DYNAMICS OF SOIL N-MINERAL BY REPEATEDLY GIVING LABELED 15N PLANT RESIDUE
Abstract
TThis study aims the dynamics of the mineral plant residues. The research was conducted in three stages; Stage 1. Planting soybean and rice plants labeled 15N with 4 concentrations of 15N, namely: 0 mM (N0), 0.625 mM (N1), 2.5 mM (N2), and 10 mM (N3) given in the form of urea, CO (15NH2)2 with a concentration of 10% atomic excess in a 5 kg plastic pot. Stage 2.Experiment with adding plant residues with the first 15N label on the unwashed condition and Stage 3. Experiment with adding the second 15N-labeled plant residue on the unwashed condition. Each stage use a factorial Completely Randomized Design (CRD). The results showed that soybean and rice residues gave the dynamics of mineral N in the soil with the same pattern, which increased with increasing concentration of 15N given. The N3T1 treatment (concentration 15N 10 mN soybean residue) showed the highest nitrate, ammonium, and microbial biomass N content, respectively, at 330.28 mg kg-1: 231.29 mg kg-1, and 376.39 mgkg-1 during a 14-week incubation. The repetition of adding new soybean residues increased the content of nitrate, ammonium, and microbial biomass N by 26.65%, 21.99%, and 67.24%, respectively, while the repetition of adding rice straw residue increased the content of nitrate, ammonium, and microbial biomass N by 38.49%, 45.48% and 11.41% respectively.
