Effect of Leaf Area Index on Yield of Spring Wheat in Dryland under Coupled Change of Supplementary Irrigation and Straw Mulching Amount

Leaf area index of spring wheat had a great effect on yield under coupling change of supplemental irrigation amount and straw mulching amount in no-tillage mulching．Based on historical meteorological data from 1979 to 2019 in Anding District, Dingxi City, Gansu Province, the APSIM model was used to simulate leaf area index, yield and its component factors of dryland spring wheat under coupling change of supplemental irrigation amount and straw mulching amount, and DPS software was used for analysis and experiment．To study effect mechanism of leaf area index on yield of dryland spring wheat under coupling change of supplemental irrigation amount and straw mulching amount．Results showed that in experimental design range, effect of different leaf area index on thousand grain weight of spring wheat changed in an upward quadratic parabola during period of flowering and grain filling．In other periods, effects of different spring wheat leaf area index on spring wheat yield and grain weight showed downward quadratic parabola changes, while effects of different spring wheat leaf area index on spring wheat grain number showed upward quadratic parabola changes．In experimental range, there was no threshold for thousand grain weight of spring wheat in each period, and there was no threshold for grain number of spring wheat in tiller-jointing stage．The minimum value of grain number of spring wheat was 8716.59 grain/m² when leaf area index of spring wheat was 1.72．When leaf area index of spring wheat was 0.94, 2.31, 1.67, 1.18, 1.24, 0.79, the maximum yield of spring wheat was 3818.71, 3827.06, 3851.41, 3904.35, 3819.03, 3853.72 kg/hm²．When leaf area index of spring wheat was 0.77, 2.01, 1.44, 1.07, 1.00, 0.70, the minimum grain number of spring wheat was 9579.34, 8745.26, 9638.01, 9050.71, 8554.04, 9038.38 grain/m²．Leaf area index of spring wheat had positive effect on yield and grain weight, but negative effect on grain number．Reasonable adjustment of leaf area index of spring wheat could promote increase of light transmittance rate and production of photosynthate, which has positive significance for increase of spring wheat yield．