High biochar rates may suppress rice (Oryza sativa) growth by altering the ratios of C to N and available N to P in paddy soils |
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Authors: | Binh Thanh Nguyen Vinh Ngoc Nguyen Tong Xuan Nguyen My Hoang Nguyen Hao Phu Dong Gai Dai Dinh Nghia Van Nguyen Tan-Viet Pham |
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Institution: | 1. Institute of Environmental Science, Engineering, and Management, Industrial University of Ho Chi Minh City, Ho Chi Minh City, Vietnam;2. Department of Environmental Engineering, International University, Vietnam National University, Ho Chi Minh City, Vietnam;3. Faculty of Safety Engineering, School of Engineering and Technology, Van Lang University, Ho Chi Minh City, Vietnam;4. Institute of Biotechnology and Food Technology, Industrial University of Ho Chi Minh City, Ho Chi Minh City, Vietnam |
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Abstract: | Although most studies have indicated that biochar can boost rice (Oryza sativa) growth, the material may also suppress it, depending on ratios of carbon (C) to nitrogen (N) and available N to available phosphorous (P). The current study sought to examine the impacts of biochar on rice growth and to identify underlying mechanisms. A pot experiment was conducted using two soils of high (3.05%) and low (0.54%) organic carbon (OC) content, mixed with 0, 1.5, 3, 6, and 12% biochar and planted with rice. Rice growth components, five rice tissue nutrients, and nine soil properties were measured. The results showed that the response of rice growth to biochar rates could be described using an exponential-growth function in high-OC soil but an inverted U-shaped curve in low-OC soil. In high-OC soil, the 12% biochar rate led to the greatest total biomass, increased by 47%, whereas in low-OC soil, the 3 and 6% rates exhibited the highest total biomass, increased by 44%, compared to the no-biochar added soils. Biochar elevated the C:N ratio from 11.5 to 39.1, with an optimal range of 20–30 corresponding to the highest rice growth. Biochar declined the ratio of NH4-N to Mehlich-1 P, causing N deficiency. In brief, high biochar rates may suppress rice growth when the soil C:N ratio exceeds 30. The applied biochar rate should be considered based on soil properties typically OC and N content to obtain the C:N ratio between 20 and 30 for optimal rice growth. |
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Keywords: | biochar rate C:N ratio rice growth soil nitrogen concentration soil organic carbon |
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