Effects Of Green Manure And Chemical Fertilizer Application On The Transformation Of Clay Minerals In Purple Tide Soil Particles

In recent years,the emphasis and unreasonable use of chemical fertilizers have made the role of green fertilizers known again.Chinese milk vetch is a high-quality organic fertilizer source in southern China,and it can improve the basic physical and chemical properties of the soil and increase soil fertility,while clay minerals can reflect the degree of weathering and fertility of the soil.Therefore,studying the effect of green manure combined with chemical fertilizers on clay minerals helps to reveal the improvement effect of green manure on soil.This paper takes the Chinese milk long-term location test field Purple Tide of Sanxian Lake in Nanxian,Hunan Province as the research object,and selects no fertilizer(CK),only chemical fertilizer treatment(F100)and Chinese milk vetch combined with different quantitative fertilizer treatments(Returning Chinese milk vetch and applying full quantitative fertilizer / MV + F100;Returning Chinese milk vetch and applying 80% chemical fertilizer / MV + F80;Returning Chinese milk vetch and applying 60% chemical fertilizer / MV + F60;Returning Chinese milk vetch and applying 40% chemical fertilizer / MV + F40)20-40 cm soil samples,and 0-20 cm soil samples of without fertilization and Returning Chinese milk vetch with full quantitative fertilizer two treatment,were separated into different sizes Soil particles(> 2000,2000-450,450-100,and 100-25 nm)by nano-particle ultra-filter(AUD)and other equipment.Synchronous radiation X-ray diffraction(XRD),atomic absorption spectroscopy(AAS),and plasma emission spectroscopy(ICP)were used to study the type,content,and structure characteristics of layered silicate minerals and transformation of iron and aluminum oxide in soil particles under the combined application of green and chemical fertilizers,provide a basis for rational fertilization and improvement of soil productivity.The main results show that:(1)Chinese milk vetch to the field can improve the physical and chemical properties of the soil and increase soil fertility.Chinese milk vetch returning as green manure educed soil p H value,increased soil organic matter content,and better 0-20 cm soil layer effect;Chinese milk vetch returned to the field significantly increased the amount of cation exchange and clay content in the soil,and the content of clay particles increased with the decrease of the amount of chemical fertilizer,reached the maximum value when the amount of chemical fertilizer was 40%.Chinese milk vetch returning increased the Zeta potential value of the soil and slowed its agglomeration.(2)Long-term fertilization can significantly change the relative content of clay minerals in the soil.Long-term application of Chinese milk vetch of Purple Tide soil reduces the relative content of kaolinite,illite and vermiculite and increases the relative content of HIV in the 0-20 cm soil layer;Long-term application of Chinese milk vetch increases the relative content of illite in the 20-40 cm soil layer,while the content of kaolinite decreases and the crystallinity increases;At the same time,the relative content of illite decreases first and then increases with the decrease in the amount of fertilizer applied,but change of kaolinite is the opposite,reaches an extreme value when the amount of fertilizer is 80%;The relative content of illite in the 2000-450 nm particles increased with the decrease in the amount of fertilizer,and the relative content of illite in the 450-100 and 100-25 nm particles decreased first and then increased.(3)The interlayer hydroxy minerals contained in the Purple Tide soil are mainly interlayer hydroxyvermiculite,and the interlayer hydroxy materials are mainly iron hydroxy and silicon,and contain only a small amount of aluminum hydroxy;Chinese milk vetch returns to the soil has a significant effect on the interlayer hydroxy minerals,increasing the content of hydroxyferrous iron in the soil;After Chinese milk vetch was returned to the field,the extraction content of hydroxyl iron of > 2000 and 100-25 nm soil particles was positively correlated with the amount of chemical fertilizer,which was the lowest when the amount of chemical fertilizer was 40%.The extractive amount of hydroxyiron of the 2000-450 and 450-100 nm particles decreases first and then decreases with the decrease of the amount of fertilizer,and reached the minimum value in the treatment of MV+F60.the content of iron,aluminum and silicon extracted by all treatment decreases first and then decreases with the decrease in particle size,reaching the lowest value in 450-100 nm particle size.(4)The oxide minerals in the Purple Tide soil are mainly goethite and hematite,and the primary minerals are quartz,feldspar and calcite.The combined application of Chinese milk vetch and full-quantity fertilizer increased the content and crystallinity of oxide minerals in the soil,and the effect of 0-20 cm soil layer increase was more significant.Under the condition of Chinese milk vetch returning to the field,the relative content of primary minerals in the>2000 and 2000-450 nm particles decreased with the decrease in the amount of chemical fertilizers,has a positive correlation with the amount of chemical fertilizer;but the relative content of primary minerals in 450-100 and 100-25 nm particles increases first and then decreases;as the particle size decreases,the content of primary minerals decreases,the content of secondary minerals increases,and the crystallinity of the minerals decreases.(5)The content of free iron content in 0-20 cm soil layer soil is lower than the 20-40 cm soil layer in Purple Tide soil,while the content of complex iron and the degree of activation are higher than 20-40 cm.Chinese milk vetch with chemical fertilizer increased the content of amorphous iron oxide,complex iron oxide and the degree of iron oxide activation in the soil;The content of free iron decreases first and then increases with the decrease in the amount of fertilizer applied,reaching the lowest value at 60% of the amount of fertilizer applied;and the contents of amorphous iron oxide and complex iron oxide with the decrease of the fertilizer application showed the opposite change with free iron,which reached the maximum when the fertilizer application rate was 80%;The content of iron oxide in the soil particles increased as the particle size decreased,and at the nanoparticle level reaching the maximum value.Under the condition that chinese milk vetch to the field,the content of free iron in the 450-100 nm particle size first decreased and then increased with the decrease in the amount of fertilizer applied,and the change rule of the 100-25 nm particle was the opposite.With the decrease of chemical fertilizer application,the content of amorphous iron in each particle size(> 2000,2000-450,450-100 and 100-25 nm)increased first and then decreased,reached the highest value in MV+F80.