine if shoot dry matter (DM), nutrient uptake, and soil water use could explain the tillage by compost interaction for corn-grain yield. A corn-soybean [Glycine max (L.) Merr.]-wheat (Triticum aestivum L.)/clover (Trifolium spp.) rotation, in all phases, with or without compost amendment, was initiated in 1998 in plots that had been managed with moldboard plow (MP), chisel plow (CT), or no-tillage (NT) since 1988. Compost amendment increased corn whole-plant P and K uptake 19 and 21%, averaged across 2 yr. No-tillage increased whole-plant P uptake 1 yr compared to MP and CT (113 vs. 65 kg ha^-1) and increased grain P concentration (3.1 vs. 1.5 g kg^-1). Compost provided no benefit (2 yr) or a negative effect (1 yr, 22%) to corn yield in MP. Compost provided no benefit to corn yield in CT. Corn growing in NT derived no benefit (2 yr) or a positive (1 yr, 9%) effect on grain yield from compost amendment. The tillage and compost responses observed in this study cannot be explained by plant N, soil water use, leaf gas exchange, or DM partitioning. Grain yield from soil managed using NT may respond to compost amendment, but reasons for this response remain unclear.