| In order to explore the effects of continuous application of controll loss urea on crop yield,nitrate nitrogen content and nitrogen use efficiency of winter wheat/summer maize rotation crops,and provide a theoretical basis for the rational application of controlled loss of urea,a field experiment of control loss urea was conducted in a typical rotation area of winter wheat/summer corn in Fengqiu,Xinxiang from October 2016 to September 2018.This study systematically analyzed the effects of control loss urea on main growth indices of winter wheat,yield and yield components of winter wheat-summer maize,nitrogen use efficiency and soil nitrate nitrogen accumulation.The experiment was designed to have four treatments on nitrogen fertilizer management,application of control loss urea as basal(CLU),application of conventional urea split as basal and topdressing(U+U),aplication of control loss urea as basal and conventional urea as topdressing(C+U),and application of conventional urea as basal and control loss urea as topdressing(U+C),and four N application rates for each treatment,0,80,160 and 240 kg·hm-2.All the treatments,except Treatment CLU,received 60% the fertilizer as basal and 40% as topdressing at the jointing stage of winter wheat and at the flaring stage of summer maize.The main results were as follows:(1)The main growth indices(SPAD,leaf area index,population amount and above-ground dry matter accumulation)of winter wheat without nitrogen treatment were significantly lower than those of nitrogen fertilizer management during the whole growth period.In terms of all nitrogen management treatments,SPAD and population amount were significantly increased at the regreening stage,while leaf area index and above-ground dry matter accumulation were significantly increased at the heading and maturity stage,respectively.The four growth indices under all treatments in the wheat season of 2017-2018 were significantly higher than that of2016-2017.Under the conditions of equal nitrogen supply,the four growth indices of application of control loss urea as basal were all higher than those of the other three nitrogen treatments.(2)The grain yield of each nitrogen fertilizer treatment increased first and then decreased slowly with the increase of nitrogen application rate.When the nitrogen application rate was 160~240kg·hm-2,there was no significant difference in grain yield among different nitrogen management treatments in the wheat seasons of 2016-2017 and 2017-2018,and the year,nitrogen fertilizer type and nitrogen application rate had an extremely significant impact on grain yield.When the nitrogen application rate was 160~240 kg·hm-2,there was no significant difference in grain yield among application of control loss urea as basal and application of control loss urea as basal and conventional urea as topdressing in the 2017 corn season.there was no significant difference in grain yield among application of control loss urea as basal and application of conventional urea as basal and control loss urea as topdressing in the 2018 corn season.and the year and nitrogen application had extremely significant effects on the maize grain yield.The results of four seasons of winter wheat-summer maize rotation showed that the grain yields of winter wheat and summer maize treated with application of control loss urea as basalwere higher than those of the other three nitrogen treatments when the nitrogen application rate was 160 kg·hm-2.Compared with no nitrogen application,the crops with application of control loss urea as basal increased by 168.6%,116.1%,86.6% and 106.6%,respectively,for 4 consecutive seasons.There was a significant secondary correlation between grain yield and nitrogen application rate of winter wheat and summer maize under different nitrogen fertilizer management.(3)Soil nitrate nitrogen(0~20 cm)of each treatment showed a linear upward trend with the increase of nitrogen application,while the soil nitrate nitrogen content under all nitrogen treatments showed a no obvious change trend when the nitrogen fertilizer management did not exceed the range of 80 kg·hm-2.In the critical growth period of winter wheat and summer maize,the soil nitrate nitrogen content of each nitrogen treatment was significantly higher than that of no nitrogen treatment.The soil nitrate nitrogen content at the seedling stage of winter wheat-summer maize under the application of control loss urea as basal was higher than that of the other three nitrogen treatments,while it was lower than that of the other three nitrogen treatments at the maturity stage.With the planting year,the soil nitrate nitrogen accumulated in the deep layer at winter wheat maturity stage,and the soil nitrate nitrogen accumulation in 2017-2018 wheat season was significantly higher than that in 2016-2017 wheat season.The soil nitrate nitrogen accumulation under different nitrogen fertilizer management treatments increased with the increase of nitrogen application rate.And when the nitrogen application rate was in the range of160~240 kg hm-2,it of application of control loss urea as basal treatment was lower than that of the other three nitrogen treatments.It mainly occurred in the 0~160 cm soil layer and accumulated in a large amount of 60~120 cm soil layer,with a peak at 80~100 cm.(4)Nitrogen application could significantly increase above-ground nitrogen accumulation and nitrogen use efficiency in winter wheat-summer maize.When the nitrogen application rate was in the range of 160~240 kg·hm-2,the continuous topdressing of controlloss urea or common urea treatment for 4 consecutive seasons had no significant effect on crop grain nitrogen accumulation.Among them,there were significant differences in nitrogen of grains under application of control loss urea as basal treatment,which were 101.5 kg·hm-2,89.6 kg·hm-2,68.3 kg·hm-2 and 70.8kg·hm-2 higher than those without nitrogen treatment,respectively.After two years’ planting of winter wheat-summer maize,the agronomic efficiency,partial productivity and nitrogen uptake efficiency of all treatments decreased significantly with the increase of nitrogen application rate,while the contribution rate increased first and then decreased slowly.When the nitrogen application rate was 160 kg·hm-2,and the nitrogen agronomic efficiency,nitrogen partial productivity,nitrogen absorption efficiency,nitrogen contribution rate,average annual yield and average annual output value of application of control loss urea as basal treatment treatment were significantly higher than those of other three nitrogen treatments.Although the cost of urea loss by base application was higher,the average economic benefit could be obtained by eliminating the cost of topdressing fertilizer.In summary,when the nitrogen application rate was 160 kg·hm-2,the treatment of application of control loss urea as basal not only improving crop yield and nitrogen fertilizer utilization rate,the groundwater pollution caused by soil nitrate nitrogen leaching into deep soil could be alleviated,so as to achieve the purposes of fertilizer saving,high efficiency and environmental friendliness. |
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