| According to the survey of the national modern agriculture industrytechnical system in2008, soil compaction is becoming one of the major limit factorsto grain yield improving. As an effective manner to resolve soil compaction andincrease grain yield, improving soil tillage is found by prior studies. To overcome soilcompaction and improve soil quality, the effects of deep tillage and straw retain on thephysical, chemical and biological properties of the clay soil in Luohe and the loamsoil in Hebi were studied during2010-2011. The results were as follows:1. Both deep tillage and straw retained can improve soil physical properties.Soil depth, soil tillage manner and soil texture have significant effects on soilbulk density, soil porosity, soil water content and R-value of the three-phase ratio ofsoil. Soil bulk density and R-value of the three-phase ratio of soil were increased bythe increase of soil depth. Soil water content and soil porosity was decreased by theincrease of soil depth. Soil bulk density and R-value of the three-phase ratio of soilwere reduced by0.7%and19.0%, soil porosity, soil water content and plow layerdepth was respectively increased by1.3%,3.8%and71.4%in the deep tillagetreatment. R-value of the three-phase ratio of soil was decreased by9.3%, and soilwater content was increased by3.2%in the straw retained treatment. There wassignificant difference between clay soil and loam soil. Soil bulk density, soil watercontent and R-value of the three-phase ratio of soil in clay soil were higher than inloam soil by0.7%,1.3%and16.1%, respectively. R-value of the three-phase ratio ofsoil could clearly reflect the variation of the three-phase of soil between differenttreatments.2. Both deep tillage and straw retained have significant effects on soil aggregate.The mean weight-diameter (MWD) of water stable soil aggregate in the20-30cm soil layer of loam and clay soil increased42.4%and52.3%under deep tillage, respectively; and increased51.6%and52.4%under straw retained, respectively. TheMWD of soil aggregate increased with the increased of soil depth. The MWD ofmechanical stable soil aggregate in0-10cm was lowered than that of10-20cm and20-30cm by4.8%and10.8%. And the MWD of water stable soil aggregate in0-10cm was lowered than that of10-20cm and20-30cm by24.1%and29.6%. Themechanical stable soil aggregate of diameter over10mm and the water stableaggregate of diameter below0.25mm are two major part of soil aggregate. Themechanical stable soil aggregate of diameter over10mm is about34.3-71.5%and58.6-77.1%in the loam and clay soil, respectively. The water stable aggregate ofdiameter below0.25mm is about37.9-65.7%and22.0-37.9%in the loam and claysoil, respectively. The effects of deep tillage and straw retained on soil aggregate inloam and clay soil was different. This might be caused by the difference of thecementing substance during the soil aggregate formation in the two soil types. Thecontent of soil aggregate diameter over0.25mm could be used as an evaluationindicator of soil when the major cementing substance was organic matter during soilaggregate formation.3. Both deep tillage and straw retained can increase soil nutrition content and reducethe ratio of soil carbon and nitrogen (C/N).By deep tillage treatment in loam soil, soil total nitrogen content, phosphorus andavailable potassium increased by3.4%,14.2%and4.7%, respectively; C/N of soildecreased by5.2%. By deep tillage treatment in clay soil, soil total nitrogen content,phosphorus and available potassium increased by8.6%,7.6%and3.9%, respectively;C/N of soil decreased by7.0%. By the straw retain treatment in loam soil, soil organicmatter, soil total nitrogen content, phosphorus and available potassium increased by3.0%,13.8%,11.0%and11.8%, respectively; C/N of soil decreased by10.0%. By thestraw retained treatment in clay soil, soil organic matter, soil total nitrogen content,phosphorus and available potassium increased by1.6%,20.2%,10.8%and6.0%,respectively; C/N of soil decreased by15.8%.4. Both deep tillage and straw retained have significant effects on soil microbialgroups.In the deep tillage treatment, the number of soil bacteria, fungi andactinomycetes of loam soil increased by16.4%,14.6%and52.3%, respectively; thenumber of soil bacteria, fungi and actinomycetes of clay soil increased by14.5%,31.3%and24.3%, respectively. In the straw retain treatment, the number of soil bacteria, fungi and actinomycetes of loam soil increased by50.0%,158.2%and77.0%, respectively; the number of soil bacteria, fungi and actinomycetes of clay soilincreased by62.7%,54.0%and177.5%, respectively. Both deep tillage and strawretained can accelerate soil respiration during summer maize growing season. Andsoil respiration rate during summer maize growth is: jointing stage>silkingstage>maturity stage. Soil microbial quantity and soil respiration rate were increasedby the improved soil physical environment due to deep tillage and more carbon sourceprovided by straw retain.5. Both deep tillage and straw retained significantly improved the activities of soilenzymes.In the deep tillage treatment, the activities of catalase, phosphatase, urease andsucrase in the loam soil increased by19.6%,9.0%,5.5%and2.5%, respectively; theactivities of catalase, phosphatase, urease and sucrase in the clay soil increased by10.3%,25.6%,1.5%and7.2%, respectively. In the straw retained treatment, theactivities of catalase, phosphatase, urease and sucrase in the loam soil increased by15.8%,51.3%,15.1%and20.4%, respectively; the activities of catalase, phosphatase,urease and sucrase in the clay soil increased by7.8%,30.5%,11.5%and14.4%,respectively. Reductase activity was lower and hydrolytic enzyme activity in clay soilwas higher than in loam soil, which is better for the conversion from straw to soilorganic matter.6. Both deep tillage and straw retained improved grain yield.Compared with the conventional tillage, yield of summer maize and winterwheat increased by6.0%and3.5%in the deep tillage treatment, and increased by5.0%and9.7%in the straw retained treatment. The effects of deep tillage and strawretained on yield increase rate of winter wheat were higher than summer maize, andthe effects became stable with the time passed by. Summer maize straw retainedexhibit more pronounced effects on yield improvement than winter wheat strawretained. Finely chopped straw and adequate harrowing was suggested to improve thestability of the effects of deep tillage and straw retained on grain yield improvement. |
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