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

Dinesh Panday, Maysoon M. Mikha, Bijesh Maharjan
Agrosystems, geosciences & environment 2020 v.3 no.1 pp. e20123
ammonia, ammonium nitrogen, cation exchange capacity, coal, combustion, crop yield, hydrolysis, sandy loam soils, soil pH, sorption, urea, volatilization
Ammonia (NH₃) volatilization loss adversely affects N availability in soil‐plant systems, reduces crop yield, and negatively impacts environment. Char (coal combustion residue), which contains up to 293 g kg⁻¹ total C by weight, has been shown to reduce NH₃ volatilization due to its considerably high surface area and cation exchange capacity. The NH₃ loss can be greatly affected by a shift in soil pH or urea hydrolysis. A 21‐d 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 all treatment combinations and each set was analyzed for soil moisture, pH, NH₃ volatilization, and residual N (urea, NH₄, and NO₃) every other day for 3 wk. Char application reduced cumulative NH₃ loss in the 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 to treatments without char. Char did not affect urea hydrolysis process but it lowered soil pH in the fertilized treatments in the first week. This study supported our hypothesis that char altered soil pH and thereby reduced NH₃ volatilization loss from the fertilized soil.