长期施用氮磷钾肥和石灰对红壤性水稻土酸性特征的影响

摘要

利用34年的长期定位施肥试验,研究不施肥(CK)、施氮磷钾肥(NPK)和氮磷钾化肥配施石灰(NPK+CaO)对红壤性水稻土不同形态酸、土壤盐基离子及水稻植株阳离子吸收量的影响,探讨土壤交换性H+和Al3+占交换性酸的比例、土壤盐基离子、植株带出阳离子数量与土壤酸度的关系.结果表明,长期NPK处理早、晚稻土壤pH 较CK处理分别降低0.2和0.3个单位,交换性酸提高2.3倍和4.2倍,水解性酸提高35.4%和40.0%;NPK+CaO处理早、晚稻土壤pH较NPK处理分别提高0.5和0.7个单位,较CK处理分别提高0.3和0.4个单位,交换性酸、水解性酸均显著低于NPK和CK处理(p<0.05).土壤交换性H+、Al3+含量高低顺序均为NPK+CaO CK> NPK. Exchangeable Al3+ was dominant to exchangeable acidity in acidic soil,and the ratio of exchangeable Al3+ to exchangeable acidity increased with increasing soil acidification. The effects of fertilization,regardless of fertilization mode,on soil CEC,exchangeable Ca2+,Mg2+,exchangeable base ions and base saturation were all very significant. Soil exchangeable base ions were dominated with exchangeable Ca2+,accounting for 81.8%~89.3%. Long-term liming significantly increased the content of soil exchangeable Ca2+. Treatment NPK+CaO was 40.1% and 62.9% higher in soil exchangeable Ca2+ than Treatments CK and NPK,respectively. Exchangeable Ca2+,exchangeable base ions and base saturation were positively related to soil pH,but negatively to exchangeable acidity and hydrolytic acid,and exchangeable Mg2+ was negatively to exchangeable acidity and hydrolytic acid,while exchangeable Na+ was negatively to hydrolytic acidity only. Treatments NPK+CaO and NPK did not vary much,but were both significantly higher than CK(p<0.05)in yield of early and late rice. In terms of calcium uptake by rice,the treatments followed an order of NPK+CaO> NPK> CK,in terms of potassium and magnesium uptake and total cation uptake by the crop,the followed an order of NPK> NPK+CaO> CK,and in terms of sodium uptake they followed an order of CK> NPK> NPK+CaO. The removal of Ca,Mg,K and Na and the cations in total with the crops harvested did affect soil pH,exchangeable acidity and hydrolytic acid to a varying extent,but no apparent relationships between them were observed. The findings in this experiment indicate that long-term fertilization plus liming significantly raises soil exchangeable Ca2+,exchangeable base cation and base saturation. From the angle of amelioration of acidified soils,long-term liming in addition of fertilization may alleviate the pressure of soil acidification of paddy fields to a certain extent and hence promote ecological remediation and ameriolation of acidic paddy soils.