Study On The Characteristic Of Salinity In Coastal Saline Cotton Fields And Its Effect On Cotton Yield And Quality

Soil salinity is one of the major obstacles to limiting agricultural production. China is one of the countries suffered from serious salinization hazards. The area of saline-alkali land in our country is larger. And the area of secondary saline-alkali soil is increasing year by year. As a pioneer of the saline-alkali land crops, cotton is gradually focusing on saline-alkali soil with the reduction of arable land in China. Therefore, the research of high yield and efficient way to cotton cultivation under saline-alkali soil conditions is particularly important. The field experiment was conducted with CCRI-102(salinity-sensitivity) and CCRI-103(salinity-tolerance) in rice and wheat foundation seed farm in Dafeng Jiangsu province (120°28’E,33°12’N)to conduct salinity level (mild:Ec=6.29dS m-1, saltness1.99mg g-1;moderate:Ec=9.51dS m-1,saltness3.14mg g-1; severe:Ec=12.83dS m-1,saltness4.61mg g-1) to study the saltness and nutrient characteristics of saline soil in coastal saline cotton fields in2010. In this research, we focused on:(1) The effects of soil salinity on cotton dry matter accumulation, yield and quality in coastal saline;(2) The saltness and nutrient characteristics of saline soil in coastal saline cotton fields;(3) The laws of absorption and distribution of salinity and nutrient in cotton planted in coastal saline fields;(4) Effects of soil salinity on cotton leaf carbon and nitrogen metabolism in coastal salineThe main results were as follows:1. The effects of soil salinity on cotton dry matter accumulation, yield and quality in coastal salineThe amount of dry matter accumulation of both cotton plants and reproductive organs reduced obviously with salinity level increased. The amount of dry matter accumulation of both cotton plants and reproductive organs in CCRI-102were higher than CCRI-103at the same salinity level. The number of final cotton plant bolls reduced with the salinity level increased and there was no obvious difference between the two cottons. The number of bolls in CCRI-103is little higher. The effect of soil salinity wasn’t obvious on both cotton fibre qualities at the three levels. The variation trend of the amount of osmotic adjustment matter accumulation in main cotton stems and leaves was closely related to cotton salinity-tolerance and its mechanism. The amount of amino acid in cotton leaves increased with soil salinity level increased, while the amount of soluble sugar was reduced.2. The saltness and nutrient characteristics of saline soil in coastal saline cotton fieldsThere is a significant positive correlation between the soluble salt content and electrical conductivity of saline soil, soil extract pH and salinity levels were not correlated. Soluble salt ions were Na+and Cl-primarily, and accounting for about70%of the total cation content and the total anion content respectively. Cationic also included Ca2+、Mg2+K+. Anionic included SO42-and a small amount of HCO3-. The ion content and the trend of difference were not the same in different in soil levels. Along with the soil depth increased, the ion content in the soil decreased, and the fluctuation range was the topsoil. Soil nutrient content was decreased in total N, available K, available P from high to low. Soil nutrients mainly concentrated in the topsoil, with soil depth increased, nutrient content was gradually decreased. The cotton plant uptake and utilization of soil nutrients were mainly concentrated in the topsoil. Topsoil nutrient content of the cotton growth period fluctuated to a larger extent. There was a certain correlation between the cotton field soil salinity and nutrients. The higher the soil salinity levels, the higher its potassium content.3. The laws of absorption and distribution of salinity and nutrient in cotton planted in coastal saline fieldsCoastal saline cotton fields soil affects absorption and distribution of soil nutrient and salinity by cotton plants. The nitrogen retention by roots increased with soil salinity level increased. And the stems of cotton plants increased first and then reduced with soil salinity level increased. The effect of soil salinity on nitrogen absorption wasn’t obvious in other organs.The differences among the amounts of nitrogen wasn’t obvious at three salinity levels. Soil salinity promoted the phosphorus absorption and storage of cotton plants leaves and stems, and the promotion is more obvious in salinity-sensitivity cotton. The amounts of potassium in each organs weren’t distinct at different soil salinity levels, which indicated the effect of soil salinity on potassium absorption of cotton plants wasn’t obvious. As one of the storage organs, the amount of salt ionic retention in leaves was higher than other cotton organs in the same condition. The amount of sodion in CCRI-102was higher than in CCRI-103at the same salinity level. The difference of the amount of sodion was the most obvious in leaves, which showed the ability of sodion retention in CCRI-102was higher than in CCRI-103. While the effect of soil salinity on the amount of sodion in cotton reproductive organ wasn’t obvious. The effect of soil salinity levels on variation trend and amplitude of calcium ion in different organs of cotton plants was obvious, while the effect on final amount of calcium ion in different organs wasn’t obvious.4. Effects of soil salinity on cotton leaf carbon and nitrogen metabolism in coastal salineStarch content in the functional leaf had a single trend during cotton growth process. With the increased soil salinity, starch content in the functional leaf was significantly decreased, then indicating that cotton functional leaf could be significantly affected by soil salinity. The variation trend of the amount of osmotic adjustment matter accumulation in main cotton stems and leaves was closely related to cotton salinity-tolerance and its mechanism. The amount of amino acid in cotton leaves increased with soil salinity level increased, while the amount of soluble sugar was reduced. With the increased soil salinity, C/N ratio in the functional leaf was significantly decreased in both cultivars, then suggesting the nutrient use efficiency in cotton functional leaf increased in the treatments with soil salinity.