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为研究水田土壤中氮的行为,施给15NH4+或15NO3-标记的硝胺(NH415NO3或15NH4NO3)的沙壤土(Shirasu soil)添充在根箱里,对Japonica水稻(品种Hinohikari)进行温室栽培6周。收割后,水稻植株分地上部和根部,对各自的全氮,15Natom%进行测定。根箱各区域的土壤按着鲜土形态进行采取后,对此全氮,NO3-N,水溶性NH4-N,KCl抽出NH4-N和其各自的15Natom%进行测定。研究结果表明,土壤全氮含量与栽培前相比,在非根际明显降低,但在根际比非根际要高,保持了与栽培前相同的水平。土壤NO3-N浓度从非根际到根际递增,但与其栽培前相比显著地降低,在整个根箱里,施给NO3-N的79%为因脱氮而损失。土壤中NO3-N的大部分来自于土壤氮化合物,来自施肥的比例却较低,尤其是在根际。反而,施给NO3-N的残存率约仅为16%左右,但其中有机态氮所占的比率在非根际里55%~86%,在根际却达到了93%。土壤水溶性NH4-N和KCl抽出NH4-N浓度靠近根际逐渐降低,而且在非根际两者匀由1∶10的比例存在,但在根际里水溶性NH4-N没被检索到。在非根际里,土壤KCl抽出NH4-N的35%~66%为来自施肥,但其比例在根际里却降到15%左右。在土壤中残存的来自施给NH4-N的氮化合物之中,有机态氮所占的比例在非根际里约为11%~65%,但在根际却达到了92%。以上结果表明,在水稻根际,氮的无机化和有机化的活性比非根际显著。
In order to study the behavior of nitrogen in paddy soils, Shirasu soil with 15NH4 + or 15NO3-labeled nitramines (NH415NO3 or 15NH4NO3) was added to the root box and Japonica rice (variety Hinohikari) was cultivated in a greenhouse for 6 weeks. After harvesting, the rice plants were divided into the upper part and the root part, and the total nitrogen content of 15Natom% was measured. After all the soil in the root zone was taken in the form of fresh soil, the total nitrogen, NO3-N, water-soluble NH4-N and KCl extracted NH4-N and their respective 15Natom% were measured. The results showed that soil total nitrogen content decreased significantly in non-rhizosphere compared with that before planting, but higher in rhizosphere than in non-rhizosphere, maintaining the same level as before planting. Soil NO3-N concentrations increased from non-rhizosphere to rhizosphere but significantly decreased compared to their pre-cultivation, with 79% of NO3-N donated throughout the root canals due to denitrification. Much of NO3-N in soil comes from soil nitrogen compounds, but the proportion from fertilization is lower, especially at the rhizosphere. On the contrary, the residual rate of applying NO3-N was only about 16%, but the proportion of organic nitrogen accounted for 55% ~ 86% in non-rhizosphere and 93% in rhizosphere. NH4-N concentration of soil water-soluble NH4-N and KCl extracted gradually decreased near the rhizosphere, and in the non-rhizosphere, the ratio of 1:10 existed, but the water-soluble NH4-N was not found in the rhizosphere. In the non-rhizosphere, 35% to 66% of NH4-N extracted from soil KCl comes from fertilization, but its proportion dropped to about 15% in rhizosphere. Of the nitrogen compounds remaining in the soil from NH4-N application, the proportion of organic nitrogen was about 11% to 65% in the non-rhizosphere, but 92% in the rhizosphere. The above results show that in rice rhizosphere, inorganic nitrogen and organic activity than non-rhizospheric significantly.