Journal
JOURNAL OF SOIL SCIENCE AND PLANT NUTRITION
Volume 21, Issue 3, Pages 2007-2019Publisher
SPRINGER INTERNATIONAL PUBLISHING AG
DOI: 10.1007/s42729-021-00497-x
Keywords
Nitrogen; Fertilizer; Biochar; Polylactic acid; Controlled release fertilizer; Coating
Categories
Funding
- South Dakota Governor's Office of Economic Development [POC2020-04]
- USDA NIFA program through the Hatch Project of the South Dakota Agricultural Experimental Station [3AR676, 3AH658]
- North Central Regional Sun Grant Center [3FG386]
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This study aims to develop a biochar-based controlled-release nitrogen fertilizer (BCRNF) to improve nitrogen supply time and rate, thereby increasing nitrogen use efficiency. Through impregnating ammonium sulfate in biochar and coating with polylactic acid, 70% of nitrogen was released in 12 days in water and 25 days in soil. The thermal stability was good, and the PLA concentration significantly affected the nitrogen release time and rate.
Conventional nitrogen (N) fertilizers used in crop production typically have use efficiencies of only 30 to 40%. While reduced efficiency can be a result of multiple factors (rate, placement, source), mismatched timing between N availability and N crop demand is a significant cause of reduced efficiency. This study aims to develop a biochar-based controlled release nitrogenous fertilizer (BCRNF) from relatively low-cost renewable materials to improve N availability when needed by the corn crop thus reducing N losses and improving nitrogen use efficiency. Ammonium sulfate was impregnated in biochar and then pelletized into particles. Three concentrations (3%, 6%, and 10%) of polylactic acid (PLA) solutions were used to coat the particles to produce BCRNF. The effects of different PLA concentrations on N release and physical properties of BCNRFs were investigated in both water and soil conditions. Water absorption and retention, thermal stability, and microstructures of BCRNFs were also analyzed to determine the N release mechanism of BCRNFs. The BCRNF coated by 10% and 6% of PLA both released 70% of N over 12 days in water and 25 days in soil. The biochar held 14% N that was not released into the water. However, coating with PLA, increased N holding to 16% inside BCRNF particles. The thermal properties of BCRNFs were stable under 230 degrees C. The PLA concentration of the coating layer significantly affected not only the N releasing time and rate but also the morphology and thermal properties of BCRNFs. Higher PLA concentrations resulted in a longer releasing time at lower N release rates. This study demonstrates that a biochar-based controlled-release nitrogen fertilizer (BCRNF) can enhance N release time and rate in both water and soil environments through the integration of biochar absorption and a PLA coating. Further development could yield a BCRNF that can optimally synchronize timing and amount of available N with crop N demand to increase N use efficiency.
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