Water And Fertilizer Regulation Effect On Kenaf And Their Optimal Supply Mode

Annual demand of kenaf fiber in the international market is increased by8%, and the requirement of fibre quality is also gradually increased. But in China, the product quality of kenaf fibre is poor, which can not meet the demands of the international market. Planting area of kenaf is substantially reduced. At the same time, unreasonable irrigation and fertilizer inputs reduce nutrient and water use efficiency, and cannot play the due effect of kenaf varieties with high quality. In this study, taking the hybrid kenaf (Hongyou2) and conventional kenaf (Fuhong992) as the experimental plants, efficient use of water and fertilizer resources for kenaf was systematically and deeply studied.1. Under irrigation level in different stages experiment,(1) In vigorous growth stage and squaring and fruit stage, agronomic traits, dry bark weight and shoot dry weight of Kenaf increased obviously with the increase of irrigation level.(2) Middle irrigation (soil water content were controlled at50%of field capacity) at the seedling stage, and high irrigation (soil water content were controlled at80%of field capacity) at the vigorous growth stage and squaring and fruit stage, two varieties of kenaf had the highest raw flax yield. And Hongyou2had higher raw flax yield than Fuhong992.(3) Low irrigation (soil water content were controlled at40%of field capacity) at the seedling stage, and high irrigation (soil water content were controlled at80%of field capacity) at the vigorous growth stage, Low irrigation (soil water content were controlled at60%of field capacity) at the squaring and fruit stage, water use efficiency of kenaf reached the maximum value. Vigorous growth stage of kenaf is the critical stage on irrigation, which should be sufficient irrigation.(4) At high irrigation, yield of Hongyou2was significantly higher than that of Fuhong992. But at low irrigation, the result was in contrast.2. Under fertilization management experiment experiment,(1) Compared with low fertilization (N0.1Og/kg soil, P2O50.05g/kg soil and K2O0.10g/kg soil), middle fertilization (N0.15g/kg soil, P2O50.075g/kg soil and K2O0.15g/kg soil) and high fertilization (N0.20g/kg soil, P2O50.lOg/kg soil and K2O0.20g/kg soil) significantly increased yield and shoot dry mass of kenaf, NPK content and total amount absorption of different organs, and the soil available nutrients, but the difference of the yield of kenaf was not significant between middle fertilization and high fertilization.(2) compared with all NK fertilizer as top dressing, all NK fertilizer as base fertilization or40%NK fertilizer as top dressing significantly increased the plant height and others agronomic traits, yield and shoot dry mass of kenaf, N content and total amount absorption of different organs, but decreased K contents in different organs, K uptake and available soil nutrients. Therefore, middle fertilization with all NK fertilizer as base fertilization or40%NK fertilizer as top dressing is the best fertilization management method.3. Under irrigation and fertilization management experiment,(1) in middle fertilization, fiber yield, fiber length and width reached the maximums, and fiber strength and fiber line density reduced not significantly.(2) All NK fertilizer as base fertilization was beneficial to K absorption and utilization, improved the linear density of fibers, and got the highest yield, while N uptake and fiber strength did not reduce significantly.(3) Middle irrigation in seedling stage, high irrigation in vigorous growth stage and squaring and fruit stage, fiber yield, strength and length were higher than other treatments, and the fiber linear density did not decrease significantly. Therefore, the best strategy of irrigation and fertilization mode is middle fertilization (N0.15g/kg soil, P2O50.075g/kg soil and K2O0.15g/kg soil) with all NK fertilizer as base fertilization, and Middle irrigation in seedling stage, high irrigation in vigorous growth stage and squaring and fruit stage.4. Under reducing fertilization and irrigation experiment,(1) compared with adequate fertilization, reducing25%fertilization significantly reduced agronomic traits, dry bark weight and shoot dry weight of Kenaf. It showed that adequate fertilization was the guaranteed of high and stable yield.(2) Compared with adequate irrigation, reducing20%irrigation and40%irrigation decreased significantly agronomic traits and dry bark weight of Kenaf. It showed that irrigation was necessary for high yield.(3) In adequate fertilization and irrigation, yield of kenaf was significantly higher than other treatments. In reducing25%fertilizer amount, reducing20%irrigation was the most adaptive irrigation level. This indicated that one of irrigation and fertilization was short supply, it should reduce the others.5. Under irrigation and fertilization method experiment,(1) The furrow irrigation, yield and quality of Fuhong992was better than Hongyou2, and60%NK fertilization as top dressing could get the highest yield.(2) Compared with furrow irrigation, drip irrigation might reduced the fiber strength of hongyou2, but improved dry bark weight, fiber yield and fiber linear density remarkable; but the effect of irrigation method on fiber yield of Fuhong992was not observably.(3) In drip fertigation with60%NK fertilizer as top dressing, dry bark weight and fiber yield got the highest yield, while fiber quality was better; fiber quality of Fuhong992has improved, but fiber yield was significantly lower than Hongyou2.(4) Without irrigation and fertilization, fiber yield was not significantly difference between Fuhong992and Hongyou2, but fiber strength of Fuhong992was better than Hongyou2.To sum up, with good conditions of irrigation and fertilization, Hongyou2should be the cultivation; otherwise, Fuhong992was profitable. Recommended irrigation system of kenaf is middle irrigation in seedling stage (soil water content were controlled at50%of field capacity), high irrigation in vigorous growth stage and squaring and fruit stage (soil water content were controlled at80%of field capacity). When the water resources were limited, vigorous growth stage should be first meet. The recommended strategy of irrigation and fertilization management is fertilization level is N200kg/hm2, P2O566.7kg/hm2and K.2O133.4kg/hm2, and drip fertigation with60%NK fertilizer as top dressing.