Programme de bourses "Echanges Universitaires"

Assessment of the influence of dry and wet conditions on drift from pesticide application in a tropical mountainous region in Colombia


In Colombia agriculture is still an integral part of the economy, thus the use of pesticides to reduce yield losses is nevertheless very important. An incorrect use of pesticides can negatively affect human health and the environment and lead to increased expenditures, mainly caused by the mechanism of pesticide drift.
For this reason pesticide drift in soil, water, air and farmers was monitored for the first time last fall 2008 during the wet season in the highlands of Colombia, leading at the end to an equation which describes pesticide drift outside the field in dependence to wind speed. In this study the same methods were applied to investigate pesticide drift under different meteorological conditions, transition from dry to wet season (March-April 2009) and to validate the former developed equation. Water sensitive papers (WSP) as a measure for the amount of drift into the compartments soil, air and human, were placed in the field, outside the field, on a vertical mesh and on the applicator. Spraying simulations were done through back-pack spraying with a mix of water and the fluorescent tracer Uranine. In this study the amount of drift reaching the different compartments was compared to the total amount of tracer/water sprayed and was evaluated once by simply weighting the papers before and after the experiments and once by measuring the amount of the tracer Uranine sprayed. A weather station near the field measured the meteorological conditions during the experiments. It is important to analyze pesticide drift during different periods to formulate a reliable model which can be used by the applicators to assess the application risks in the course of the different cultivation stages.

In average the weight method estimated 2.24% more drift for the different compartments than the tracer method and did show good results only for measurements done on the soil outside the field, for the first 4 m after the field border. The tracer method, which proved to be in general more reliable than the weight method, showed that in average a relative amount of 89.05% of the sprayed tracer ended in the soil inside the sprayed field and 3.68% drifted into the soil outside the field, up to 20 m from the field border. Over all, without taking into account the hand exposure, 0.19% of the tracer was measured on the applicator’s body. In average 96% of this amount was found on the legs. Only small amounts reached the front and the back of the body and even a smaller amount get on the arms.

The drift amount into the air near to the sprayed area was rather difficult to estimate and new methods should be developed to assess the amount of pesticide suspended in the air. At the end of the analyses the former developed equation was validated, which describes the drift into the soil outside the field with dependence to the distance from the field border and the wind speed. The knowledge of drift acquired by this study may improve the knowledge of spatial risks for human health and environment due to the pesticide.

Researcher:

cand. MSc. Stefanie Karrer
Department of Biology
ETH Zürich
E-Mail: karrers@student.ethz.ch



Collaborators and collaborating institutions:

Prof. Dr. Claudia Binder
Social and Industrial Ecology
Department of Geography
University of Zurich
E-Mail: claudia.binder@geo.uzh.ch

Dr. Glenda Garcia Santos
Social and Industrial Ecology
Department of Geography
University of Zurich
E-Mail: glenda.santos@geo.uzh.ch

Ing. Jaime Diaz
Research Director
Environmental Engineering
Universidad de Boyaca, Colombia
E-Mail: jaimediaz@uniboyaca.edu.co

Leonidas, the applicant farmer, while spraying the field with the tracer-water mix.

Water sensitive papers placed outside the field.