Journal
CHEMOSPHERE
Volume 303, Issue -, Pages -Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.chemosphere.2022.134663
Keywords
Molybdenum slow-release fertilizer; Biochar; Nitrogen assimilation; Nitrate reduction; Nitrogen use efficiency
Categories
Funding
- National Key Research and Development Program of China, China [2019YFC1605602]
- Innovative Green Development Team Program of Modern Agricultural Science and Technology of Guangdong Province, China [2021KJ112, 2022KJ112]
- National Natural Science Foundation of China Youth Fund, China [31800432, 41877117]
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In this study, the application of biochar-based slow-release fertilizer (Mo-biochar) was found to enhance molybdenum (Mo) bioavailability in acidic soil and nitrogen assimilation in Chinese flowering cabbage. The constant and sufficient supply of Mo nutrients by Mo-biochar improved the rate-limiting steps of nitrogen assimilation and reduced nitrate accumulation in vegetables.
Low molybdenum (Mo) bioavailability in acidic soil obstructs vegetable nitrogen assimilation and thus increases the health risk of vegetable ingestion due to nitrate accumulation. Constantly providing available Mo in acidic soil is a challenge for decreasing nitrate accumulation in vegetables. In this study, three Mo application methods, including biochar-based Mo slow-release fertilizer (Mo-biochar), seed dressing, and basal application, were investigated to enhance Mo bioavailability in acidic soil and nitrogen assimilation in Chinese flowering cabbage (Brassica parachinensis). The results showed that Mo-biochar constantly and sufficiently supplied Mo nutrients throughout the growing period of Brassica parachinensis, as evidenced by the soil available Mo, plant Mo uptake, and Mo values. The improved Mo supply was attributed to the alleviation of acidic soil (pH from 5.10 to 6.99) and the slow release of Mo adsorbed on biochar. Mo-biochar increased the nitrate reductase (NR) activity by 238.6% and glutamate dehydrogenase activity by 27.5%, indicating an enhancement of the rate-limiting steps of nitrogen assimilation, especially for nitrate reduction and amino acid synthesis. The increase in Mo-containing NR could be directly ascribed to the high level of Mo in Brassica parachinensis. Compared with the control, the nitrate content of Brassica parachinensis decreased by 42.9% due to the nitrate reduction induced by increased NR. Additionally, Mo-biochar was beneficial to vegetable growth and quality. In contrast, the transformation from NO3- to NH4+ was blocked with Mo seed dressing and basal application because of low Mo bioavailability in the soil, resulting in a high nitrate content in Brassica parachinensis. Conclusively, Mo-biochar can slowly release Mo and improve the neutral environment for Mo bioavailability, which is an effective strategy to mitigate the high nitrate accumulation of vegetables planted in acidic soil.
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