Effect Of Elevated CO₂ On Soil Carbon And Nitrogen Processes In Maize Field

The increase of atmospheric CO₂ concentration and the change of climate and environment caused by it will inevitably affect the process of crop growth and development,which will directly or indirectly affect the circulation and transformation of nutrient elements in soil.China,as a populous and large agricultural country,faces an increasing population and a declining contradiction of cultivated land,which is one of the major food crops in China and the world,and Shaanxi is one of the main producing areas of maize.Therefore,it is necessary to study the effect of the elevated CO₂ on soil nutrient,especially carbon and nitrogen cycle,in the dry-landed maize field in the arid and semi-arid area of the Loess Plateau,and the negative effect of the current atmospheric CO₂ enrichment on yield and food safety issues have important practical significance.At present,under the condition of elevated CO₂,the crop growth has a lot of related research work at home and abroad,especially for rice,wheat and other C3 crops and nitrogen regulation,has been more mature.However,the study on the effect of elevated CO₂ on C4 crops such as maize is not enough.In particular,the research on soil carbon and nitrogen processes in maize field of dryland is relatively lacking.In response to the increasing CO₂ concentration,the global warming trend high-yielding cultivation of crops lack of theoretical guidance.In this study,OTC field simulation test and field experiment were carried out in the long-term location test field of farmland ecosystem in dryland of Changwu County Agricultural and Soil Conservation Research Institute,Institute of Soil and Water Conservation,Chinese Academy of Sciences.Maize was used as representative crop,two CO₂ concentration?natural atmosphere and 700 ?mol · mol-1?and four water and fertilizer management models?MN290,MN225,N225 and N0?.The improved OTC system was used to simulate the effect of climate change in the field,and the improved OTC was applied to the field experiment to study the effects of atmospheric CO₂ enrichment on the soil carbon and nitrogen processes in dry maize field in arid and semiarid region of Loess Plateau.And to further analyze the mechanism of carbon and nitrogen regulation in maize cropland soil under the condition of increasing CO₂ concentration,aiming at the production of high-yielding cultivated maize and the management of farmland water and fertilizer in arid and semi-arid areas under the increasing current CO₂ concentration provide acertain theoretical basis and technical support.The main conclusions are as follows:1.Improved controllable CO₂ OTC system can accurately control the CO₂ concentration,control error range is small,can be put into trial use.The average temperature of controlled CO₂ OTC increased by 0.4 ? and the relative humidity of air decreased by 3.1% on average,and the difference was not significant.The system could provide the growth conditions close to the natural environment for the crops and could be used for future atmospheric CO₂ enrichment simulation test.2.The results showed that the elevated CO₂ could significantly decrease the soil organic carbon by 17.5% under the condition of no nitrogen and no nitrogen fertilizer in the soil profile of spring maize?p <0.05?,but there was no significant difference between the high nitrogen and the conventional nitrogen level.The results can provide some theoretical basis and data support for optimizing the cultivation techniques of dry-film mulched maize in arid and semi-arid areas of Loess Plateau under the condition of elevated CO₂.3.The effect of elevated atmospheric CO₂ concentration on the cumulative distribution of total nitrogen and inorganic nitrogen?nitrate and ammonium nitrogen?in soil profile of spring maize field was studied.The results showed that the increase of atmospheric CO₂ concentration could significantly reduce the accumulation of total nitrogen and inorganic nitrogen in maize,and the range was 2.8%-8.0% and 32.6%-129.8% at high nitrogen level,respectively.While the accumulation of total nitrogen in the soil was lower than that in the conventional and low nitrogen deficiencies,and the accumulation of NO3--N in the soil at the high nitrogen level was decreased trend,in the R3 and R5 stage showed an increase in the phenomenon.There was no obvious regular effect on the accumulation of ammonium nitrogen in soil during the growth period.The results can provide some theoretical basis and data support for optimizing the cultivation techniques of dry-film mulched maize in arid and semi-arid areas of Loess Plateau under the condition of elevated CO₂.