Herbicides and nutrients interaction on earthworm activity in tomato cultivated soil and toxicity appraisal

While nutrients are administered through various sources and combinations, herbicides are used for pre-plant and pre-emergence weed control in the tomato fields. Therefore, a study was conducted to understand the effects of nutrient fertilisation through inorganic and organic sources along with farmers practice and the application of three herbicides, namely glyphosate, pendimethalin, and metribuzin, individually or in combinations, on earthworm activity in tomato crops. The herbicides caused a significant reduction in earthworm biomass and escapement to the lower 15 cm depth. Application of pendimethalin and metribuzin to soils inorganically fertilised with major and micronutrients resulted in low survival rates and a high ecological risk quotient. The effect was attenuated when farmyard manure was applied. The study suggests that when 2 to 3 herbicides are applied in succession and combined with inorganic fertilisers as nutrient sources, stringent measures like adding organic nutrient sources, applying the correct herbicide combination, etc., must be followed to reduce their toxicity to earthworms. This helps to protect and sustain earthworm activity and biodiversity in the soil.