Effects of different organic wastes on soil biochemical properties and yield in an olive grove

The main objective of this work was to study the effect of three organic wastes (municipal solid waste, MSW, sheep manure, SM, and green forage vermicomposts, GFV) applied during five consecutive years to a calcaric Cambisol soil located near Cordoba (Spain). The effects of these amendments on soil biochemical properties (enzymatic activities and humus-enzymatic complexes) and olive yield were determined. At the end of the experimental period, soil enzymatic activities were highest in soils amended with GFV, followed by SM and MSW, whereas the humus-enzyme complexes were highest in soils amended with MSW, followed by SM and GFV. The application of organic matter to soil increased the levels of macro- and micronutrients in leaf. At the end of the experiment, the leaf N concentration was 49.6%, 43% and 34.1% higher in GFV, SM and MSW treatments, when compared with non-organic amended soil. Similarly, and compared with the non-organic amended soil, leaf P, K, Ca and Mg contents increased in GFV, SM and MSW-amended soils. Compared to the non-organic amended soil and at the end of the experimental period, olive yield increased 26.8% in soils amended with SM and 35.5% in soils amended with GFV. Also, the olive oil content in fruits showed only significant differences with the GFV treatment. These results suggested that the organic matter quality influenced the olive yield, suggesting that this parameter increased in soils amended with organic matter with higher fulvic acid and higher protein content and low molecular weight contents, readily degradable by soil microorganisms and assimilated by the olive tree.