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

Abstract

Restoring soil carbon (C) lost due to intensive farming is a long-term endeavor under current conservation management practices. Application of coal combustion residue (293 g C kg −1) from a sugar beet (Beta vulgaris L.) processing factory, hereafter referred to as char, could rapidly restore soil C and productivity in degraded croplands, but data on this potential strategy are unavailable. We assessed the impacts of char application to two relatively low-C soils (10.1 and 12.2 g C kg −1) and one relatively high-C soil (17.3 g C kg −1) on soil C, soil physical and fertility properties, and crop yields in no-till systems in the Great Plains after 2 yr. Char was disked to 15 cm soil depth at char-C application rates ranging from 0 to 19.7 Mg C ha −1 , corresponding to char application rates ranging from 0 to 67.3 Mg ha −1. The highest char rate increased C concentration in all soils but increased C stock only in low-C soils. Char did not affect soil penetration resistance, available water, aggregate stability, most nutrients, and crop yields. Char application at high rates increased sulfate, Ca, Mg, and Na concentrations but did not influence other properties. Carbon recovery of the char applied at the highest rate varied among soils from 50 to 85%, but the mechanisms for such differences need further investigation. Short-term duration, low char C concentration, and low application rates may explain the limited char effects. Overall, char application at 19.7 Mg char-C ha −1 (i.e., 67.3 Mg char ha −1) increased soil C concentration but had negligible effects on other soil properties and crop yields after 2 yr. 1 INTRODUCTION Intensively tilled soils coupled with crop-fallow systems in semiarid regions such as those in the U.S. Great Plains Abbreviations: CEC, cation exchange capacity; HighC, high-carbon soil at the Sidney site; LowC1, low-carbon soil at the Scottsbluff site; LowC2, low-carbon soil at the Sidney site.

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

“…Ammonium (NH 4 ) is the predominant form at pH below 7.5 (Fan et al., 1993; Sherlock, Freney, Bacon, & Van der Weerden, 1994). The NH 3 forms quickly and becomes dominant as soil pH increases above 7.5 and it becomes susceptible to loss via volatilization (Behera et al., 2013). The reduction in soil pH in fertilized soil is due to acidifying nature associated with NH 3 –based fertilizer transformation (Stewart, 2008).…”

Potential amendments for improving productivity of low carbon semiarid soil

“…Most positive results on biochar were reported from acidic soils due to the potential liming effect of biochar on crop yields (Burell et al, 2016;Liu et al, 2012). Blanco-Canqui et al (2020) reported char that at >67.3 Mg ha −1 increased soil C where the initial SOC was >10 g kg −1 . In contrast, the current study soil had a much lower initial organic C (7 g kg −1 ), and char as low as 22.3 Mg ha −1 increased soil C compared with the control.…”

“…Blanco‐Canqui et al. (2020) reported char that at >67.3 Mg ha −1 increased soil C where the initial SOC was >10 g kg −1 . In contrast, the current study soil had a much lower initial organic C (7 g kg −1 ), and char as low as 22.3 Mg ha −1 increased soil C compared with the control.…”

“…Blanco‐Canqui et al. (2020) also found that char application increased SOC after 2 yr of its application, although its benefits on other soil properties or crop yields would take >2 yr.…”

“…Coal char, which is the residue from the inefficient burning of coal in a sugar factory in western Nebraska, contains up to 293 g kg −1 C. Its application to fertilized soils at optimal levels can reduce ammonia volatilization loss (Panday et al, 2020). Blanco-Canqui et al (2020) also found that char application increased SOC after 2 yr of its application, although its benefits on other soil properties or crop yields would take >2 yr.…”