| There is a serious shortage of water resources in China,and the contradiction between supply and demand of water resources is becoming increasingly prominent.Therefore,it is urgent to improve the efficiency of agricultural water use.China’s agriculture has a large proportion of water use.With the increasing shortage of water resources,agricultural production is bound to develop in the direction of high and stable yield.Therefore,it is necessary to develop water-saving irrigation technology centered on making full use of limited precipitation and water-saving and water conservation technology of dryland farmland.In agricultural production,SAP can improve the utilization rate of soil water and fertilizer,and achieve the purpose of water saving and yield increasing.It provides a new way and method for agricultural drought resistance and water saving,and is also an effective water saving measure in line with China’s national conditions.This paper adopts the idea of combining indoor and outdoor experiments to carry out the experimental research on the basic properties of agricultural SAP in the indoor,and explores the water-absorbing principle of SAP in the soil environment and its influence principle on soil properties by using the geotechnical experiments.At the same time,the stability of the water-retaining properties of the SAP in the soil environment of acid,alkali and salt was simulated in the laboratory.Combined with field experiments,the effects of different water retention agent dosage on soil moisture content,growth characters and yield indexes of corn were investigated.It provides theoretical basis and data support for the planting of corn,soybean and other crops in the experimental area.Through the experiment and analysis,the following conclusions can be drawn:(1)The water absorption rate of the SAP selected in this paper was 27.9 g/g.The water absorption stage was rapid water absorption,stable water absorption and slow water absorption,reaching saturation for about 80min and complete water release for about 22 h.The water absorption decreased significantly after repeated water absorption for three times.The SAP will not absorb water quickly,but can absorb and retain water stably.It can release water slowly at natural temperature,and has a certain stability of repeated water absorption,which can meet the needs of planting corn in the region to improve soil water condition.(2)The dosage of five SAPs set in the field experiment could significantly increase the soil moisture content of surface soil and the soil moisture content in the root depth of corn.Moreover,the application of 75 kg/hm~2had the most significant effect on the growth and development characters and yield indexes of corn.Although the application of 90 kg/hm~2increased the soil water content of corn in the growth period,it inhibited the growth and development of corn to some extent,leading to corn yield reduction.In the region,60kg/hm~2or 75 kg/hm~2of SAP should be selected according to the crop size and the comprehensive economic benefit of the selected quantity of SAP.(3)After water absorption and expansion of SAP in the soil,the saturated water content of the soil can be significantly increased,the evaporation of soil water can be inhibited,and the soil density can be reduced.The more SAP is used,the more obvious the phenomenon is.The drying and wetting process of soil weakens the improvement effect of SAP on soil properties,and the more the drying and wetting alternating times,the more obvious the weakening effect is.However,the SAP can maintain relatively good stability in the drying and wetting alternately for 3h.In regional crop planting,appropriate irrigation measures can be used to keep the soil moist,prolong the service life of SAP,and provide good soil moisture state for crops.(4)The properties of soil and SAP will be affected in acid,alkali and salt environment.The change of soil structure and enzyme activity caused the decrease of soil water holding capacity by acid and alkali.Both H~+and OH~-in the solution will react with the composition of the SAP,which will destroy the structure of the SAP and limit some properties of the SAP.The salt content in the salt solution will also change the soil structure and morphology,resulting in the change of soil properties.Cations in the solution will produce hydration group,which is not conducive to the absorption of water retention agent.The SAP still has certain stability in acid,alkali and salt solutions,but it is extremely unfavorable to the soil in acid,alkali and salt environments for a long time.The service life of SAP will continue to decline,and the economic benefits of planting crops will also decline.Therefore,environmental treatment should be the primary task. |
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