Soil Aggregate Composition Characteristic And Its Effects On Tomato Yield And Fruit Quality In The Soil Amended With Straw And Lime In Greenhouse

In recent years,facility agriculture has developed rapidly.While meeting the supply of anti-season vegetables,it has become an important production method for farmers to increase production and income.However,due to the high frequency of multiple cropping,the absence of natural rainfall and the large amount of fertilizer used throughout the year,a series of problems such as structural deterioration of the facility soil,decreased fertility,secondary salinization and heavy metal accumulation have occurred.Carrying out long-term positioning fertilization research on the composition of aggregates and distribution of heavy metals in facility soil is of theoretical significance and practical value for improving the fertility of facility soil and ensuring the safe production of agricultural products.To this end,based on the greenhouse tomato long-term fertilization positioning experiment base of Shenyang Agricultural University,this paper studied the positioning application of chicken manure(M),straw(R),quicklime(Ca),potassium sulfate(K)and different combinations for 10 consecutive years.Compound fertilizers have an effect on the particle size composition and stability of water-stable aggregates in soil.The distribution rules of heavy metals(Cr,Cd,Hg,Pb,As,Cu,Zn)in different soil aggregate particle sizes have been analyzed.The relationship between the accumulation of heavy metals in tomato fruits and the content of heavy metals in each grade was discussed.On this basis,the effects of excessive Cd and Pb application on the composition and stability of aggregates in soil were studied through soil culture experiments.With a view to providing data support and theoretical reference for scientific application of organic fertilizer and long-term safe and effective use of protected areas.The main findings are as follows:(1)Different fertilization treatments can promote the formation of large particle aggregates in the soil and reduce the content of fine particle aggregates.Among them,the content of> 0.25 mm agglomerated particles increased by 99.67% under the treatment of chicken manure,straw and quicklime compared with no fertilization,which significantly increased the content of large agglomerates(P <0.01).(2)Different fertilization treatments can increase the content of heavy metals in each grade of soil aggregates.Among them,heavy metals are mainly distributed in the aggregate group of <0.25 mm aggregates.MRKCa and MR treatment can significantly increase the heavy metals in each aggregate of soil Content;different fertilization treatments can increase the distribution factors and mass loading factors of heavy metals in the aggregate group from 0.053 to 0.25 mm aggregate size,the most obvious of which is MRKCa treatment.(3)From the relationship between the metal content in each particle size of the agglomerates and the heavy metal content in the tomato fruit,it can be seen that the heavy metal content in each particle size of the agglomerate will affect the accumulation of heavy metals in the fruit,of which the contribution to the heavy metal content in the tomato fruit The largest is the heavy metal content in the aggregate size group of >1mm and 0.053 ~ 0.25 mm.(4)In the soil samples with heavy metals Cd and Pb exceeding the standard,the combined application of chicken manure,straw,quicklime and potassium sulfate increased the content of aggregates> 0.25 mm aggregates by 95.21% ~ 177.53%,and the heavy metals Cd and Pb were 0.053 ~ 0.25 mm The enrichment in the grades decreased by 5.09% ~ 15.03%,1.65% ~ 5.68%.Among them,the stability of the aggregates under MRK treatment was the best.In summary,for the soil of the protected area,the combined application of chicken manure,straw,quicklime and potassium sulfate can increase the content of large aggregates and improve the quality of the soil.Guarantee production safety.