不同施肥和耕作处理紫色土坡耕地碳、氮、磷流失特征

Characteristics of carbon,nitrogen and phosphorus loss in sloping farmland of purple soil under different fertilization and cultivation methods

【目的】坡耕地营养元素流失是下游水体环境污染的主要原因之一。探明不同施肥处理和耕作方式下紫色土坡耕地碳(C)、氮(N)、磷(P)营养元素流失特征,对采取科学的田间管理措施,降低水生生态系统污染风险具有重要意义。【方法】以该区典型坡耕地为研究对象,设置5个施肥和耕作处理:顺坡耕作对照(CK)、顺坡耕作施化肥+猪粪(T1)、顺坡耕作单施化肥(T2)、顺坡耕作单施1.5倍化肥(T3)和横坡耕作单施化肥(T4)。在玉米苗期、拔节期、抽穗期、成熟期,监测了径流量,测定了土壤和径流中的C、N和P含量,计算流失量。【结果】与对照相比,T1和T4处理显著增加土壤中有机碳、全氮、全磷含量(P<0.05)。顺坡耕作T1处理径流中的可溶性有机碳浓度较T2处理降低了33.66%(P<0.05),其他指标浓度的降低幅度未达显著水平;T3处理的径流中碳、氮、可溶性总磷的浓度较T2处理有所升高,其中可溶性有机碳和NH_(4)^(+)-N的提高效果达到显著水平(P<0.05);T4处理中仅径流NO_(3)^(-)-N浓度显著低于T2处理(P<0.05),其他指标与T2处理差异不显著。5个处理的径流量以CK最高,T4处理最低,单施化肥的T2和T3处理均大于化肥猪粪配合的处理T1。横坡耕作的T4处理径流量较其他处理降低了44.65%~67.36%,化肥+猪粪T1处理的径流量较T2、T3处理分别减少了15.65%、22.76%。与T2处理相比,化肥有机肥配施T1处理下的径流可溶性有机碳、全氮和全磷流失量分别减少43.10%、27.51%和31.26%;横坡耕作T4处理下径流可溶性有机碳、全氮和全磷流失量分别降低59.16%、58.57%和68.42%;提高施化肥量T3处理的径流可溶性有机碳、全氮和全磷流失量最高,分别为6.02、0.86和0.20 kg/hm^(2)。【结论】在紫色土坡耕地上,与单施化肥相比,相同耕作方向下化肥有机肥配施降低了径流中可溶性有机碳、全氮和全磷浓度,且可溶性有机碳浓度显著降低,横坡耕作主要是大大减少了径流量,因此,采用横坡耕作和化肥有机肥配施是减少土壤C、N、P流失,降低周围水体污染风险的有效措施。

【Objectives】Loss of elemental nutrients in sloping land is one of the main causes of water pollution downstream.Exploring the effects of fertilization and cultivation methods on the losses of carbon(C),nitrogen(N)and phosphorus(P)in sloping farmland plays a vital role in field management,promoting the quality of cultivated land and reducing the risk of the aquatic environment pollution.【Methods】The study site was located in a typical sloping land.The five treatments in this research included down-slope tillage control treatment(CK),down-slope tillage with combining application of chemical fertilizer and pig manure treatment(T1),downslope tillage with chemical fertilizer application only(T2),down-slope tillage with 1.5 times chemical fertilizer application(T3),and cross-slope tillage with chemical fertilizer application only(T4).The concentrations of C,N,and P in soil and runoff during the growth period of maize(seedling,jointing,heading,maturity)were analyzed The corresponding quantities of nutrient lost were calculated.【Results】Compared to CK,T1 and T4 increased the contents of soil C,N,and P(P<0.05).With down-slope tillage,the soluble organic carbon(DOC)concentration of T1 run-off was 33.66%lower than T2,but the differences of other nutrient concentrations were not significant.The C,N and TDP concentrations in the run-off of T3 were all higher than in T2,and the increase of DOC and NH_(4)^(+)-N reached a significant level(P<0.05).The NO_(3)^(-)-N concentration in the run-off of T4 was notablely lower than in T2,but the decreases of other nutrients were not remarkable.The highest run-off was in CK and the lowest in T4;T2 and T3 had larger run-off than T1.Compared with other treatments,the run-off of T4 decreased by 44.65%-67.36%,and that of chemical fertilizer+pig manure T1 declined by 15.65%and 22.76%compared with T2 and T3,respectively.Compared with T2,T1 decreased the DOC,TN,and TP lost by 43.10%,27.51%,and 31.26%,respectively.T4 declined DOC,total N,and total P lost by 59.16%,58.57%,and 68.42%,respectively.The DOC,total N,and total P quantity lost were the highest in T3,reaching 6.02 kg/hm^(2),0.86 kg/hm^(2)and 0.20 kg/hm^(2),respectively.【Conclusions】The combined application of chemical and organic fertilizers decreases the concentration of DOC,total N,and total P in the run-off,and the reduction of DOC is significant,but not the amount of run-off.In contrast,cross-slope tillage is found effective in declining the total run-off but not DOC,total N,and total P concentration.Therefore,combining the application of chemical and organic fertilizers,and cross-tillage are recommended to reduce soil C,N,and P loss through run-off and attenuate the surrounding water pollution in the purple sloping farmland.