Effects Of Water Retaining Materials On Water Saving And High Yield Of Millet In Arid Farming Areas Of The Loess Plateau Of Inner Mongolia

In order to address a series of issues such as poor germination,low water use efficiency,and unstable yield in the dry and water-deficient loess plateau region of Inner Mongolia.A field experiment was conducted over a period of two years in Qingshuihe County,Hohhot City,using the K1 variety of millet as the experimental material.The study aimed to investigate the effects of different water-retaining materials and their application rates on soil evaporation and physicochemical properties,millet growth,photosynthetic characteristics,yield formation,water use efficiency,and economic benefits.The five water-retaining materials used in the experiment were hydrogel carrier,polyacrylamide（PAM）,superabsorbent polymer（SAP）,bentonite,and Huashen agricultural and forestry water-retaining agent.Three application rates were set for each water-retaining material,with no application serving as the control（CK）.The main research findings are as follows:（1）All tested water-retaining materials were able to reduce soil evaporation and increase soil water content.The five water-retaining materials,hydrogel carrier,PAM,bentonite,Huashen agricultural and forestry water-retaining agent,and SAP,significantly（P<0.05）reduced total soil evaporation by 51.57 mm,54.16 mm,37.40 mm,40.56 mm,and 45.19 mm,respectively.Soil water storage was significantly（P<0.05）increased by 32.11mm,35.12 mm,18.02 mm,34.52 mm,and 32.75 mm,respectively.The overall water retention effectiveness ranked as PAM>hydrogel carrier>bentonite>SAP>Huashen agricultural and forestry water-retaining agent.For a given water-retaining material,soil water content showed an initial rapid increase followed by a slower increase with increasing application rate,and after a certain threshold,soil water content no longer increased significantly（P<0.05）.（2）Water-retaining materials improved the physicochemical properties of the 0-20 cm soil layer.All five water-retaining materials led to improvements in soil physicochemical properties,with a decrease in soil bulk density of0.03-0.06 g?cm^-3,an increase in soil porosity of 1.30%-2.11%,an increase in organic matter content of 0.17-0.54 mg?kg^-1,an increase in available phosphorus content of 0.22-0.41 mg?kg^-1,an increase in available potassium content of1.46-3.14 mg?kg^-1,and an increase in alkali hydrolyzable nitrogen content of1.05-2.30 mg?kg^-1.（3）All five water-retaining materials improved millet germination rate,morphological indicators,and leaf photosynthetic performance.The increase in germination rate ranged from 10.41%-13.19%,leaf photosynthetic rate increased by 7.15%-13.97%,plant height increased by 0.30-24.3 cm,stem diameter increased by 0.06-1.31 mm,individual leaf area increased by107.4-361.04 cm²,and aboveground biomass increased by 0.55%-0.21%.（4）Millet grain yield,mature biomass,and water use efficiency increased with the application rate of water-retaining materials,but these indicators no longer increased significantly after reaching a certain application rate.