Past organic fertilizer treatments: Influence on the herbicide diflufenican soil metabolism in wheat crops

Abstract

The influence of several organic fertilizer treatment regimens, applied at the beginning of crop rotation cycles, were compared as to their slowing down effect on the herbicide diflufenican soil metabolism in wheat crops. In a first trial made at the site "Longs Tours", the organic fertilizers treatment schemes had been repeatedly applied in the past since 30 years, according to a 3 years rotation cycle. The following organic fertilizers treatment regimens were compared: treatment (1) no organic fertilizer at all; treatment (2) cow manure; treatment (3) pig slurry + green manure + crop wastes; treatment (4) green manure + crop wastes; treatment (5) straw cereal wastes alone. A spring wheat crop was sown and diflufenican was applied, i.e. 1.6 years after the latest external organic fertilizers application. During the 4 first crop months, the difiufenican soil half-lives were 59, 91, 117, 81 and 70 days in the treatments 1, 2, 3, 4 and 5 treated plots, respectively. During the end period of the crop, the effect of the organic fertilizers treatments disappeared, the diflufenican and its metabolites soil concentrations becoming very low and similar in the organic fertilizers treated and untreated control plots. A second trial was made with winter wheat at the site "Les Pompes". The organic fertilizers regimens however had been applied only one time 1.2 years before sowing and diflufenican application. In this trial, the organic fertilizers treatments had no significant influence on diflufenican soil half-life.