Influence of Agro-chemical Inputs on Suitability of Physicochemical Conditions of Rice-Fields for Mosquito Breeding in Minna, Nigeria

Abstract

The influence of chemicals used in rice farming in Minna, on physicochemical properties of rice-field mosquito larval habitats was investigated during the rainy season of 2013. Standard water quality analyses techniques were followed in determining the concentrations of the different physicochemical parameters. The results showed that Temperature, Dissolved Oxygen (DO) and Biological Oxygen Demand (BOD) did not vary significantly among the types of rice fields (range = 30.00±0.00 to 30.50±0.11oC, 6.00±0.00 to 7.00±1.41 mg/l, and 4.00±0.00 to 4.50±2.12 mg/l, respectively). Turbidity and Nitrates were significantly (p<0.05) highest in rice fields without chemical inputs (site A), with values ranging from 0.27±0.21 to 0.24±0.18 NTU and 9.92±1.94 to 7.72±2.23 mg/l, respectively. However, these two parameters were not significantly different (p>0.05) between site B (rice field with chemical fertilizer only) and site C (rice field with chemical fertilizer and herbicide). Levels of Alkalinity, Hardness, Sodium and Conductivity were highest in site B and least in Site C, with values ranging from 31.00±15.56 to 132.00±19.79 mg/l, 32.00±14.14 to 81.00±41.01 mg/l, 38.15±2.75 to 51.70±1.41 mg/l and 194.00±43.84 to 508.50±44.5 μs/cm, respectively. While the concentration of Potassium was significantly (p<0.05) lowest in site A (10.40±0.14 mg/l), the concentration of Chloride was significantly lowest in site C (23.41±15.03 mg/l) and highest in site A (31.45±4.03 mg/l). Significant positive and negative correlations between some of the parameters were also recorded. These results suggest differential suitability of rice field physicochemical condition for mosquito breeding in Minna and, thus, should provide baseline guide for mosquito vector control in relation to sustainable rice farming in the area.