The effect of pelletised and powdered lime on soil Ph, crop yield and crop quality on Richards Bay KZN soil

Abstract

In the 20th century, food security was constrained due to the increase in population and the pressure it placed on food demand. By 2050 further strain is going to be placed on food security as the population is anticipated to double. Land and natural resources are scarce, and soil acidity is a major concern in most parts of the world. A solution to treat acidic soil to increase its fertility to obtain better crop yields and quality is the treatment of lime together with gypsum. Lime is found in two forms pelletised and powdered; however, there lacks practical evidence to support; which is the best form to obtain optimised crop yields and crop quality. Therefore this study was conducted to determine the effect of each lime form together with gypsum on soil pH stabilisation, crop yield and crop quality on a peanut harvest. A quantitative research paradigm and an experimental research strategy were adopted. The pilot study found that the dosage range for pelletised lime being 3 tons/hectare plus 20%vol/lime gypsum and powdered lime was 5 tons/hectare plus 20%vol/lime gypsum. These dosage rates resulted in optimised crop yield and crop quality of peanuts. To ascertain the effects of elevated dosage rates the main study found the effect of both powdered and pelletised lime at two times and three times the optimised dosage range on soil pH stabilisation, crop yield and crop quality. Experimental error was minimised with the use of replicate samples, and a control (the untreated soil) was used as a reference. The optimum dosage range of pelletised lime resulted in a higher crop yield, and 100% of the crop met the quality standard as all peanuts yielded filled the shell cavity. However, the optimum dosage range for powdered lime resulted in a lower crop yield Furthermore, only 65% of the crop met the quality standard. It was found that less pelletised lime is required to stabilise soil pH than powdered lime over a period. Soil treated with pelletised lime had an increased crop yield and quality of peanuts over the use of powdered lime. Despite the above findings, it was evident that overtreatment of both pelletised and powdered lime alone and together with gypsum did not result in a better crop yield or quality. The overtreatment of either pelletised lime or powdered lime and gypsum showed a decrease in crop yield and quality once the optimised dose was exceeded. Consequently the overtreatment of either lime form or gypsum possibly had a toxic effect and inhibited crop yield and crop quality.