Effects of calcium lignosulphonate on Mehlich‐III extractable calcium, magnesium, and potassium quantity‐intensity relationship in the soil with or without potassium dihydrogen phosphate

Abstract

Calcium lignosulphonate (CaLS), a waste product from the pulp and paper industry, is expected to affect reaction of K fertilizer in the soil, thus influences their availability to crops. A clay soil (Typic Humaquept) was incubated with various amounts of CaLS (0 to 150 g kg^‐1 soil) and potassium dihydrogen phosphate (0–25.64 mmol kg^‐1 soil) for 240 h under moist conditions at 5 and 15°C. Subsamples were extracted with deionized water and the Mehlich‐III (M3) solution for the analyses of pH, and P, Ca, K and Mg concentrations and K adsorption (K_ad). Higher temperature reduced M3 extractable K (K_M3). CaLS and K additions increased M3 extractable Mg (Mg_M3) with Ca contributed more than did K as indicated by the standardized estimates. Additions of CaLS increased K_M3. Potassium adsorption decreased with the increases in CaLS addition rates. Significant positive linear relationships were observed between K_ad and the concentration ratio of [K⁺]/[Ca²⁺]^½, suggesting that the potassium buffering capacity of the soil was reduced by the additions of CaLS, with the desugared CaLS being more effective than the non‐desugared CaLS. The increased slope values with the increases in CaLS additions of the linear relationships between K_M3 and [K]/[Ca²⁺]^½ indicated that CaLS improved the quantity and intensity relationships and increased the power of the soil supplying plants with K.