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研究了渭-库三角洲绿洲连作5、10、15、20、25 a的棉田土壤颗粒组成、p H、盐分、有机质等理化特征。结果表明:(1)连作15 a土壤黏粒含量最高,连作20 a最低;连作15 a粉粒含量最高,连作25 a最低;连作25 a砂粒含量最高,连作15 a最低。(2)连作10 a土壤盐分含量最高为8.07 g kg-1,连作15 a最低为5.68 g kg-1;随连作年限的增加,土壤趋向硫酸盐型盐渍化发展;土壤p H值波动不大,土壤呈微碱性或碱性。(3)连作15 a土壤有机质含量最高为12.65 g kg-1,连作5 a最低为8.46 g kg-1;全氮连作5~15 a略有增加,连作15~25 a有所减小;全磷连作20 a最低为0.82 g kg-1,连作10 a最高为1.12 g kg-1;全钾连作5~10 a明显增加,连作15~20 a明显减小,连作20 a之后又增加。(4)土壤粒度、盐分、有机质、全氮的变化基本表现为棉田连作15 a较明显,因此,在研究区棉田最适宜的连作年限为15 a,棉田连作15 a后,会导致土壤砂粒含量增多、含盐量增加、硫酸盐类盐渍化增强、p H值提高、有机质含量降低,使得养分含量失衡、肥力下降,从而影响到棉花产出和效益。
The physical and chemical characteristics such as soil particle composition, p H, salinity and organic matter in cotton fields of continuous continuous cropping of 5, 10, 15, 20, 25 a were studied in the oasis of the Wei-Qaer Delta. The results showed that: (1) The content of clay was the highest in continuous cropping for 15 years, the lowest in continuous cropping for 20 years. The content of flour was the highest in continuous cropping for 15 years and the lowest in continuous cropping for 25 years. (2) The highest salt content in the continuous cropping season was 8.07 g kg -1, and the lowest in the continuous cropping 15 a was 5.68 g kg -1. With the increase of continuous cropping years, the soil tended to be salinized and the p H value of the soil fluctuated not Large, soil was alkaline or alkaline. (3) The highest content of soil organic matter in continuous cropping was 12.65 g kg-1 in 15 years, and the lowest in continuous cropping was 8.46 g kg-1 in 5 years. Total nitrogen increased slightly from 5 to 15 years and decreased from 15 to 25 years in continuous cropping. The maximum of continuous cropping 10 a was 1.12 g kg-1 for continuous cropping of phosphorus at 20 a and 0.82 g kg-1 at 20 a for continuous cropping. The percentage of total potassium increased from 5 to 10 a in continuous cropping and decreased significantly after continuous cropping for 15-20 h. (4) The change of soil grain size, salt, organic matter and total nitrogen basically showed that the continuous cropping of cotton field for 15 years was more obvious. Therefore, the most suitable continuous cropping season in cotton field was 15 years in cotton field and 15 days in cotton field. Increased salt content, increased sulfate salinization, p H value increased, organic matter content decreased, making the nutrient content imbalance, fertility decline, thus affecting the cotton output and benefits.