Simulation Of Evaporation For Saline-alkali Soil Under Straw Mulching Conditions In The Yellow River Delta

In order to explore the characteristics of coastal soil water,heat,salt distribution as well as soil evaporation process and its simulation under straw mulching conditions.Coastal saline-alkali soil from Binzhou Wudi City was taken as the main research objects,and laboratory experiments with different straw amount（0,0.3,0.6,0.9 and 1.2 kg/m² which named CK,S1,S2,S3 and S4,respectively）were carried out.Soil water and salt distribution,meteorological factors,turbulent exchange of heat and evaporation rate were measured,and the dynamic model of soil moisture resistance and coverage resistance under different straw mulching amount were established,in the end,the accuracy of the established model was evaluated using the measured and calculated data.The main research results and conclusions are as follows:（1）The characteristics of soil,water and salt distribution under straw mulching conditions are explained.The average water content of the surface soil and the whole profile layer were higher than CK,which were increased by 51.63%～87.86%and 41.2%～65.7%,respectively.The average salinity content of the surface layer for the straw mulching treatments were16.9%～35.3%lower than that of CK.（2）Straw mulching can effectively effect soil surface temperature,air temperature,humidity and heat transfer.The surface soil temperature and average air temperature of the straw mulching treatments were 21.9%～33.5%and 0.59%～1.54%higher than that of CK,respectively.Average air humidity of the straw mulching treatments were 1.5%～1.9%lower than that of CK.Moreover,turbulent exchange coefficient,turbulent heat flux and latent heat flux were reduced by 29.9%～73.3%,52.8%～80.2%and 57.6%～84.9%,respectively for CK,when compared with the mulching treatments.（3）Relationship between straw mulching and soil evaporation rate as well as cumulative evaporation amount were explained.The effect of straw mulching on soil evaporation is mainly in the early stage（0～5000 min）,which were 21.56%～65.06%lower than that of CK,while it increased by 2.1%-95.8%in the late stage（5000～18000 min）as the amout of soil content decrease.The cumulative soil evaporation showed an exponential increase trend with time,moreover,cumulative evaporation decreases with the increase of straw coverage.Time,straw mulching and their interaction have an significant impact（p<0.01）on soil evaporation rate and cumulative evaporation amount.（4）Resistance model was established and evaporation simulation was realized under different straw mulching amount conditions.A significant positive correlation（p<0.05）relationship was showen between mulching resistance and straw amount.Moreover,the resistance increased and then decreased with time for the same straw treatment during the evaporation process.The RMSE,MAE and NS between the simulated and the actual evaporation was 4.18×10^-4 mm/min,3.85×10^-5mm/min,and 0.90,respectively,and the slope k was 0.926,indicating that the calculated mulching resistance model can accurately calculate soil evaporation under straw mulching conditions.The results of this study provide theoretical and technical support for the regulation of soil water and salt,as well as improve agricultural water use efficiency and high-quality development for saline-alkali soils in the Yellow River Delta.