Nitrogen Nutrition Of Rice Cultivated On Upland Soil Mulched With Half-Decomposed Rice Straw

Field experiments of rice cultivated on upland soil (RCUS) mulched with different materials and cultivated on waterlogged soil (WT) were carried out to study biological response of rice crop to upland condition. Five rates of nitrogen fertilizer were applied to the upland soil mulched with half-decomposed rice straw to study the changes of soil inorganic N and N absorption b~ rice. Different rates of 5N fertilizers were applied to the soil in different stages during rice growth to study the distribution of 1~N in different parts of rice crop. 揘 transformation and residual 揘 use efficiency by following wheat crop. Rhizoboxes with a three-compartments were designed to study the nitrogen nutritional characteristics of the rice and time and horizontal spatial variations of NW4-N and NOVN in rhizospheric soil. Results indicated that soil NO;~N was the main form absorbed by the RCUS. It was found that N contents of the different organs of the RCUS was always higher than those of WTGreat absorption and accumulation of N of RCUS happened mostly after jointing stage. while the rice crop in waterlogged soil absorbed N in large amounts from transplanting stage to filling stage. The highest rice yield on upland soil was found in the treatment of the soil mulched with HM but a little bit lower than that in waterlogged soil. The water consumption. however, in upland soil was much less than that in waterlogged soil. thus, the irrigation water use efticienc~ of RCUS was 12 times as much as WT. NO>N content v~. as increased with the increase of nitrogen fertilizer. The 94 highest rice yield and nitrogen fertilizer use efficiency were found in the treatment of N,,,. The largest amount of nitrogen absorption and accumulation occurred at the middle rice growth stage. The dependence of rice on soil N was decreased with increasing of nitrogen fertilizer application rate. The Ndflb/a (percentage of nitrogen content from nitrogen in fertilizer). uptake. 揘 use efficiency and the remaining effect were significantly affected by the time and rates of 慛 application. Maximum Ndft% was obtained in the treatment in which 揘 fertilizer was applied at tillering stage. and the minimum was found in the treatment of 揘 applied as base fertilizer. The minimum and maxinum of total 慛 use efficiency by the crop were 5.58% and 51.53%. and those remained in soil were 13.810/0 and 29.87%. respectively. Immobilization of 慛 as base fertilizer by soil microbes and 揘OVN content from base 揘 were bigger within I Sds after application, but both were founded extreamil v smaller to the tillering and panicle-dressing. There existed a close relationship between immobilization of base ?N b~?soil microbes and the 揘 absorbed by rice(r=O. 739) in all panicle stage. The order of residual ?N use efficiency by wheat was found in the order of base>tillering>panicle of the fertilization way in rice season. and the 揘 residual effect in wheat season was very lower. The loss of the residual 揘 also occurred during wheat season. The contents of NH>N and NO>-N in rhizospheric soil were found almost equal within I month after transplanting in every treatment. NH4-N was relatively depleted in the root zone and near rhizosphere while the N 0.-N was accumulated within the rhizosphere area of 1 mm ?mm from the root plane. Thereafter the content of NH4-N in the whole rice rhizosphere w...