Pesticide behavior in agricultural soils with special reference to the tropical region.

ABSTRACT: Agriculture areas in the tropical region has high occurrence of pests that requires more intense control practices usually by using pesticides, and soil and water contamination is an increasing problem in the tropics. Once applied in the field, the pesticides undergo several processes of retention (sorption), biotic and abiotic transformation and transport. The behavior of pesticides in tropical soils and climates conditions is differentiated from other regions. Some specific weather conditions and soil characteristics can be important drivers of distinct pesticide behavior patterns in the tropics. Hence, brief descriptions of the climates and soils in the tropics are presented as a starting point. Considerations on climate change particularly in the tropics and its effects on soils are also presented. Properties and conditions of unsaturated zone of the soil, especially in the top layer, have both direct and indirect effects on the fate of pesticides that are applied to the soil or reach the soil after application and significantly affect the environmental fate of pesticides. Some combinations of predominant soils in the tropics with specific tropical climates, together with distinct agricultural practices, can involve unique sets of characteristics. The warmer climates, more variable rainfall, main soil types, and distinct biota that characterize most tropical locations imply the behavior, fate and effects of pesticides may be different from those in temperate locations. If the onsite behavior and offsite losses of pesticides from an agricultural area is to be understood, soil sorption and degradation, volatilization, surface runoff and leaching data for relevant tropical conditions are required, considering the soil moisture and temperature, organic matter content and composition, and previous pesticide application practices. This is an important challenge in agricultural and environmental sciences.