| The Weibei Dryland in Shaanxi Province is located in a semi-humid and drought-prone area in the southern part of the Loess Plateau.Low temperature in early spring and barren land in the Weibei Dryland resulted in a wide application of plastic film mulching in agriculture.The negative effects of plastic film mulching combined with traditional urea base fertilizer cannot be ignored.In order to study the effects of interactions of plastic film mulching and controlled/slow release fertilizer on the growth and nitrogen(N)utilization of spring maize,field experiments of two years(2017-2018)were conducted at three different sites(Yongshou,Sanyuan,and Changwu)on the Weibei Dryland.The experiments included two cropping patterns(e.g.full plastic film mulching,M;flat planting,F),and three types of nitrogen fertilizer(e.g.urea fertilizer,U;control release fertilizer,CU;slow release fertilizer,SU).A total of six different treatments were involved consequently.The experimental study focused on the influences on the growth and yield,the accumulation and translocation of plant nitrogen in late growing season of spring maize,and the accumulation and supply characteristics of soil nitrogen and change of organic matter.Some main results are given as follows.(1)Compared with the flat cropping,plastic film mulching had positive effects on leaf area growth and shoot dry matter accumulation during the vegetative growth stage,and could significantly promote dry matter accumulation in ears.However,under condition of basal urea fertilizer combined with film mulching,plasic film mulching caused premature decline of leaf area,accelerated the growth process,and reduced the dry matter accumulation rate in the later growing season.Because of the interannual variations of meteorological conditions,the effect of film mulching in 2017 was more significant than that in 2018.Compared with urea base application,controlled/slow release fertilizers could alleviate leaf area aging,accelerate dry matter accumulation rate,and finally increase maize yield under film mulching.(2)Under the same fertilizer type,plastic film mulching remarkably increased N transport,transport efficiency and root uptake in vegetative organs after flowering compared with the flat cropping.Compared with basal urea fertilizer,controlled/slow release fertilizer had same effects under plastic film mulching.Controlled/slow-release fertilizers at flowering stage of maize remarkably increased N content in vegetative organs compared with the basal urea fertilizer under the mulching conditions.Compared with the flat cropping,all of N absorption and utilization indexes were remarkably improved under plastic film mulching.Compared with the basal urea fertilizer,controlled/slow release fertilizer obviously increased N uptake rate and use efficiency under film mulching treatment.When the same fertilizer was applied,film mulching significantly increased the efficiency of rainfall production compared with flat cropping.Compared with urea-based fertilizer,controlled/slow-release fertilizer significantly increased rainfall production efficiency under the same cultivation conditions.(3)Nitrogen accumulation in the basal urea fertilizer treatment and plastic film mulching was higher than that with controlled/slow release fertilizer at flowering stage,but there was no significant difference in N accumulation between the two kinds of treatments at the harvest stage.Compared with flowering stage,soil N supply decreased in the treatment with basal urea fertilizer and plastic film mulching.Under plastic film mulching,the proportion of N accumulation of 0-40 cm soil layer in the treatment with controlled/slow release fertilizer was significantly higher than that with basal urea fertilizer.Controlled/slow release fertilizer obviously delayed the release of N,which made soil N stay more in the soil root layer.Under same fertilizer type,the proportion of N accumulation of 0-40 cm soil layer in the treatment with plastic film mulching was higher than that in the flat-cropping treatment,which alleviated the leaching of nitrate N from soil profile into deep soil layer.Under the same fertilizer type,plastic film mulching remarkably increased the organic matter content in soil root zone and N use efficiency of spring maize.Compared with basal urea fertilizer,controlled-release fertilizer obviously increased the organic matter content in soil profile as well.(4)The DNDC model seemed to overestimate maize yield under the condition of basal urea fertilizer combined with plastic film mulching.The maize yields of treatments with controlled/slow-release fertilizer differed greatly in the three experimental sites.In Yongshou,the simulated maize yield of the slow release fertilizer treatment was 5.2-10.6% higher than that of urea treatment.The model did not respond to the application of control release fertilizer.In Sanyuan,the DNDC simulated yield of the slow release treatment was slightly lower than that of the urea treatment in 2017,while simulated yield of the control/slow release fertilizer treatment was 6.7-23.1% higher than that of the urea treatment.In Changwu,the DNDC simulated yields of the control release fertilizer and the slow release fertilizer treatments were slightly lower than those of the urea treatment by 1.8-10.4%.Thus,the combination of plastic film mulching and controlled/slow release fertilizer can be used as an effective measure to increase maize yield and N use efficiency in the Weibei Dryland in Shaanxi Province. |
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