Residual Effects of Fertilization with Pig Slurry: Double Cropping and Soil

Abstract

Intensive pig (Sus scrofa domesticus) production is an important economic activity in the northeast of Spain. Pig slurry (PS) is applied annually to maize (Zea mays L.) fields and supplemented with mineral N fertilizer at sidedressing. Fertilization with PS at different rates during four consecutive years was evaluated for its effects on soil salinity, water‐stable aggregates (WSA), and crop response of two consecutive barley (Hordeum vulgare L.) and maize crops. We observed that the fertilization of maize with PS for four consecutive years did not increase soil salinity compared with mineral fertilization. We observed, however, an improvement in soil stability, which was measured by WSA, under PS fertilization (WSA = 16.0 ± 6.9%) compared with mineral fertilization (WSA = 5.6 ± 2.4%). The agronomic residual effect of the PS treatments on the barley crop was quantified in terms of the N fertilizer replacement value (NFRV) as 77 kg N ha−1 and was not associated with PS rates applied during the previous 4 yr. For the maize crop, a significant N residual effect was also detected; the NFRV ranged between 11 and 56 kg N ha−1 and was significantly related to the PS rates applied the previous years. These results indicate that the annual application of PS to sprinkler‐irrigated maize at agronomic rates does not induce soil salinization, can have beneficial effects on some soils by increasing aggregate stability, and can provide significant amounts of N to subsequent crops. It is important to consider residual N effects in fertilizer planning to avoid N losses from the system.