Pig slurry as fertilizer on willow plantation

The aim of this study is to investigate the effect of the use of pig slurry as fertilizer on the productivity of a willow plantation, while evaluating the risk of a negative impact on the environment. We evaluated plant response to increasing slurry amounts and compared this response to the effect of mineral fertilization. We also verified the impact of slurry on soil nutritional content as well as on nitrate and phosphorus concentrations in the soil. Although slurry nitrogen was less efficient than mineral fertilizer, the results of our study show that slurry constitutes an effective fertilizer for willow plantations. In fact, yields over two years on plots that received increasing amounts of slurry were on the order of 30.0–32.9 t/ha. We observed an increase in soil levels of nitrates, copper and zinc as a function of increasing slurry amounts. These levels actually decreased during the second growing season, possibly due to uptake by the willows. Springtime concentrations of water in lysimeters indicated that the maximum quantity of slurry tested was accompanied by a certain risk of nitrates leaching into the soil.

► Biomass yields and nutritional uptake by willows in response to doses of pig slurry were investigated.
► When the highest dose of slurry was applied nitrate leaching was observed.
► Results obtained make it possible to envisage that typical three-year rotation cycles could be reduced to two.
► Pig slurry constitutes an economic fertilizer which can substitute the conventional fertilizer.