Soil Amendment for the Immobilization of Herbicide in Contaminated Soil Using Sawdust

Abstract

Over the past years, the number of different herbicides has increased significantly. This has led to growing concern about the possible adverse effect on human health such as cancer, birth defects, reproductive problems, tumours, and damage to the liver, kidney and neural organs. The environment is affected as abuse of herbicides leads to contamination of soil, water, and air, thereby damaging the surrounding ecosystem and other living organisms necessary for maintaining ecological balance. The study investigates the effect of sawdust organic amendment on mobility of herbicide residues in contaminated soil, in which African Spinach (Amaranthus hybridus) is grown. Sawdust of Locust Beans tree (Parkia biglobosa) and Teak tree (Tectonia grandis) were used in a randomized complete block design. A composite sample of topsoil (110 kg), and sawdust compost (10kg) was used, and 120kg of topsoil without sawdust compost was used as a control. Amaranthus hybridus was planted in the potted mixtures and 120ml of herbicide (Glyphosate 41% SL) which was diluted with 5 litres of water and was applied to all treatments at an equal rate after sowing. The Gas Chromatography Mass Spectroscopy (GCMS) analysis of the active ingredient in the glyphosate 41% SL indicates that the quantity of Isopropylamine was 34.093ppm. From the GCMS results, the highest mean of Isopropylamine (32.75ppm) was found in the control treatment prepared without saw dust amendment, as compared to other samples. However, no herbicide was detected in the vegetable raised in soils amended with compost made from Parkia biglobosa and Tectona grandis species. The study recommends reduced use of herbicides, especially on vegetables, by farmers.