Weed control performance of different sowing modes in organic wheat production

Serious weed infestations are one of the main factors restricting yield increases in organic wheat. The effect of different sowing modes on the growth competitiveness between wheat and weeds under field conditions was studied to explore new methods of agronomic weed control in organic wheat fields. In 2019 and 2020, the spring wheat cultivar "Yongliang 4" was sown using three sowing modes: wide-range uniform sowing (W0), wide-range 7 cm sowing (W7) and conventional drill sowing (CK). The differences in agronomic traits, light transmission rate, wheat grain yield and quality, weed density and weed biomass at different days after sowing (DAS) were studied. The results showed that compared with the CK treatment, the W0 treatment significantly increased the morphological indices (plant height, flag leaf area, leaf area per plant), photosynthetic physiological indices (flag leaf SPAD value, net photosynthetic rate) and population indices (leaf area index, dry matter weight) of wheat at the flowering stage. The light transmission rates in different layers of the wheat canopy in the W0 and W7 treatments were significantly reduced. The density of root length, root surface area, root volume, and root weight in different soil layers in the W0 treatment significantly increased. The grain yields of the W0 and W7 treatments were significantly increased by 28.2% and 15.0%, respectively. The total weed density and total weed biomass of the W0 and W7 treatments decreased significantly at different DAS. Correlation analysis showed that total weed biomass and total weed density were significantly negatively correlated with leaf area index, dry matter weight, leaf area per plant, grain yield, grain protein content, density of root length, root surface area, root volume, and root weight and significantly positively correlated with light transmission rate in the upper, middle and lower parts of the wheat canopy layer. In conclusion, wide-range uniform sowing increases wheat competitiveness against weeds for aboveground and underground resources, suppresses weed germination and growth, and improves wheat grain yield and quality by establishing an appropriate population canopy structure and welldeveloped root system of organic wheat.