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Effects Of Winter-Spring Irrigation On Soil Water-Salt Dynamics And Cotton Growth

Posted on:2019-05-10Degree:DoctorType:Dissertation
Country:ChinaCandidate:X P WangFull Text:PDF
GTID:1360330572998882Subject:Agricultural Soil and Water Engineering
Abstract/Summary:PDF Full Text Request
Winter and spring irrigation is an effective method to inhibit soil salinization in cotton fields in Southern Xinjiang district,but unreasonable winter and spring irrigation method and salt leaching quota would lead to water resources waste and low water utilization.In order to determine the suitable salt leaching method and irrigation quota for the cotton fields in southern Xinjiang.Through the soil column test,plot controlled test and field experiment in the 10th Irrigation Test Base of the First Division Water Conservancy Bureau of Xinjiang Production and Construction Corps in 2017 and 2018,the effect of winter and spring irrigation on the dynamic changes of soil water and salt content and the cotton growth in Southern Xinjiang district,and on the model simulation of soil water transport were studied.The main results are as follows:?1?Dynamic changes of soil water-salt and characteristics of returning salt in cotton field during rest periodCotton soil moisture in the surface layer?0-40 cm?was greatly affected by the winter-spring irrigation and winter irrigation,and there were differences in the depths of the“arid zone”and“wet zone”formed by different leaching quotas.In the following year,the ground temperature increased,and the soil water moisture content increased with the increase of winter irrigation quota as a result of ground water moving to soil.However,more soil water stored with the increase of spring irrigation quota as a result of irrigation supplying.Therefore,compared to winter-spring irrigation and winter irrigation,spring irrigation with same irrigation quota is more conducive to replenish soil moisture in cotton fields before sowing.The results of leaching on salt content varied with different winter irrigation leaching quotas.The higher the winter irrigation quota was watered,the greater the salt leaching depth was achieved.Compared to winter-spring irrigation method,the results of salt leaching were much more efficiently with winter irrigation method.In the following year,the phenomenon of“returning of salt to the surface”occurred in all winter and spring irrigation treatments owing to soil salt ion migrated with the movement of soil water.However,spring irrigation can effectively wash the soil salt,and at the same time maintain the high soil moisture content,which is more conducive to cotton sowing.?2?Effects of initial soil water-salt conditions and winter-spring irrigation on cotton growth and yieldWhen the soil salinity is less than 0.3%,cotton spring irrigation quota or cotton supplement irrigation quota can be guided according to the initial soil moisture content before sowing?volume?20%<?0<24%of 0-20 cm soil depth.And it was suitable for cotton seedling growth when the soil salt concentration was less than 4g/L.The cotton seedling germination rate in spring irrigation treatment was significantly higher than that in winter-spring irrigation and winter irrigation.Under the same field management conditions,cotton yield reached maximum under the treatment of spring irrigation followed by the treatment of winter-spring irrigation and winter irrigation,respectively.While at the same irrigation method,cotton yield increased with the increase of leaching quotas,but there was no significant difference on cotton yield between in quotas of 120 m3/mu and of 160 m3/mu.?3?Optimum leaching quota of winter and spring irrigation and soil water migration simulationSoil water flow movement model based on water balance principle and Darcy's law could well simulate the variation of soil profile moisture content under different groundwater levels and irrigation conditions.By analyzing the relationship between different irrigation quota and groundwater depth,the relationship between groundwater and soil water accumulation was obtained.In the southern Xinjiang region,When the groundwater level is less than 1m,irrigation amount of cotton should be controlled to be less than 120mm;when the groundwater level is 1.5m,irrigation amount of cotton should be controlled to be less than 150mm;when the groundwater level is 2m,irrigation amount of cotton should be controlled be less than 210mm.?4?Simulation of cotton growth and yield based on winter and spring irrigation methodThe results of DSSAT-CROPGRO model showed that:this model could well simulate the change of cotton phenology and yield.However,the model was not able to simulate for cotton biomass.When the irrigation quota is 24mm-30mm,the cotton seed cotton yield is highest when the initial soil moisture content reaches the field water holding capacity.While,the highest yield of cotton achieved with 36 mm irrigation quota only when the initial soil moisture content is 80%?-??field water holding capacity?.
Keywords/Search Tags:Cotton field, Winter-spring irrigation, Salt-leaching, Dynamic changes of soil water-salt, Cotton growth and yield
PDF Full Text Request
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