Effects Of Biogas Residue And Biochar Seedling Culture Medium On The Growth Of Rice Seedlings

Rice is a major food crop in Heilongjiang Province,and the seedling nursery process requires a large amount of nutrient soil.Seedling soil extraction causes serious damage to land resources,and the use of digestate and biochar instead of seedling soil can solve the problem of difficult soil extraction for seedling nursery.The comparative analysis of different sources of seedling substrates on rice seedling quality aims to provide applicable production techniques for seedling nursery with digestate and biochar substrates.Therefore,this study investigated the effect of different substrates of digestate mixed with biochar on the quality and nutrient uptake characteristics of rice seedlings by using decomposed digestate as rice seedling nursery substrate.The substrates used were straw digestate(Z1),digestate with a 4:1 ratio of straw and cow dung(Z2),and digestate with a 2:1 ratio of straw and cow dung(Z3),and the treatments were divided into those with unmixed biochar(Z1H1,Z2H1 and Z3H1)and mixed biochar(Z1H2,Z2H2 and Z3H2).The main findings were as follows:(1)The substrate of digestate promoted the plant height and stem base width of seedlings.the plant height of rice seedlings was significantly higher in Z1,Z2 and Z3 treatments than in CK at 30 days,increasing by 66.51%,67.27% and 73.09%,respectively.the stem base width of rice in Z3 treatment was significantly higher than in CK at 30 days.the substrate mixed with biochar promoted the plant height,stem base width and aboveground Dry weight.The plant height,stem basal width,and aboveground biomass of rice seedlings increased with the increase of seedling age after the substrate mixed with biochar.At 30 days of rice seedling nursery,the stem base width of rice seedlings in Z1H2 treatment was significantly higher than that in CK1.The above-ground biomass of Z1H2 treatment at 30 days was significantly higher than that in CK1.(2)The total root length,root surface area and below-ground biomass of rice seedlings were promoted by the substrate of digestate.The total root length of Z2 treatment was significantly higher than that of CK at 30 days.The root surface area of Z2 treatment was significantly higher than that of CK at 30 days.The below-ground biomass of Z1 and Z3 treatments was significantly higher than that of CK at 30 days.The substrate mixed with biochar promoted the total root length,root surface area,root volume and below-ground biomass of rice seedlings.The addition of biochar promoted the total root length of rice seedlings.the total surface area of Z2H1 treatment was significantly higher than CK1 at the end of rice seedling nursery.at 30 days,the root volume of Z2H1 treatment was significantly higher than CK1 at 30 days.the Z1H2 treatment promoted the belowground biomass.the root vigor of Z3H1 treatment was significantly higher than CK1 at 30 days of rice seedling nursery.(3)The digestate substrate seedling nursery promoted the strong seedling index,G value,fullness and strong seedling index of seedlings.the strong seedling index of Z3 treatment was significantly higher than CK;the G value of Z1,Z2 and Z3 treatments were significantly higher than CK,increasing by 49.21%,122.22% and 90.48%,respectively.the fullness and seedling index of Z2 and Z3 substrates were significantly higher than CK.the substrate mixed with biochar promoted the G value of the seedlings.the seedling filling index and seedling filling index of Z2H1 were significantly higher than those of CK1.the G values of Z1H2 and Z2H1 were significantly higher than those of CK1,increasing by 66.12% and 78.51%,respectively.(4)The digestate substrate seedling nursery promoted the nitrogen accumulation and potassium accumulation of seedlings.The net nitrogen,phosphorus and potassium accumulation decreased and then increased with the increase of seedling age.nitrogen accumulation in Z3 treatment was significantly higher than that in CK.potassium accumulation in all treatments was significantly higher than that in CK.after the substrate was mixed with biochar,phosphorus accumulation in Z2H2 and Z3H2 treatments was significantly higher than that in CK1 at 30 days of rice transplanting,and potassium accumulation in all treatments was significantly higher than that in CK1.The above results suggest that digestate can provide a new solution for rice substrate seedling nursery.