| The development of fertilizer industry has promoted the increase of grain production and ensured the supply of food security.As human beings continue to apply a large amount of chemical fertilizers in the land,the negative effects of agricultural non-point source pollution are gradually highlighted,which brings great risks to human survival and health.In the future,agriculture will develop at the direction of green and environmental protection,which is of great significance to solve the problem of balance between agricultural production increase and environment.In the dry farming area of the Loess Plateau,the soil layer is deep and the rainfall is uneven,which provides conditions for agricultural non-point source pollution.Therefore,taking different nitrogen management measures in this area has important guiding significance for improving grain crop yield and maintaining ecological environment security.The experiment was carried out at Changwu State Key Agro-Ecological Station.Pioneer 335,a spring maize,was planted with halfplastic film mulching,the experiment was designed by completely randomized grouping.The experiment inclueded four treatments and three replicates,they were:(1)Different nitrogen application rates,0,80,100,130,160,200,250 kgh/hm2 respectively;(2)On the basis of 200 kgh/hm2 nitrogen application,we set up different application ratios of slow-controlled fertilizer and ordinary urea,which took up the proportion 35%+65%,50%+50%,65%+35%respectively;(3)When applying 200 kg/hm2 nitrogen,we set up different nitrification inhibitor concentration,The amount of nitrification inhibitor was 1%,5%,10%and 15%of total nitrogen application respectively.(4)Based on the application of 200 kg/hm2 and 250 kg/hm2 of nitrogen,Measures for straw deep buried was taken.In the experimental treatment zone of Slow-Controlled Fertilizer and nitrification inhibitor,we took root soil sample and measured soil nitrate nitrogen content during the growth period of spring maize.Soil and plant samples were taken during the harvest period of spring maize,and measured soil nitrate nitrogen content and grain yield,to confirm the effects of different nitrogen managements on soil nitrate nitrogen leaching and spring maize grain yield.The experiment was carried out from in 2017-2018 for two years.The main results are as follows:(1)Appropriate amount of nitrogen application promoted the yield of spring maize and reduced soil nitrate nitrogen leaching and accumulation.The grain yield of spring maize increased at first and then decreased within the range of 0～250 kg/hm2 of nitrogen application,and functional simulation analysis showed that the maximum yield could be achieved when nitrogen application was 227 kg/hm2.Soil nitrate nitrogen content remained at a reasonable low level when nitrogen application within the range of 0～160 kg/hm2,which would not cause a large amount of leaching and accumulation.When the amount of nitrogen applied exceeded 160kg/hm2,the soil nitrate nitrogen leached into deep soil layer significantly,resulting in a sharp increase of soil nitrate nitrogen accumulation in the soil 0-300 layer.Therefore,the threshold of nitrogen application for soil nitrate nitrogen leaching and accumulation is 160 kgh/hm2.When the nitrogen application rate was 200 kg/hm2,the total nitrogen uptake and nitrogen use efficiency of the plant reached the highest level.When the nitrogen application rate reached 250 kg/hm2,grain yield of spring maize and nitrogen use efficiency were reduced.(2)The application of slow-controlled fertilizer can effectively control the leaching of soil nitrate nitrogen,and reduce the accumulation of soil nitrate nitrogen.Among all treatments,when slow-controlled fertilizer and ordinary urea application proportion was each half,the soil nitrate nitrogen leached into deep soil layer was the least,reached the best control effect.The application of slow-controlled fertilizer reduced soil nitrate nitrogen accumulation in 0-300 cm soil layer by 37.39%.The application of slow-controlled fertilizer reduced the root layer soil nitrate nitrogen content at different growth stages of Spring Maize,and there was no significant difference among all slow-controlled fertilizer treatments.The application of slow-controlled fertilizer reduced the grain yield of spring maize,mainly because slow-controlled fertilizer efficiency released slowly in the early stage of spring maize growth,which is not synchronized with nitrogen uptake by spring maize roots,and reduced the total nitrogen uptake and nitrogen use efficiency of crops,at last reducing the spring maize yield.(3)Appropriate amount of nitrification inhibitors can effectively prevent the leaching of soil nitrate nitrogen and reduce the accumulation of soil nitrate nitrogen.With the increase of nitrification inhibitors dosage,the risk of soil nitrate nitrogen leaching to deep soil increased,and the accumulation of soil nitrate nitrogen tended to increase.The nitrate nitrogen content in soil profile was the lowest when the amount of nitrification inhibitor was 1%of nitrogen application,and the nitrate nitrogen accumulation in 0-300 cm soil layer was the lowest(Compared with the control,it decreased by 55.68%).The application of nitrification inhibitors significantly reduced the nitrate nitrogen content in root layer of Spring Maize at growth stages,but there was no significant difference between different amount of nitrification inhibitor treatments.Compared with the treatment without nitrification inhibitor,adding nitrification inhibitor had no positive effect on the yield of spring maize,but appropriate concentration of nitrification inhibitor had inhibitory effect on soil nitrate nitrogen leaching.(4)Straw deep buried can effectively control the leaching of soil nitrate nitrogen,and reduce the accumulation of soil nitrate nitrogen.When nitrogen application was 200 kg/hm2,the accumulation of soil nitrate nitrogen in 0-300 cm soil layer was reduced by 25.29%due to straw deep buried.When nitrogen application was 250kg/hm2,the accumulation of soil nitrate nitrogen in 0-300 cm soil layer was reduced by 5.49%due to straw deep buried.When apply the same amount of nitrogen,the measures of straw burying can effectively improve the grain yield of spring maize,promote the absorption of nitrogen by plants,and improve the nitrogen use efficiency of crops.In summary,under the conditions of local climate and experimental management,the maximum yield of spring maize can be obtained when the amount of nitrogen applied reaches 227.38 kg/hm2 through mathematical simulation analysis in the dry farming area of the Loess Plateau.The measure of straw deep buried can promote the yield of spring maize,the measures of controlling the amount of nitrogen applied,deep burying of straw and using slow-controlled fertilizer can control the leaching and accumulation of nitrate nitrogen in soil.Nitrification inhibitor of 1%nitrogen application could inhibit the leaching of soil nitrate nitrogen. |
PDF Full Text Request