In many farm systems, both inorganic and organic fertilisers, including manure and slurry, are applied to the soil to replenish nutrient offtake in agricultural products and additional nutrient losses to soil as well as surface water and groundwater. With respect to sole reliance on inorganic fertilisers, the use of manure/slurry as a nutrient resource offers important benefits, including the reuse and recycling of nitrogen (N) and phosphorus (P) within farming systems as well as a reduction in the reliance on agricultural production on finite inorganic fertiliser reserves. There is increasing interest in the extent to which additives can enhance the nutrient value of slurry/manure. However, little is known about the impacts of these amended slurries/manures on the quantity and composition of N and P within agricultural and pasture soils. We report data from incubation experiments in which soils received a range of treatments, including the application of livestock slurry that had received a mixture of commercial additives. Our experiments were designed to understand how slurry that has received additives ultimately affects nutrient availability in organic, clay-loam and sandy-loam grassland soils. The addition of the additives to slurry resulted in a slight increase or no difference in total solids, pH, total N, ammonium-N, total P, total potassium, total magnesium and total sodium compared to the untreated counterpart. We considered the effects of our treatments on a range of agronomically important soil parameters, including Olsen-P, mineral-N, available-K, pH and organic matter content. This experiment aimed to understand the extent to which soil fertility could be enhanced through the application of slurries/manures that have received additives. The application of both amended and unamended slurry treatments on soil led to higher values of NH4-N, available-K, available Mg and pH than the addition of inorganic fertiliser. In addition, no substantial differences were observed between the treatment of the three soils with unamended and amended slurry.
Effects on nutrient availability in agricultural soils following the application of slurry amended with additives