| Object:Autumn tillage is an important process of agricultural production in northern Xinjiang.A reasonable autumn tillage method will improve the water storage,salt suppression and fertilizer control ability of seasonal freeze-thaw soil,thereby improving the soil tilth of spring sowing.At present,there were few studies on autumn tillage control technology and lack of systematic theoretical system.Therefore,this thesis aims to explore the regulation effect of autumn tillage on soil water-heat-salt-nitrogen status and spring sowing soil tilth during seasonal freeze-thaw period in northern Xinjiang,so as to provide reference for improving spring sowing soil moisture and preventing soil salinization in northern Xinjiang and similar arid and semi-arid areas.Methods:Based on the two-year micro-field experiment,five autumn tillage treatments were set in this study,namely,tillage（FG）,no-tillage（MG）,ridge and furrow alternation（LG）,tillage-straw mulch（FJ）and tillage-activated charcoal mulch（FH）.The field was prepared in a randomized block design with 3replicates.In this thesis,field monitoring and indoor analysis were used to carry out experimental research.By analyzing the spatial-temporal variation and interaction relationship of soil water-heat-salt-nitrogen,the regulation mechanism of autumn tillage on soil water-heat-salt-nitrogen migration and spring sowing soil moisture during seasonal freezing and thawing period was revealed.Results:（1）There was a significant correlation between soil temperature gradient and air temperature（P<0.01）.Compared with FG treatment,MG,LG,FH and FJ treatments all weakened the correlation between soil temperature and air temperature,and reduced the range of soil temperature rise and fall and the day variation coefficient of soil temperature during the whole freezing and thawing period.The ability to maintain the stability of soil temperature sequence is FJ>FH>LG>MG>FG.Compared with FG treatment,the thermal insulation effect of MG,LG,FH and FJ treatments during freezing period was strengthened,and FH and FJ treatments had more obvious advantages in improving soil thermal status before spring sowing.（2）During the whole seasonal freeze-thaw period,the temporal-spatial changes of soil moisture content and electrical conductivity in the tillage layer（0～60 cm）were similar,which followed the rule of‘salt going with water’.During the freezing period,LG,FH and FJ treatments promoted the upward migration of soil water,heat and salt,and improved the soil water and heat status of the tillage layer,but showed a negative effect on soil salt control.During the thawing period,FG,MG and LG treatments were significantly affected by surface evaporation,soil water and salt migrated upward together,soil water loss and salt return were serious.FH and FJ treatments significantly weakened the influence of surface evaporation and promoted the synergistic downward migration of soil water and salt under the effect of surface cover,and the soil water storage and salt suppression were the best.（3）The spatial-temporal variation of soil nitrate nitrogen was the most significant response to hydrothermal movement,and the difference between different autumn tillage treatments was the most obvious.During freezing period,the content of soil nitrate nitrogen in FH and FJ treatments was negatively correlated with soil temperature gradient（P<0.05）,and positively correlated with humidity gradient（P<0.05）,which was beneficial to reduce soil heat loss and promote the accumulation of soil moisture and nitrate nitrogen in tillage layer.During the melting period,the content of soil nitrate nitrogen in FH and FJ treatments showed a significant quadratic function relationship with soil temperature gradient（P<0.05）,and a significant positive correlation with humidity gradient（P<0.05）,which was beneficial to reduce the leaching loss of nitrate nitrogen.During the whole seasonal freeze-thaw period,the interaction among water,heat and nitrate nitrogen in FH and FJ treatments was the best,showing a very significant correlation（P<0.01）.FH and FJ treatments showed obvious advantages in optimizing the synergistic migration mechanism of soil water,heat and nitrate nitrogen.Similarly,the interaction between soil ammonium nitrogen,total nitrogen and soil water and heat under FH and FJ treatments was significantly stronger than that under FG,MG and FJ treatments,which further proved the feasibility of regulating soil moisture by autumn tillage.（4）Overall,FH and FJ treatments provide good water,heat and nutrient conditions for cotton emergence during spring sowing,and are the most suitable autumn tillage methods for promotion in northern Xinjiang.On the premise of ensuring the emergence of crops,the pure nitrogen application amount of 40.66 kg·hm-2and 50.03 kg·hm-2can be reduced in theory,which is beneficial to energy conservation and emission reduction and efficient utilization of agricultural water and soil resources,and provides guidance for optimizing irrigation and fertilization scheme in engineering. |
PDF Full Text Request