Dynamics of Pig Slurry Nitrogen in Soil and Plant as Determined with 15N.

The fate of pig (Sus scrofa) slurry labeled with 15N 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 mays L.) in 2000 and to barley (Hordeum vulgare L.) 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 for 15N content in plant, in whole soil, and in soil NH4+-N, NO3--N, organic N, and clayfixed N pools. Percentage 15N recovery was >93% in both soils at Day 1 and decreased slowly thereafter. Rapid clay fixation of slurry 15 occurred at Day 1, and was greater in the clay soil (34% of applied 15N) than in the sandy loam (11%). At Day 96, less of the applied slurry 15N was recovered in maize grown on the clay soil (29%), as compared with the sandy loam (50%). At the same period, the residual soil 15N 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. The 15N recovery was generally higher in the clay soil than in the sandy loam, but total 15N recovery from the soil-plant system was similar for both soils. We conclude that soil type had little influence on the total 15 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. [ABSTRACT FROM AUTHOR]