Effects Of Water And Nitrogen Management On Peanut Yield,Water And Nitrogen Use,and Farmland Carbon Balance

In order to reveal the relationship between water,carbon and nitrogen consumption and utilization of the peanut “soil-plant” system in dryland and to establish a scientific water and nitrogen agriculture management method,this paper takes “Nong hua 9” as the experimental research object and adopts a split zone test design method,different irrigation modes(full irrigation during the whole growth period,W0;regulated deficit irrigation during flowering and fruit filling periods,W1)are the main areas,and the upper limit of irrigation for W0 and W1 is the field water holding rate(percentage of soil volume),the irrigation limit of W0 is 75%~80% ?f,and the irrigation limit of W1 is 55%~60% ?f.The other growth periods are the same as W0,with different pure nitrogen levels(N0,0 kg·hm-2,N1,50 kg·hm-2,N2,100 kg·hm-2 and N3,150 kg·hm-2)are sub-regions.The effects of different irrigation modes and nitrogen fertilizers on peanut growth characteristics,accumulation and distribution of dry matter and carbon and nitrogen,yield,water and nitrogen use efficiency,and farmland carbon balance were studied.The test results are as follows:(1)Water and nitrogen fertilizer have significant effects on peanut plant height,leaf area and dry matter accumulation.Increasing nitrogen fertilizer 100 kg·hm-2 can significantly increase peanut plant height,leaf area and dry matter accumulation.adjusted deficit irrigation(W1)mode is more conducive to dry matter accumulation,which is 9.28%(2018)and 5.90%(2019)higher than full irrigation(W0)mode.Under adjusted deficit irrigation(W1)mode,adding 100 kg·hm-2 of nitrogen fertilizer can promote peanut plant height and leaf area growth,while significantly increasing peanut dry matter accumulation.(2)Water and nitrogen fertilizers have significant effects on peanut yield,hundred fruit weight and hundred kernel weight.Peanut production in 2018 and 2019 was the highest under the W1 irrigation mode with an additional 100 kg·hm-2 nitrogen fertilizer,with values of 5850.08 kg·hm-2(2018)and 5930.88 kg·hm-2(2019),respectively.The two-year peanut weight and hundred-kernel weight were the highest under the W1 irrigation mode with 50 kg·hm-2 nitrogen fertilizer.The two-year peanut weight was 198.41 g(2018)and 199.05 g(2019),two-year peanut hundred kernel weight 85.43 g(2018)and 85.78 g(2019).(3)Water and nitrogen fertilizers have significant effects on regulating carbon and nitrogen accumulation in peanuts.adjusted deficit irrigation(W1)mode can significantly increase the carbon and nitrogen content and carbon nitrogen ratio(C/N)of leaves and stems.With the increase of nitrogen application,the carbon content of leaves and stems increased first and then decreased;while the nitrogen content of leaves and stems showed an increasing trend.The carbon nitrogen ratio(C/N)of peanut leaves and stems behaved differently during the whole growth period.The carbon nitrogen ratio(C/N)of the leaves increased and then decreased with the increase of nitrogen application rate,with an increase of 100 kg·hm-2 When the nitrogen fertilizer was applied,the carbon nitrogen ratio(C/N)of the leaves was higher,which could maintain the carbon nitrogen accumulation balance,which was beneficial to the increase of peanut yield.The carbon nitrogen ratio(C/N)of peanut stems increased with the increase of nitrogen application Decreased,the(C/N)of the stem was lower when 100 kg·hm-2 nitrogen fertilizer was added,which was beneficial to the transport of carbon assimilation by the stem and to maintain a balanced source-sink relationship.The carbon and nitrogen content of leaves and stems had a significant positive correlation with yield.When 100 kg·hm-2 of nitrogen fertilizer was added in the W1 irrigation mode,the carbon and nitrogen content and yield of leaves and stems were the highest.(4)Water and nitrogen fertilizers have significant effects on the carbon balance of peanut farmland.Under different water and nitrogen fertilizers,the peanut farmland ecosystem showed carbon sinks.Compared with full irrigation(W0),adjusted deficit irrigation(W1)reduced the cumulative emissions of soil CO2 by 7.21%(2018)and 7.45%(2019),but increased plant carbon sequestration and promoted net carbon input to farmland Increase.The cumulative CO2 emissions of soil during the whole growth period increased with the increase of nitrogen application,while the carbon sequestration of the plant first increased and then decreased.The net carbon input of the farmland was the highest when nitrogen fertilizer was added at 100 kg·hm-2.Adding nitrogen fertilizer under both irrigation modes can significantly increase the net carbon input of the farmland,and the increase in nitrogen fertilizer 100 kg·hm-2 is the most obvious in the adjusted deficit irrigation(W1)mode.The net carbon input of the two-year farmland is 428.70 kg·hm-2(2018)and 456.97 kg·hm-2(2019).(5)Water and nitrogen fertilizers have significant effects on peanut water and nitrogen use efficiency.When adding nitrogen fertilizer 100 kg·hm-2,the agronomic utilization efficiency of nitrogen fertilizer,nitrogen fertilizer absorption and utilization rate of grain and apparent nitrogen recovery rate were the highest in two years.At the same time,the water use efficiency was significantly increased by 26.79%(2018)and 28.10%(2019).Under adjusted deficit irrigation(W1)mode,the water and nitrogen utilization efficiency of peanut can be further improved.In summary,adding 100 kg·hm-2 of nitrogen fertilizer to peanut farmland under adjusted deficit irrigation(W1)mode can significantly promote the use of water and nitrogen by peanuts,increase peanut yield,improve carbon and nitrogen balance in plants,and reduce soil CO2 emissions.Improving the capacity of farmland net carbon input is the best way to manage water and nitrogen in order to achieve water and fertilizer reduction,carbon reduction,and stable carbon production.