Herbicide Residues in Soil and Varieties of Rice (Oryza sativa L.) Samples from Borno State, Nigeria

Abstract

The objectives were to determine the concentrations of herbicide residues in soil and different varieties of rice (Oryza sativa L.) and to compare the levels with allowable limits set by WHO/FAO. Four varieties of rice samples (Narica 1, Marica 2, De-gold and Faro 44 were collected from Zabarmari and Bulamari agricultural locations for the determination of herbicide residues. Extraction and cleanup of the samples were carried out using standard analytical procedures. The levels of the studied herbicide residues were determined using Agilent 7890A GC/MS. From the results of the study, it was observed that paraquat and butachlor are the most dominant used herbicides in the study area due to their higher concentrations in the soil and rice samples. The concentrations of all the studied herbicides were significantly higher in the soil samples as compared to the rice samples. The concentrations of all the herbicides in the soil samples were observed to be higher at depth of 0-10cm, while the lowest concentrations were detected at the depth of 20-30 cm. The study clearly indicates that some of the studied herbicide residues in the rice samples were significantly higher than the WHO and FAO maximum residue limits (MRLs) and acceptable daily intake values (ADIs). Hence, this high values of residues of herbicide call for strict vigilance and constant monitoring in other to protect further contamination of the cultivated rice by herbicides.