秸秆还田对滨海盐碱地棉苗光合特性及生长的影响

Effects of Returning Straw on the Photosynthetic Characteristics and Growth of Cotton Seedlings in a Saline Coastal Area

为探讨秸秆还田对滨海重度盐碱地棉苗光合特性及生长的影响,设置增施有机肥、播前秸秆还田、冬前秸秆还田3个处理,测定了棉花苗期3个层次土壤含盐量、水分和容重,棉花叶片光合参数、叶片SPAD值以及干物质积累和棉花产量。结果表明,与对照相比,增施有机肥和秸秆还田的处理各个土层含盐量和容重明显降低,棉苗叶片LAI和SPAD明显增大,光合能力提高,干物质积累量、根冠比以及棉花产量明显增加。其中,冬前秸秆还田各土层含盐量低于2.00 g·kg-1,容重保持在1.15-1.40 g·cm-3,叶片SPAD值高于40.0,LAI提高65.5%,光合性能系数增高23.4%-92.8%,非光化学淬灭系数（NPQ）降低12.2%,干物质积累总量增大46.3%,根冠比提高56.5%,产量提高36.2%。因此,在本试验条件下,冬前秸秆还田更有利于滨海盐碱地改良及棉苗的正常生长。

Three different treatments were designed to investigate the effects of returning straw at different times on the physic-chemical properties of soil and the photosynthetic characteristics of cotton seedlings in a saline coastal area. The tests were performed in saline-alkaline fields： （1） with increased organic fertilizer; （2） with straw returned before planting; and （3） straw returned before winter. There was also a control plot （CK）. The leaf area index （LAI）, photosynthetic characteristics and relative chlorophyll content （SPAD） of cotton seedling leaf, dry matter accumulation and yield of cotton were measured. The salt content, moisture and soil bulk density of soil at a depth of 0-40 cm were also determined hierarchically at the seedling stage. Results showed that, compared with CK, the salt content and bulk density of soil had clearly decreased. Some characteristics in- creased significantly, such as root：shoot ratio, LAI and SPAD of the cotton leaf. The gas exchange and chlorophyll fluorescence parameters of the cotton leaf improved under all treatments. Dry matter accumulation, especially root weight, increased signifi- cantly under the organic fertilizer treatment and when straw was returned. The effect of returning straw before winter was more obvious than effects from the two other treatments. The salt content was lower than 2.00 g .kg-1 and the bulk density was be- tween 1.15 g·cm-3 and 1.40 g·cm-3 when straw was returned before winter. Compared with CK, the leaf SPAD value was more than 40.0, and LAI was enhanced by 65.5%. The photosynthetic performance coefficient was enhanced from 23.4% to 92.8% and non-photochemical quenching decreased by 12.2%. Total dry matter accumulation and root：shoot ratio increased 46.3% and 56.5%, respectively. Lint yield increased 36.2% when straw was returned before winter, and there was greater soil improvement and cotton seedlings grew normally under this treatment in a saline coastal area.