Mineral phosphorus fertilization for silage corn in manured soils in the Fraser Valley, Canada

Abstract

Efficient management of fertilizer phosphorus (P) is crucial for enhanced resilience of agro‐ecosystems. We assessed five rates (0, 5, 10, 15, and 20 kg P ha−1) of starter P fertilizer on silage corn (Zea mays L) yield in high‐P manured soils at eight sites in 2020 and 2021 in the Fraser Valley, Canada, monitoring soil phosphate concentrations using anion exchange membranes (AEM‐P). At the V3 and V6 (3‐ and 6‐leaf) stages, corn dry matter (DM) weight response to starter P was not significant, except at one site where the critical rate was 5 kg P ha−1. At maturity, corn DM yields were in the optimum provincial range (20–25 Mg ha−1), with the exception of two sites, one with low initial soil P concentrations and the other with waterlogged soils. These results indicate that during the growing season, phosphate supply from manure application alone was sufficient for silage corn growth. Root length and diameter were not affected by starter fertilizer, while root surface area, volume, and root DM weight decreased with increasing starter fertilizer at the V3 stage in 2020. In addition, AEM‐P increased with starter P only during the first week after application. We conclude that starter fertilizer P, at any application rate, in high‐P manured soils does not improve silage corn yield; farmers applying manure at plowing in soils with high P concentrations can reduce or eliminate starter fertilizer P without impacting silage corn yields, decreasing reliance on off‐farm P inputs, and reducing potential P loss to the environment.