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

Authors: PANDAY, DINESH - University Of Nebraska; Mikha, Maysoon; Collins, Harold; Jin, Virginia; KAISER, MICHAEL - University Of Nebraska; COOPER, JENNIFER - University Of Nebraska; MALAKAR, ARINDAM - University Of Nebraska; MAHARJAN, BIJESH - University Of Nebraska

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/17/2019
Publication Date: 3/16/2020
Citation: Panday, D., Mikha, M.M., Collins, H.P., Jin, V.L., Kaiser, M., Cooper, J., Malakar, A., Maharjan, B. 2020. Optimum rates of surface-applied coal char decreased soil ammonia volatilization loss. Journal of Environmental Quality. 49:256-267. https://doi.org/10.1002/jeq2.20023.
DOI: https://doi.org/10.1002/jeq2.20023

Interpretive Summary: In an agricultural system, nitrogen fertilizer (N) addition could be susceptible to loss through leaching or be lost as gas to the atmosphere. Management practices that have a potential to reduce N losses to ground water or to the atmosphere are important economically and environmentally. The addition of high carbon (C) material, such as coal char to the soil, may reduce soil N losses. In this study, the char was taken from a sugar factory in Scottsbluff, NE and contained up to 30% C by weight. The objective of this study was to evaluate the effects of char addition on N losses to the atmosphere as nitrous oxide (N2O) emission and ammonia (NH3) volatilization, and through leaching to the ground water as nitrate (NO3). The study was conducted at the University of Nebraska-Lincoln, Panhandle Research and Extension Center, Scottsbluff, NE. A 30-day laboratory study was conducted using two soil types, loam and sandy loam soils that were fertilized with urea ammonium nitrate (UAN) at 200 kg N ha-1. Five different char rates (0, 6.1, 9.2, 12.3, and 24.5 Mg C ha-1) were applied to both soils. In addition, control treatments within each soil type were included: no char (no UAN), and char at 24.5 Mg C ha-1 (no UAN). The addition of char at the rate of 9.2 and 12.3 Mg C ha-1 significantly reduced ammonia volatilization by approximately 8.7% for loam soil and by 11% for sandy loam soil compared with no char treatment (control). Char addition did not change N2O emission and NO3 - leaching values compared with control treatments. Fertilizer addition increased N2O emission by an average of 10-fold and NO3- leaching by an average of two-fold compared with unfertilized soil. Nitrate leaching was significantly greater with sandy loam by an average of 300% (17.6 mg N leached kg-1 soil) compared with loam soil (4.0 mg N leached kg-1 soil). Therefore, soil residual N was two-fold higher in loam soil compared to sandy loam soil. In general, the addition of high C content products such as char at optimal rates have the potential to reduce agricultural reactive N to the atmosphere by decreasing NH3 volatilization from fertilized soils.

Technical Abstract: Fertilizer nitrogen (N) losses from agricultural systems has both economic and environmental implications. Soil amendment with high carbon (C) materials, such as coal char, may mitigate N losses. Char, a coal combustion residue (CCR), was obtained from a sugar factory in Scottsbluff, NE and contained up to 30% C by weight. A 30-day 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-) leaching from fertilized loam and sandy loam soils. Five different char rates (0, 6.1, 9.2, 12.3, and 24.5 Mg C ha-1) were applied 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 24.5 Mg C ha-1 (no UAN). Char applied at rates up to 9.2 and 12.3 Mg C ha-1 in fertilized sandy loam and loam soils, respectively, reduced NH3 volatilization compared to no char application. Nitrous oxide emission and nitrate leaching loss were greater in fertilized compared to unfertilized soil, but there was no effect of char amendment. Since leaching loss was greater in sandy loam compared to loam, soil residual N was two-fold higher in loam compared to sandy loam. This study suggests that adding high C content products such as char at optimal rates has the potential to reduce agricultural reactive N to the atmosphere by decreasing NH3 volatilization from fertilized soils.