Optimum rates of surface‐applied coal char decreased soil ammonia volatilization loss

Abstract

Fertilizer N losses from agricultural systems have economic and environmental implications. Soil amendment with high C materials, such as coal char, may mitigate N losses. Char, a coal combustion residue, obtained from a sugar factory in Scottsbluff, NE, contained 29% C by weight. A 30‐d laboratory study was conducted to evaluate the effects of char addition on N losses via nitrous oxide (N2O) emission, ammonia (NH3) volatilization, and nitrate (NO3–N) leaching from fertilized loam and sandy loam soils. Char was applied at five different rates (0, 6.7, 10.1, 13.4, and 26.8 Mg C ha−1; char measured in C equivalent) to soils fertilized with urea ammonium nitrate (UAN) at 200 kg N ha−1. In addition, there were two negative‐UAN control treatments: no char (no UAN) and char at 26.8 Mg C ha−1 (no UAN). Treatment applied at 6.7 and 10.1 Mg C ha−1 in fertilized sandy loam reduced NH3 volatilization by 26–37% and at 6.7, 10.1, and 13.4 Mg C ha−1 in fertilized loam soils by 24% compared with no char application. Nitrous oxide emissions and NO3–N leaching losses were greater in fertilized compared with unfertilized soil, but there was no effect of char amendment on these losses. Because NO3–N leaching loss was greater in sandy loam than in loam, soil residual N was twofold higher in loam than in sandy loam. This study suggests that adding coal char at optimal rates may reduce agricultural reactive N to the atmosphere by decreasing NH3 volatilization from fertilized soils.

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

“…This explains why there was lower daily NH 3 volatilization in the treatment C1N1 compared to C0N1 only on Day 6. This observation is supported by previous research that demonstrates an importance of soil pH in retaining or releasing soil NH 4 /NH 3 (Fan et al., 1993; Panday et al., 2020; Sherlock et al., 1994). When comparing between char and no char fertilized treatments, a reduction in NH 3 loss with char treatment also coincided with a trend for higher residual NH 4 –N with that treatment than no char from Day 4 to 8.…”

“…Clay minerals can fix total applied N in soil, which can reduce the pool of available N for NH 3 volatilization (Pelster et al., 2018). The reduction in NH 3 volatilization in char added fertilized treatment by 15.3% compared to no char treatment was due to increased N sorption due to higher surface area and CEC associated with char compared to soil (Panday et al., 2020). This observation agreed with previous research that documented a reduction in NH 3 volatilization with char addition to the fertilized treatment (Wang & Alva, 2000).…”

“…Biochar can retain NH 4 during soil N transformation and possibly reduce NH 3 emissions due to biochar high surface area (DeLuca, Gundale, MacKenzie, & Jones, 2015;Steiner, Das, Melear, & Lakly, 2010). Panday et al (2020) reported that the addition of coal char up to 13.4 Mg C ha −1 in a loam soil and 10.1 Mg C ha −1 in a sandy loam soils decreased NH 3 volatilization loss by 24 and 26-37%, respectively. They also reported that the reduction in NH 3 volatilization was related to increased ammonium (NH 4 -N) sorption and retention during soil N transformation due to char high surface area (0.08 m 2 kg −1 ) and high CEC (46.9 cmol c kg −1 ).…”

Can char carbon enhance soil properties and crop yields in low‐carbon soils?

“…Panday et al. (2020) reported that char applied at 6.6 and 9.9 Mg C ha −1 in sandy loam and at 6.6, 9.9, and 13.1 Mg C ha −1 in loam soil reduced ammonia volatilization compared with no char treatment in their incubation experiment. This greater N retention in char‐applied soil should have resulted into yield gain in char treatments.…”

“…In this experiment, we used coal combustion residue, referred to as char, which was a partially combusted sub‐bituminous coal char sourced from the Western Sugar Cooperative sugar beet processing facility (Panday et al., 2020). Coal is used at the facility to fire traveling grate stoker furnaces to produce steam during the sugar extraction process.…”