Application period and dosage optimums for biochar additions in black soil with summer maize

Abstract

As a new soil conditioner, biochar not only maintains soil fertility, improves soil degradation, and resolves pollution problems, also enhances crop growth and production efficiency. To promote a low-carbon economy for the world with biochar development, the Songnen Plain black soil area was selected as the research object. A total of ten treatments were set with three biochar application levels (C5-5 t·hm-2, C10-10 t·hm-2, and C15-15 t·hm-2); three different application schemes (F1-applied in autumn, F2-half applied in spring and half in autumn. and F3-applied in spring) for each application level; and one control group (BL-no biochar applied), and each test was processed in parallel. Combined with crop growth period, and regular artificial sampling. On this basis, the characteristics of the plant root system, nitrogen (N) spatial distribution, root respiration, and N-use efficiency for different treatment conditions were compared and analyzed. A correlation function of biochar amount and N-use efficiency versus the harvest index was constructed, and then the relationship between the biochar control mode and crop production efficiency was expounded. Results of the study showed that compared to the BL treatment, root length of plants with biochar treatments increased for C5F1(1 009.10 cm), for C10F1(1 640.05 cm), and for C15F1(1 270.24 cm) as did F2 and F3 for the three biochar application treatments and the results passed the significance test of P < 0.05. The control effect of biological carbon effectively inhibited the ineffective loss of soil N, and the N fixation effect of the soil reached the best level with the C10F1 treatment. Biochar's water retention and fertility enhanced the respiration rate of the plant roots; an increase in the biochar application rate first increased and then decreased the respiration rate(P < 0.05). Regulation of biochar additions promoted the accumulation of crop yield with an increase in the biochar application rate and adjustment of the application scheme; the C10F1 treatment had the best yield, N-use efficiency, and harvest index(P < 0.05). In addition, there was a quadratic function relationship between the biochar application rate and crop yield, N-use efficiency(P < 0.05), and other indicators meaning that there was an optimal threshold between biochar supply and plant productivity. Through the above studies, it can be seen that appropriate amount of biochar, with appropriate addition period, can effectively increase the growth and metabolism of crop lines, thereby increasing the yield and production efficiency of crops. Thus, this study provided theoretical guidance for seeking a reasonable and efficient management model with biochar, and showed that appropriately increasing the amount of biochar could effectively promote plant root metabolism.