Effects And Mechanism Of Trichoderma Fertilizer Applied To Chinese Wolfberry(Lycium Chinense) In Coastal Saline-alkali Land

As an important reserve cultivated land resource in China,rational development and utilization of coastal saline-alkali land and improvement of crop nitrogen use efficiency are important ways to realize the sustainable development of agricultural economy and ecological environment.Chinense wolfberry(Lycium chinense)has developed roots,strong penetration in the effective soil layer and superior stress resistance.It is a pioneer tree species planted in saline-alkali areas.Trichoderma as plant growth-promoting bacteria can effectively improve the quality of saline soil,enhance plant nutrient absorption and promote plant growth.In this study,Chinese wolfberry was used as the experimental material to explore the effect of Trichoderma fertilizer on the soil and Chinese wolfberry growth in coastal saline-alkali land in the Yellow River Delta through the field experiment.Combined with the potted experiment,the growth-promoting mechanism was revealed from the perspective of nitrogen absorption and utilization,which provided theoretical and technical support for the cultivation of Chinese wolfberry in coastal saline-alkali land and promoted the development of planting industry in coastal saline-alkali land.The results show that:1.The application of Trichoderma fertilizer in saline soil increased the accumulation of nitrogen and phosphorus in Chinese wolfberry,enhanced the photosynthetic performance of Chinese wolfberry,and thus promoted the growth of Chinese wolfberry.Although the improvement effect was slightly lower than that of chemical fertilizer alone,the apparent nitrogen recovery efficiency,agronomic nitrogen use efficiency and partial factor productivity for applied nitrogen were significantly higher than those of chemical fertilizer.Under the treatment of Trichoderma fertilizer replacing 25%chemical fertilizer,the crop yield was increased by increasing nitrogen accumulation,enhancing photosynthetic performance,and ensuring the effective improvement of nitrogen use efficiency.2.The application of Trichoderma increased the non-capillary porosity of coastal saline soil,reduced the soil bulk density,and then increased the soil water content.The soil physical structure was effectively improved,and the improvement effect was stronger than that of chemical fertilizer.Compared with chemical fertilizer application,Trichoderma fertilizer instead of 25%chemical fertilizer could not only effectively improve the physical and chemical properties of soil,but also enhanced soil nitrogen supply capacity,thereby promoted crop yield.The results of principal component analysis showed that the biological effect of Trichoderma functional bacteria in bio-organic fertilizer directly promoted crop nutrient absorption and growth is more obvious.3.In the potted experiment of sterilized substrate salt stress,after 14 days of salt treatment,the NO₃^-and NH₄⁺efflux in the root meristematic zone and maturation zone of Chinese wolfberry,decreased the activities of NR,NIR and GS in Chinese wolfberry roots and leaves,and the total nitrogen accumulation of Chinese wolfberry decreased,resulting in the decrease of Chinese wolfberry biomass.The application of Trichoderma could significantly alleviate the NO₃^-and NH₄⁺efflux in the root meristematic zone and maturation zone of Chinese wolfberry under salt stress,and the NO₃^-and NH₄⁺showed an influx trend in the meristematic zone after 14 days of salt treatment,the inhibition of salt stress on the activities of nitrate reductase,nitrite reductase and glutamine synthetase was alleviated,and the total nitrogen accumulation of Chinese wolfberry was simultaneously enhanced,thereby improving the photosynthetic rate and photosynthetic nitrogen use efficiency,and promoting the growth of Chinese wolfberry under salt stress.In the potted experiment of coastal saline soil,the application of organic fertilizer,Trichoderma fertilizer and agent significantly increased NO₃^-and NH₄⁺influx rate in the root meristematic zone and NO₃^-influx rate in the maturation zone of Chinese wolfberry in coastal saline alkali land,and the increased amplitude was greater by Trichoderma fertilizer application than organic fertilizer application.The NH₄⁺influx rate in the maturation zone of Chinese wolfberry treated with Trichoderma fertilizer was higher than that of the control and organic fertilizer,but the difference was not significant between them.On the one hand,the application of Trichoderma fertilizer and agent in saline soil significantly increased the biomass,nitrogen content in root,stem and leaf of Chinese wolfberry and plant nitrogen accumulation,improved the nitrogen uptake efficiency of Chinese wolfberry,and elevated the activity of nitrate reductase,nitrite reductase and glutamine synthetase in Chinese wolfberry roots and leaves,on the other hand,it significantly enhanced photosynthetic rate,leaf stable carbon isotope abundance value(?¹³C)and photosynthetic nitrogen use efficiency in Chinese wolfberry,and the effect of Trichoderma fertilizer was obviously better than that of organic fertilizer.In summary,on the one hand,Trichoderma fertilizer could effectively improve the soil physical structure,and the improvement effect is better than that of chemical fertilizer.On the other hand,Trichoderma fertilizer could directly promote the absorption of nutrients such as nitrogen and phosphorus,enhance photosynthetic performance,and thus improve the yield of Chinese wolfberry,but the yield is lower than that of chemical fertilizer.Combined application of Trichoderma fertilizer and chemical fertilizer can not only improve nitrogen content and nitrogen use efficiency of Chinese wolfberry,ensure high yield of Chinese wolfberry,but also effectively improve soil physical and chemical properties and enhance soil nitrogen supply capacity.Trichoderma mainly increased nitrogen absorption,assimilation and accumulation of Chinese wolfberry under salt stress,enhanced photosynthetic carbon sequestration capacity and improved photosynthetic nitrogen use efficiency,thus promoted the growth of Chinese wolfberry.