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

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+Ca O)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p H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+Ca O处理早、晚稻土壤p H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(p0.05)。土壤交换性H+、Al3+含量高低顺序均为NPK+Ca OCKNPK。土壤交换性盐基离子以交换性Ca2+所占比例最大(81.8%~89.3%),NPK+Ca O处理交换性Ca2+较CK和NPK处理分别提高40.1%和62.9%。交换性Ca2+、交换性盐基离子、盐基饱和度与土壤p H正相关,与交换性酸、水解性酸负相关,交换性Mg2+与交换性酸、水解性酸负相关,交换性Na+与水解性酸负相关。植株移出带走的钙、镁、钾、钠离子量及其总量对土壤p H、交换性酸和水解性酸有一定影响,但其相关性均不显著。研究表明长期施用化肥条件下通过配施石灰可有效缓解稻田土壤的酸化,促进酸性稻田土壤的生态修复与改良。

Effect of Long-term Fertilization and Lime Application on Soil Acidity of Reddish Paddy Soil

Soil acidification is a main form of soil degradation and also a main factor limiting sustainable development of agriculture therein. In recent years,due to aggravating acid deposition and frequent agricultural practices,including increasing fertilization rate,harvesting crops with nutrients removed,etc., soil acidification of the farmlands is speeding up. Therefore how to ameliorate or remedy acidified soils and its mechanism have become subjects of some important theoretical and practical significance to rebuilding healthy soil and guaranteeing national food security. Based on a 34-year long stationary fertilization experiment, effects of no fertilization(CK),application of NPK fertilizer(NPK)and application of NPK fertilizer plus lime(NPK+CaO)on soil pH,exchangeable acidity,hydrolytic acidity,soil cation exchange capacity, base-exchangeable ions,rice yield and plant cation absorption,and further on proportion of exchangeable H+,Al3+ to exchangeable acidity,soil base-exchangeable ions,base-exchangeable ions removal by plant with harvest and their relationships with soil acidity. Results show that long-term application of chemical fertilizers (NPK)leads to soil acidification,and mitigates the effect when lime is amended(NPK+CaO). After 34 years of rice cultivation of double cropping system,Treatment NPK was 0.2 and 0.3 lower in soil pH,2.3 and 4.2 times higher in exchangeable acidity,and 35.4% and 40.0% higher in hydrolytic acidity than CK(p<0.05)in the soil under early rice and under late rice,respectively,while Treatment NPK+CaO was 0.5 and 0.7 higher than NPK,and 0.3 and 0.4 higher than with CK in soil pH in the early and late rice seasons, respectively,and much lower than Treatment NPK and CK in exchangeable acidity and hydrolytic acidity in both rice seasons(p<0.05). In terms of exchangeable H+ and exchangeable Al3+,the three treatments in the experiment followed an order of 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.