Response of silage maize to placement of cattle slurry

Abstract

Placement of nitrogen (N) or phosphorus (P) fertilizers can improve the efficiency of fertilizer use, reduce the input needed for maximum production, and better balance the nutrient put in with fertilizers and removed with crop products. From this perspective, the effect of the placement of cattle slurry on the dry matter (DM) yield of silage maize was studied in five experiments on sandy soils in 1993 and 1994. Slurry was injected in spring at a rate of 30 m3 ha-1 in slots 25 cm apart ('standard injection') or in slots 75 cm apart ('banded injection'). Subsequently, maize was planted at a row spacing of 75 cm parallel to the slots, either at random lateral positions in the 'standard injection' treatment or 10 cm next to the injection slots of the 'banded injection' treatment. All treatments, including a control without slurry, were combined with 0 and 20-31 kg ha-1 subsurface banded P starter fertilizer. DM yields of silage maize were on average reduced by 8% when conventionally injected slurry ('standard injected') was not supplemented with a P-starter. However, the yield reduction was limited to 2% when slurry was banded ('banded injection'). Observations on the distribution of soil mineral N and roots in two of the experiments indicated that during the first 5-7 weeks after planting, nutrients were predominantly supplied by the soil volume close to the plant row. This may explain the positive response of maize to placement which was strongest and significant on P-responsive sites, indicating that placement mainly improved the availability of slurry P. Improvements in the availability of slurry N may have played a secondary role. Our results suggest that slurry placement can minimize the risk of yield loss associated with reduced fertilizer inputs and contribute to a better nutrient balance between fertilizer inputs and removal in crop products.