| In order to increase crop yield and nitrogen use efficiency of winter wheat-summer soybean rotation system in Yili Valley and reduce nitrogen loss in farmland.Under field experiment conditions,winter wheat-summer soybean rotation system was taken as the research object.Four nitrogen application levels were set in the previous cropping season:0 kg·hm-2(WN0),104 kg·hm2(WN1),173 kg·hm-2(WN2),242 kg·hm-2(WN3),and three nitrogen application levels in the later cropping season were 0 kg·hm-2(SN0),69 kg·hm-2(SN1),138 kg·hm-2(SN2),respectively.Effects of nitrogen on soil ammonia volatilization loss,soil nitrogen,crop yield and nitrogen use efficiency.The aim is to provide theoretical basis and technical support for annual rational nitrogen application in winter wheat-summer soybean rotation system in Yili Valley.The main results are as follows:1.Soil ammonia volatilization mainly occurred within 2 weeks after fertilization,and reached its peak in 2 d～4 d after fertilization.The loss of ammonia volatilization increased with the increase of the amount of nitrogen applied in the season,and the higher the amount of nitrogen applied in the season,the higher the ammonia volatilization rate and the accumulation amount of ammonia volatilization were.The total annual ammonia volatiles loss of farmland soil ranged from 22.23 kg·hm-2 to 48.52 kg·hm-2,equivalent to 6.95%·8.18%of the annual nitrogen application.The ammonia volatilization loss under different fertilization treatments in winter wheat season reached 19.62 kg·hm-2～34.40 kg·hm-2,accounting for 66.03%of the annual ammonia volatilization loss.The loss of ammonia volatiles during the annual nitrogen application in soybean season was 8.98 kg·hm-2～13.86 kg·hm-2,accounting for 33.97%of the total ammonia volatiles during the annual nitrogen application.2.Winter wheat season N application significantly increased winter wheat and summer soybean harvest after the soil nitrate nitrogen,ammonium nitrogen content,and increases with the increase of N application rate,and N application rate,the greater the soil inorganic nitrogen residual amount is larger,in winter wheat after harvest,characteristic n application rate of 242 kg·hm-2,the maximum soil inorganic nitrogen retention rate 40.05%,significantly higher than WN1,WN2 processing,but WN1 treatment with WN2 there was no significant difference;The residual nitrate and ammonium nitrogen in the soil after summer soybean harvest were further increased by applying nitrogen in summer soybean season.When the nitrogen application amount was 138 kg·hm-2,the residual rate of inorganic nitrogen in the soil reached 31.80%,significantly higher than 69 kg·hm-2,which aggravated the leaching loss of soil nitrate nitrogen.3.Nitrogen application of 173 kg·hm-2 in wheat season was beneficial to increase dry matter accumulation in all organs of winter wheat after flowering,increase dry matter transfer volume before flowering and its contribution to grains,promote dry matter transfer from vegetative organs to grains and increase yield.Nitrogen application in the previous wheat season also significantly affected dry matter accumulation in the following summer soybean,which increased with the increase of nitrogen application,but there was no significant difference between WN2 treatment and WN3 treatment.Nitrogen application of 69 kg·hm-2 in summer soybeans during the season promoted the dry matter accumulation of organs after flowering and increased the total dry matter accumulation,but nitrogen application of more than 69 kg·hm-2 in summer soybeans during the season had no significant effect on pod,grain and total dry matter accumulation.4.Nitrogen application in wheat season was beneficial to the increase of panicle number,grain number per panicle and 1000-grain weight of winter wheat,thereby increasing wheat yield.When applying 173 kg·hm-2 nitrogen in wheat season,the maximum yield of winter wheat was 7828.64 kg·hm-2,which increased by 35.45%,16.77%and 6.26%respectively compared with WN0,WN1 and WN3 treatments.Nitrogen application in the previous wheat season and in the current summer soybean season significantly increased the number of pods and grains of summer soybean and promoted the increase of summer soybean yield.With the increase of nitrogen application in the previous wheat season,summer soybean yield showed an increasing trend,but there was no significant difference in summer soybean yield when nitrogen application reached 173 kg·hm-2 and 242 kg·hm-2.On the basis of the previous wheat season of 173 kg·hm-2 nitrogen application,the summer soybean yield reached the maximum of 2988.93 kg·hm-2 when the summer soybean was applied with 69 kg·hm-2 nitrogen application.WN2SN1 was beneficial to increase the yield and nitrogen utilization of winter wheat and summer soybean. |
