The effect of applying biochar on crop yields

Soil fertility is traditionally restored by applying organic and mineral fertilizers. The actual ways to solve the problem of soil fertility losses is the use of biochar. Biochar affects the water-air properties of the soil, pH, availability of nutrients, availability of organic carbon, structural and aggregate state of soils, reduces the amount of pollutants, sequesters carbon. One of the reasons for the use of biochar in agriculture is its ability to increase crop yields. The novelty of the research is the use of biochar in the soil and climatic conditions of the south of Primorsky Krai (Far East of Russia). The purpose of this research is to assess the effect of doses of biochar application, as well as its combined use with organic and mineral fertilizers on crop yields on Luvic Anthrosols in the south of Primorsky Krai. The experiment was conducted at the Primorsky Vegetable Experimental Station, a branch of the Federal State Scientific Institution "Federal Scientific Center of Vegetable Growing" (43°25'22.4"N 132°18'50.6"E, Surazhevka village, Primorsky Krai, Russian Federation). The increase in crop yields during the growing seasons of 2018, 2019 and 2020 was estimated. Two fields (field № 1 and field № 2) have been selected on the territory of the experimental one. The biochar was added to field № 1 on June 15, 2018. The biochar was added to field № 2 on June 19, 2020. 9 plots with an area of 21.6 m2 (1.8 x 12 m) were selected in the fields (See Fig. 1): Control - a plot without the introduction of biochar and fertilizers, BC1kg - a plot with the introduction of 1 kg/m2 of biochar, BC3kg - a plot with the introduction of 3 kg/m2 of biochar, Min - a plot with the introduction of mineral fertilizers at a dose of 300 kg/ha N50P125K125, MinBC1kg - a plot with the application of mineral fertilizers together with 1 kg/m2 of biochar, MinBC3kg - a plot with the application of mineral fertilizers together with 3 kg/m2 of biochar, Org - a plot with the application of organic fertilizer "Gigantin" at a dose of 10 t/ha, OrgBC1kg - a plot with the introduction of organic fertilizer together with 1 kg/m2 of biochar, OrgBC3kg - a plot with the introduction of organic fertilizer together with 3 kg/m2 of biochar. Biochar is made from Betula alba birch by slow pyrolysis. The properties of biochar were determined before its application in the vegetation experiment according to the international standard IBI (International Biochar Initiative). Biochar does not contain in its composition the maximum permissible concentrations of hazardous chemical elements, has a high-strength (H/C = 0.052 and O/C = 0.145) and highly porous structure (pore surface area 73.25 m2/g). The carbon content in the studied biochar is 78.13%, the pH is 8.09±0.07, the water absorption capacity in the original fraction is 110% ± 6.56%. Cabbage was grown in field № 1 in 2018. The cabbage was planted on June 15, 2018. The harvest was carried out on November 2-3, 2018 by weighing each plant with separation into root, cover leaves and forks. Soybeans were grown in field № 1 in 2019. The planting of soybeans was carried out on June 28, 2019. Soybean harvesting was carried out from October 10 to October 12, 2019. During the growing season of 2020, beets were grown on field № 2, the planting of the crop was carried out on July 10. The harvest was carried out in the third decade of October 2020. The soil in the studied areas is classified as Luvic An-throsols and has a medium loamy granulometric composition (in Russian classification), silt loam by classification FAO. Soils have pHH2O = 6.8, pHKCl = 5.45. As a result of the study, it was shown that biochar increases the biomass of cabbage (See Table 1). In the range of Control, BC1kg and BC3kg, the introduction of biochar significantly increased the yield of cabbage (P = 0.001). The Control had the lowest value of cabbage biomass (10.84 t/ha). At the BC1kg, the biomass increased by 111% compared to the control. The increase in biomass at the BC3kg was 205% compared to the control. In the ranks of Min, MinBC1kg and MinBC3kg and Org, OrgBC1kg and OrgBC3kg, a similar increase in cabbage biomass was observed (P = 1.9*10-7 and 9.6*10-10, respectively). The largest increase in cabbage biomass was recorded at the MinBC3kg - 415% compared to the control and 53% compared to the Min. The head : cover leaves : root ratio showed that the Control has the lowest percentage of cabbage head biomass and the highest percentage of cover leaves biomass (35 : 42 : 22). The introduction of biochar increases the percentage of biomass of the cabbage head. So at the BC1kg, the ratio of head : cover leaves : root was 51 : 29 : 19. At the BC3kg, the ratio of head : cover leaves: root was 54:27:18. No effect of biochar on soybean biomass was revealed when comparing Control, BC1kg, BC3kg plots (P = 0.99) (See Table 2). No effect of biochar together with mineral and organic fertilizers on biomass was revealed when comparing the variants of the experiment Min, MinB1kg and MinB3kg (P = 0.98) and Org, OrgB1kg and OrgB3kg (P = 0.96). In all variants of the experiment, a decrease in soybean biomass in comparison with the control was noted. A comparison of the results of the biomass of one soybean plant, the average number of beans in the bush and the average height of the bush showed that biochar contributes to a decrease in the number of soybeans in the bush and an increase in the green biomass of soybeans. The results of measurements of beet biomass showed an increase in its biomass when using biochar (See Table 3). There was no significant difference in beet biomass between plots with different doses of biochar. The calculation of the percentage of beetroot biomass from the total beet biomass showed a decrease in root biomass in case with biochar applying. Similarly, to the change in the percentage of root biomass to total beet biomass, the percentage of green part biomass to total beet biomass increased or decreased. The results of the measurement showed that degree of biochar's influence on crop yields is controversial and is mainly related to the choice of crop. When considering the effect of biochar on the yield of white cabbage, soybean and beet, it was found out that biochar has a better effect on the biomass of the green part of the plant. The best results are discovering in the case of the influence of biochar on the yield of white cabbage were obtained, which is associated with the formation of the main part of the plant from green biomass. In the plot with 1 kg/m2 of biochar, an increase in the total biomass of cabbage two times compared to the control was observed. In the plot with 3 kg/m2 of biochar, an increase in the total biomass of cabbage three times compared to the control was observed. The effect of biochar on the yield of beets had a positive, but less pronounced result compared to the effect of biochar on the cabbage yield. In areas without organic and mineral fertilizers the largest increase in beet biomass when 1 kg/m2 of biochar was added (86%) compared to the control was obtained. The effect of applying 3 kg/m2 of biochar did not have a better result on beet yield compared to the effect of 1 kg/m2 of biochar. The application of biochar demonstrate the percentage reduce of root crop biomass and increased the percentage of green part biomass in relation to the total beet biomass in the variants with biochar application and in variants with mineral fertilizers, but not in the variants with organic fertilizers. The application of biochar did not have a significant positive effect on soybean yield. It was revealed that biochar increased the biomass of the green part of soybeans and reduced the number of beans. The paper contains 2 Figures, 3 Tables, and 30 References. The Authors declare no conflict of interest.

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