Effects of residual mulch film on transport and redistribution of water,salt and nitrogen in silt loam soil
In order to explore the effects of residual mulch film(hereinafter referred to as "residual-film")on the transport and redistribution of soil water,salt and nitrogen,an indoor one-dimensional vertical soil column infiltration-evaporation tests with different residual film contents(0,100,200,400 kg/hm2)was set up,and the changes of soil moisture content,conductivity,nitrate nitrogen and am-monium nitrogen in each soil layer during the process of water redistribution were measured.The results show that the residual film changes the infiltration performance of the soil,and when the residual film amount in the soil is lower than 200 kg/hm2,the soil wet peak migration distance and the cumulative infiltration rate increases.When the residual film amount is more than 400 kg/hm2,the soil wetting peak migration distance and cumulative infiltration reduces by 3.59%and 4.07%,respectively,com-pared with CK treatment.With the increase of residual film content,the leaching effect of water on salt decreases,and the leaching effect on nitrogen fertilizer increases.The residual film hinder the upward transport of salt and nitrate nitrogen,and the upward transport of ammonium nitrogen changes from an obstructing effect to a promoting effect with the decrease of mass ratio of ammonium nitrogen.When the residual film amount is more than 400 kg/hm2,the soil moisture and salt CV values increases by 10.15%and 6.51%,respectively,compared with CK treatment.With the increase of residual film con-tent,the CV value of mass ratio of nitrate nitrogen decreases significantly,and the CV value of mass ratio of ammonium nitrogen in the same soil layer of different treated soils is quite different,and there is no obvious difference in the variation degree of ammonium nitrogen in the soil profile.At the end of the evaporation experiment,the promotion effect of the residual film on water evaporation changes into a hindering effect as the residual film content increases.This study can explore the transport and redis-tribution of water,salt and nitrogen in the soil contaminated by residual film,and can provide a theo-retical basis for the formulation of a reasonable irrigation system for farmlands containing residual films.
residual filminfiltrationevaporationredistribution of water,salt and nitrogencoefficient of variation
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