Effects of long-term localized fertilization on soil potassium supply in a sheltered vegetable field

Based on 16 years localized fertilization experiment,the effects of different fertilization on soil available potassium(K)and soil K supply in a sheltered vegetable field were studied.The results showed that the soil total K in the sheltered vegetable field maintained a higher level of 22.43-26.92 g·kg-1.Long-term application of organic plus chemical fertilizers induced a lower content of soil total K,comparing with applying chemical fertilizers alone,while different chemical fertilizers had little effects on soil total K.The intensity of soil K supply and the effectiveness of soil K were both low when chemical fertilizers were applied alone or in combinations,while the content of soil available K increased obviously with the application of organic fertilizers.The contents of soil available K were 195.60,460.14 and 621.06 mg·kg-1 when chemical potassium,organic fertilizer,and chemical potassium plus organic fertilizer were applied respectively.The intensity of soil K supply and the effectiveness of soil K were both increased with organic fertilization.