| Tobacco is China’s important economic crop, and Sichuan is the country stretching across the province. Soil samples of Sichuan tobacco area were as materials, the soil fertility status and impact on soil fertility with different rotation pattern were researched in this study. The results were as follows:(1) The soil of Sichuan tobacco area had weak acidic or neutral pH. The content of soil nutrient was maldistribution, and showed great variability. The content of oganic matter(OM) was general low with the average value of 23.25 g/kg, which was in middle or lower level; The content of available nitrogen(AN) was relatively rich with the average value of 111 mg/kg in Sichuan Province; Available phosphorus(AP) and available potassium(AK) changed greatly, which was in middle level.The content of available ferrum(Fe) and available manganese(Mn) were abundant with 85.27 mg/kg and 39.64 mg/kg average value, respectively. While the average content of available copper(Cu) was 2.84 mg/kg and placed in upper level. The average value of available zinc(Zn) was 2.49 mg/kg. Available boron(B) was 0.32 mg/kg and variation range was 0.08-3.38 mg/kg. The content of available B was deficient. The mean value of chlorine(Cl) was 23.46 mg/kg, ranging from 5.49 mg/kg to 83.07 mg/kg.(2) Soil pH value was improved which within the suitable range of 5.5-6.5 after the flue-cured tobacco rotated with other crops, thus proving, to some extent, crop rotation is helpful in solving soil acidification which caused by continuous cropping of tobaccos. The content of organic matter(OM) in soil in the Sichuan tobacco-planting area was improved when flue-cured tobacco rotated with other crops, especially rotated with buckwheat and green manure such as vicia villosa and common vetch, with has increased respectively by 113%(vicia villosa), 103%(buckwheat) and 81.2%(common vetch). In this study, the total nitrogen content of soil of rotational cropping and continuous cropping made little difference. The content of AN in the soil of continuous cropping and rotational cropping of tabacco and crops that need a large quantity of nitrogen such as rice shown a decreasing trend, on the contrary, the content of AN in the soil of tobacco rotated with legumes such as pea, lima bean and vicia villosa shown a significant increase. The content of AP was reduced in soil of continuous cropping and tobacco rotated with rape, contrarily, the content of AP was raised in the soil of tobacco rotated buckwheat, pea and sweet potato. Tobacco is a hi-potassium-plant, and tobacco rotated with other crops can improve the content of potassium to come extent. Though the content of slowly available potassium in the soil varies greatly. The content of slowly available potassium in the soil of rotational cropping was higher than that soil of continuous cropping which proves rotational cropping can relieve the imbalance of soil nutrient caused by the single absorption of potassium of continuous cropping.There is a little influence concerning different crop rotation models to medium element and microelement. Expect Liangshan tobacco-planting area, the content of exchangeable calcium in soil was high, which proves the exchangeable calcium content of soil of rotational cropping and continuous cropping made little difference. In addition, the content of exchangeable calcium in soil of tobacco rotated with corn was lower than that soil of other crop rotation models. The content of available Fe and available Mn in soil were high in Sichuan tobacco-planting area, and the content of available Fe and available Mn in the soil of rotational cropping were higher than that soil of continuous cropping. Therefore, it is essential to be care of the toxic action caused by high content of available Fe and available Mn when to choose the crops for rotation. The soil in Sichuan tobacco-planting area was lack of available B, and there was no significant effect on solving the lack of available B whether concerning the crop rotation or not.(3)Under the monoculture model, the soil pH was declining, which is more significant compared with tobacco-crops rotation model. This suggests that rotation model is more useful in mitigate acidification than monoculture; The contents of soil organic matter in tobacco monoculture, tobacco-buckwheat rotation, tobacco-cole rotation and tobacco-corn rotation have no significant difference, but under the tobacco-vetch rotation model and tobacco-sweet potato rotation model, the contents of organic matter were increased; As for soil TN, under the monoculture model, the contents in four tobacco area were have no significant difference expecting Guangyuan area, which TN content declined. While under the rotation model, the results have no significant difference; Soil alkali solution nitrogen content was increased generally after tobacco continuous cropping.the paper proved that expecting the tobacco-vetch rotation, tobacco-buckwheat rotation, tobacco-cole rotation, tobacco-corn rotation and tobacco-sweet potato rotation model can be used to retard the increase of alkali solution nitrogen content; After 5 years tobacco continuous planting, the quantity of soil phosphorus has accumulated, however, the content has no apparent difference after 5 years rotation; After 5 years tobacco continuous planting, the contents of available K have a significant increase in all tobacco area, but after 5 years rotation(expected tobacco-sweet potato rotation), the incremental of available K were not as much as tobacco monoculture. |
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