Biochemical variability of olive-orchard soils under different management systems

This work undertakes the biochemical characterization of olive-orchard soils cultivated under three different management systems: conventional, integrated, and organic. The orchards are located in two districts of Andalusia (S Spain): Pedroches Valley (Cordoba province) and Montes Orientales (Granada province). In each soil, the activities of various enzymes were determined - oxide reductases (dehydrogenase, o-diphenol oxidase), hydrolytic activities linked to the C- and P-cycles (beta-glucosidase and phosphatase) and indolacetic acid production (auxins) - as were phenol concentrations, pH, and total organic carbon of the soil. The biochemical activity of the soils studied differed depending on the cultivation or weed-control system. The soils developed under organic management in general presented greater biological activity and greater hydrolytic activity than those under integrated or conventional cultivation. The data, processed by discriminant analysis, divided the soils into three well-differentiated groups. Of all the soils considered a priori as soils under organic management, 89% were classitied as belonging to the same group, while the remaining 11% showed characteristics similar to those of the integrated management group. The discriminant analysis proved especially effective to differentiate olive-orchard soils treated with herbicides from those without such treatment; the tit between the soils considered as belonging to each of the weed-control systems and those predicted by the discriminant model was 100%. The biochemical response of the soil, therefore, differed according to the type of management, and this could be used as a possible control system of crops under organic cultivation. (c) 2005 Elsevier B.V. All rights reserved.