Evaluation of the Soil Response to the Successive Application of Aqueous Extracts from Canavalia Ensiformis Leaves Used as a Post-emergent Bioherbicide

Abstract

Soil is normally the final destination of pesticides applied to cultures. After a series of applications, various pesticides reach the soil due to direct application or leaf washing. However, some amount of the pesticides, particularly foliar pesticides, are intercepted and absorbed by the leaves of the weeds or by the culture itself. Plants contaminated with pesticides may return to the soil during the culture cycle (leaf senescence) or after harvesting (as crop residues). The destination of the pesticide residues in the soil from plant material is both generally ignored and unknown. The pesticide and its degradation products can be released into the soil during the decomposition of the plant, leading to an additional risk of environmental contamination. The greatest consideration when using pesticides (herbicides, insecticides, etc.) is the sensitivity and danger to other non-target species and organisms in the area of application. The adverse effects caused by the indiscriminate use of pesticides, especially herbicides, receive substantial attention because they account for 45% of the world's total pesticide market. In this work, Tukey’s test was used (with a 5% level of probability) to compare soil responses to successive applications of aqueous extracts containing bioherbicides. In general, the existence of bioherbicide residues in soil did not change its properties relative to a control soil. The nutrients evaluated herein did not show a tendency to decrease or increase in concentration during successive applications of the extracts onto the weeds, including possible contact with the soil. The use of bioherbicide did not interfere with the availability of the nutrients or affect the soil fertility characteristics, and it consequently promoted the development of plants throughout the experiment. The persistence of the bioherbicide or its byproducts in soil should not be considered an environmental risk.