新疆绿洲连作棉田土壤微量元素含量的时空变化研究

THE STUDY ON TEMPORAL AND SPATIAL VARIATION OF SOIL MICROELEMENT CONTENTS IN MONOCULTURAL COTTON FIELD IN XINJIANG

为了解棉花长期单一种植对土壤微量元素含量的影响,明确连作棉田土壤质量变化规律,在南疆棉区分别选择新开垦1a和连续植棉5、15、20、30 a的棉田,研究了不同时间尺度上棉田0~100cm土壤剖面Mo、Cu、Zn、Mn、Fe等5种微量元素全量的变化规律,分析了棉田微量元素含量与连作年限之间的关系。结果表明,棉花长期连作后,土壤0~20cm耕作层全钼含量随连作年限的增加持续下降,与连作年限呈一元负线性关系;全铜、全锌、全锰含量随年限的增加先升后降,与年限呈二次函数关系,分别在连作7~10、10~12、17~18 a达到最高累积量,之后持续下降,分别在14~17、20~22、32~34 a降回到开垦初期的水平。土壤剖面中部30~50cm土层各元素全量均随连作年限增加剧烈下降,与连作年限呈一元负线性关系,长期连作易导致该层微量元素缺乏。剖面下层50~90cm土层各元素全量在长期连作后表现出一定的累积趋势,然而与连作年限之间没有明显的函数关系。随连作年限延长,0~60cm土层中含量水平越低的元素,含量下降越明显,Mo表现最明显,其次为Zn和Cu,而Mn和Fe下降较少。在长期连作棉田,棉花种植应注重Mo、Zn、Cu等微量元素肥料的补充施用,并结合土壤深度翻耕,提高中部土层微量养分含量。

Cotton production plays an extremely important role in the local economy,and the income from cotton cultivation is one of the major financial sources for farmers in Xinjiang.The cotton production of Xinjiang that is the biggest cotton production base in China has been developing rapidly since the 1990s,and now the sowing area,yield per hectare and total yield of cotton all rank first among the provinces in China.To better understand effect of long-term monoculture of cotton on temporal and spatial variation of 5 soil microelement（Total Mo,Total Cu,Total Zn,Total Mn,Total Fe） contents in the field,cotton fields different in cultivation history（1,5,15,20 and 30 years） were selected in South Xinjiang for the study on relationship between soil microelement contents and history of continuous cropping.Results show that with the cropping going on,in the plow layer（0~20cm） total Mo decreased,showing a unitary negative linear relationship,while total Cu,total Zn and total Mn first rose up,peaking in year 7~10,10~12 and 17~18,separately and then declined,dropping back in year 14~17,20~22 and 32~34 separately to the initial value,showing a quadratic functional relationship.In the sublayer（30~50cm）,the microelements decreased significantly,showing a unitary negative linear relationship with the time and demonstrating a tendency of long-term monoculture leading to deficiency of microelements in the layer.And in the botton layer（50~60 cm）,the totals of these microelements increased to a various degree,but did not show any apparent functional relationship with the time.With the monoculture going on,the lower the microelement in content in the soil layer（0~60cm）,the more apparent the fall of its content,with Mo in particular,which was followed by Zn,Cu,Mn and Fe.Therefore,in fields that have long been cultivated with cotton continuously,it is essential to supplement microelement fertilizers,like Mo,Zn and Cu,and in addition perform deep tillage so as to raise microelement contents in the sublayer.