不同供氮水平对水稻/花生间作系统中氮素行为的影响

水稻旱作／花生间作栽培是一种新兴的节水农业技术。用”N稀释标记法在盆栽条件下研究了间作系统在15kghm^-2、75kghm^-2和150kghm^-23个氮素供应水平条件下花生生物固氮以及水稻旱作／花生间作系统中氮素的转移，同时用^15N的富积标记法研究了花生根系腐解对间作系统氮素转移的贡献。结果表明，在15和75kghm^-22个氮素水平下，间作水稻比单作水稻的干物质量分别增加了23．5％和12．2％，在P=0．05的水平有显著差异。间作水稻和单作水稻的氮素吸收量分别为135、143mg株 ^-1和117、131mg株^-1，分别比单作增加14．8％和8．8％。不同栽培方式对花生的干物质积累和氮素吸收影响很小。在3个氮素水平下间作花生和单作花生的固氮量分别为76．1％、53．3％、50．7％和72．8％、56．5％、35．4％，在低氮水平下的生物固氮显著高于高氮条件，间作对花生的生物固氮有一定促进作用。间作系统中的氮素转移率和转移量在3个氮素水平分别为12．2％、9．2％、6．2％和16．3、13．0、10．4mg株^-1，氮素的转移率和转移的数量显著地随氮素水平的增加而减少。用^15N花生叶片标记直接证明了氮素从花生体内向水稻的转移，随刈割时间氮素转移量显著下降，表明花生根系腐解对间作系统的氮素转移有积极作用。

EFFECTS OF N LEVELS ON BIOLOGICAL N FIXATION AND N TRANSFER IN INTERCROPPING SYSTEM OF GROUNDNUT WITH RICE CULTIVATED IN AEROBIC SOIL

A novel rice cultivation in aerobic soil in China has made it possible to intercrop the rice with legumes,which is one of the ways in sustainable production of rice.Pot experiments using 15 N isotope dilution method were carried out to study biological nitrogen fixation by groundnut and nitrogen transfer from groundnut to associated rice in aerobic soil at three N fertilizer application rates (15 kg hm^-2,75 kg hm^-2 and 150 kg hm^-2).Decomposition experiment of groundnut root labeled by 15 N foliar enrichment was also conducted at the same time to investigate the contributed nitrogen transfer from the decomposition of groundnut root to the associated rice.The results showed that at 15 kg hm^-2 and 75 kg hm^-2 N fertilizer application rates the dry weights of rice in intercropping condition were increased by 23.5% and 12.2% respectively compared with rice in monocropped condition.The total N accumulated in rice in intercropped was 135 and 144 mg plant^-1 at the N fertilizer application of 15 and 75 kg hm^-2 respect ively while they were 117 and 131 mg plant^-1 in monocroopped treatment respectively,showing that inter-cropping could significantly increase the dry weight and nitrogen content of rice,especially at low N application rate.The dry weight and nitrogen content of groundnut intercropped were not significantly different from that monocropped.At three N application rates,biological N fixation(BNF) rates by groundnut were 72.8%,56.5%,35.4% and 76.1%,53.3%,50.7% in mono-and intercropped condition respectively,indicating that the BNF by groundnut was significantly increased in intercropped condition and the BNF decreased with increasing N fert ilizer application rates.The N transferred rates and the amount of N trans-ferred were 12.2%,9.2%,6.2% and 16.3 mg plant^-1,13.0 mg plant^-1 and 10.4 mg plant^-1,respectively,with N fertilizer application rates of 15 kg hm^-2,75 kg hm^-2 and 150 kg hm^-2,indicated N transfer decreased with increasing N fertilizer application rates in rice/groundnut intercropping system.Using 15 N foliar labeled method,it was shown that the decomposition of groundnut root had a significant contribution to N transfer happened in groundnut associated with rice system.