Adaptability Of Hemp Growth To Nitrogen Level Under Soilless Culture

The abuse of chemical fertilizer not only increases the production cost but also causes environmental pollution.This study aims to explore the biological characteristics of industrial hemp under different nitrogen treatment,in order to provide experimental data support for the cultivation and utilization of N-efficient hemp varieties.At the same time,it is expected to reduce the application of nitrogen fertilizer and environmental pollution on the premise of ensuring the normal growth of hemp,so as to provide reference for the realization of green cultivation of industrial hemp.This study take four hemp varieties(Yunma 1,Yunma 7,Bamahuoma,Wanma 1)as experimental materials.The growth and physiological indexes of hemp were measured by soilless pot culture and artificial nutrient solution design were applied using six N levels(0,1.5,3,6,12 and 24mM).The main results were as follows:(1)Four varieties of hemp have different growth conditions at 0 ~ 24 mM nitrogen treatment.Except for the control,the comprehensive growth of the low(1.5mM)nitrogen treatment is the worst,with short plants,yellow and white leaves;under high(12mM,24mM)nitrogen treatment,the stem diameter,plant height,and biomass were significantly higher than that of low(1.5mM)nitrogen treatment.Under medium(6mM)nitrogen treatment,the plant height and stem biomass of the four varieties of cannabis tested were not significantly different from those under high nitrogen(12mM)treatment.And the plant height of Yunma 1,Bamahuoma,Yunma 7 has no significant difference under high nitrogen(24mM)treatment with these varieties under medium(6mM)nitrogen treatment.(2)Different varieties have different physiological indexes under different level of nitrogen treatment.Under high(24mM)treatment,the content of chlorophyll,MDA and soluble protein of four varieties increased,while nitrate reductase,SOD and POD content decreased.Under medium(6mM)nitrogen treatment,the activities of NR,POD activity and SOD of the four varieties reached the peak;the soluble sugar content of Yunma 7 reached the maximum.The physiological indexes of three varieties(Yunma 1,Bamahouma and Wanma 1)were higher than that of control(0mM)even at sub-low(3mM)nitrogen treatment.(3)The plant nitrogen content(N uptake)of four hemp varieties increased with the increase of N supply level,while the plant phosphorus content decreased with the increase of N supply concentration.However,the K uptake of Yunma 1 and Wanma 1decreased with the increase of N supply level,while that of Bamahuoma decreased with the increase of N supply level The accumulation of K content in Yunma 7 was irregular.In conclusion,the increased application of nitrogen can increase the growth of hemp,chlorophyll content in leaves,SOD activity,POD activity,etc.However,applying a large amount of nitrogen fertilizer increased the MDA and soluble protein content in the leaves of hemp under high nitrogen treatment,and reducing the amount of nitrogen fertilizer properly could also make hemp grow well and achieve a higher biological yield.