Effects Of Straw Incorporation From Rapeseed-rice Rotation On Soil Nutrients And Loss Of Nitrogen,phosphorus And COD In Runoff

Excessive application of chemical fertilizers destroyed soil environmental quality.Runoff leaching increased the nitrogen and phosphorus losses in soil and increased nitrogen and phosphorus concentration in water.Chaohu Lake,as one of the five largest freshwater lakes in China,has a serious agricultural non-point source pollution problem.It is urgent to ensure crop yield and reduce agricultural non-point source pollution for the protection of Chaohu Lake.Straw production in China ranks first in the world,and straw pollution has become one of the main factors of agricultural non-point source pollution.Therefore,this study aims to explore the impact of straw incorporation on the surrounding water environment.Through field plot experiment,six treatments were set up:no straw returning+no fertilization treatment(CK),straw incorporation+no fertilization treatment(S),no straw incorporation+conventional fertilization treatment(F),straw incorporation+conventional fertilization treatment(SF),straw incorporation+conventional fertilization treatment(SFR),straw natural composting+conventional fertilization treatment(SC).To study the effects of different treatments on farmland nutrients and runoff in Chaohu Lake Basin.The main results are as follows:1)straw incorporation increased soil nutrient content.In rape season,compared with F,SF and SFR could significantly increase the contents of organic matter,total phosphorus,alkali-hydrolyzed nitrogen and available phosphorus,and significantly reduce soil pH value.In rice season,SF and SFR could significantly increase total phosphorus content compared with F treatment.2)Straw incorporation increased the number of soil microorganisms,and in terms of the degree of influence,fungi>bacteria>actinomycetes.Compared with F,SF and SFR in the rape season increased bacterial number 28.3%,11.7%,fungi quantity 53.9%,34.2%,actinomyces quantity 18.6%,8.2%;In the rice season,SF and SFR in the rape season increased bacterial number 31.2%,9.1%,Fungi quantity 106.6%,60.7%,Actinomyces quantity 4.1%,-5.7%.3)The total nitrogen loss from runoff was significantly reduced by straw incorporation treatment,because straw incorporation treatment increased the total phosphorus and COD content to a certain extent,thus increasing the risk of total phosphorus and COD loss,but did not reach significant difference,which was mainly affected by the current runoff loss,and straw incorporation treatment reduced the runoff loss.In 2017,compared with F treatment,total nitrogen loss of SF and SFR treatment decreased by 25.6%?33.6%and 25.8%?40.0%in rapeseed season,21.4%?34.0%and 24.0%?42.2%in rice season;In rapeseed season,decreased by 16.9%?19.8%and 27.1%?29.4%respectively in rapeseed season,and 7.9%-33.3%and 24.2%-44.6%in rice season.4)SC reduced crop yield,significantly increased the risk of loss of nitrogen,phosphorus and COD,and posed a great threat to water quality in Chaohu Lake Basin.In 2018,compared with SFR,the loss of nitrogen,phosphorus and COD in SC treatment increased by 34.8%-53.3%,61.7%?84.8%,66.9%-86.6%in rape season,90.2%?158.3%,94.3%?122.1%and 20.6%?30.1%in rice season,respectively.