Feasibility of coal combustion fly ash alone and in combination with gypsum and green manure for reclamation of degraded sodic soils of the Indo‐Gangetic Plains: A mechanism evaluation

Abstract

The disposal of coal combustion fly ash (FA) generated from thermal power plants is a worldwide problem. However, its low bulk density and presence of calcium and ironaluminium sesquioxide make it a prospective ameliorant alternative to gypsum for amending degraded sodic soils. A field experiment consisting of eight treatments with variable doses of FA and gypsum along with green manure (GM) was conducted for evaluating the amelioration mechanism by measuring changes in pH, exchangeable sodium percentage, zeta (ζ) potential, and properties of meso-aggregates (0.5-2.0 mm). The results showed that compared with control, FA significantly reduced ζ-potential, bulk density, and pH. The GM with FA further decreased ζ-potential and increased hydraulic conductivity. The hydrolysis of iron and aluminium sesquioxide, present in FA, functioned to lower soil pH, whereas the reduction in exchangeable sodium percentage is attributed to bioavailable Ca (27.4%). A lower FA application rate produced better crop yields. FA 2.5% (w/w) alone, compared to the FA 5% (w/w), resulted in higher yield of rice (1.96 tonnes ha −1 ), whereas 25% gypsum requirement (25GR) + FA 2.5% (w/w) and 25GR + FA 2.5% (w/w) + GM provided wheat yield on par with 50% gypsum requirement (50GR). The study identifies that where gypsum is scarce, the recommended amendment is 25GR + FA 2.5% or 25GR + FA 2.5% + GM when applied for sodic soil to achieve a similar yield response to standard 50GR. If gypsum is unavailable, a one-time application of FA 2.5% (w/w) alone will improve the productivity of degraded sodic soils corresponding to more exchangeable calcium and organic carbon, which were found to be higher for meso-aggregates (0.5-2.0 mm).

Utilization of marine gypsum as an alternative to mineral gypsum in the reclamation of degraded sodic soil and as a means of enhancing crop productivity

“…Singh et al (2016) had earlier reported increased rice yield with increasing levels of GYP, which was highest at 50 GR GYP and the reason ascribed to the decreased soil pH from 10.5 to 8.91. This was also found to be in agreement with earlier findings (Mishra et al, 2019), where the lowest soil pH was recorded in the 50 GR GYP, and the crop yield response was directly related to reduction in soil pH, BD, and dispersion ratio.…”

“…Looking into the rising costs and limited availability of GYP for agriculture use researchers have focused on alternatives. For example: industrial by‐products like phosphogypsum (Nayak et al, 2009), fly‐ash (Dhindsa et al, 2016; Mishra et al, 2019) and flue gas desulphurized gypsum (Zhao et al, 2019) have already been used as alternatives to GYP for sodic soil reclamation. Each of these amendments have their own limitations for application in agriculture.…”

Does conservation tillage on partially reclaimed sodic soil restore land degradation by influencing boron dynamics, bioavailability for plant's uptake and nutritional security?

“…The soil samples were dried in the air, ground by wooden mortar and pestle to pass through a 2 mm sieve. pH and EC of the soil were determined potentiometrically using a Thermo Orion® ion analyzer (Mishra et al, 2019), using pH and conductivity electrode, soil organic carbon (OC) by chromic acid titration method (Nelson & Sommer, 1982). Cation exchange capacity (CEC) and exchangeable sodium percentage (ESP) was determined by the following methods as adopted by US Salinity Laboratory Staff (1954), soil clay content by international pipette method (Piper, 1966), bulk density using core method (Blake & Hartge, 1986), hydraulic conductivity (HC) by using the procedure of Greene et al (1988), and calcium carbonate (CaCO 3 ) was determined by reaction with hydrochloric acid followed by back titration of remaining acid (Nelson, 1982).…”

Assessing soil quality for rehabilitation of salt-affected agroecosystem: A comprehensive review

“…Application of N @120 and P @ 26 kg ha −1 + FYM/press mud/gypsum improved SOC and sustained wheat yield in sodic soil (pH 1:2 ) when irrigated with sodic water (RSC 8.5 me L −1 ; SAR of 8.8) in sodic areas of northwestern India (Yaduvanshi and Sharma 2008;Yaduvanshi and Swarup, 2005). Reclamation of soil declined soil pH 1:2 and SAR e and improved SOC, and increased the uptake of KMnO 4 -N, Olsen's P, and NH 4 OAc extractable K. The results from the participatory experiments carried out at 10 locations in the central Indo-Gangetic plain showed a reduced level of sodicity (as decrement in ESP, SAR e , and soil pH 1:2 and EC 1:2 Singh) and increased SOC and improved soil porosity, void ratio, and saturated hydraulic conductivity because of green manuring in the rice-wheat cropping system , although the phosphogypsum (PG) application is questionable because of the presence of heavy metals (Mishra et al, 2019). However, the application of PG was associated with declined soil pH 1:2 , EC 1:2 , ESP, and SAR e and improved soil fertility (increased Olsen's P, NH 4 OAc extractable K, and DTPA extractable Fe, Mn, Zn, Cu etc.…”