Matching of Soil Phosphorus Distribution and Root Distribution in Cotton Field Based on Diffusive Gradients in Thin-Films (DGT)

This study aimed to optimize the period of drip phosphorus (P) fertilization to increase P migration distance in soil and content in cotton, so as to achieve the coordinated above and belowground growth of cotton plants. A field experiment was conducted to study soil P in response to P application by drip irrigation during different periods of cotton cultivation using diffusive gradients in thin films (DGT) in situ. The root length density, biomass, P content and lint yield of cotton were investigated. Compared with broadcast P fertilization before plowing, drip P fertilization after sowing significantly increased DGT-P and root length density in the top 0–15 cm soil layer, and significantly increased the biomass P content and lint yield of cotton, but reduced the root/shoot ratio. In addition, drip P fertilization at bud stage could also increase the DGT-P and root length density in the top 0–10 cm soil layer compared with the broadcast P fertilization treatment. Our results indicate that drip P fertilization after sowing is an effective method to expand the vertical migration of P in soil, increase the length, density, and P content of shoot, and improve the growth of cotton.