In order to understand the effect of alfalfa cultivation on soil nutrients and guide the scientific fertilization of alfalfa in Ningxia Yellow River Irrigation Area.The characteristics of soil available nutrients of 8 alfalfa varieties grew for 5 years in Ningxia Yellow River Irrigation Area were studied.The results showed that:organic matter and alkali-hydro N contents were significant differences at 20~60cm soil lay-er,while available phosphorus and available potassium were significant difference only in 0~10cm soil lay-er among different alfalfa varieties when alfalfa was planted 5 years later.Four kinds of nutrients were sig-nificantly decreased with the increase of soil depth,in addition available Phosphorus had a significant accu-mulation on the soil surface.Long-term cultivation of alfalfa can improve the content of organic matter, but reduce the content of available N,P and K.Change of available K was the largest.There was a signifi-cant negative correlation between the change amounts of available K and alfalfa yield,therefore available K was the main effect factor on alfalfa yield.Therefore alfalfa should be scientifically and reasonably fertilized according to alfalfa varieties and soil nutrients,specially pay attention to the use of available K in Ningxia Yellow River Irrigation Area.%对宁夏引黄灌区8个苜蓿品种种植5年后的土壤有效养分和有机质变化特征进行研究,结果表明:8个苜蓿品种种植5年后土壤碱解氮和有机质含量在20~60cm土层差异显著;有效磷和速效钾含量仅在表层土壤存在显著差异.所有苜蓿品种的土壤碱解氮、有效磷、速效钾和有机质含量均随土层深度的增加显著降低,且有效磷存在明显的"表聚"现象.长期种植苜蓿提高了土壤中的有机质含量,但降低碱解氮、有效磷和速效钾含量,其中速效钾降幅最大.速效钾变化量与苜蓿干草产量呈显著负相关,是影响苜蓿产量的主要影响因素.因此,在宁夏引黄灌区种植苜蓿要根据苜蓿品种、土壤养分变化进行科学合理的施肥,尤其要注重增加钾肥的使用.
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