Enhancing Biochar as Scaffolding for Slow Release of Nitrogen Fertilizer
Santanu Bakshi, Chumki Banik, David A. Laird, Ryan Smith, Robert C. Brown
Abstract
Nitrogen (N) is an essential macronutrient for plant growth; however, excessive use of N fertilizers and complexities of the N cycle in soil cause negative environmental impacts. This imposes several challenges in controlling the N availability timing and losses. The objective of this study was to develop a biochar-based slow-release fertilizer (SRF) to reduce N loss and increase N use efficiency in crop production. We provided a laboratory-based assessment of several H3PO4 activated (5 and 15%) biochar-based SRFs, produced from different combinations of biochar to urea (1:2, 1:3, 1:4, and 1:6), calcium lignosulfonate (5%), and paraffin wax (10%). Characterization analyses (SEM–EDS, XRD, FTIR, and XPS) of developed SRFs suggest successful urea grafting onto biochar through both the urea amine N and carbonyl C═O modes, without urea crystal structure disruption. The SRFs were more efficient than uncoated urea (control): (1) urea released in aqueous medium was 61–90% in 4320 min for the SRFs versus 99.6% in 12 min for the control; (2) cumulative N leached from soil columns was 68–71% after 41 leaching events for SRF versus 99.9% after four leaching events for the control; and (3) NH3-N volatilization from soil was 0.2–0.9% for the SRFs versus 2% for the control. Inclusively, our results suggest that the developed SRFs are effective for reducing N loss from soil and provide larger quantities of NH4+-N to plants for a longer time (improved N use efficiency). We attribute this to that the developed SRFs are optimal for synchronizing with plant N uptake for providing better sustainability in modern agriculture.