Screening and Verification of Cotton (Gossypium hirsutum L.) Cultivars for Low-Phosphorus and the Critical Phosphorus Rate

To provide ideal materials for studying the effect of low-phosphorus tolerance in cotton yield and quality, 16 cotton cultivars were tested both under sand culture and its repeat experiment under 0.01 mmol L^-1 and 1 mmol L^-1 phosphorus concentration, and a cluster analysis was made according to the subjection values of low-phosphorus stress coefficient at seedling stage. Results showed that the relative changed value of leaf area, aboveground biomass and total phosphorus accumulation in a plant were identified as the best indicators to evaluate the cottons ability for low-phosphorus tolerance at seedling stage. The low-phosphorus tolerance differed with cultivar. Among the 16 cultivars, the Yuzaomian 9110, Lumianyan 36 and K836-1 were steadily low-phosphorus tolerance, the Hannongmianzao 1, De 0720 and K836-2 were steadily and moderately low-phosphorus tolerance, while the Lu 54 and Huamian 3109 were steadily low-phosphorus sensitive. Moreover, two cotton cultivars, Lu 54 and Yuzaomian 9110, had the most significant difference in physiological indicators, yield and quality, which were verified in the field test under different phosphorus rates (0, 50, 100, 150, 200 kg P₂O₅ ha^-1) in 2016. Thereafter, a critical phosphorus rate of Nanjing, 100 kg P₂O₅ ha^-1, had been found.