Effect Of Deep Application Of Straw On Composition And Structure Of Humus In Aggregates

There are some problems about traditional straw application such as affecting seed germination and growth, slowing soil temperature and increasing plant diseases and insect pests. Deep application of straw(DAS) not only solves the problem of burning straw, but also improves the soil fertility, water storage capacity and crop production and improves straw application. Exploring the influence of DAS on soil humus can provide theoretical basis for improving soil fertility and creating reasonable arable layer by DAS. The research objects are the black soil and the meadow cinnamon soil. They are divided into 4 soil aggregates which include the sizes of >2mm、2~0.25mm、0.25~0.053 mm and <0.053 mm and determined the organic carbon content of soil humus components and extracted humic acid(HA) and humin(Hu) of soil by the humus composition modification method. Determining the structure characteristics of the HA and Hu element composition by infrared spectroscopy and differential thermal analysis, and then determine the effects of DAS on composition and structural characteristics of humus in soil aggregates. The results show that:(1) The advantages aggregate of black soil and meadow cinnamon soil are 2~0.25 mm. The advantages aggregate content of black soil in surface is lower than content in subsoil layer. DAS increases the advantage aggregates in the black soil and two large aggregate of meadow cinnamon soil.(2) The organic carbon content of black soil is higher than that of meadow cinnamon soil. The organic carbon content of surface is higher than that of subsoil layer in the N-CK, F-CK and F-800.(3) The maximum value of organic carbon content of FA、HA and Hu in aggregates of meadow cinnamon soil respectively exists in <0.053 mm, 2~0.25 mm and >2mm. PQ maximum of meadow cinnamon soil exists in 2~0.25 mm. PQ and organic carbon content of HA and Hu turn from topsoil higher than subsoil layer to topsoil lower than subsoil layer with increasing of DAS amount. DAS is advantageous for accumulating of carbon content of HA and Hu in subsoil layer, rising of PQ, increasing of humification degree, improvement of humus quality.(4) Compared with meadow cinnamon soil, Carbon content and condensation degree of HA are higher, oxidation degrees are lower, and qualities are higher in the black control soil. HA Carbon content is the most, oxidation degrees is least for 2~0.25 mm in the meadow cinnamon soil, values is on the contrary for <0.053 mm. Compared with the subsoil layer, average carbon content of HA in the black and meadow cinnamon soil is higher, oxidation degree is lower, while condensation degree and thermal stability of the black soil are lower, the aliphatic-C/carboxylic-C(2920/1720) and aliphatic-C/aromatic-C(2920/1620) ratios are higher, HA structure is younger and simpler in the surface layer soil. DAS reduces HA oxidation degree of black soil, and decreases condensation degree and thermal stability of black soil.(5) Carbon content and condensation degree of Hu is higher, oxidation degree is lower than HA for black soil. DAS reduces oxidizability, aliphatic hydrocarbon chain and stability of Hu in soil aggregates of the black soil, and the structure of Hu tends to be simpler and younger.