Effects Of Tillage And Exogenous Carbon On Water Stable Aggregates Of Meadow Black Soil

The influence of tillage and exogenous carbon on aggregate particle size distribution and water stability were studied to promote sustainable utilization of meadow black soil.Using a two-year field large-area positioning test,based on the application of exogenous carbon fertilizers under two tillage methods.The experiment included two tillage methods:deep tillage(D)and rotary tillage(S),three fertilizationmethods:conventional fertilization(CF),CF+application of organic fertilizer(M)and CF+application of bio-charcoal(B).The treatments included DCF,DM,DB,SCF,SM,and SB.The sampling depth was divided into 0-20 cm,20-40 cm and 40-60 cm.All soil samples were separated into six aggregate-size classes(>5 mm,5-2 mm,2-1 mm,1-0.5 mm,0.5-0.25 mm and 0.5-0.106 mm)by wet sieving.Water stability index of the aggregates was determined.The humic carbon,humic acid carbon,fulvic acid carbon and free-form iron-aluminum oxide,amorphus iron-aluminum oxide were determined.Analyzed the influence of the above factors on the stability of meadow black soil water-stable aggregates.The results were as follows:(1)The water-stable aggregates particle size were mainly gather at 5-2mm and 1-0.5mm in 0-60 cm soil layer(40.1%).SM treatment in 0-20 cm soil layer and DCF treatment in 20-60 cm soil layer had the highest content of 5-2mm particle size components in three soil layers(45.6%,36.2%).(2)The average weight diameter,water-stable aggregate percentage,and geometric mean diameter of SM treatment in 0-20 cm soil layer,DB and SB treatments in 20-40 cm soil layer,DCF and SB treatments in 40-60 cm soil layer were significantly improved,meanwhile,percentage of water stable aggregate disruption and fractal dimension were significantly reduced.It showed that the above treatments had a higher content of water-stable macroaggregate in the respective soil layers,which promoted the transformation of macroaggregate in black meadow soil and enhanced the water stability.(3)The carbon content of the organic matter fractions in 0-20 cm soil layer was smaller than the 20-60 cm soil layer.Deep tillage promoted the increase of carbon content of organic matter fractions in 0-20 cm soil layer.The carbon content increase rate of organic matter components was 15.66%~175.00% compared with the rotary tillage treatment with the same fertilizer.DM,DB and DCF treatments had the highest carbon content of humus and fulvic acid in 0-20 cm,20-40 cm and 40-60 cm soil layer respectively,while DM,SCFand DB treatments promoted the increase of humic acid carbon content in 0-20 cm,20-40 cm and 40-60 cm soil layer respectively.(4)The free-form iron-aluminum oxide content in 0-60 cm soil layer was higher than the amorphous iron-aluminum oxide content.However,amorphous iron-aluminum oxide had a higher correlation with aggregation and stability of macro particle water stable aggregate in 0-60 cm soil layer compared to free-form iron-aluminum oxide.Tillage methods and exogenous carbon application promoted the content of FeDCB with DCF treatment in 40-60 cm soil layer significantly.Compared with other treatments,it increased by 20.53%~52.70%,At the same time,DCF treatment in 0-60 cm soil layer had the higher content of AlDCB and FeOXA while DCF,DB,DB treatments had a higher content of AlOXA in 0-20 cm,20-40 cm and 40-60 cm soil layer respectively.(5)The multivariate analysis results showed that tillage methods,exogenous carbon and their interactions reached extremely significant levels with carbon content of organic matter fractions(HF,HA,FA)in 0-20 cm soil layer,while reached a significant or extremely significant level with the water-stable aggregates of different particle sizes and iron-aluminum oxide content in 0-60 cm soil layer.It could be seen that the tillage methods and exogenous carbon application designed in this experiment had affected the particle size distribution of water-stable aggregates and the content of organic and inorganic substances in the soil to some extent,changed the structural characteristics and physical,chemical properties of meadow black soil under different depths.(6)The RDA and multiple linear regression analysis results showed that the total contribution rate of environmental factors(HF,HA,FA,free-form iron-aluminum oxide and amorphus iron-aluminum oxide)to the particle size distribution of marco water-stable aggregates in 0-20 cm,20-40 cm and 40-60 cm soil layers were 57.1%,59.1% and 55.0%,respectively.Higher than the contribution rate of each factor.>5mm,5-2mm particle size water-stable aggregates were the most relevant fractions to promote the water stability of aggregates.FeOXA,AlDCB,and AlOXA were beneficial to improve the water stability of 0-20 cm soil aggregates by promoting the formation of >5 mm and 5-2 mm particle size aggregates.AlDCB,AlOXAand HA were beneficial to improve the water stability of 20-40 cm soil aggregates by promoting the formation of > 5mm and 5-2 mm particle size aggregates.All environmental factors were beneficial to improve the water stability of 40-60 cm soil aggregates by promoting the formation of >5mm and 5-2 mm particle size aggregates.In summary,different tillage methods and exogenous carbon application changed the distribution of water-stable aggregates of various particle sizes through organic-inorganic cementation,which affected the water stability of aggregates in different depths of Northeastern meadows black soil,soil structure and its physical-chemical properties had also been improved.