Effect of pesticide application rate on yield of vegetables and soil microbial communities

Abstract

Lindane is listed among the Prior Informed Consent (PIC) pesticides, and agricultural uses of lindane have been banned in 52 countries due to its hazardous nature. However, lindane is still widely used in vegetable cultivation in Ghana. The effect of increasing rates of application of lindane (156.0, 244.0 and 312.0 g ha-1), unden (propoxur) (125.0, 187.5 and 250.0 g ha-1), dithane and karate (166.6, 209.8 and 333.3 g ha-1) on garden eggs, okro and tomatoes was studied to find out if it has any advantage that makes its use attractive to farmers despite its ban. Yields of garden eggs were suppressed by all the rates of lindane applied. In tomatoes, lower rates of lindane increased yields whereas the higher rates suppressed yields lower than the control. In okro yields were higher than the control at all levels of lindane applied though yield increments were low. Unden application had the highest effect on garden egg yields followed by tomatoes and least on okro. In the garden egg and tomato treatments, increasing concentration of unden resulted in decreasing yields though yields were higher on the control plots. The optimum unden rate for garden egg and tomato was U20 (i.e. 125.0 g ha-1). Increasing rates of unden on okro did not have any significant effect. Pesticide application had a higher effect on fungal population (50-70% reduction) than on bacterial population in the soil (23.0-38.4% reduction). Dithane suppressed bacteria most whereas karate suppressed fungal population most. Lower levels of chloride residues in tomato fruits corresponded to lower rates of lindane application. Lindane did not have any advantage over the other pesticides as it caused the least increase in yield. It is recommend that farmers are educated on the adverse effects of lindane use, and government enforces the restriction on lindane importation and use in agriculture.

Agrochemicals and the Ghanaian Environment, a Review

“…Studies in Ghana [17,24,31,32] have reported the detection of different kinds of pesticides especially organochlorines in soil and sediment in different parts of Ghana ( Table 6). The fate of propoxur residues in cocoa ecosystem studied revealed that no residue of propoxur could be detected after 21 days after spraying [33].…”

“…Glover-Amengor et al, [31] and Nuertey et al, [32] measured the effect of excessive use of pesticides on biomass and microorganisms in oil palm and vegetable agro-ecosystems. They observed that the pesticides inhibit bacterial population resulting in inhibited nitrification and blockage of other soil microorganisms of both organic and inorganic constituents in the soil, hence decreasing the soil fertility.…”

“…In connection with these, studies of both DOM and nitrate was shown to the degradation of pesticides by sunlight. Moisture and organic matter content was found to facilitate depletion of herbicides in soils [31,35,36]. The degree to which this could occur may highly depend upon the composition and amount of photosensitizers present.…”

Awareness of Health Implications of Agrochemical Use: Effects on Maize Production in Ejura-Sekyedumase Municipality, Ghana

“…This will lead to the avoidance of over/underapplication of agrochemicals and reduce the loss of time due to an illness of the farmer thereby increasing the efficiency and productivity of the crops and farmers. According to Glover-Amengor and Tetteh [25], apart from agrochemicals affecting the environment as poisons, most pesticides used in agriculture in Ghana also affect the crops directly by causing increases in yield at optimum rates and decreases in yield with increasing concentrations.…”

Epidemiological Studies of Tomato Leaf Curl Virus and Whitefly Population and Their Management Using Botanicals

“…But in present study, out of four varieties none of the cultivar showed resistance against TLCV and whitefly infestation. Insecticidal control of vector is often ineffective and frequent use of synthetic chemical insecticides results in acute and chronic toxicity to growers and consumers, contamination of groundwater and resistance development in specific insect pests (Perring et al, 1999;Glover-Amengor and Tetteh 2008). To combat this problem botanicals and detergent were used to minimize the hazards of environmental pollution associated with insecticide sprays.…”