Study On Nitrogen Uptake By Potatoes And Nitrogen Balance In Farmland Under Drip Fertigation And Sprinkler Fertigation

The shortage of water resources and the environmental effects of nitrogen surplus from nitrogen fertilizer applied in agricultural ecosystem have attracted widespread attention.Now,there have been many reports on the advantages of increased output in drip fertigation and sprinkler fertigation.However,systematic research on the utilization rate of nitrogen fertilizer,nitrogen surplus,nitrogen cycle and balance of three irrigation modes,i.e.drip fertigation,sprinkler fertigation and furrow irrigation,needs to be further strengthened.In this study,the potato?Favorite?field at the southern area of Yinshan Mountain in Inner Mongolia were taken as research objects.In-situ experimental observations were carried out in the field for three years on end.Random block design was used.Fertilization treatment and non-fertilization control treatment of drip fertigation,sprinkler fertigation,and traditional furrow irrigation were set up.Influences of NH₃ and greenhouse gas N₂O emission process,characteristics,intensity and driving mechanism,nitrogen utilization of potato and interception loss of nitrogen in the soil on potato field under different modes of production with irrigation were quantitatively determined.by using ventilation method,static box method and numerical simulation method.The mechanism of nitrogen balance in potato field irrigated by sprinkler fertigation and drip fertigation was revealed.Establishment of nitrogen management index system provides a scientific basis for objectively evaluating the nitrogen management level and environmental effect of sprinkler fertigation and drip fertigation.Data support is provided to explore the principle of production system that is beneficial to achieving the benefits of agricultural production and environmental effects.The results of this study are presented as follows:?1?Results of field observation in potato field showed that compared with traditional furrow irrigation,sprinkler fertigation and drip fertigation has advantages for potato growth.The amount of chemical fertilizer applied in farmland under drip fertigation and sprinkler fertigation and furrow irrigaion is equal,which are 273.0 kg N·ha^-1.The yield of potatoes under drip fertigation ranged from 45.23 to 48.08 t·ha^-1,36.59 to 42.39 t·ha^-1 under sprinkler fertigation,and 29.84 to 35.36 t·ha^-1 under the traditional furrow irrigation from 2015 to 2017.The yield of potato under drip fertigation was 13.4%-17.6%and 36.0%-51.6%higher than that of sprinkler fertigation and furrow irrigation,respectively.The yield of potato under sprinkler fertigation was 19.9%-32.7%higher than that under furrow irrigation.?2?The temporal and spatial distribution of soil moisture in potato field by drip fertigation and sprinkler fertigation was clarified.Drip fertigation and sprinkler fertigation will not produce deep leakage of water.The vertical distribution of moisture in the soil of potato field under drip fertigation and sprinkler fertigation could be divided into the active layer of 0-30 cm,and the distribution of moisture is even.The moisture at layer of 30-40 cm under sprinkler fertigation and 20-30 cm under drip fertigation is changed suddenly.The moisture at layer of 40-60 cm under sprinkler fertigation and 30-40 cm under drip fertigation is slowly reduced.The moisture at the layer of 60-120 cm under sprinkler fertigation,and 40-120 cm under drip fertigation is relatively stable.The moisture at the layer of 0-80 cm under furrow irrigation increases with the increase of depth in the soil,and the wetting layer reaches 80 cm.The horizontal distribution of moisture in the soil was that the highest moisture under drip fertigation is at 0-10 cm at distance from the dripper.The highest moisture under sprinkler fertigation is at 10-20 cm at distance of horizontal direction below the sprinkler.The highest moisture under furrow irrigation is at 40 cm at distance of horizontal direction from the ridge center.?3?The spatial and temporal variations of N in the soil of potato field under sprinkler fertigation and drip fertigation were revealed.The amount of NO₃-N interception in the soil of different modes of production with irrigation was determined.The concentration of NO₃-N at the layers of soil with different modes of irrigation varied significantly on the profile?p<0.01?.NO₃-N content accumulated at the depth of 10-30 cm under drip fertrrigation,and the highest value appeared at 10cm away from dripper and 10-20 cm in depth,averaging 27.58 mg·kg^-1.NO₃-N content accumulated at the depth of 20-40 cm under drip fertigation,and the highest value appeared at 20 cm away from sprinkler and 20-30 cm in depth,averaging 34.52mg·kg^-1.However,NO₃-N content at the depth of 0-30 cm under furrow irrigation is low,and significantly increases at depth of 30-80 cm.The maximum value appeared in 40-80 cm on layer of soil,with an average of 73.66 mg·kg^-1.Average interception of nitrogen at the soil mass of 1-120 cm is 54.6 kg·ha^-1 under drip fertigation,and72.27 kg·ha^-11 under sprinkler fertigation.Nitrogen interception on traditional furrow irrigation was 4.72 times as much as that on drip fertigation,and 3.57 times as much as that in sprinkler fertigation.After three growing seasons of crop,the nitrogen interception of 0-120 cm under traditional furrow irrigation increased in the soil year by year,while the nitrogen interception of drip fertigation and sprinkler