Use of Mussel Shells as a Soil Amendment: Effects on Bulk and Rhizosphere Soil and Pasture Production

Large quantities of mussel shells (66 000-94 000 t year(-1)), an alkaline material that can be used as a soil amendment, are generated as waste in Galicia, NW Spain. A field trial was carried out by planting different pasture species in a Haplic Umbrisol using a randomized block design with four blocks and six treatments (not amended control or soil amended with lime, finely ground shell, coarsely ground shell, finely ground calcined shell or coarsely ground calcined shell) to compare the effects of lime and mussel shells additions on a soil with a low cation exchange capacity and high Al saturation. The trial was established in March 2007, and samples of plants and soil were collected when plots were harvested in summer 2008 (separating the bulk and rhizosphere soil). The soils were analyzed for pH, total C, total N, available P, exchangeable cations, effective cation exchange capacity and available micronutrients. Dry matter yield was measured in all plots and plants were analyzed for nutrients. Application of mussel shells and the commercial lime resulted in an increase in pH and exchangeable Ca and a decrease in exchangeable Al and Al saturation. The stability of pH over time was high. These effects were most noticeable in the rhizosphere. The amendment also had a positive effect on dry matter yield and concentration of Ca in the plant.