Effects Of Saline-water Furrow Irrigation On Soil Physicochemical Properties And Cotton Yield

Because of fresh water resources are scarce in the Heilonggang area,the research on the safe irrigation technology for cotton with saline water has great significance for the rational exploitation and utilization of shallow underground saline water,to alleviate the crisis of regional fresh water resources and ensure the sustainable development of cotton industry.This study was carried out on the basis of long-term saline-water furrow irrigation experiment（since2006）.Six irrigation water salinity levels（1,2,4,6,8 and 10 g/L）were set up,to study the distribution characteristics and transport law of soil water and salt in cotton field in the 15th year of continuous furrow irrigation with different salinity,explain the response characteristics of soil physicochemical properties to saline-water furrow irrigation,and explore the effects of saline-water furrow irrigation on cotton yield and water use efficiency.The main achievements are as follows:（1）During the growth period of cotton,soil water and salt content increased with the increase of salinity of irrigation water,and the fluctuation range of soil water and salt decreased with the increase of soil depth.The effects of collecting water and leaching salt at the ditch and preserving soil moisture and inhibiting evaporation with plastic film mulching promoted the great difference in the spatial distribution of soil water and salt in the cotton field under saline-water furrow irrigation.In the early stage of cotton growth,the soil water and salt content at the ditch was higher than that on the ridge.With the progress of the growth process,the difference of water and salt between the ditch and the ridge decreased,and the soil salt at the ditch tended to move to the ridge.Compared with that before cotton sowing,the soil salinity in 0-100 cm soil layer of all treatments decreased after harvest.Compared with that before the experiment in 2006,the soil salinity treated with saline water≤4 g/L did not significantly increase,and the balance of salt supplement and discharge could be basically achieved.（2）Saline-water furrow irrigation tends to worsen soil physicochemical properties.With the increase of salinity of irrigation water,soil EC_1:5,p H,SAR and bulk density of 0-20 cm soil layer in cotton field gradually increase,while SOC,porosity,stability of water stable aggregates and soil water availability decrease gradually,But when the salinity of irrigation water≤4 g/L,there was no significant difference in soil physicochemical indexes（except SAR）in cotton field between treatments.In addition,except for the SOC,the physicochemical properties of the soil at the ditch were better than those on the ridge in each treatment.（3）Saline-water furrow irrigation with appropriate concentration（≤4 g/L）had no significant effect on cotton growth and development and seed cotton yield,but when the salinity of irrigation water≥6 g/L,cotton seedling percentage,height,stem diameter,LAI,branch number,aboveground dry matter and seed cotton yield decreased significantly.Saline-water furrow irrigation with salinity≤10 g/L had little effect on the up half average length,uniformity,elongation,specific breaking strength and mic value of cotton,and there was no significant difference among treatments.（4）Cotton water consumption decreased with the increase of salinity of irrigation water.Compared with 1g/L treatment,cotton water consumption of 2,4,6,8 and 10 g/L irrigation treatments decreased by 2.65%,3.79%,6.46%,8.77%and 10.93%,respectively.There were significant differences between 6,8,10 g/L and 1 g/L treatments.With the increase of salinity of irrigation water,the water use efficiency of cotton increased at first and then decreased.The treatment with the highest water use efficiency corresponding to the salinity of irrigation water was 2g/L.Compared with 1g/L irrigation treatment,only 8g/L and 10g/L irrigation treatments significantly decreased the water use efficiency.（5）Under the premise of ensuring the basic balance of soil salt supplement and discharge in cotton root zone,no significant deterioration of soil physicochemical properties in plough layer,and no significant decrease in cotton yield,fiber quality and water use efficiency,it is suggested that the salinity threshold of saline water under furrow irrigation on cotton in the experimental area is 4g/L,while treatments with saline water≥6 g/L can cause soil salt accumulation,destroy soil physicochemical properties,and inhibit the growth and development of cotton,so it is not suitable to be directly used for furrow irrigation of cotton.