Buried straw layer and plastic mulching increase microflora diversity in salinized soil

Salt stress has been increasingly constraining crop productivity in arid lands of the world. In our recent study, salt stress was aleviated and crop productivity was improved remarkably by straw layer burial plus plastic iflm mulching in a saline soil. However, its impact on the microlfora diversity is not wel documented. Field micro-plot experiments were conducted from 2010 to 2011 using four tilage methods： （i） deep tilage with plastic iflm mulching （CK）, （i） straw layer burial at 40 cm （S）, （ii） straw layer burial plus surface soil mulching with straw material （S＋S）, and （iv） plastic iflm mulching plus buried straw layer （P＋S）. Culturable microbes and predominant bacterial communities were studied; based on 16S rDNA, bacterial com-munity structure and abundance were characterized using denaturing gradient gel electrophoresis （DGGE） and polymerase chain reaction （PCR）. Results showed that P＋S was the most favorable for culturable bacteria, actinomyces and fungi and induced the most diverse genera of bacteria compared to other tilage methods. Soil temperature had signiifcant positive correlations with the number of bacteria, actinomyces and fungi （P〈0.01）. However, soil water was poorly correlated with any of the microbes. Salt content had a signiifcant negative correlation with the number of microbers, especialy for bacteria and fungi （P〈0.01）. DGGE analysis showed that the P＋S exhibited the highest diversity of bacteria with 20 visible bands folowed by S＋S, S and CK. Moreover, P＋S had the highest similarity （68%） of bacterial communities with CK. The major bacterial genera in al soil samples wereFirmicutes,Proteobacteria andActinobacteria. Given the considerable increase in microbial growth, the combined use of straw layer burial and plastic iflm mulching could be a practical option for aleviating salt stress effects on soil microbial community and thereby improving crop production in arid saline soils.

Estimation of the Effects of Maize Straw Return on Soil Carbon and Nutrients Using Response Surface Methodology

Straw incorporation is generally considered an effective agricultural management practice that improves nutrient cycling and maintains soil fertility. To study the interactive effects of straw returning factors on soil organic carbon and available nutrients, a17-month(May 6, 2016 to October 6, 2017) experiment was conducted on straw incorporation by using response surface methodology under a three-factor(straw length, amount, and burying depth), five-level quadratic orthogonal rotation experimental design. Weight was assigned to each indicator for soil carbon and nutrients and then a comprehensive indicator was established. Then, a second-order polynomial model of the three straw returning factors was established using response surface methodology. Results indicated that17 months after straw incorporation, straw amount and burying depth had significant effects on the comprehensive indicator of soil carbon and nutrients. Straw length and the interactions of straw amount and burying depth showed no significant effects on the comprehensive indicator of soil carbon and nutrients. It was concluded that 17 months after straw incorporation, the highest value of the comprehensive indicator of soil carbon and nutrients was achieved when the straw length, amount, and burying depth were approximately 17–20 cm, 740–840 g m^(-2), and 9–13 cm, respectively, which can be recommended as the most suitable parameters for use in straw returning in the study area.

Effects of straw size in buried straw layers on water movement in adjacent soil layers

Deeply buried straw retention can improve the soil content of organic matter,its capacity for moisture preservation,the agroecological environment utilization efficiency of water resources,ensuring a stable crop yield;at the same time,the quantitative effects of deeply buried straw retention on soil moisture have a direct influence on the promotion and application of the technology.Using an infiltration and evaporation experiment of a one-dimensional soil column,the effects of straw size on the water content of the straw and the adjacent soil were evaluated when the straw was deeply buried in soil;the infiltration and evaporation features of different sized straw and its adjacent soil were analyzed;the hydraulic conductivity,sorptivity and saturated water content of the straw were obtained;in the end,the water distribution laws of straw and adjacent soil under the same conditions were concluded.The experiment was comprised of rod-shaped straw(RS),segment-shaped straw(SS)and filament-shaped straw(FS)to control treatment(CK).The results indicated that from the perspective of infiltration,the infiltration rate of filament-shape straw was the lowest at the stage of straw unsaturation.The hydraulic conductivities of rod-shaped,filament-shaped and segment-shaped straws are 4.01 mm/min,1.33 mm/min and 0.03 mm/min at the stage of straw and adjacent soil saturation,respectively.There is a strong effect on preventing infiltration from segment-shaped straw;with the help of the Philip model of long duration,the sorptivity of the soil with rod-shaped,filament-shaped and segment-shaped straws was 12.31 mm/min0.5,11.02 mm/min0.5 and 24.26 mm/min0.5 at the unsaturation stage,respectively.The segment-shape straw improved the water absorption capacity of the soil and straw column.The water retention capacities indicated that the saturated water contents of sandy loam,filament-shaped straw,segment-shaped straw and rod-shaped straw were 0.38 cm^(3)/cm^(3),0.29 cm^(3)/cm^(3),0.26 cm^(3)/cm^(3)and 0.13 cm^(3)/cm^(3),respectively.Additionally,the evaporation rate indicated that the soil moisture content of soil below different straw layers retained approximately 30%;that the more crushed the straw was,the more moisture the straw layer lost;and that the cumulative evaporation of rod-shaped straw,filament-shaped straw and segment-shaped straw within 120 days was 1.5 mm,13.5 mm and 25.5 mm,respectively.