Direct and residual response of wheat to swine slurry application method

Abstract

Swine production represents more than 25% of net agricultural incomes in some Spanish regions. Most of the 25 million t of swine slurry produced yearly in Spain is applied to agricultural fields by surface broadcasting (splash-plate) with important atmospheric N losses that reduce the fertilizer value of the slurry. Surface banding, incorporation, and injection into the soil are recommended methods to reduce N losses. We examined during two consecutive years the response of a wheat crop to swine slurry (SS) applied in the first year at two rates (30 and 60 Mg ha−1) using two application methods: splash-plate (SP) and soil incorporation (SI). After SS application, the soil was sampled intensively to establish the actual amount of SS in the soil (N recovery) and its spatial variability (distribution uniformity) in the two methods. Wheat yield, above ground dry matter and N uptake were measured along the 2 years. Swine slurry distribution uniformity and soil N-recovery were higher in SI than in SP, but grain yield and N uptake were independent of the application method in the 2 years. Reliable management practices compatible with the protection of the environment require further studies on the pathways and the availability of N to crops subject to SS incorporation in the soil at the moment of application.