Effects of Supplemental Irrigation at Sowing Stage on Soil Moisture and Grain Yield of Wheat

To clarify the effects of soil pondage and its longitudinal distribution in 0-200 cm soil layer at sowing stage on emergence,population growth and grain yield of wheat,during the wheat growing season in 2013-2014,supplemental irrigation was conducted with different plan wetting soil layer depth,target soil water content at sowing stage according to the irrigation quota formula,under the condition with consistent soil bulk density and field capacity,but different soil pondage before planting in field A and B.Results show that the infiltration depth of irrigation water in field B was larger,but mainly concentrated in 0-60 cm soil layer,under the condition of the field A and field B with 201.5and 266.3mm of soil pondage in 0-100 cm soil layer respectively,and with 554.2and 586.4mm ofsoil pondage in 0-200 cm soil layer respectively.The increase of soil moisture in 0-10 cm and 0-20 cm soil layer in different treatments was higher than that in the other soil layers.The seedling emergence of wheat was mainly affected by the soil moisture in 0-10 cm soil layer at sowing stage,but population development,dry matter accumulation and yield formation are affected by the soil pondage before planting and the level of supplemental irrigation at sowing stage.Lower soil moisture in upper soil layer was bad for seedling growth,which decreased the stem number per unit area during overwintering to jointing stages significantly;lower soil pondage in 0-100 cm soil layer before planting restricted the growth of wheat during the middle and later growth stages,which reduced ear number and dry matter accumulation amount,and decreased yield,even though irrigation was increased within a certain range at sowing stage,and then supplemental irrigation was conducted at jointing and anthesis stages.Under the same available soil water stored at planting condition,the total water consumption of wheat and grain yield increased with the increase of the target relative water content of supplemental irrigation at sowing stage,but the grain yield was no longer increased,and the water use efficiency was lower,as the irrigation water was too much.