长期施用有机肥对潮土土壤肥力及硝态氮运移规律的影响

以连续不同年限定位施用有机肥的小麦-玉米轮作农田为研究对象,设置4个处理:连续施用化肥(长期施用化肥,未施用有机肥);3年连续施用有机肥(不施化肥);5年连续施用有机肥(不施化肥);20年连续施用有机肥(不施化肥),探索不同年限连续有机施肥下土壤肥力、小麦产量和土体硝态氮累积量分布的变化。结果表明,连续施用有机肥可显著降低土壤容重、增加土壤中速效养分含量,且年限越长,效果越明显。化肥处理的小麦产量显著高于有机肥处理,有机肥处理中小麦产量随施肥年限的增加而降低,但无显著性差异。不同土壤深度硝态氮累积量表现为有机肥处理大于无机肥处理,小麦季大于玉米季;随着土壤深度增加土壤硝态氮累积量呈现先降低后增加的趋势,且各土层硝态氮累积量随施用有机肥年限增加而增加;通过分析80~100 cm土层硝态氮累积量发现,20年连续施用有机肥处理在此层的累积量最大达240 kg·hm~(-2)。由此可见,连续施用有机肥可降低小麦产量,连续20年施用有机肥土壤硝态氮总累积量和土体下层累积量均达到最大,具有一定的硝态氮淋失风险。因此,需采取一定的措施来增加作物产量,减少硝态氮累积,防止地下水硝态氮污染。

Effects of long-term application of organic manure on soil fertility and nitrate-N transport in fluvo-aquic soil

The environmental problems caused by long-term fertilization,especially groundwater pollution resulting from leaching of nitrate nitrogen (NO₃^--N),have received increasing attention.A long-term field experiment was established in an intensively cultivated alluvial soil in the North China Plain,where a wheat-maize rotation was practiced.Treatments included continuous application of mineral fertilizer (no organic manure application) and three durations of organic manure application with no mineral fertilizer (3,5,and 20 years).Changes in soil fertility,crop yield,and soil nitrate accumulation were explored.The results showed that the longer the period of continuous organic manure application,the more significantly the soil bulk density decreased and the soil nutrient content increased.The crop yield from the mineral fertilizer treatment was significantly higher than that from the organic manure treatments.The yield decreased as the number of organic manure application years increased,but there was no significant difference among the three organic manure treatments.In the soil profiles,it was shown that the NO₃^--N accumulation in the organic manure treatment was greater than that in the mineral fertilizer treatment.The NO₃^--N accumulation firstly decreased and then increased with increasing soil depth,and there was a positive relationship between NO₃^--N content and the number of organic manure application years.The amount of accumulated NO₃^--N in the 80~100 cm soil layer was up to 240 kg·hm^-2 after 20 years of continuous organic manure application.Therefore,continuous application of organic manure could reduce crop yield and there is a definite risk of nitrate leaching after 20 years of organic manure application.More research is required to develop measures to increase crop yield,alleviate the accumulation of NO₃^--N,and prevent nitrate pollution of groundwater when continuously applying organic manure.