| Agriculture is an important greenhouse gases emission source.Tillage,fertilizer and other farming measures will not only cause various physical and chemical changes in farmland ecosystem,but also bring about a significant impact on the global climate change.Rainfed agriculture is an essential part of agriculture,it is of great importance to study the effect of different farming measures on greenhouse gases emission and develop the reduction measures for the implementation of rainfed agriculture sustainable development.In this study,the experiments were carried out in Hohhot Wuchuan County which was typical semi-arid sub-humid area.Potato was the experiment crop.Field experiments were carried out as well as pot experiment and related indoor experiments in 2014 to 2015 to quantitatively analyze the impact of different farming measures to farmland soil greenhouse gases emission and potato production.The experiments involved crop rotation and continuous cropping,plastic film mulching and microbial fertilize three aspects.The results showed:?1?Rainfed potato field was the source of N2O.The results showed that there was a significant positive correlation between potato field N2O emission flux and 525cm soil moisture.And this correlation had 2 to 5 days lag.The correlation between N2O emission flux and 525cm soil temperature was negatively.Comprehensive analysis the two-year rotation system?20142015?showed that the cumulative N2O emission of crop rotation were reduced by 42.9%45.4%?P <0.01?than that in continuous cropping.Compared to no film mulching,film mulching and film-uncovering after flowering period decreased the cumulative N2O emissions by 43.6%?P<0.01?and 51.6%?P<0.01?respectively by increasing the soil temperature and humidity and the membrane blocking effect.?2?Rainfed potato field was the sink of atmospheric CH4.Affected by methaneoxidizing bacteria,there was significantly negatively correlated?P <0.05?between the farmland CH4 absorption and 5cm soil water content.That 5cm soil moisture increased,the CH4 absorption reduced.Comprehensive analysis the two-year rotation system?20142015?showed that the cumulative CH4 absorption of crop rotation increased by 42.9%45.4%?P <0.01?than that in continuous cropping.Film mulching covered the whole potato growing period had no significant impact on CH4 absorption while film-uncovering after flowering period reduced CH4 absorption in potato field.?3?The water requirements of potato were very big.Precipitation and its seasonal distribution had a great impact on potato yield.The results of 20142015 field experiments showed that water consumption in crop rotation was higher than that in continuous cropping ever year,but the potato production of crop rotation improved 15.4%22.9%?P <0.01?.Compared to film mulching,the treatment of film-uncovering after flowering period increased potato yield and water use efficiency better.?4?Bacillus megaterium could transform the soil inorganic nitrogen into soil microbial nitrogen.Microbial fertilizer with Bacillus megaterium reduced the relative abundance of Nitrospirae and nitrification.During the test,the cumulative N2O emission of microbial fertilizer treatment decreased by 4%53% under different nitrogen levels.In addition,with the fertilizer concentration increased,the reduction effect gradually strengthened.Bacillus megaterium applied to farmland as a buffer agent of nitrogenous fertilizer,and with the growth of crops,Bacillus megaterium gradually died and the microbial nitrogen would be decomposed utilized again.The results show that in the arid and semiarid areas in northern China,Farming measures like crop rotation,platic film mulching?especially film-uncovering after flowering period?,and microbial slow-release fertilizer could control greenhouse gases emission in rainfed farm land well,then promote sustainable development in dry land farming. |
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