不同灌溉定额下地膜残留量对土壤物理性质及棉花根系生长的影响

Effects of mulching film residue on soil physical properties and cotton root growth under different irrigation quotas.

地膜覆盖是干旱半干旱地区农业节水和增产的主要措施。当前长期高强度的使用地膜造成严重的“白色污染”,这是不可持续的。本研究在模拟残膜蓄积量和干旱情景下,探讨残膜污染对土壤物理特征和棉花根系生长发育的影响。设计土柱试验,评估2个灌溉定额下[1950 m3·hm^(-2)(田间持水量50%,中度干旱)和3900 m^(3)·hm^(-2)(田间持水量100%,充分灌溉)],4个残膜量水平(0、160、270和490 kg·hm^(-2))的影响。结果表明:土壤物理性质主要受残膜量的影响,残膜量的增加使土壤容重增大,饱和含水率、田间持水率、毛管持水率、总孔隙度降低;并抑制了棉花根系扩展,降低了根重量、根表面积、根体积、根长和根直径,以及根系在土壤0~20 cm土层中的占比;上述指标除田间持水量外,其余均在残膜量超过270 kg·hm^(-2)时,表现出显著的处理间差异。同一残膜量下,高灌溉定额根系构型优于干旱处理;综合分析,土壤容重增幅1.88%,饱和含水率、毛管持水率、总孔隙率的降幅分别达7.97%、6.42%和9.39%;根系重量、根表面积、根体积和根直径的降幅分别达41.34%、64.10%、47.27%和86.67%。研究表明,残膜污染严重破坏土壤结构,抑制根系生长,导致土壤物理性能和根系水肥吸收能力下降,降低这一影响可能需要消耗更多的水分,必将进一步加剧缺水危机下水资源的承载压力,因此相应的残留阈值应严格控制在270 kg·hm^(-2)以下。研究结果为农田残膜污染的风险评估和防治策略提供了理论支撑。

Plastic film mulching is a major management strategy for agricultural water-saving and yield-increasing in arid and semi-arid areas.However,long-term and high-intensity plastic film mulching has caused serious“white pollution”and thus is not sustainable.In this study,we investigated the effects of residual film pollution on soil physical characteristics and cotton root growth under simulated residual film accumulation and drought.We designed a soil column installation with two irrigation amounts[1950 m3·hm^(-2)(50%field water-holding capacity,moderate drought),3900 m3·hm^(-2)(100%field water-holding capacity,full irrigation)]and four residual film levels(0,160,270,and 490 kg·hm^(-2)).The results showed that soil physical properties were mainly affected by residual film amount.With the increases of residual film amount,soil bulk density increased,while saturated water content,field water-holding capacity,capillary water-holding capacity,and total porosity decreased.The increased residual film amount inhibited the expansion of cotton root,decreased root biomass,root surface area,root volume,root length,and root diameter,as well as the proportion of cotton roots in the 0-20 cm soil layer.Except for field waterholding capacity,all the above mentioned indices showed significant differences when the residual film amount exceeded 270 kg·hm^(-2).Under the same amount of residual film,root architecture of the high irrigation quota was better than that of the drought treatment.A comprehensive analysis showed that the increasing range in soil bulk density was 1.88%,while the decrease ranges in saturated water content,capillary water retention,and total porosity were 7.97%,6.42%,and 9.39%,respectively.Root biomass,root surface area,root volume,and root diameter decreased by 41.34%,64.10%,47.27%,and 86.67%,respectively.In conclusion,residual film pollution severely damaged soil structure,inhibits root growth,and led to decreases in soil physical properties,root water and fertilizer absorption capacity.The reduction of such effect may require more water consumption,which will further exacerbate the water shortage crisis.Therefore,the corresponding residual threshold should be strictly controlled below 270 kg·hm^(-2).The results provide theoretical support for the risk assessment and control strategy of farmland residual film pollution.