Short-term effects of different soil management practices on biodiversity and soil quality of Mediterranean ancient olive orchards

Abstract

Environmental quality can be positively or negatively affected by agricultural practices depending on cropping systems and farm conditions. The Mediterranean basin is one of the 34 biodiversity hot spots on Earth characterized, among others, by the presence of ancient olive orchards. Natural value, environmental quality and cultural heritage linked to extensive farming practices would allow characterizing them as “high natural-value farmlands”. Due to the simplification of agricultural practices aimed at decreasing production costs, the practice of leaving the soil bare is widespread in Mediterranean ancient olive orchards (AOOs); consequently, degradation of soil quality and reduction of plant biodiversity are increasing. Grassingis an alternative practice based on covering the soil with selected autochthonous plant species that was proposed as an alternative to leaving the soil bare, to decrease the cost of soil management and preserving in the meantime soil quality and biodiversity. The present work regards the analysis of the impact of different soil management systems and the evaluation of two different grassing types: natural cover and seed mixtures available on market based on the species present and previously recorded in the monumental olive orchards. In the Torre Guaceto State Nature Reserve, in Apulia Region, South Italy, on the Adriatic coast, from 2011 to 2013, in six olive groves, a comparison was done considering the following agricultural practices: conventional with bare soil, organic with soil covered with seed mixtures available and organic left to natural cover. The comparison was carried on by monitoring the above ground biodiversity of the fields and by investigating the soil quality parameters (physical, chemical and biological soil properties). The research aimed (i) to further investigate whether organic farming practices are able to improve plant biodiversity and soil quality in Mediterranean AOOs; (ii) to define a minimum indicators’ set (MDS) to evaluate the agricultural practices effectiveness in the environmental performance; (iii) to achieve and collect further information about the short-term effects of the grassing on biodiversity and soil quality. Few soil quality indicators showed responsiveness in describing the effects of management systems and of the grassing on biodiversity and soil properties. Among the organic systems tested, differences were found in the performance of the different mixtures used for the grassing. A clear positive influence of the organic management systems was found on some soil quality parameters and on biodiversity.