Study On Factors Affecting Yield Of Industrial Hemp

Hemp (Cannabis sativa L.) is an important bast fiber crop in the world. Industrial hemp distributes widely in China, and has great potentiality in the yield. At present, further improvement of the yield has been limited due to the ecological disadvantage and lack of cultivation techniques of hemp with high-yield and top-quality. Based on the ecological conditions at Kunming, we firstly adopted the orthogonal experiment design to explore the effects of factors such as density, variety and fertilizer rate on growth and yield, then studied the effects of fertilizers amount and ratio on the yield of industrial hemp using single-factor randomized block design, by which to provide theoretical basis and technical support for hemp cultivation.The main results were shown as below:1) In the3factors experiment including fertilizer amount, variety and planting density, fertilizer was the main one that affected the growth, agronomic traits and yield indices of hemp, especially for the effects on chlorophyll content, stem diameter and total biomass significantly, all these indices were improved along with the increment of fertilization, and we had got its greatest yield under high fertilization treatment. Variety had significant effects on dry bast yield of hemp, and ’Yunma No.5’was the best. Althought planting density had little effect on all indices, medium planting density performed better. From the above, optimized cultivation measures for high-yielding had been preliminarily established:density was460000plants/hm2, compound fertilizer was1200kg/hm2, urea was180kg/hm2and variety was’Yunma No.5’.2) Increasing fertilizer amount and nitrogen ratio had obvious promoted effect on the growth of ’Yunma No.5’, not only increased the plant height, stem diameter and bast thickness, but also raised nitrate reductase activity, restrained the cellulase activity and promoted protein synthesizing, which made it possible for yield improvement. Furthermore, NPK nutrients accumulation and their percentage in each part of hemp plant were improved along with the increment of fertilizer amount and nitrogen ratio. The accumulation of each nutrient in mature plant ranked as follows:potassium> nitrogen> phosphorus, and the distribution of NPK nutrients in each part of plant was: Leaves> Basts> Boles. NPK nutrients use efficiency showed a downward trend after the first rise with the increase of fertilizer amount. Increasing the ratios of P or K, especially for high ratio of P, could significantly improve N utilization efficiency. Increasing the ratio of N also improved P and K utilization efficiency.In conclusion, fertilization was the most important factor that affected the yield among the factors tested in this study. NPK fertilizers rate and ratio played an important role in improving growth, yield components and nutrient use efficiency of industrial hemp. However, other factors that affect the growth of hemp under different conditions should not be neglected and agricultural measures be adjusted accordingly to achieve high yield of industrial hemp.