Coal char affects soil pH to reduce ammonia volatilization from sandy loam soil

Authors: PANDAY, DINESH - University Of Tennessee; Mikha, Maysoon; MAHARJAN, BIJESH - University Of Nebraska

Submitted to: Agrosystems, Geosciences & Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/19/2020
Publication Date: 11/22/2020
Publication URL: https://handle.nal.usda.gov/10113/7709421
Citation: Panday, D., Mikha, M.M., Maharjan, B. 2020. Coal char affects soil pH to reduce ammonia volatilization from sandy loam soil. Agrosystems, Geosciences & Environment. 3(1). Article e20123. https://doi.org/10.1002/agg2.20123.
DOI: https://doi.org/10.1002/agg2.20123

Interpretive Summary: The global meta-analysis revealed that up to 64% of surface applied N fertilizer could volatilize as ammonia (NH3) and lost from the soils system to the atmosphere. Ammonia volatilization affects N availability in soil-plant systems and reduces crop yield as well as negatively impacts the environment. Char addition (as organic ammendments) has shown to reduce Ammonia volatilization due to char high surface N sorption and high cation exchange capacity (CEC). This study was conducted under lab condition for 21 day to evaluate the effects of char on soil pH, N transformations, and Ammonia volatilization using sandy loam soil. Two rates of char and urea were mixed to generate four fertilizer treatment combinations in four replications as follow: control with no char or urea (C0N0), urea fertilizer at 200 kg N ha-1 with no char (C0N1), char at 13.4 Mg C ha-1 with no fertilizer (C1N0) and char at 13.4 Mg C ha-1 with urea at 200 kg N ha-1 (C1N1). Char rate at 13.4 Mg C ha-1 was effective in reducing Ammonia volatilization from soil by lowering soil pH. In addition to char properties of high surface area, high CEC, total C content, and its effect on reducing soil pH makes char a promising soil amendment particularly in high pH and low C soil. This study supported our hypothesis that char reduced soil pH and thereby reduced Ammonia volatilization loss from the soil system. Further research is warranted to evaluate the potential use of char in farmland to reduce Ammonia losses and enhance N use efficiency for crop production.

Technical Abstract: Ammonia (NH3) volatilization loss adversely affects N availability in soil-plant systems and reduces crop yield as well as negatively impacts the environment. Char, coal combustion residue, which contains up to 293 g kg-1 total C by weight, has shown to reduce NH3 volatilization due to its considerably high surface N sorption and high cation exchange capacity (CEC). The NH3 loss can be greatly affected by a shift in soil pH or urea hydrolysis due to the environmental conditions. A 21-day laboratory study was conducted to evaluate the effects of char on soil pH, N transformations, and subsequent NH3 volatilization in sandy loam soil. Two char rates (0 and 13.4 Mg C ha-1) and two urea rates (0 and 200 kg N ha-1) were mixed in soil in four 2-way combinations with four replications of each. There were 11 sets of the treatment combinations and each set was analyzed for soil pH, NH3 volatilization, and residual N (urea, NH4 and NO3) every other day for three weeks. Daily NH3 volatilization loss in fertilized treatment with char was lower than with no char on Day 6. Char application reduced cumulative NH3 loss and soil pH in fertilized treatment. Reduction in NH3 loss due to char addition was evidenced by greater residual NH4-N on certain days in treatments with char compared with treatments without char. Although char did not affect urea hydrolysis process, but this study supported our hypothesis that char altered soil pH and thereby reduced NH3 volatilization loss from the soil system.