Hoàng Thị Minh, R. Schaefer
Từ khoá: thay đổi, mùa, N, N khoáng, phân giải, chất hữu cơ, đất, lúa
Seasonal change in the mineral N of the decomposition of organic matter under field conditions on rice soil
Placement of soil (1kg homogenized) in nylon mesh bags enriched with 3% rice straw, rice stubble, rice roots, sesbania, azolla (dry crushed). Soil A and B (0-10cm) were used: A was rainfed, B received a weekly rehumidification. Every month one set of all the blocks was extracted. Brought to the lab and analyzed for pHH2O, pHKCl, mineral N (NH4+, NO3– and total N. Results: difference between pHH2O and pHKCl, values are rather constant around 0.5 pH. In soil A: lower values at end of June and October. Values of A higher than in B. no influence of the organic treatment seems to be evident. Total N is higher level during the dry period; and slightly depressed during the high humidity phases. Effect of organic residues appears distinctly. Impact of N through the OM (azolla, sesbania) is clearly evident when compared with straw and root. Mineral N: more NO3– is accumulated in dry periods in soil A, or the beginning of wet periods in B. NH4+accumiulates in the beginning of wet period in soil A but decreases fast wen humidity is at its maximum and increases again thereafter. An effect of the substrates is not very evident.