施用有机肥对咸水灌溉农田耕层土壤有机质及水稳性团聚体的影响

Effects of Organic Fertilizer Application on Soil Organic Matter and Water-Stable Aggregates of Plow Layer in Farmland with Saline Water Irrigation

为探索施用有机肥对咸水灌溉农田耕层土壤水稳性团聚体的调控效应,在麦玉两熟制农田咸水灌溉(1,2,4,6 g/L)配施有机肥(OF)和未施有机肥(NOF)长期定位试验的基础上,研究了2018—2019年不同处理对农田耕层0—20 cm土壤盐度(EC_(1∶5))、土壤有机质(SOM)含量和水稳性团聚体稳定性的影响。结果表明:咸水灌溉有增加耕层土壤盐度,降低SOM含量和水稳性团聚体稳定性的趋势,随灌溉水矿化度的升高,SOM含量、>0.25 mm水稳性大团聚体质量分数(WR_(0.25))、团聚体平均重量直径(MWD)和几何平均直径(GMD)逐渐减小,土壤EC_(1∶5)和分形维数(D_(m))逐渐增大,其中4,6 g/L与1 g/L灌水处理间的差异达显著水平。增施有机肥可降低咸水灌溉农田0—20 cm土壤EC_(1∶5),当灌溉水矿化度≥2 g/L时,OF处理的耕层土壤EC_(1∶5)较NOF处理降低4.64%~48.29%;施用有机肥显著提高农田SOM含量、WR_(0.25)、MWD和GMD,各灌水处理的提高幅度分别为80.75%~127.32%,10.36%~90.44%,12.90%~129.11%和11.88%~81.57%。在该研究条件下,≥4 g/L咸水灌溉会显著增加土壤盐度,降低有机质含量,破坏土壤团粒结构,应谨慎使用;施用有机肥能促进耕层土壤盐分淋洗,降低盐分对土壤环境的负面影响,有助于实现咸水资源安全高效利用。

It is necessary to explore the effects of saline water irrigation combined with application of organic fertilizer on water-stable aggregates of plow layer soil.In this study,a long-term saline water irrigation experiment combined with application of organic fertilizer was carried out under winter wheat-summer maize double cropping system.Treatments were set up with four irrigation water salinities(1,2,4,6 g/L)and with organic fertilizer applied(OF)or not(NOF).We measured the effects of different treatments on variation of soil salinity(EC_(1∶5)),soil organic matter(SOM)content and the stability of water-stable aggregates in 0—20 cm soil layer form 2018 to 2019.The results indicated that saline water irrigation tended to increase soil salinity and decrease SOM content and the stability of water-stable aggregates.Meanwhile,with the increasing salinities of irrigation water,SOM content and the mass fraction of water-stable aggregate(>0.25 mm)(WR_(0.25)),mean weight diameter(MWD)and geometric mean diameter(GMD)decreased;on the contrary,soil EC_(1∶5) and fractal dimension(D_(m))increased.In addition,there were significant differences only between 4 g/L,6 g/L and 1 g/L treatments.It was found that applying organic fertilizer could reduce EC_(1∶5) in 0—20 cm soil layer.When the salinity of irrigation water was≥2 g/L,the EC_(1∶5) of plow layer with organic fertilizer application was 4.64%~48.29%lower than those of treatments without organic fertilizer application.Applying organic fertilizer significantly increased SOM content,WR_(0.25),MWD and GMD,with the increases of 80.75%~127.32%,10.36%~90.44%,12.90%~129.11%and 11.88%~81.57%.In summary,irrigation water salinity of≥4 g/L could significantly increase soil salinity,reduce organic matter content and destroy soil aggregate structure,so it should be used cautiously.The application of organic fertilizer could promote the salt leaching from the surface soil to the deep layer,reduce the negative impacts of salt on soil environment,and contribute to the safe and efficient utilization of saline water resources.