旱作水稻根际土壤铵态氮和硝态氮的时空变异

Time and Horizontal Spatial Variations of NH_4^+-N and NO_3^--N of Rhizospheric Soil with Rice Cultivation on Upland Condition Mulched with Half-decomposed Rice Straw

应用根际培养箱 (三室法 )研究半腐解秸秆覆盖后 ,旱作水稻在不同尿素态氮肥用量 0mg/kg(N0 )、6 7mg/kg(N10 )、93mg/kg(N14 )、12 0mg/kg(N18)施用下 ,根际土壤中NH+ 4 -N和NO-3 -N的动态变化、根际土壤硝化活性、土壤 pH以及水稻生长后期根部和叶部NO-3 -N和硝酸还原酶 (NR)的动态变化。结果表明 ,在水稻移栽前 2 0d内 ,根际NH+ 4 -N和NO-3 -N含量基本接近 ,以NH+ 4 -N为主 ;其后在水稻全生育期内 ,各施氮处理土体中NH+ 4 -N都低于 5mg/kg ,而NO-3 -N均在 15mg/kg以上。土壤的硝化活性随据根区的距离增加而降低 ,水稻植株根部NO-3 -N含量大于叶部而NR的活性却相反。

Rhizoboxes with a three compartments were designed to study the nitrogen nutritional characteristics of the rice and the time and horizontal spatial variations of NH + 4-N and NO - 3-N in rhizospheric soil in which rice was grown on upland mulched with half decomposed rice straw. Urea N fertelizer 0 mg/kg(N 0), 67 mg/kg(N 10 ),93 mg/kg(N 14 ),120 mg/kg(N 18 )were applied in the forms of basal and topdrsseing. The results showed that the contents of NH + 4-N and NO - 3-N in rhizospheric soil were founded almost equal within 20 days after transplanting in every treatment and NH + 4-N was relatively dominant in the root zone and near rhizosphere. Thereafter the content of NH + 4-N in the whole rice rhizosphere was less than 5mg/kg, but the NO - 3-N was more than 15mg/kg and accumulated within the rhizosphere area of 1～5mm from the root plane. The soil nitrification activity dropped down gradually with the increase of distance away from the root. The content of NO - 3-N in rice root was largely higher than that in leaf, but the reverse was true for nitrate reductase activity.