| In this study,the Yellow River Delta region in northern Shandong Province was taken as the research object,and the local soil salinization control was closely combined.In view of the characteristics of saline-alkali farmland in the Yellow River Delta,such as shallow groundwater level,high salinity and uneven rainfall during the growth period,chemical improvement methods were.Through theoretical analysis,indoor and outdoor experimental research,and model simulation,the migration law of coastal soil water and salt during the growth of winter wheat was mastered,and the influence of modifiers in different periods on water and salt distribution and crop growth was explored.Details are as follows:(1)Carboxymethyl cellulose(CMC)and humic acid(HA)had the effect of reducing soil water infiltration and are positively correlated with the application rate,and the effect of CMC on reducing soil water infiltration is more obvious.With the increase of CMC and HA application rate,Philip model parameter moisture absorption rate S and Green-Ampt model parameter Ks*hf values decreased,showing a negative correlation.There is a good exponential relationship between parameters and dosage of different modifiers.CMC and HA increased the water holding capacity of soil.At the same infiltration time,the application rate was negatively correlated with the leaching salt.Infiltration to the same depth,salt washing effect is stronger than CK treatment.(2)The content of CMC was positively correlated with saturated water content ?s and intake suction reciprocal ?,and negatively correlated with saturated hydraulic conductivity Ks and shape coefficient n.The influence order of CMC on hydraulic parameters is:saturated hydraulic conductivity,intake suction reciprocal,shape coefficient and saturated water content.The saturated water content ?s of HA increases with the increase of HA dosage,and the saturated hydraulic conductivity Ks decreases with the increase of HA dosage.The shape coefficient and the reciprocal of inlet suction do not change significantly in the selected dosage range.The order of the influence of HA on hydraulic parameters from high to low is:saturated hydraulic conductivity>saturated water content.(3)During the growth period of winter wheat,the water content of 20-80 cm soil layer was positively correlated with the depth,and the variation trend of average water content of each soil layer was basically the same in time scale.The water content of 0-20 cm soil layer was most severely affected by rainfall and irrigation,while that of 70-80 cm soil layer was less affected by natural conditions,and the variation range of water content was small.The changes of water and salt are closely related and basically synchronized in time and space.Application of CMC and HA can slow down field water loss rate.Carboxymethyl cellulose inhibited the salt washing process caused by rainfall and the salt accumulation process of surface soil caused by evaporation.Because the effect of humic acid on reducing infiltration was weaker than that of carboxymethyl cellulose,the inhibition of salt washing process in the field was not reflected,and the effect of inhibiting evaporation was slightly weaker than that of carboxymethyl cellulose.Total salt accumulation rate of all treatments during growth period was less than that of CK.(4)Plant height,leaf area index and aboveground biomass of winter wheat were positively correlated with humic acid(HA)application rate.With the increase of carboxymethyl cellulose(CMC)application rate,each index increased first and then decreased.The maximum value appeared in 30 kg·hm-2 treatment,and the growth indexes of the treatment were higher than those of control treatment.With the increase of CMC application rate,crop yield and water use efficiency first increased and then decreased,showing a positive correlation with HA application rate.In the experiment,when the humic acid application rate was 350 kg·hm-2,the yield was the best and the efficiency was the best at 250 kg·hm-2.The yield of 30 kg·hm-2 CMC was the best,and 250-350 kg·hm-2 humic acid was recommended.(5)The SHAW model was used to simulate the soil temperature,soil moisture and soil salinity during the growth period of coastal winter wheat,and the model was tested.The SHAW model is feasible to simulate the thermal migration of soil water and salt during the growth period of coastal winter wheat.SHAW model was used to analyze the distribution characteristics of water and salt under different irrigation amounts.The depth and breadth of soil wetting were positively correlated with irrigation amount,and the soil salt leaching effect was negatively correlated with irrigation amount.Each irrigation amount should be less than 150 mm,and each optimal irrigation amount should be 20 mm.The sum of winter irrigation amount and rainfall at this stage should be greater than 80 mm. |
PDF Full Text Request