论文部分内容阅读
旱作春小麦(Triticum aestivum L.)是西部黄土高原最重要的禾谷类作物,该区苜蓿(Medicago sativa L.)分布也非常广泛。持续的作物连作和多年苜蓿种植系统都存在很多问题。雨养农业系统发展的关键是最佳水分利用策略的应用。发展合理的苜蓿-小麦轮作系统对该区农业的发展有十分重要的意义。由于苜蓿终止时间严重影响土壤水分,所以在适宜的时间终止苜蓿就显得十分重要。然而,关于苜蓿-小麦轮作中老苜蓿在一年中适宜终止时间的研究鲜见报道。本研究利用黄土高原西部典型的半干旱雨养农业区30年老苜蓿布设田间试验,旨在探索老苜蓿地土壤水分状况、苜蓿终止时间和少量氮肥施用对系统生产力及土壤水分的影响。结果表明,长期种植苜蓿后0~3m土壤水分很少,即便遇到丰水年(2003年),3年的时间都不足以恢复土壤水分。30年苜蓿在一年中春季还是秋季终止对土壤水分状况无显著影响。种植苜蓿30年后杂草竞争力增强,苜蓿干物质和产量水平都相当低,且对1kg hm-2的氮肥使用无明显响应。由于土壤水分含量太低,后茬春小麦对1kg hm-2的氮肥使用和苜蓿终止时间也无明显响应。因此,苜蓿持续种植时间太长会耗竭土壤水分,使后茬春小麦对苜蓿在一年中的终止时间及少量的氮肥使用无响应,需要3年以上时间才有可能恢复土壤含水量。
Triticum aestivum L. is the most important cereal crop in the western Loess Plateau. The alfalfa (Medicago sativa L.) is also widely distributed in this region. There are many problems with continuous cropping and many years of alfalfa cultivation. The key to the development of rain-fed agricultural systems is the application of optimal water use strategies. The development of a reasonable alfalfa-wheat rotation system is of great importance to the development of agriculture in this area. Because alfalfa’s deadline severely affects soil moisture, it is important to stop alfalfa at the right time. However, little is known about the appropriate termination of alfalfa-wheat alfalfa in one year during the year. In this study, a field experiment was conducted on the 30-year-old alfalfa field in a typical semi-arid rainfed farming area in the western Loess Plateau to explore the effects of soil moisture status, alfalfa termination time and the application of small amounts of nitrogen fertilizer on system productivity and soil moisture in old alfalfa fields. The results showed that after long-term planting alfalfa 0 ~ 3m soil moisture is very small, even in the wet years (2003), 3 years are not enough to restore soil moisture. 30 years of alfalfa spring or fall in the year end of the year had no significant effect on soil moisture status. After 30 years of planting alfalfa weeds competitiveness increased, alfalfa dry matter and yield levels are quite low, and no significant response to 1kg hm-2 nitrogen use. Due to the low soil moisture content, there was no obvious response to the nitrogen use of 1 kg hm-2 and the termination time of alfalfa in the following spring wheat. Therefore, long-term planting alfalfa will be depleted soil moisture for too long, so that after the spring wheat after alfalfa termination of the year and a small amount of nitrogen use is not responsive, take more than 3 years to be possible to restore soil moisture.