苏南稻田4种冬绿肥养分特性及对翻压前土壤无机氮的影响

为充分利用苏南冬闲稻田发展适宜绿肥作物种植，在大田试验条件下，研究了毛叶苕子（Vicia villosa Roth）、 光叶苕子（Vicia villosa var.）、 紫云英（Astragalus sinicus L.）和肥田萝卜（Raphanus sativus L.）4种绿肥作物的生长、 营养特性，比较分析了绿肥作物翻压前不同处理间耕层土壤无机氮含量与构成的差异。结果表明，在绿肥作物翻压期，4种绿肥作物均达到较高生物量和养分累积量，鲜重、 干重分别为24.8 30.7 t/hm2和3.6 4.2 t/hm2，不同绿肥作物间无显著差异。 4种绿肥作物的吸氮量为69.8 136.4 kg/hm2，毛叶苕子最高，肥田萝卜最低。吸磷量为7.1~11.3 kg/hm2，肥田萝卜最高，紫云英最低。吸钾量为117.6~151.3 kg/hm2，毛叶苕子最高，光叶苕子最低。与对照冬闲相比，种植绿肥作物不同程度地降低了耕层土壤无机氮含量（平均降低38.9 kg/hm2），其中硝态氮含量下降明显，铵态氮含量均较对照土壤有增加趋势（平均提高6.5 kg/hm2），毛叶苕子和光叶苕子处理铵态氮含量增加显著。4种绿肥作物均适合苏南冬闲稻田种植，能潜在降低无机氮的损失风险和为后季水稻作物生长提供养分。

Nutrient characteristics of four kinds of winter green manure and their influences on soil mineral nitrogen before incorporation

In order to replace the winter bare fallow with green manure crop in rice cropping system in South of Jiangsu province, the field experiment was carried out to investigate the growth and nutrient characteristics of hairy vetch (Vicia villosa Roth ), smooth vetch (Vicia villosa var.), milk vetch (Astragalus sinicus L.) and radish（Raphanus sativus L.） as winter green manure crops and their influences on soil mineral nitrogen before incorporation. The results showed that four kinds of green manure crops in our study all produced relatively high aboveground biomass and N, P, K nutrients accumulation, the fresh and dry biomass ranged from 24.8 t/ha to 30.7 t/ha and from 3.6 t/ha to 4.2 t/ha individually. No significant differences were found among different green manure crops. The nitrogen uptake ranged from 69.8 for  radish to 136.4 kg/ha for hairy vetch. The phosphorus uptake ranged from 7.1 for radish to 11.3 kg/ha for milk vetch. The potassium uptake ranged from 117.6 for smooth vetch to 151.3 kg/ha for hairy vetch. Compared with bare fallow treatment, planting green manure crops decreased the mineral nitrogen content in plow layer soil to different extents (averagely decreased by 38.9 kg/ha). The decrease of soil mineral nitrogen content was related to significant decrease of soil nitrate nitrogen content. The soil ammonium nitrogen content had an increasing trend (averagely increased by 6.5 kg/ha). There were significant increases in ammonium nitrogen for hairy vetch and smooth vetch treatment compared with that in the bare fallow treatment. Four kinds of green manure crops in our study all suitable for planting as green manure crop in rice cropping system in South of Jiangsu province, and potentially reduced the loss risk of soil mineral nitrogen and supplied the nutrients for rice growth in the next season.