渭-库三角洲绿洲不同连作年限棉田土壤理化特征分析

Soil Physical and Chemical Characteristics of Cotton Field with Different Continuous Cropping Years in Weigan-Kuqa River Delta Oasis

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。

This paper investigated soil particle composition, pH, salinity, organic matter and other physicochemical characteristics in cotton field with continuous cropping for 5, 10, 15, 20 and 25 years in Weigan-Kuqa River Delta Oasis. The results showed that： （1） The content of clay was the highest for 15-year cropping and the lowest for 20-year cropping in cotton field. The highest and lowest contents of silt were found for 15-year and for 25-year cropping, respectively. The highest content of sand was in 25-year cropping and the lowest was for 15 years. （2） The highest soil salinity was 8.07 g kg-1 after 10-year continuous cropping of cotton, and the lowest was 5.68 g kg^-1 for 15 years; With continuous cropping years, soil tended to sulfate salinization; There was a little fluctuation for soil pH （alkalescent or alkaline）. （3） The highest content of soil organic matter was 12.65 g kg^-1 for 15-year cropping, and the lowest was 8.46 g kg^-1for 5-year continuous cropping; The content of total soil nitrogen increased slowly after 5 to 10year continuous cropping, then decreased after 15 to 25-year cropping; The content of total soil phosphorus got minimum of 0.82 g kg^-1 for 20-year cropping and maximum of 1.12 g kg^-1 for 10-year cropping; The content of total soil potassium increased significantly for 5 to 10-year cropping, decreased significantly for 15 to 20- year cropping, and then increased sharply for 20-year continuous cropping. （4） The changes in soil particle size, and contents of salt, organic matter and total nitrogen were most obvious for 15-year continuous cropping in cotton field. Therefore, the most suitable period for continuous cropping cotton was forl5 years in the study area. After 15-year continuous cropping, sand proportion, soil salinity and pH value increased sharply, sulfate salinization became serious, and the content of soil organic matter reduced obviously, which led to soil nutrient imbalance soil fertility decline, and further affected the cotton output and efficiency.