Balancing nutrient inputs from manure and supplemental inorganic fertilizers with crop requirements should achieve crop yield goals and agro-environmental targets. We asked if composted dairy cattle manure, alone or in combination with inorganic fertilizers, could sustain the corn and soybean yields, without increasing the residual soil N and soil P saturation of a sandy-loam soil in southern Quebec, Canada. Cropping systems were continuous silage corn and corn-soybean rotation, with each phase of the rotation grown every year, for 5-yr. Cropping systems were amended with compost at rates of 0, 15, 30 and 45 Mg (wet weight) ha-1, and received supplemental inorganic fertilizer to supply 200 kg N ha-1 yr-1 to corn while assuring that corn and soybean received 45 kg P ha-1 yr-1 and 125 kg K ha-1 yr-1 from compost and inorganic fertilizer. Crop yields were similar in composted-amended and inorganically-fertilized plots. Corn yield was limited by N availability, and there was no P or K limitation in corn and soybean. Soil P saturation in the 0–15 cm layer exceeded the agro-environmental limit of 13.1% P/Al for a sandy-loam soil in Quebec, indicating that the P input exceeded crop uptake. Residual soil N concentration was affected more by the crop than the fertilizer source, with greater residual soil N in plots with higher grain production. Crop-induced priming can explain how N fertilizer cycles through the soil microbial community and is gradually mineralized during the growing season, and why crop senescence may trigger residual soil N release after harvest.
A Modified Pressure–Sinkage Model for Studying the Effect of a Hard Layer in Sandy Loam Soil