On-farm pesticide use in four Northern German regions as influenced by farm and production conditions

In scientific and public communities pesticide use in arable cropping is a strongly discussed management measure. Nevertheless, information about on-farm pesticide use intensities is scarce. We studied the contribution of regional and farm effects to average pesticide use and its variability and major influencing factors. Data on chemical plant protection measures of 60 farms in four regions of Northern Germany were examined for twelve field crops between 2005 and 2014. The regions correspond to administrative districts of similar size located on gradients of climatic, soil, and structural production conditions. First, we analysed pesticide use intensity described as Standardised Treatment Index (STI) per district and crop. Second, we estimated the variance components on STIs ('District', 'Farm', 'Field', 'Year') for total and groups of pesticides. We found a decreasing gradient in pesticide use intensity from the west to the east in Northern Germany. STIs were lower in districts with less favourable conditions for arable land use. However, analysis of variance components showed that the influence of the natural gradient is smaller than the influence of the farm. Hence, differences in farm management and socio-economic characteristics superimpose the production conditions. Finally, we checked the meaningfulness of our results by comparing them with previous and on-going large scale surveys. We determined differences (lower STIs) to the statistical means of the German reference farm network Plant Protection. We assume that this is caused by the higher aggregation level of regions of the German reference farm network Plant Protection.