豆科作物-小麦轮作方式下旱地小麦花后干物质及养分累积、转移与产量的关系

Accumulation and translocation of dry matter and nutrients of wheat rotated with legumes and its relation to grain yield in a dryland area

研究旱作条件下豆科绿肥轮作影响旱地小麦产量变化的作物营养生态机制,对优化旱地作物种植施肥制度,促进水分资源高效利用、土壤培肥、作物增产有重要意义。通过两年定位试验,分析了与不同豆科作物轮作引起的后茬小麦产量变化及其与干物质、氮磷钾养分累积、转移的关系。结果表明:与秋豆轮作的第一季,小麦籽粒产量无显著变化,但第二季小麦产量提高23.4%;与绿豆轮作,两季产量分别降低19.2%和4.4%;与大豆轮作,产量无显著变化。与秋豆轮作增加了小麦花后干物质及氮、磷养分累积,和对照相比分别增加了35.1%,128.8%和14.0%,而与大豆和绿豆轮作花后干物质累积分别降低26.7%和17.0%,花后氮累积分别降低44.2%和24.4%,花后磷累积与对照相比无显著差异。与此对应,秋豆-小麦轮作,其后茬小麦花后干物质及养分累积对产量形成的贡献显著增加,茎叶花前累积氮、磷向籽粒的转移对产量的贡献明显小于大豆-小麦和绿豆-小麦轮作处理。与氮、磷不同,小麦茎叶花前累积钾素向籽粒转移的同时,花后植株钾素没有累积,反而明显损失,其中与秋豆轮作的小麦花后植株钾素损失量较小,为3.8 kg/hm2,籽粒钾素占转移钾的81.0%;休闲或与大豆、绿豆轮作的小麦花后植株钾素损失较多,分别为10.9,12.6和5.5kg/hm2,籽粒钾素占转移钾的52.9%,52.9%和66.8%。与秋豆-小麦轮作处理小麦增产的主要原因是花后植株能累积更多干物质和氮、磷养分,减少了花前累积于茎叶的钾素在花后的损失。

Winter wheat is one of the major food crops in the Loess Plateau, where low rainfall during the wheat growing season and poor soil fertility restrict the growth and development of the crop. An important research goal is to identify ways of increasing both the amount of water stored in the soil profile and the soil nutrient content during the summer fallow season. Attaining this goal could result in significant improvements in wheat yield. Legumes have an especially high nitrogen concentration due to atmospheric nitrogen fixation by rhizobia in root nodules. The incorporation of legumes into the soil can increase soil fertility. However it is not known if the inclusion of a legume in a crop rotation could increase wheat yield or the soil nutrient content in a dryland area. To answer this question, a field experiment was conducted between 2008 and 2009 at Changwu, Shaanxi Province, China. The experiment used a completely randomized block design with four croprotations （mung bean-winter wheat, local bean-winter wheat, soybean-winter wheat, and fallow-winter wheat）. Nitrogen fertilizer was applied to all treatments at the rate of 108 kg/hm2. The local bean-winter wheat treatment had no significant effect on wheat yields in 2008--2009. However in 2009--2010, the local bean-winter wheat treatment increased wheat yields by 23.4% compared to the control （fallow-winter wheat treatment）. In contrast, the mung bean-winter wheat treatment reduced wheat yields by 19.2% in 2008-2009 and by g. 4% in 2009-2010. The soybean-winter wheat treatment had no significant effect on wheat yields during either cropping season. Comparison of the four treatments showed that the wheat dry weight, nitrogen accumulation, and phosphorus accumulation were highest in the local bean-winter wheat treatment. The local bean-winter wheat treatment increased the wheat dry weight by 35.1% compared to the control, the nitrogen accumulation increased by 128.8%, and the phosphorous accumulation increased by 140%. In contrast, the soybean-winter wheat treatment reduced the wheat dry weight by 26.7% and the nitrogen accumulation by 44.2%. The mung bean-winter wheat treatment reduced the wheat dry weight by 17.0% and the nitrogen accumulation by 24.4%. The phosphorus accumulation of wheat was not significantly affected by either the soybean-winter wheat treatment or the mung bean-winter wheat treatment. In contrast to nitrogen and phosphorus, the potassium accumulation of wheat decreased as the plants matured. The decline in the potassium accumulation varied among the rotations. The post-anthesis potassium loss in the local bean-winter wheat treatment was 3.8 kg/hm2. In comparison, the potassium loss in the soybean-winter wheat treatment was 12.6 kg/hm2. The potassium loss in the mung bean-winter wheat treatment was 5.5 kg/hmz. The percentage of grain potassium to translocated potassium in the local bean-winter wheat treatment was 81.0%. This amount was higher than that of the control. In comparison, the percentage of grain potassium to translocated potassium was 52.9% in the soybean-winter wheat treatment and 66.8% in the mung bean-winter wheat treatment. This indicated that pre-anthesis dry matter and nutrient accumulation played an important role in grain yields formation. However, post-anthesis dry matter and nutrient accumulation was the main reason for the differences in wheat grain yields among the four rotation systems. The reason for the increased yields in the local bean-wheat treatment was that more dry matter, nitrogen and phosphorous were accumulated during the post-anthesis stage and less potassium was lost.