Effects of Organic Fertilizers on Soil Physicochemistry and on the Yield and Botanical Composition of Forage over 3 Years

ABSTRACT

Organic wastes have been reported to reduce saturation of the exchange complex by Al in Al-rich acid soils. For 3 years, the main soil fertility properties were studied in plots sown with mixed pasture species. These plots were fertilized with cattle slurry, dairy sludge (DS), or granulated broiler litter (BL) in comparison with mineral fertilizer. Al saturation levels were low after the initial inorganic liming treatment (19.00–33.71%) but tended to rise under all treatments (21.09–61.37%) except BL (8.45–30.98%), which was also associated with the highest average soil pH and the highest average levels of exchangeable Ca²⁺, Mg²⁺, and K⁺. Treatment DS performed similarly to mineral fertilizer in most respects, but it led to greater available P levels. Under the dry conditions of the second and third years of the study, BL and DS treatments were associated with significantly greater forage yields than the other treatments. Under DS treatment, available P levels were too low to allow the maintenance of mixed pasture, clover being eliminated by the less P-dependent species.

IMPLICATIONS

This paper presents important information for the enterprises that produce these types of organic waste. They could use these residues as new resources to achieve a new profit in two ways: sell the product (BL) or save money (not to pay to an environmental management company to apply a landfill program under actual European Union [EU] regulations) and to help some of them to achieve the Environmental Management Certificate (dairy industry) and be under EU environmental law.

ACKNOWLEDGMENTS

This work was supported by the Spanish Ministry of Science and Technology under projects AGF1999-0418-C02-02 and AGL200307385, by the Xunta de Galicia under project PGIDT01AGRO2E, and by a grant awarded to Mariana Matos-Moreira by the Fundação para a Ciência e a Tecnologia (Portugal).