Assessing the liming effect of ground eggshells relative to aglime on two texture contrasting acidic soils

Abstract

Soil acidity is one of the major land degradation problems that affects almost 50% of the world’s arable land. It is usually associated with toxicities of elements such as aluminum and manganese, deficiencies of calcium and magnesium, and reduced microbial activity and diversity. Consequently, all these factors can result in reduced crop yield and economic losses for the farmers. The current effective method of mitigating soil acidity is the application of lime. However, the costs associated with the acquisition of lime make it challenging for small-scale farmers to lime their soils since large quantities of lime are required for substantial effects. Alternative cost-effective liming materials have been sought and these include industrial by-products such as fly ash and stainless steel slag. However, there are environmental and health concerns about using these liming materials since they contain potentially toxic elements. Eggshells were discovered to be composed of almost 97% CaCO3 and 40% pure calcium, which is similar to traditional aglime. Moreover, eggshells contain very small amounts of potentially toxic elements and thus would not pose the risk of food chain contamination. However, due to limited research of eggshells on soil application, the question remains on the effectiveness of eggshells as a liming material. The aim of this study was to evaluate the liming potential of ground eggshells relative to aglime in two texture contrasting acidic soils, and their subsequent effect on the growth of Swiss chard (Beta vulgaris L). The soils used in the study were, sandy clay loam, which had an initial pH of 4.52 and sandy loam with an initial pH of 5.23. The set objectives of the study were then achieved through an incubation and greenhouse study for 120 days. Both studies showed that the application of both eggshells and aglime significantly increased the soil pH in comparison to the control for all application rates in both soils, moreover, there was no significant difference between the two applied lime sources. The results also showed a quick response within 7 days from the application of the two lime sources. The subsequent effects of the applied liming sources in the incubation period of the study were analyzed through the exchangeable acidity and plant-available phosphorus, whereas the subsequent effect of the liming materials in the greenhouse study were analyzed through plant-available phosphorus and plant dry weight of Swiss chard. The applied lime sources completely neutralized the acidity in the soil, and the exchangeable acidity under the application of the two lime sources was significantly lower than the controls at all application rates. The plant-available phosphorus was not significantly different between the applied lime sources at all application rates and the controls, however, the two lime sources increased the plant-available phosphorus above 25 ppm, which is the minimum health level of

plant-available phosphorus. There was no significant difference between the two applied lime sources compared to the controls at all application rates on the plant dry weight. However, it was observed that Swiss chard growing at the 0 t/ha (control) in the sandy clay loam showed poor and stunted growth throughout the study while Swiss chard growing at the 0 t/ha (control) in the sandy loam did not exhibit poorand stunted growth. According to the study’s results, eggshells have a similar liming effect asaglime and their dissolution rate is similar, therefore, eggshells can be used together with aglime or as a substitute of aglime in increasing soil pH.