Gypsum application lowers cadmium uptake in cacao in soils with high cation exchange capacity only: A soil chemical analysis

Abstract

Soil liming to lower cadmium (Cd) bioavailability is challenged in perennial cacao orchards by the low penetration of lime in soils, not reaching deeper roots. Some studies suggest that gypsum (CaSO4) could reduce Cd uptake by enhanced Ca2+:Cd2+ competition at the root surface. A pot experiment was conducted to identify soil conditions affecting gypsum efficacy in cacao plantlets (5‐month‐old CCN‐51). Plants grew for 115 days in soils sampled from six locations with variable cation exchange capacity (CEC, 6–50 cmolc.kg−1) and soil solution Ca2+ (1.3–17 mM). Soils were either mixed or not mixed with a dose equivalent to 4.0 Mg gypsum ha−1. Leaf Cd concentration in plants grown on gypsum applied soils was statistically lower compared to unamended soils in only one of the six soils. The reduction factor of leaf Cd concentrations due to gypsum (RF = control/amended Cd concentration ratio) ranged from 2.32 (high effect) to 0.76 (no effect), and it was positively correlated with the Ca2+ in the solution of the unamended soil (R2 = 0.58) and with increasing CEC (R2 = 0.52), that is, gypsum only reduced Cd bioavailability in high CEC soils, confirming a trend found in earlier publications. Soil solution analyses showed that gypsum application enhanced total dissolved Cd by forming CdSO40 complexes with, in some cases, even enhanced Cd2+ ion activities, likely related to Ca2+‐induced Cd2+ mobilisation. Data suggest that Ca2+ derived from gypsum has counteracting effects on Cd mobilisation and ion competition at the root surface. The former reactions are less pronounced in high CEC soils. More research is needed to unravel gypsum effects on high Ca2+ soils to corroborate our findings. Highlights The effect of soil properties on the efficacy of gypsum to reduce Cd uptake in cacao was studied. Gypsum only reduced Cd uptake in cacao in the soil sample with highest CEC and highest Ca in solution. This finding implies a possible competition between Ca2+ and Cd2+ for root uptake in cacao.

Elucidating Amendment Resources for Reclaiming Efficacy of Sodic Soils around Abaya and Chamo Lakes, South Ethiopia Rift Valley

“…This could be because gypsum is a calcium sulfate mineral, and when it dissolves in water, it releases calcium ions (Ca 2+ ) into the soil solution. These calcium ions can then be adsorbed onto the soil colloid, increasing the amount of exchangeable calcium in the soil [ 38 , 96 ]. Sole application of farmyard manure (FYM) had a significant effect ( p < 0.05) on potassium (K) in sodic soil by improving soil structure and increasing cation exchange capacity ( Table 2 ).…”

“…Calcium accumulation on the exchange sites can contribute to better soil aggregation in sodic soil, which in turn can help reduce the soil’s bulk density [ 37 ]. Calcium is typically obtained from amendments that have either soluble Ca 2+ or can dissolve Ca 2+ upon reacting with soil [ 38 ]. Gypsum and organic matter have recently been used for soil reclamation [ 27 ].…”

Effects of Different Liming Materials on the Uptake of Cadmium and Mineral Nutrients in Cacao Plants

“…This might be caused by competitive desorption of Cd 2+ bound to the soil with the increase of Ca 2+ concentration due to the application of the Ca and Mg–Ca liming materials. , The equilibrium between the solution and exchangeable cations in the soil is altered by the addition of liming materials as the result of two competing phenomena: (i) the increase in pH and (ii) the increase in ion activity by the addition of base cations . For instance, Argüello et al observed that the Cd uptake in cacao plants upon gypsum application to soils from six different cacao farms was reduced only for a soil with high CEC and naturally high Ca 2+ concentrations. The authors attributed these results to the displacement of exchangeable Cd 2+ by the release of Ca 2+ after gypsum dissolution in soils without a naturally high base saturation capacity.…”

Efeitos Da Nutrição De Matrizes Gestantes No Imprinting Fetal Em Suínos: Revisão

“…Instead, gypsum increased the concentrations of soluble metals in the soil solution and enhanced the metal plant uptake. The calcium cations from solubilized gypsum possibly displaced the metals in the exchangeable soil complex, making them more available to the plants and increasing the environmental hazard; thus, gypsum was ineffective and considered inappropriate as a soil remediation method to ameliorate soils polluted by metals Argüello et al (2022). also found limited effects of gypsum in cadmium-contaminated soils cultivated with cacao and, in some cases, even increased cadmium dissolution and plant-available by forming cadmium sulfate (CdSO 4 ) complexes.…”