| As the effective conservation tillage technology,straw incorporation and no-tillagearethe growing concern in the world widely. On the one hand, we can make full use of straw resources to avoid pollution caused by burning straw, on the other hand,it can reduce costs and improve agricultural productivity. It is helpful for sustainable development of our countryagriculture, to carry out research about straw incorporation and no-till in the farmland of rice-rape rotation.In this paper, based on the long-term experimental stations of rice-rape rotation in Jingzhou and Wuxue of Hubei province, this research investigated the effects of straw incorporation and no-tillageon soil physicalproperties(bulk density, total soil porosity, capillary porosity and aeration porosity) and chemical properties(p H, organic matter, nitrogen, alkalytic nitrogen, available phosphorus and available potassium), and we explored the effect of straw incorporation and no-tillage on farmland soil aggregates stability, by using the method of dry sieve and wet sieve separation of different particle size of soil aggregates. We studied changes of humic acid component content and structure in the surface layer after straw incorporation, by extraction and analysis of soil aggregates humicacid component(humic acid, humilic acid and fulivc acid). The result showed,(1)In Wuxue and Jingzhou, Straw incorporation reduced surface soil bulk density(reduced by 7.91% and 1.34%respectively), and increased the total soil porosity, capillary porosityand aerationporosity,thenit couldenhance the ability of the soil to retain moisture.In Wuxue, no-tillage increasedsurface soil bulk density(increased by 3.74%), and reduced the total soil porosity, capillary porosityand aerationporosity, and the treatment of combining no-tillage with straw incorporationcould reducesoil bulk density(reduced by 3.07%) and increasesoil porosity. Bulk density of upland soil were higher than paddy soil, on the contrary, total soil porosity, capillary porosityand aerationporosity of upland soil werelower than paddy soil. In the different period of rice-rape rotation, the effect of straw incorporation and no tillage on the surface soil porosity weredifferent.(2)The straw incorporation and no-tillage could affect the distribution of soil aggregate, the content of <0.25 mm aggregate was the highest(about 50%). Secondly >5 mm and 0.25~0.5 mm, 20% and 15% respectively,then 2~5 mm, 1~2 mm and 0.5~1.0 mm(about 5% respectively).and straw incorporation and no-tillage increased the soil >0.25 mm percentage of water stable aggregate, MWD and GMD on 0-20 cm layer, but decreased PSD. The >0.25 mm percentage of water stable aggregate and PSD showed a significant negative correlation(correlation coefficient R, respectively, Wuxue:-0.997; Jingzhou:-0.993). But the >0.25 mm percentage of water stable aggregate and MWD, GMD both had significant positive correlation. So straw incorporation and no-tillage could enhance the soil aggregate stability, and helped to improve soil structure.(3)In Wuxue, straw incorporation could increase surface soil(0~20 cm)organic matter,nitrogen, alkalytic nitrogen and available potassium(respectively 8.92%, 6.75%, 8.10% and 69.79%), and no-tillagecould increase surface soil organic matter,nitrogen, alkalytic nitrogen and available potassium(respectively 9.84%, 5.47%, 4.66% and 13.51%). It was the best to conbine straw incorporation with no-tillage(increase 11.00%, 10.24%, 8.11% and 75.73% respectively). In Jingzhou, straw incorporation could increase surface soil(0~20 cm) organic matter,nitrogen, alkalytic nitrogen, available phosphorus and available potassium(respectively 13.80%, 6.66%, 10.71%, 15.09% and 29.68%). In total, the effect of staw incorporation on nutrient was better than no-tillage. Then different treatment of the layer(20~40 cm) had no significant difference. Soil nutrient content of the layer(0~20 cm) were all significantly higher than the layer(20~40 cm). p Hof the surface soil(0~20 cm) were all significantly lower than the layer(20~40 cm). Straw incorporation and no-tillage had little effect on p H. In the different period of rice-rape rotation, the effect of straw incorporation and no tillage on the surface soil oranic matter and nutrient were different.(4)Straw incorporation had a positive effect on soil carbon-pool management index. But the effects of Straw incorporation on soil carbon-pool management index were different on the different condition of rice-rape rotation. In the upland soil, straw incorporation helped increase the content ofsoil organic carbon(SOC), active organic carbon(ROC) and carbon management index. But in the paddy soil, straw incorporation helped decrease the content ofsoil organic carbon(SOC) significantly, and increase active organic carbon(ROC) and carbon management index significantly.(5) On the control treatment, as the soil particle size decreased, total organic carbon and the content of acid humic acid(HE) carbon, humilic acid(HA) carbon and fulvic acid(FA) carbonwere on the decline. Straw incorporation had a different effect on different soil particle size of aggregate.Straw incorporation helped increase the content ofsoil HA and the ratio of HA/FA in the surface soil and the large aggregates(>0.25 mm).(6)Infrared spectrum of the soil and aggregates HA after straw incorporation showed that, on the control treatment, the 3400/1620 ratio of HA and HE decreased in<0.053 mm aggregate,aromatic property/aliphatic property ratio increased, and the structure of HA and HE became complex, the 3400/1620 ratio of HA and HE increased in >5 mm mm aggregate, aromatic property/aliphatic property ratio decreased, and the structure of HA and HE became sample. Compared with the control treatment, the 3400/1620 ratio of HA and HE decreased in the aggregate, aromatic property increased, aliphatic property decreased, and the structure of HA and HE became complex. |
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