Using treated pig slurry as substitute of mineral-P basal fertilization of maize: effects on early plant growth and soil properties

Abstract

Agricultural valorization of animal slurry is considered a priority in some countries, but that practice needs to be carried out minimizing potential environmental impacts, allowing an improvement in soil quality, without a reduction in productivity. A greenhouse experiment used a Haplic Arenosol, fertilized with raw pig slurry, and the materials obtained by its solid-liquid separation and acidification (pH 5.3–5.4), to evaluate the basal- P fertilization of maize ( Zea mays L.), only via organic materials (140 kg P 2 O 5 /ha), leveling the N application with a mineral fertilizer. Slurry-derived fertilizers, which are richer in other essential nutrients, produced significantly greater biomass and promoted faster early plant growth than the mineral fertilizer. The best performance was achieved with raw slurry, acidified slurry, and the liquid fraction of acidified slurry, highlighting the benefits of acidification for nutrient availability. Up to the evaluated growth stage (approximately 100 cm), the P supplied exclusively by the organic materials was sufficient to sustain plant growth. Although leaf P concentrations were significantly lower than in the mineral- P control, they remained within the normal range. However, because of the higher biomass achieved in the organic treatments, total P exported by the plants fertilized with the pig slurry fractions were, as an absolute value, higher, or identical, to the control with mineral- P fertilization. Both fertilizers created nutrient-rich conditions, that appeared to inhibit the establishment of a functional symbiosis with the native arbuscular mycorrhizal fungi during that growth phase, whereas evidence of such a symbiosis was observed in the non-fertilized control plants. The single application of slurry-derived materials did not effectively increase the soil organic matter (OM) content, but it was possible to observe a stimulation in some soil enzymes with the organic fertilizer application, namely dehydrogenase, β-glucosidase and acid phosphatase activities, especially reflecting the combined positive effect of solid OM and slurry acidification on overall microbial metabolism.