不同深耕时间对滨海盐碱棉田土壤理化性质及棉苗光合特性的影响

Effects of Different Deep Ploughing Time on Physico-chemical Properties of Soil and Photosynthetic Characteristics of Cotton Seedlings in Coastal Saline Area

为探讨不同深耕时间对土壤理化性质及棉苗光合生产的影响,于冬前（T1）、开春（T2）、播前（T3）对滨海重度盐碱棉田进行深耕,测定棉花苗期叶面积指数（LAI）、光合特性、叶绿素含量（SPAD）以及干物质积累和分配情况,并对0~40 cm土层土壤含盐量、含水率和容重进行分层测定。结果表明,与T0（免耕直播）处理相比,T1处理各土层含盐量和含水率无明显变化,容重下降4.0%~9.1%,棉苗叶片SPAD、LAI以及根冠比增大8.0%~29.4%,光合参数增大4.1%~14.8%,棉苗总干质量增大9.8%;T2处理各土层含盐量降低47.2%~50.9%,10~40 cm土层含水率无显著变化,容重下降9.6%~18.2%,棉苗叶片SPAD、LAI以及根冠比增大23.6%~56.0%,光合参数增大14.2%~49.4%,棉苗总干质量增大45.6%;T3处理各土层含盐量增加14.5%~57.7%,含水率降低2.4%~8.7%,容重下降18.5%~25.4%,叶片SPAD和LAI分别降低13.0%和24.0%,光合参数降低21.4%~64.6%,棉苗总干质量降低21.9%。可见,开春深耕（T2处理）可有效改良滨海盐碱土壤,更有利于棉苗光合特性提高及其正常生长发育。

Three different treatments were designed to investigate the effects of different deep ploughing time on physico-chemical properties of soil and photosynthetic characteristics of cotton seedling in coastal saline area. The tests were performed using saline-alkali fields that were deeply ploughed before winter（ T1）,at the beginning of spring（ T2）,before planting（ T3）,with no-tillage direct-seeding（ T0） as CK.The leaf area index（ LAI）,photosynthetic characteristics,chlorophyll content（ SPAD） and dry matter ac-cumulation and distribution of cotton leaf were measured and the salt content,moisture content,and soil bulk density of 0—40 cm depth soil were also determined hierarchically in the seedling stage. Results showed that compared with the T0 treatment,the soil salt content and moisture content did not obviously change,and the soil bulk density reduced by 4. 0% —9. 1% under T1 treatment. The SPAD,LAI and root cap ratio increased by 8. 0% —29. 4%,photosynthetic parameters of leaf increased by 4. 1% —14. 8%,and the total dry matter accumulation of cotton seedling increased by 9. 8%. The soil salt content reduced by 47. 2 % —50. 9%,the moisture content of 10—40 cm soil did not obviously change,the soil bulk density reduced by 9. 6% —18. 2% under the T2 treatment. The SPAD,LAI and root cap ratio increased by23. 6% —56. 0%,photosynthetic parameters of leaf increased by 14. 2% —49. 4%,and the total dry matter accumulation of cotton seedling increased by 45. 6%. The soil salt content increased by 14. 5% —57. 7%,and the soil moisture content and bulk density reduced respectively by 2. 4% —8. 7% and18. 5% —25. 4% under the T3 treatment. The SPAD and LAI reduced by 13. 0% and 24. 0% respectively,photosynthetic parameters of leaf reduced by 21. 4% —64. 6%,and the total dry matter accumulation of cotton seedling reduced by 21. 9%. It was more advantageous to soil improvement,photosynthetic characteristics improvement and normal growth of cotton seedling in coastal saline area under deep ploughing at the beginning of spring（ T2）.