Study On Water And Salt Dynamics Of Sunflower Farmland In Hetao Irrigation Area Under Drip Irrigation

Based on the saline soil Hetao irrigation area in Inner Mongolia as background,the effects of different irrigation lower limits of drip irrigation on the water transport of mild salinized soil and moderately salinized soil,and the effects on the growth index and yield of sunflower were discussed in this paper.The optimal drip irrigation system suitable for mild salinization soil and moderate salinization soil can provide basis and reference for the use of mild salinized soil and moderately salinized soil in drip irrigation of Hetao irrigation area.The main conclusions were as follows:(1)When salinized soils of different degrees reach the same lower limit of water supply,the soil with high salt content is low,and the water content of medium salinized soil reaches the target matrix is harder to reach than that of mild salinized soil,and the time is longer.(2)In the same irrigation lower limit level,the water distribution radius of moderate salinization soil is smaller than that of light salinization soil water distribution radius.The water content in the membrane was highest under the different irrigation treatments,followed by the membrane edge,and the water content outside the membrane was the lowest.With increasing distance from the drip irrigation belt in the horizontal direction,the water content was lower.With the increase of the lower limit of irrigation,the range of water change increases,and the deep salinized soil shows deep leakage when the lower limit of irrigation is-20kPa and-30kPa,and the medium saline soil shows deep leakage at-20kPa,-The leakage at 20kPa is deeper than-30kPa.-40kPa due to the least number of irrigation,the minimum radius of water after irrigation,can not meet the normal water absorption of the main root zone of sunflower.From the point of view of water saving,the lower limit of irrigation of mild salinized soil is-30kPa,while that of moderately salinized soil can be-30kPa and-20kPa.(3)The average salt content in all growth stages showed the lowest in the membrane,followed by the membrane and larger outside the membrane,and the salt concentration in the outer layer of the membrane.With the increase of the lower limit of irrigation,the amount of soil salinity in the membrane increased,and the leaching effect of moderately salinized soil was higher than that of the slightly salinized soil.In the growth period,the lower limit of irrigation is-30kPa,and the accumulation of salt in the surface soil outside the membrane is least.During the growth period,moderately salinized soil and lightly salinized soil can be washed to soil salinity in the main root zone of sunflower under the treatment of-20kPa and-30kPa.At the end of Sunflower growth period,the lower limit of controlled irrigation in mild saline soil can effectively wash the 0-100 cm soil layer at the lower limit of-20 kPa and-30 kPa,but there is a phenomenon of salt accumulation in the 0-40 cm soil layer,and outside the film is more serious than the film.The inside is more serious.Medium salinization soil control irrigation lower limit-20 kPa can effectively wash 0?100 cm soil layer,if you do not consider the problem of salt outside the membrane,control irrigation lower limit-20 kPa and-30kPa can effectively wash the membrane 0?60 cm soil layer.The 40-80cm soil layer of each treatment is the main desalting area of sunflower in drip irrigation.(4)The surface soil salinity is the main factor affecting the emergence rate of sunflower.Excessively low and high emergence water will reduce the seedling emergence rate of sunflower,and the best setting for the emergence water is 150 m3·ha-1.The plant height and stem dianeter of sunflower during the seedling stage and budding period were the highest values under mild irrigation soil with-30kPa minimum salinization,and the maximum stem diameter value was-20kPa from the flowering stage.The increase of the lower limit of irrigation makes the effect of water on the height of sunflower is greater than that of sunflower,and the effect of soil salinity on the height of sunflower was greater,and the influence on the stem diameter of sunflower was smaller.When the lower limit of irrigation is high,the high soil salt will delay the growth of the crop.When the lower limit of irrigation is low,the high soil salt will cause the growth of the sunflower to be damaged and the development will be poor.Mild salinized soil and moderate salinized soil have the highest sunflower yield when the lower irrigation threshold is-30kPa.