Response Mechanism Of Coastal Saline-Alkali Soil-plant System To Biochar Addition In The Yellow River Delta

The coastal saline soil has serious problems such as poor permeability and water retention capacity,and restrict the developmont of agriculture in the Yellow River Delta.Biochar provides new ideas for improving the saline soil in the Yellow River Delta.In this study,the pot and field experiments were carried out to analyze the response of soil physics,chemistry,microhial,physiological ecology characteristics,crop growth to biochar addition and to explore the improvement effect of biochar addition on coastal saline soil-plant system.The main results are as follows:(1)Biochar addition reduced the bulk density of coastal saline soil.Compared with the control,the effect of 4% biochar addition was the most significant,with a decrease of 16.14%(P<0.05).The addition of biochar significantly increased the water content of coastal saline soil at the bud stage,mature stage and harvest stage of Gossypium spp.In the harvest period,compared with the control,the soil moisture contents of the 2%,4% biochar addition treatment were significantly increased by 13.99%,23.41%,respectively.The addition of biochar significantly increased the available nitrogen,phosphorus and total organic carbon content in the coastal saline soil.The greatest effect on available phosphorus was 4% biochar addition treatment,while the greatest effect on available nitrogen was 2% biochar addition treatment.The addition of biochar significantly increased the conductivity of the coastal saline soil,which may be due to the increase in the water-soluble salt content of the soil by the adsorption of the applied fertilizer.However,compared with the addition of biochar,it can be seen that the soil conductivity of 4% added is still less than 1% and 2%,indicating that biochar still has improvement effect on soil conductivity.(2)High-throughput sequencing results of soil samples indicate,the Shannon and Simpson indices were not significantly different between the biochar addition treatment and the control,and the 2% biochar addition treatment significantly increased the number of bacterial OTU,which indicated that the addition of biochar had little effect on the diversity of the flora,but increase the number of flora.Lower amounts of biochar addition(1% or 2%)increased the activity of antioxidant enzymes and the content of osmotic adjustment substances in the leaves of Suaeda salsa;while the addition of higher amounts of biochar(4% and 8%)decreased the antioxidant enzyme activity and its osmotic adjustment substance content in the leaves of Suaeda salsa.This can be due to the fact that higher biochar addition treatment ameliorate the soil environment so as to lower the stress effect on plants.The addition of biochar significantly increased the net photosynthetic rate of Cynodon dactylon.The net photosynthetic rate of 2%,4%,and 8% biochar additon treatment significantly increased by 6.39%,9.42%,and 16.05%,respectively.(3)In the range of biochar application rate(1-8%),the 8% addition significantly increased the water use efficiency of Cynodon dactylon,the increasement was 37.04% compared with the control.The total root length,total root area,aboveground and underground biomass of Gossypium spp Cynodon dactylon increased significantly with the increase of biochar addition,and the highest increasement was 4% biochar addition treatment.Compared with the control,the total biomass of bermudagrass increased by 189.71% in the 4% biochar addition treatment.The total biomass of 8% slightly increased,but there was no significant difference between 8% and 4% biochar addition treatment.Compared with the control,4% biochar treatment significantly increased the Gossypium spp yield by 28.14%.In conclusion,from the perspective of promoting Gossypium spp yield,increasing the biomass of Gossypium spp Cynodon dactylon and promoting Gossypium spp Cynodon dactylon root growth,4% biochar addition has the best effect on the improvement of saline-alkali soil-plant system.