Abstract: The effects of Long-term fertilization on soil water and nutrient contents of continuous wheat or continuous alfalfa lands under rainfed conditions were studied based on the data of 20-year experiment since 1984. The results show that P application alone didn’t result in the significant increase of wheat yield,but significantly increased the alfalfa yield by 183.5%.The soil water content of alfalfa lands was low and the wheat lands were also found the same trend of getting drier.Long-term P application significantly increased P availability of the soils;soil total P and soil available P of alfalfa lands increased by 13.6% and 83.8% and those of wheat lands increased by 22.9% and 367.9%,respectively.Alfalfa planting had a significant effect on soil fertility,the total N and available N of alfalfa lands increased,but decreased for wheat lands.The application of balanced N-P fertilizer and manure supplied the demanded nutrients to plants and greatly increased the crop yield and soil fertility.

Key words: Wheat, Alfalfa, Directional fertilization, Yield, Soil nutrient

摘要： 研究黄土高原旱地小麦(Wheat)和苜蓿(Alfalfa)连作20年后的产量、土壤水分及养分的变化。结果表明:磷肥对小麦增产不显著,而对苜蓿则增产显著(增产183.5%);施肥可以延缓苜蓿的衰老,提高产草量;苜蓿地土壤干燥化明显,施用氮磷有机肥后小麦地也出现干燥化趋势;长期施磷肥有利于改善土壤磷素有效性,其中苜蓿地全磷和有效磷含量,增加了13.6%和83.8%,小麦土壤增加了22.9%和367.9%;苜蓿土壤全氮和速效氮均呈增加,而小麦地则减少;平衡施用氮磷有机肥能培肥土壤,使产量大幅度提高;在该区采取合理的轮作方式和培肥措施能有效地改善农田生态系统的生产力。

关键词: 小麦, 苜蓿, 定位施肥, 产量, 土壤养分