Effects Of Salinity Stress On Cotton (Gossypium Hirsutum L.) Root Growth And Cotton Field Soil Micro-Ecology

Soil salinization is a key environmental stress factor that limits crop growth and population development, it is very important to exploit and utilize this soil. Two cotton cultivars with different salt-tolerance (CCRI-44, Sumian 12) were used, and five salinity rates (0%.0.35%.0.60%,0.80%,1.00%), standing for five levels respectively were applied. The study focused on:(1) Effects of salinity stress on cotton field soil nutrient content at different growth stages in cotton field; (2) Effects of salinity stress on cotton field soil microbe quantity at different growth stages in cotton field; (3) Effects of salinity stress on cotton field soil enzyme activity at different growth stages in cotton field. The main results were as follows:1. Effects of salinity stress on cotton (Gossypium hirsutum L.) field soil nutrient content at different growth stageUnder the same soil water treatment, with increasing of soil salinity, the content of soil organic matter, available nitrogen, available phosphorus and rapidly available potassium decreased. At the same time, the growth of cotton was inhabited by soil salinity stress. Root vigor, root dry weight, biomass, and seed cotton yield all declined with the increase of soil salinity. but R/S-ratio improved. Under the same soil salinity, the content of soil nutrient were much higher in well-watering treatment than in water stress treatment. Soil water stress aggravated the effects of soil salinity stress. Compared to Sumian 12, CCRI-44 was less affected by soil salinity at different growth stages of cotton. Correlation analysis showed that the seed cotton yield had a significant positive correlation with soil nutrient content, and the biomass was closely related with seed cotton yield. Soil microbe and soil enzyme, which are sensitive to soil salinity stress and closely related with cotton yield, are the important reasons of cotton yield decreasing and important indices to extent of soil salinity stress. These results reveal that soil salinity not only influences the soil nutrient the decomposition to transform and to absorb, but also directly affects the growth of cotton and the vield of cotton. 2. Effects of salinity stress on cotton (Gossypium hirsutum L.) field soil microbe quantity at different growth stageUnder the same soil water treatment, with increasing of soil salinity, the number of bacteria, fungi and actinomyces decreased. Under the same soil salinity, the number of soil microbe and activity of soil enzyme were much higher in well-watering treatment than in water stress treatment. Soil water stress aggravated the effects of soil salinity stress. Compared to Sumian 12, CCRI-44 was less affected by soil salinity at different growth stages of cotton. Correlation analysis showed that the seed cotton yield had a significant positive correlation with soil microbe and soil nutrient content, and the number of soil microbe was closely related with soil nutrient content, including the content of soil organic matter, available nitrogen, available phosphorus and rapidly available potassium. Soil microbe, which are sensitive to soil salinity stress and closely related with soil nutrient content, are the important reasons of cotton yield decreasing and important indices to extent of soil salinity stress.3. Effects of salinity stress on cotton (Gossypium hirsutum L.) field soil enzyme activity at different growth stageUnder the same soil water treatment, with increasing of soil salinity, the activity of urease, invertase, phosphatase, celluloytic enzyme decreased. At the same time, the growth of cotton was inhabited by soil salinity stress. Under the same soil salinity, the activity of soil enzyme were much higher in well-watering treatment than in water stress treatment. Soil water stress aggravated the effects of soil salinity stress. Compared to Sumian 12, CCRI-44 was less affected by soil salinity at different growth stages of cotton. Correlation analysis showed that the seed cotton yield, root vigor, root dry weight. R/S-ratio and biomass had a significant positive correlation with soil microbe and soil enzyme, and the number of soil microbe was closely related with activity of soil enzyme. Soil microbe and soil enzyme, which are sensitive to soil salinity stress and closely related with cotton yield, are the important reasons of cotton yield decreasing and important indices to extent of soil salinity stress.