Cotton photosynthetic productivity enhancement through uniform row-spacing with optimal plant density in Xinjiang, China.

Xinjiang is currently the most dominant cotton ( L.)-growing region in China and possesses abundant radiation resource. The cultivation techniques such as wide and narrow row-spacing and high density are widely adopted to obtain high cotton yield in the region. However, the region is facing some problems including poor light transmittance in the field and low exploitation for light resources under the current planting pattern which impedes further growth in cotton yields. Therefore, it is essential to develop some cultivation practices to increase radiation use efficiency (RUE) and cotton yields in Xinjiang. Here we conducted a field experiment to quantify the effects of row spacing pattern and plant density on RUE, intercepted photosynthetically active radiation from May to August (IRAR), and lint yield during 2017 and 2018. In this study, we designed two row-spacing configurations (R, wide and narrow configuration, 66 cm + 10 cm; R, uniform row-spacing configuration, 76 cm) and six plant densities (4.5, 9.0, 13.5, 18.0, 22.5, and 27.0 plants m). The RUE, lint yield, and number of bolls were higher in R than R by 4.1-5.9, 2.5-4.8, and 9.1-14.2%, respectively. The RUE significantly increased with plant density, but lint yield stabilized at 18.0 plants m. Moreover, RUE had more significant positive effects on boll number and lint yield. Overall, we found that R combined with optimal plant densities (13.5-18.0 plants m) would be an effective strategy to achieve higher RUE and yields in the Xinjiang cotton system.