| Leaching of nitrogen(N)has been widely considered as one of the non-point sources of groundwater pollution at a regional level especially in cropping systems.Several factors have been proposed to influence N leaching in agricultural systems,soil properties,rainfall amount,fertilizer application,land use patterns,slope and tillage skills.As a way of tillage skills,film mulching would affect soil temperature,soil water content,nitrogen amount,and furthermore would affect soil nitrogen leaching.Considering a limited study situation of removing plastic film mulching,an in-situ field 'experiment was conducted at Wulongchi watershed to analyze the effects of different plastic film mulching ways which included whole film mulching treatment,middle removing plastic film treatment and whole with no film mulching treatment on soil water content,soil temperature,nitrogen amount and nitrate nitrogen leaching in soil where corn was planted.Pearson relevance index optimal regression equation and two-way ANOVA analysis ways were chosen to analysis the quantitative relationships between soil nitrogen leaching and many factors.The effect of different mulching ways on nitrogen leaching in cultivated soil was revealed,so as to further deepen the influence mechanism of tillage on soil nitrogen loss in cropland.The major results including:(1)Both plastic filming and removing plastic filming treatment could decrease leaching of total nitrogen and NO3--N.The results showed that the total leaching amount(NO3--N+NH4+-N+NO2--N)decreased by 2.25%after plastic film mulching,NO3--N leaching amount decreased by 1.47%after plastic film mulching.The total leaching amount(NO3--N+NH4+-N+NO2--N)decreased by 1.93%after plastic film removing,NO3--N leaching amount decreased by 3.38%after plastic film removing.(2)Changes of soil temperature and soil water content could be differently regulated by plastic filming and removing plastic filming.Firstly,the film-mulching ridges have a effect in temperature that could increase the soil temperature in both 0-10,10?20,20?30 cm soil,and the soil temperature could be decreased through removing plastic filming.Secondly,the film-mulching ridges could decrease soil water evaporation in topsoil(0?10 cm),could hold water efficiently.In heading stage of maize,the water storage of deep soil was reduced,which was shown in 10?20 and 20?30 cm soil layers.The soil water storage of the film was 1.39 mm and 1.36 mm lower than that of the mulching film.In mature stage of maize,film-mulching could increase water loss in 10?20 and 20?30 cm soil compared with removing plastic film treatment.Thirdly,compared with removing film treatment,the content of nitrogen is higher in film mulching.NO3--N content in 0?10 cm soil was higher in film-mulching treatment compared with removing film treatment,NO3--N content amount increased by 61.14%compared with removing plastic film treatment.And total nitrogen content in 0-10 cm soil was higher in film-mulching treatment too,total nitrogen content amount was 1.25 times higher than removing plastic film treatment.10?20 cm had a similar trend compared to 0?10 cm soil.However,in 20?30 cm soil layer,the total nitrogen content was higher in no film mulching than that of the plastic film mulching and removing plastic film treatment,32.93%and 20.89%respectively.(3)There were relevance relationships between soil nitrogen leaching and soil water and heat conditions,soil nitrogen content and rainfall during the growth of maize.In the different growth stages of maize,NO3--N leaching amount had a different degree of correlation with rainfall,soil temperature,soil water content and total nitrogen content in plastic film-removing treatment and plastic film mulching treatment in 0?10 cm soil:NO3--N leaching amount was significantly correlated with soil temperature in seedling stage of two treatments(P<0.05),NO3--N leaching amount had a significant positive correlation with the amount of rainfall in heading stage of maize in plastic film-removing treatment and plastic film mulching treatment(P<0.01).Leaching amount of NH4+-N?NO2--N had a correlation with their content,There was a significant correlation between NH4+-N and NO2--N leaching amount and their contents(P<0.05).But rainfall amount was the main factor of NO3--N leaching amount.Types of rainfall had significant effects on NO3--N leaching in mulched soil.Under the condition of light rain,the amount of leaching increased with the increase of soil depth;under the condition of moderate rain,the amount of leaching in the 0-10 cm and 20-30 cm was 1.75 and 8.41 times of that in 10?20 cm;under the condition of heavy rain,leaching in the 0-10 cm and 20-30 cm were 18.97%and 60.69%lower than that of 10?20 cm,respectively.NO3--N leaching in soil was affected by soil water content,which weakened with the increase of soil depth. |
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