Farmland Microclimate and Yield of Winter Wheat under Different Row Spacing

To gain new insights into the underlying mechanisms responsible for farmland microclimate and yield of winter wheat under different row spacings [row spacing: 7 cm (RS7); 14 cm (RS14); 24.5 cm (RS24.5); 49 cm (RS49)], field experiments were conducted at Taian, China. At approximately 13:00 – 14:00, low values of RH and air temperature at 5 cm above the ground for the various row spacings were obtained. The average RH of RS7, RS14, RS24.5, and RS49 was 91.0%, 90.3%, 85.7%, and 76.4%, respectively; the order of average air temperature was as follows: RS14 < RS7 < RS24.5 < RS49. The soil temperature of RS49 was obviously higher than those of RS7 and RS14. The maximum values of eddy thermal diffusivity, as well as sensible and soil heat fluxes, were obtained at 12:00. The order of these parameters was similar to that of the air temperature, but opposite to that of the latent heat flux. The yield of RS49 was significantly lower than those of the other treatments ( P < 0.05). The present study indicates that increasing the row spacing may result in severe dissipation of energy. RS14 is the optimum condition under uniform planting density.