Physiological responses of cotton to regulated deficit irrigation and its optimized agronomic techniques

Under the condition of mobile rain-proof shelter, combined pot experiment with the pond culture, the effects of regulated deficit irrigation(RDI) on the photosynthetic rate(Pn), transpiration rate(Tr), distribution and accumulation of photosynthetic products, economic yield and water use efficiency during the different growth stages of cotton were analyzed. A two-factor(RDI stages and the amount of water deficit) randomized-block design was adopted in pot experiment and a three-factor(the amount of water deficit, fertilizer level, plant density)quadratic rotational regression combination design was adopted in pond culture. Results show that under appropriate amount of water deficit at right stages, Tr decreases obviously, and Pn does not obviously decrease. There are super-compensation effects in photosynthesis and photosynthetic products accumulation after re-watering,which is beneficial for the translocation and distribution of seed cotton. The suitable indexes of RDI for water-saving and high-yield of cotton as follows: the regulated water deficit during seedling stages is low and moderate water deficit, and the amount of water deficit at 0～40 cm soil layer is 60%FC(field water capacity)～60%FC. Regulated water deficit during bud stages is low water deficit, and the amount of water deficit is 60%FC. During flowering-boll forming stages, regulated deficit irrigation is not suitable, and the amount of water deficit is above 75%FC. Regulated water deficit during boll-opening stage is moderate water deficit, the amount of water deficit is 50%FC～55%FC.