The depth variation characteristics of soil potassium in continuous cotton field and its changes with different cultivation practices | 连作棉田土壤剖面钾含量变化特征及对不同耕作方式的响应

Chinese. 【目的】研究新疆绿洲农田棉花长期连作下土壤钾的消耗特征,明确不同耕作方式对连作棉田土壤剖面钾含量分布的影响,为绿洲棉田土地利用、管理和棉花可持续生产提供理论依据。【方法】在南疆宜棉区分别选择初垦1年和连续植棉5年、15年、20年、30年的连作棉田以及连作30年后采用深翻(60 cm)和水稻轮作措施的棉田,研究0―100 cm土壤剖面全钾和速效钾的变化特征。【结果】连作棉田土壤剖面全钾和速效钾自上而下呈现先降后升的变化趋势,在40―50 cm土层最低;连作年限不同的棉田土壤剖面不同深度土层全钾和速效钾含量发生明显分异。随连作年限的延长,上部0―20 cm耕作层含量先升后降,中部20―70 cm持续下降,下部70―100 cm有升高趋势。对长期连作棉田进行深翻,土壤剖面0―60 cm各土层全钾含量趋于平均化,中部土层速效钾的释放增强,棉花全生育期可维持较高的水平。采取棉花与水稻轮作,土壤全钾和速效钾含量自剖面上部至底部沉积的趋势明显,淋溶损失增强,下茬棉花全生育期0―40 cm速效钾含量偏低。【结论】棉花对土壤钾的消耗较多,每年通过籽棉收获从棉田迁出的钾每公顷可达63 kg左右;棉花长期连作对砂性土壤剖面中部钾消耗严重,以40―50 cm耗竭最重;深翻可打破连作条件下钾含量在土壤剖面的分布状态,显著提高剖面中部钾含量,并能促进速效钾的释放;稻棉轮作加速了钾的淋溶损失,导致后作棉花生育期间土壤钾含量普遍偏低,因此在砂性土壤上进行稻棉轮作应加强后茬棉花钾肥的补充。

English. 【Objective】 This study was undertaken to elucidate the consumption characteristics of soil potassium, and clarify the effects of different tillage practices on the distribution of potassium in soil profile under cotton monoculture conditions. 【Method】 Some cotton monoculture fields, 1-year cropping, 5-year cropping, 15-year cropping, 20-year cropping, 30-year cropping and 30-year cropping with deep tillaged or rice-cotton rotated practice, were adopted to analyse the variation characteristics of total K and available K in 0-100 cm depth of soil profile. 【Result】 From surface to deep soil, the contents of total K and available K decreased to minimum content at 40-50 cm soil layer, then increased under cotton monoculture conditions. There was distinctive content of total K and available K in soil vertical layer related to different cropping years. With the increase of cropping year, the content of total K and available K were increased and then decreased, continuous decreased and increased in 0-20 cm, 20-70 cm and 70-100 cm soil vertical, respectively. When deep tillaged practice was adopted, the content of total K was even in 0-60 cm soil vertical and the release degree of available K was enhanced. Thus, the content of available K was high during the cotton development stage in middle soil vertical. When rice-cotton rotation practice was adopted, the content of total K and available K accumulated remarkably in deep soil layer from surface layer, and eluviation-illuviation was increased. Thus, the content of available K was low in 0-40 cm soil layer at the following cotton development stage. 【Conclusion】 Many of K, about 63 kg?hm-2?year-1, was carried away through seed cotton from soil. The consumption of K was severe in middle layer of sandy loam soil under cotton monoculture conditions, especially 40-50 cm layer. However, using deep tillaged practice, the distribution of K was changed in soil layer. Furthermore, the content of K was enhanced in middle soil layer and the release of available K was accelerated in soil. On the other hand, using rice-cotton rotation practice, leaching loss of K was increased from soil. Therefore, it was recommend that application of K should be reinforced during the following cotton development stage under monoculture conditions using rice-cotton rotated practice in sandy loam soil.