fertigation decreased in the soil of potato field gradually.?4?The rules of accumulative nitrogen and distribution of nitrogen in potato organs under sprinkler fertigation and drip fertigation were revealed,and the critical period of nitrogen supplied on the potato was analyzed.The accumulative nitrogen in roots,stems and leaves of potato increased gradually after vegetative growth,and reached the maximum at tube bulking.Nitrogen accumulation of leaves was the highest,with an average of 881.6 mg plant^-1 in potato field under drip fertigation.Nitrogen accumulation of leaves under traditional furrow irrigation was the lowest,with an average of 504.3 mg plant^-1.Nitrogen accumulation of roots,stems and leaves of potato decreased at maturity.There is an increasing trend on nitrogen accumulation of tuber from vegetative growth to maturation.The nitrogen distributive proportion of leaves from vegetative growth to tuber set was the highest.The nitrogen distributive proportion of leaves under drip fertigation was the highest,with an average of 42.6%,and the lowest under traditional furrow irrigation,with an average of 29.9%under three different modes of production with irrigation.The distributive proportion of nitrogen in the tuber was the highest at tuber bulking and maturation.The period from tuber set to tuber bulking for the potato is an important period for supply of N.?5?The effects of sprinkler fertigation and drip fertigation on the emission of N₂O in the soil of potato fields were clarified.Soil moisture content,soil temperature and N₂O emission were positively correlated.Compared with traditional furrow irrigation,drip fertigation and sprinkler fertigation can significantly reduce N₂O emissions and have obvious effect of emission reduction.There were obvious seasonal variations in N₂O emission fluxes of soil in potato fields under different modes of irrigation,and the emission peaks appeared in July and August.The average of accumulative emission of N₂O under drip fertigation was 137.29 mg m^-2,and 164.63 mg m^-22 under sprinkler fertigation,and 373.72 mg m^-22 under furrow irrigation.The Global Warming Potential decreased by 50.0%-65.5%under drip fertigation and by40.7%-59.7%under sprinkler fertigation compared with traditional furrow irrigation.?6?The driving mechanism of process and intensity on the emission of NH₃ from the soil in potato field under sprinkler fertigation and drip fertigation were determined.Compared with traditional furrow irrigation,drip fertigation and sprinkler fertigation can significantly reduce the emissions of NH₃.NH₃ emission fluxes were positively correlated with soil temperature?r=0.85,p<0.01,n=36?,soil moisture?r=0.84,p<0.01,n=36?,NH₄⁺-N?r=0.84,p<0.01,n=36?and NO₃^--N content?r=0.80,p<0.01,n=36?.The emission flux of NH₃ could be determined by the stepwise regression equation determined by soil NH₄⁺-N and soil NO₃^--N content?r²=0.85,n=36,p=0.001?.The emission of NH₃ from potato fields with different modes of irrigation was significantly higher in topdressing period than that in basal fertilizer period.The peak value appeared 2-7 days after topdressing,and the emission of NH₃ was the highest in July and August.The cumulative emission of NH₃in traditional furrow irrigation was the highest,with an average of 118.68 kg·ha^-1,while that in sprinkler fertigation was the lowest,with an average of 69.58 kg·ha^-1.The cumulative emission of NH₃ from drip fertigation in the soil was 33.03%less than that from traditional furrow irrigation,and the cumulative emission of NH₃ from sprinkler fertigation in the soil was 39.83%less than that from traditional furrow irrigation.?7?The characteristics of uptake and utilization for nitrogen from potato under drip fertigation and sprinkler fertigation were clarified.It is clear that the potato field irrigated by sprinkler fertigation and drip fertigation has the level of efficient nitrogen management.Drip fertigation and sprinkler fertigation can significantly increase Nitrogen Use Efficiency,Agronomic Efficiency of Nitrogen and Partial Productivity of Nitrogen.The Nitrogen Use Efficiency was the highest?68.13%-83.84%?under drip fertigation.The Nitrogen Use Efficiency was 65.20%-76.22%under sprinkler fertigation.The Nitrogen Use Efficiency in drip fertigation and sprinkler fertigation is2.50-2.62 times and 2.30-2.50 times higher than that of traditional furrow irrigation.Average nitrogen uptake by crops under drip fertigation is 417.63 kg·ha^-1,and that under sprinkler fertigation is 359.70 kg·ha^-1,and that under furrow irrigation is162.00 kg·ha^-1.?8?The balance law of nitrogen input,output and surplus in potato field under drip fertigation and sprinkler fertigation was revealed.Drip fertigation and sprinkler fertigation significantly reduced the nitrogen surplus in potato field,which was 45.6%-61.8%lower than that of traditional furrow irrigation.The nitrogen leaching loss,NH₃ emission,N₂O emission loss and environmental cost were significantly reduced by sprinkler fertigation and drip fertigation.The applied nitrogen fertilizer is the main input of nitrogen,and the uptake of N for potato and interception of N in the soil are the main export items of nitrogen in potato field for traditional furrow irrigation.The applied nitrogen fertilizer and the mineralized nitrogen in the soil is the main input of nitrogen,and the uptake of N for potato is the main export item of introgen in potato field for drip fertigation and sprinkler fertigation.The main way of nitrogen loss by gas is emission of NH₃.