Effects Of Biochar-based Multi-element Compound Soil Conditioner On Rice Physiological Characteristics And Cadmium Absorption

Biochar,activated silicon,and cytokinin producing bacteria agent have been found to promote plant growth,alleviate plant biological and abiotic stresses,improve plant stress resistance,and increase crop yield.In recent years,most studies have paid more attention to the role of a single soil conditioner,but less research has been conducted on the combination of two or three kinds of soil conditioners.Therefore,in order to study the effects of three different soil conditioners and their compatibility on rice growth physiology and cadmium absorption,Random block design was planed in the soil pot experiment and field experiment,and there were 8 treatments in pot experiment:CK（control）,T1（Miscanthus lutarioriparius biochar,MB）,T2（active silicon,Si）,T3（cytokinin producing bacteria agent,CPB）,T4（MB+CPB）,T5（Si+CPB）,T6（MB+Si）and T7（MB+Si+CPB）.The physiological effects of Huanghuazhan at different growth stages were grown in soil with a cadmium content of 1.84mg/kg.In the field experiment,Taoyouxiangzhan and Liangyou 336 were used as materials,and three treatments were set up:CK1（biochar-based compound fertilizer）,A（biochar-based compound fertilizer+active silicon）,B（biochar-based compound fertilizer+active silicon+ cytokinin-producing bacteria agent）.Measure its effect on rice yield and cadmium content.The main research results are as follows:1.The results of the pot experiment showed that different combinations of soil conditioners of Miscanthus lutarioriparius biochar,active silicon and cytokinin producing bacteria agent could improve the physiological resistance of rice at different growth stages and the application effect of multi-factor compound soil conditioner have better than those of the single substance soil conditioners.At booting stage,heading stage and filling stage,the content of malondialdehyde in the flag leaves of each treatments were lower than that of the control.The activities of catalase,peroxidase and superoxide dismutase in the flag leaf antioxidant enzyme system were all higher than that of the control.2.The research results of cytokinin producing bacteria agent in pot experiment showed that T3,T4 and T7 treatments had the ability to improve rice root vitality compared with the control and the T7 root vitality had the highestin the four treatments,which T3,T4 and T7treatments were significant difference with the control.T3,T4 and T7 treatments affected the species composition and abundance of rhizosphere bacteria and fungi.There were differences in the effects of T3 and T4 treated with biochar on different types of bacteria,the relative abundances at the phylum level differed greatly from the control about Proteobacteria,Actinobacteria,and Firmicutes.3.The research results of the pot experiment showed that soil conditioners with different material properties could increase the photosynthesis parameters such as net photosynthetic rate,transpiration rate,stomatal conductance and intercellular CO₂concentration of rice flag leaves,thereby increasing the yield of rice and the application effect of binary and multi-element compound soil conditioners were better than that of single soil conditioner.At booting stage,T6,T7 and CK have significant differences in the net photosynthetic rate.At the heading stage,the net photosynthetic rate of each treatment was significantly higher than that of CK,and the maximum net photosynthetic rate value of T7was 17.67μmol/m²/s.The 1000-grain weight and relative yield of each treatment were higher than CK,and the relative yield of each treatment was significant difference from CK.The increase rate of each treatment ranged from 15.14%to 20.70%,but there was no significant difference between the treatments.4.The research results of pot experiments showed that different types of soil conditioners could reduce the cadmium content in grains and the cadmium-to-grain cadmium transfer coefficient and the two-factor or three-factor material compound soil conditioners haad lower cadmium content than those of the single-substance soil conditioner.The cadmium content in rice grains and the cadmium-to-grain cadmium transport coefficient were CK>T1>T2>T3>T4>T5>T7>T6,the cadmium content of grains in T6 and T7 were as low as 0.17 mg/kg and 0.20 mg/kg.5.In field research experiment,the combination of different soil conditioners had increased rice yield,reduced rice stalk and grain cadmium content,and improved rice grain quality.The increasing yield of Taoyouxiangzhanhad accounted for 8.63%～10.36%,and the increasing yield of Liangyou 336 ranged from 6.78%～8.36%.The grain cadmium content of Taoyouxiangzhan and Liangyou 336 of B treatment was as low as 0.45 mg/kg,and 0.27mg/kg,respectively.Among them,the cadmium content of Taoyouxiangzhan was significantly reduced in A and B treatments compared with CK1.The research results of these experiments had indicated that the application of biochar-based multi-element compound soil conditioner was better than the application of single soil conditioner.It would provide a certain theoretical basis for the safe production and application technology of rice in cadmium contaminated areas.