Coal char effects on soil chemical properties and maize yields in semi‐arid region

Abstract

Soil amendments with high carbon (C) content can be effective in semi‐arid regions where soils are characterized by low C. A field study was conducted in 2016–2018 to evaluate the effect of char on soil chemical properties and irrigated maize (Zea mays L.) yields in sandy loam fertilized with urea or composted manure. Carbon‐rich char used was a product of coal combustion residue from a local factory in western Nebraska. The experiment was arranged in a split‐plot randomized complete block design in four replications with char (0, 6.7, 13.4, 20.1, and 26.8 Mg C ha−1) as main and N treatment (0, 90, 180, and 270 kg urea‐N ha−1 and 33.6 and 67.2 Mg ha−1 of composted manure) as subplot factors. A handheld spectral sensor was used to determine normalized difference red edge (NDRE) at growth stages (V6, V8, V10, and R1) in 2017 and 2018. After 2 yr, char increased Fe, reduced pH at lower rates, and increased K and Mg at higher rates in top 20 cm soil but did not affect crop yields. Char applied at ≥13.4 Mg C ha−1 increased soil organic C by ≥8% and composted manure increased soil P and K compared to the control. There was a strong correlation of NDRE with N rates and grain yields at V8 and V10. This study found no adverse effect of char on soil properties. However, more site‐specific research is needed before char can be used as a regular soil amendment in semi‐arid regions.

Coal combustion residue for crop productivity in the semiarid US High Plains

“…(2020) and Panday et al. (2021) did not observe any yield benefits in a maize–dry bean–maize rotation when CCR was applied to soils with a C content of 10.1–15.0 g C kg −1 . In contrast, Maharjan et al.…”

“…(2021) reported improved maize yield in a dry bean–maize–sugar beet rotation with CCR applied at >6.5 Mg C ha −1 on exposed sub‐soil with C of 7 g C kg −1 , indicating that CCR amendments might have more pronounced benefits in soils with lower C content compared to those with higher C content. This underlines the significance of soil type in influencing the effects of CCR on crop yield, with low C‐content soils potentially benefiting from CCR due to enhanced soil water retention and nutrient availability (Blanco‐Canqui et al., 2020; Panday et al., 2021). Additionally, factors such as crop rotations and crop phases could play a role in influencing crop responses to CCR, warranting further investigation.…”

“…Numerous factors influence the effectiveness of C amendments in increasing crop yield. The CCR generally had a positive effect on soil chemistry (Blanco‐Canqui et al., 2020; Maharjan et al., 2021), but only CCR applied at rates ≤13.4 Mg C ha −1 reportedly reduced pH levels in a calcareous soil (Panday et al., 2021). The reduction in soil pH at lower CCR rates could be attributed to the dilution effect with CCR (Lai et al., 1999).…”

“…The reduction in soil pH at lower CCR rates could be attributed to the dilution effect with CCR (Lai et al., 1999). Applying CCR at higher rates can cause an increase in soil alkalinity due to the presence of high CaCO 3 in CCR, negating its pH dilution effect (Panday et al., 2021). Because of the varying effect of CCR on soil properties, there were inconsistent CCR effects on crop yields.…”

Evaluating coal char as an alternative to biochar for mitigating nutrient and carbon loss from manure‐amended soils: Insights from a greenhouse experiment

“…The relatively high C content among different types of coal combustion residues makes this char also valuable for efforts to restore soil C storage in degraded soils (Blanco-Canqui et al, 2020). However, to the best of our knowledge, data on this char material to improve agricultural soil are limited to four published studies (Blanco-Canqui et al, 2020;Panday, Mikha, Collins, et al, 2020;Panday et al, 2021). From a 30-d column experiment Panday, Mikha, Collins, et al (2020) found that char applications did not affect leaching of NO 3 or emission of N 2 O from a sandy textured soil receiving mineral fertilizer.…”