Danny Callens

Effects of recent organic fertilizer treatment on herbicide diflufenican soil metabolism in winter wheat crops

The soil dissipation and metabolism of the herbicide diflufenican was studied in a field trial in Belgium in winter wheat which, before sowing, had been treated with green manure, cow manure, or pig slurry. Wheat was sown and the soil was treated with 250 g diflufenican ha(-1) in October. Diflufenican dissipated with first-order kinetics over the first six months with half-lives of 101, 116, 215 and 176 days in control plots, green manure, pig slurry and cow manure treated plots, respectively. The organic fertilizers soil treatments thus increased the diflufenican soil persistence, and probably also its herbicide efficiency. The organic amendments also decreased the soil concentrations of the sum of the diflufenican herbicide 2 (2-[3-(trifluoromelhyl)phenoxy]-3-pyridinecarboxylic acid) and 3 (N-(2,4-difluorophenyl)-2-hydroxy-3-pyridinecarboxamide) and non herbicide 4 (2-hydroxy-3-carbbxypyridine) metabolites. As the organic fertilizers were applied just before sowing, their effects onto the diflufenican soil metabolism corresponded to the ones of the young soil organic matter. After 6 months, the organic fertilizers effect was less pronounced leading to diflufenican (1) and its metabolites soil concentrations in all treatments becoming similarly low. The diflufenican (1) and its herbicide metabolites soil residues remaining after harvest in all the organic fertilizers treated or untreated plots would be too low to be harmful to a rotational crop.

Herbicide flurochloridone soil biodegradation in potato crops

Flurochloridone herbicide has been applied pre‐emergence in potato crops at the rate of 500 g a.i. ha‐1. The field was divided into plots. Each plot was treated either with 50 tons ha‐1 cow manure or pig slurry, or with green manure. Control plots were not treated with organic fertilizers. During the 2.5 months period following flurochloridone application in the 1994 potato crop, in the control plots, and in the plots treated either with green manure, pig slurry or cow manure, flurochloridone soil half‐lives respectively were 41, 48, 67 and 74 days. In the potato crop repeated in 1995 on the same field plots, each being treated again with the same organic fertilizer, the corresponding flurochloridone soil half‐lives respectively were 50, 58, 80 and 70 days. In both 1994 and 1995 crops, after the first 2.5 months period following flurochloridone application, the rates of flurochloridone soil biodegradation increased, and its soil residues became very low and similar in the plots treated or not with organic...