Preparation of 15N-labeled composted cattle manure and the fate of 15N-labeled organic nitrogen in upland field during two growing seasons

We prepared sup(15)N-labeled composted cattle manure (sup(15)N-CCM), and aimed to evaluate the variation of sup(15)N labeling in cattle manure and investigate the fate of nitrogen in sup(15)N-CCM applied to three kinds of soils. A single head of cattle (about 120 kg in weight) was fed with sup(15)N-labeled corn silage containing 0.918 atom%sup(15)N for 10 d, and then with unlabeled feed for 7 d. The feces were collected over 17 d. The collected fresh feces were dried and smashed. After taking sub-samples from each feces, all collected feces were mixed thoroughly. Mixed labeled cattle feces (sup(15)N-CF) was moistened and composted for 71 d. The sup(15)N abundance of fecal N markedly increased with time at first and reached 0.687 atom% sup(15)N at 6 d after sup(15)N-labeled feeding (DALF). It continued to increase slightly until 11 DALF reaching 0.753 atom% sup(15)N. Organic N in feces sampled at 3, 6, 10, 14, 17 DALF, sup(15)N-CF and sup(15)N-CCM was fractionated by the method of Stewart et. al. The sup(15)N abundances among the fractions were not significantly different in any tested sample. Little N in sup(15)N-CF was lost during composting. sup(15)N tracer experiment was conducted on a Gray Lowland soil, a Low-humic Andosol and a Cumulic Andosol using the sup(15)N-CCM and sup(15)N-labeled ammonium sulfate (sup(15)N-AS). The sup(15)N-labeled materials were applied only for the first crop (sweet corn) and the following crop (cabbage) received unlabeled corresponding CCM and AS. The sup(15)N recovery in the first crop derived from sup(15)N-AS (23.5-51.7%) was higher than that form sup(15)N-CCM (8.1-12.9%). There was no significant difference in sup(15)N recovery in the first crop derived from sup(15)N-CCM among the soils. The sup(15)N recoveries in the second crop derived from sup(15)N-CCM (0.98-3.86%) were higher than those form sup(15)N-AS (0.27-0.85%) in any soils. The residual sup(15)N in the top soil (0-25 cm) derived from sup(15)N-CCM after the second cropping ranged from 52% in the Low-humic Andosol to 74% of the applied sup(15)N in the Cumulic Andosol. These values were greater than those form sup(15)N-AS ranging from 8 to 9% of the applied sup(15)N.