Dynamics of Pig Slurry Nitrogen in Soil and Plant as Determined with15N

Abstract

The fate of pig (Sus scrofa) slurry labeled with15N was investigated when applied on a clay soil (fine, mixed, frigid, Typic Humaquept) and a sandy loam (loamy, mixed, frigid, Typic Dystrochrept) cropped to maize (Zea maysL.) in 2000 and to barley (Hordeum vulgareL.) in 2001. The slurry was applied in spring 2000, and plant and soil samples were collected at 6 h (Day 1) and at Days 14, 42, 96, and 413 after application. The samples were analyzed for15N content in plant, in whole soil, and in soil NH4+–N, NO3−–N, organic N, and clay‐fixed N pools. Percentage15N recovery was >93% in both soils at Day 1 and decreased slowly thereafter. Rapid clay fixation of slurry15N occurred at Day 1, and was greater in the clay soil (34% of applied15N) than in the sandy loam (11%). At Day 96, less of the applied slurry15N was recovered in maize grown on the clay soil (29%), as compared with the sandy loam (50%). At the same period, the residual soil15N was mostly present as organic N and NO3−–N in the sandy loam, and as organic and clay‐fixed N in the clay soil. At Day 413,15N recovery in barley was about 3% of the initially applied N in both soils. The15N recovery was generally higher in the clay soil than in the sandy loam, but total15N recovery from the soil–plant system was similar for both soils. We conclude that soil type had little influence on the total15N recovery from the soil–plant system, but significantly influenced the fate of slurry N in the various soil pools and plant N uptake on the year of application.