Ground deposit of pesticides in relation to the cereal canopy density

Abstract

Pesticides not reaching the intended target may have negative effects on the environment and the field ecosystem. To estimate the potential ground water pollution and risk for soil-dwelling organisms it is necessary to estimate the amount of pesticide reaching the soil in different spraying situations. Literature shows that ground deposition may vary even within equal growth stages due to variations in canopy density. This paper discusses the feasibility of estimating the ground deposition of pesticides from canopy density in cereal fields. Spray experiments were carried out in wheat and barley with flat-fan nozzles of two sizes. Differences of ground deposition between the two nozzle sizes were insignificant. Adding surfactant to the spray solution significantly reduced the soil deposition in barley and in wheat cv Sleipner but not in cv Haven. A significant effect of Leaf Area Index (LAI) on ground deposition was obtained. A simple exponential model based on the LAI with an extinction coefficient of 0.48–0.50 may for many occasions satisfactorily describe the soil deposition of pesticides in cereals. Using non-destructive LAI-measurements combined with the deposition model may be useful in pesticide risk assessment on field, farm and larger regional scale and is optimising the application rate in site-specific farming. © 1999 Society of Chemical Industry