Soil persistence of herbicides and their carryover effects on rotational crops - A review

Herbicides are one of the crucial options in weed management in most agricultural production systems of world. The introduction of the new herbicide families has had many benefits including very low application rates and low mammalian toxicity. As these herbicides can also be absorbed through the foliage or roots and have high mobility in plants, leading to broad-spectrum control of weeds and having soil residual persistence that gives some control of emerging weeds after application. That is why the use of these herbicide products was rapidly accepted by agricultural producers for crop production. Although, this aspect of the new herbicides is useful for control of emerging weed during the growth season, but the herbicides residues can persist to the next season(s) and damage subsequent crops. A wide range of interrelated factors impact the fate of herbicides in soil. Understanding these factors and processes can make possible the best weed control as well as reducing the potential for injury to non-target crops. Pertinent environmental conditions consist of the chemical, physical and biological characteristics of the soil to which the pesticides are used and climatic features such as rainfall, wind, temperature and light regime. These factors particularly moisture and temperature are two key factors that determine the extent of sorption and degradation of herbicides in the soil matrix. Various mechanisms including phtodegradation, volatilization, leaching, sorption and degradation are determinant processes of herbicide behavior in the environment. The present paper is an overview of the most important processes namely sorption and degradation of herbicides in soil, the environmental factors and herbicides nature which affect the behavior of these chemical in the soil.