| At present,the phenomenon of secondary salinization of facility soil caused by excessive water and fertilizer application is common and serious.At the same time,the greenhouse gas emissions of facility vegetable fields are significantly higher than those of other farmlands due to the high application amount and frequency of water and fertilizer.On the other hand,the large amount of straw produced in rural areas every year needs to find a reasonable application path.In order to explore the technical ways of straw mulching to alleviate vegetable land salinization and greenhouse gas emissions in vegetable fields,we conducted straw mulching experiments for two consecutive years from 2019 to 2020 and 2020 to 2021,taking advantage of the idle stubble period of plastic greenhouses in the summer high temperature season.Using wheat straw as material,set mulching amount:No mulching(N),medium mulching(5000kg/ha;M),high mulching(10000kg/ha;H)and soil moisture:wet treatment(90%soil relative humidity,W),submergence treatment(keep a 5 cm water layer,S)a total of 6 treatment combinations of two factors were used to observe the effects of different straw mulching treatments on soil physical and chemical properties and greenhouse gas emissions,as well as the effects on the growth of subsequent vegetables.The results are as follows:1 The decomposition rate of straw was significantly higher in medium mulching than in high mulching;Flooding treatment was significantly higher than wet treatment.Straw mulching can significantly reduce the excessive available nitrogen content in the soil and alleviate the degree of soil salinization.Straw mulching had no significant effect on soil available phosphorus content,but it could significantly increase soil available potassium,total nitrogen,total phosphorus and total potassium content and increase soil nutrients.The improvement effect of high-level mulching on the above soil indicators was greater than that of medium-level mulching;compared with the wet treatment,the flooding treatment resulted in a decrease in the contents of various nutrients in the topsoil.Straw mulching can significantly reduce the excess available nitrogen content in the soil and alleviate the degree of soil salinization.Straw mulching had no significant effect on soil available phosphorus content,but it could significantly increase soil available potassium,total nitrogen,total phosphorus and total potassium content and increase soil nutrients.The improvement effect of high mulching amount on the above soil indexes was greater than that of medium mulching amount;Compared with wet treatment,water flooding treatment resulted in the decrease of various nutrient contents in topsoil.3 Straw mulching can significantly increase soil organic carbon,microbial carbon,microbial nitrogen content,and soil urease,acid phosphatase and invertase activities,and the increase rate of high mulching is significantly higher than that of medium mulching;Under the same straw mulching,the water-flooded treatment had a higher effect on soil microbial carbon,microbial nitrogen and the activity of three soil enzymes than the wet treatment,which may be caused by the higher amount of straw decomposition under the flooding treatment than the wet treatment.4 In the summer high temperature season of straw mulching in this experiment,straw mulching can reduce the soil surface temperature,and the cooling effect of high mulching is significantly higher than that of medium mulching;Wet flooding treatments can significantly reduce soil surface temperature,and the effect of flooding treatment is more significant.The decrease of soil surface temperature in high temperature season may have beneficial effects on the improvement of various physical and chemical indicators of soil.5 Fluorescence quantitative analysis of 16sRNA,AOAamoA,AOBamoA and other genes showed that straw mulching could significantly increase the total amount of soil bacteria,while different soil moisture had little effect on this.Straw mulching can significantly reduce the nitrifying denitrifying bacterial population,which may be related to the decline in soil surface available nitrogen content due to straw mulching.6 Straw mulching can significantly reduce nitrogen leakage 30 cm below the soil surface of vegetable fields,and the effect of high mulching is significantly higher than that of medium mulching;Compared with the wet treatment,the nitrogen leakage at 30 cm below the soil surface of the vegetable field was significantly increased under the flooded treatment.7 During the summer high temperature season of this experiment,straw mulching led to a significant increase in CO2 and CH4 emissions in vegetable fields,while N2O emissions decreased significantly,and the effect of high mulching was significantly higher than that of medium mulching;Compared with wet treatment,flooding mulching significantly increases CH4 emissions,but reduces N2O emissions;Straw mulching was conducive to increasing the ratio of N2O produced by nitrification,and the increase in high mulching was greater than that in medium mulching;compared with wet treatment,flooding treatment significantly improved the ratio of N2O produced by denitrification.8 Cucumbers are planted in autumn after mulching in summer,and tomatoes are planted in spring the following year.The results showed that summer straw mulching could significantly increase the yield of subsequent cucumbers and tomato,and reduce field N2O emissions,and the improvement effect of high mulching was significantly higher than that of medium mulching.9 Compared with the first year mulching,the effects of straw mulching on soil improvement,greenhouse gas emission reduction and nitrogen leakage reduction and crop yield improvement were significantly improved for two consecutive years,indicating that continuous straw mulching may achieve better results.In conclusion,straw mulching in the free stubble in the summer high temperature season of plastic greenhouses can effectively improve the physical and chemical properties of soil in salinized vegetable fields,reduce greenhouse gas emissions and nitrogen leakage,and improve the yield of subsequent crops,which has an important value of popularization and application. |
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