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对连作0、1、2、5、10、15、20、25年8个不同连作年限的棉田土壤养分进行了研究,结果表明:连作棉田土壤有机质、全氮、速效磷在连作1年后呈下降趋势;连作1-5年之间呈上升趋势,5-15年又呈下降趋势,15-25年又有上升趋势。连作棉田的速效钾在连作5年时为第一次高峰,20年为第二次高峰,含量有起伏变化,但总的趋势是降低。连作土壤的微量元素中有效锰的变化不大,有效铁、铜、锌在连作5年到15年之间呈下降趋势,在15到25年之间呈上升趋势。整体来看,土壤有机质、全氮、速效磷、速效钾以及微量元素中的有效锰、有效铁、有效铜、有效锌的含量都是在连作5年时较高,在连作5年之后都有下降趋势。
The results showed that the contents of soil organic matter, total nitrogen and available phosphorus in continuous cropping cotton one year after continuous cropping were higher than those in other continuous cropping plots. Declining trend; even 1-5 years of rising trend between 5-15 years showed a downward trend in 15-25 years, there is an upward trend. The available potassium in continuous cropping cotton was the first peak in continuous cropping five years and the second peak in twenty years. The content fluctuated but the general trend was to decrease. There was little change of available manganese in the trace elements in continuous cropping soil. The available iron, copper and zinc showed a declining trend between successive 5 years and 15 years, and increased between 15 and 25 years. Overall, available organic matter, total nitrogen, available phosphorus, available potassium, and available manganese, available iron, available copper, and available zinc in soil organic matter were all consistently higher at 5 years of continuous cropping and 5 years later Downtrend.