污灌时间对土壤肥力及土壤酶活性的影响

通过时空互代、野外调查和采样分析的方法,研究了石家庄栾城县不同污水灌溉时间下（0~52 a）耕地土壤肥力及土壤酶活性特征。结果表明：与对照点相比,污水灌溉区土壤有机质、全氮、全磷含量,蔗糖酶、脲酶和磷酸酶活性均相对较高,而土壤阳离子交换量、过氧化氢酶和脱氢酶活性无明显的变化规律;污水灌溉区土壤全氮、蔗糖酶、磷酸酶与污灌时间之间表现出显著正相关性（P〈0.05）,其他指标与污灌时间之间均无显著相关性;土壤肥力（有机质和全氮）、重金属（总Cr和总Cd）与水解酶（脲酶和磷酸酶）之间表现出显著正相关性,交换态Cr与脱氢酶活性之间呈现出显著负相关性。上述特征反映了污水灌溉时间对土壤肥力及土壤酶活性具有复杂的影响效应,而这些效应是决定污水灌溉区土地生产力能否高产的重要因素。

Effect of Sewage Irrigation Time on Soil Fertility and the Enzyme Activity

Sewage is widely used on agricultural soils in peri-urban areas of developing countries to meet the shortage of water resources.Although sewage is a good source of plant nutrients,it also increases the concentration of heavy metals in soils.Microbial responses to heavy metals may serve as early warning indicators of adverse effects of sewage irrigation on soil quality.The aim of the present work is to evaluate the effect of sewage irrigation time on soil fertility and the enzyme activity.Based on the methods of space instead of time,field investigation and sample analysis,several soil samples in the layer of 0~20 cm were collected and analyzed from seven soil sites（S1~S7） where had been irrigated with sewage for 0,16,23,25,27,32 a and 52 a,respectively in Lucheng town of Shijiazhuang.For each soil sample,we determined the concentrations of organic matter,total nitrogen,total phosphorus,cation exchange capacity,sucrase,urease,phosphatase,dehydrogenase and catalase.The results showed that the soils irrigated with sewage contained higher concentrations of organic matter,total nitrogen,total phosphorus,sucrase,urease and phosphatase than those irrigated with groundwater.For the cation exchange capacity,catalase and dehydrogenase,some soils irrigated with sewage exhibited higher concentrations than those irrigated with groundwater,while some soils irrigated with sewage exhibited lower concentrations than those irrigated with groundwater.The concentrations of total nitrogen,sucrase and phosphatase in soils were significantly correlated in a positive manner with sewage irrigation time,while the other indicators did not change significantly with time of sewage irrigation.The contents of fertility（organic matter and total nitrogen） and heavy metals（total Cr and total Cd） in soils were significantly correlated in a positive manner with the activities of hydrolase enzyme（urease and phosphatase）,and the content of exchangeable Cr was significantly correlated in a negative manner with the activity of dehydrogenase enzyme.The results indicated that sewage irrigation could have significantly complex effects on soil fertility and the enzyme activity,and these effects had great impact on the yields of agricultural land in wastewater-irrigated fields.