Characterization of Spatial Variability Structure in Three Separate Field Trials on Pesticide Dissipation

Abstract

Experiments were carried out on three Italian farms to assess the degree of spatial variation of pesticide field concentration during treatment and during dissipation trials. Test pesticides were chloridazon and metamitron (both sugar‐beet herbicides) applied as a tank mix. The classical statistical technique and geostatistics were used to summarize and evaluate variable spatial data. The results show that the actual values of pesticide concentration for application rate and initial concentration in all three areas are lower than expected, thus indicating that under field conditions only a part of the pesticide reaches the soil during the distribution. The actual values for both herbicides in all three areas expressed as percentage of expected values ranged from 44·1% to 64·2% for application rate and from 40·5% to 99·5% for initial concentration. The coefficient of variation was similar for both pesticides and ranged from 23·8 to 74·1 for application rate, 24·1 and 58·8 for initial concentration and 11·1 and 110·0 for dissipation half‐lives. The high variability in application rate and initial concentration could be ascribed to an uneven herbicide distribution, and in dissipation studies to variation in half‐lives for the rate of herbicide loss from soil in different parts of the field. Geostatistic analysis indicated little spatial correlation, probably because the sampling sites were widely spaced on the field. In all cases, the data were not sufficient to estimate the range of influence, probably because of the size of the experimental fields and the sampling strategy. © 1997 SCI.

Fate of the herbicides glyphosate, glufosinate‐ammonium, phenmedipham, ethofumesate and metamitron in two Finnish arable soils

“…Similar results were obtained by Vischetti et al 31 in their studies of metamitron and chloridazon herbicides in sugar beet cultivation. They demonstrated that only a part of the sprayed herbicides reached the soil and that the spatial variability of the herbicides in the soil surface was high.…”

Measurement and modelling of glyphosate fate compared with that of herbicides replaced as a result of the introduction of glyphosate‐resistant oilseed rape

“…Regarding the latter point, wind speed averaged 0.9 m s −1 over the day of application, with a maximum of 5.5 m s −1 . Volatilization and photodegradation are usually negligible for this substance 7, 10, 16, 50. The glyphosate dissipation on the soil surface (0–5 cm) was rapid: 34 DAA, less than 10% of applied glyphosate was detected (Fig.…”

A screening tool for vulnerability assessment of pesticide leaching to groundwater for the islands of Hawaii, USA

“…However, it is important to provide reasonable estimates of the uncertainty of these parameters in terms of standard deviations. Variability of the half‐life50–52 and the sorption53–55 of pesticides within a field may be used from previous studies when the uncertainty of pesticide parameters needs to be estimated for new pesticides. The aforementioned and similar studies do not give exact values for the new pesticides, but such data may be used to give an idea of the magnitude of the uncertainties.…”