Assessment of the impact of conventional and organic agroecosystems management options and conservation tillage on soil fertility at the Montepaldi Long Term Experiment, Tuscany

Abstract

Fertility is a characteristic of an agroecosystem which is usually and promptly identified with the crop yield. Nevertheless, it can be considered the result of many processes and factors such as climatic, edaphic and agronomic which cannot be extended and generalized to all systems and crops. This study evaluates the effects on soil fertility as influenced by organic (OR) and high-input (conventional, CO) management combined with three tillage systems, i.e., plowing (plw), chisel plowing (chp) and disk harrowing (dsh) at the Montepaldi Long Term Experiment (MoLTE), Tuscany, Italy. Fertility was evaluated through the following indicators: i) chemical (Olsen P, Kjeldahl N and, OM); ii) physical (bulk density on clods and cores, pore size distribution, penetrometry, aggregate stability, soil profile assessment, VESS, i.e. visual evaluation of soil structure); iii) biological (earthworm abundance and root distribution). As regards the effect of management, CO was higher in crop yields, available P2O5, bulk densities (clods), aggregate stability and soil penetration resistance, while OR was higher in bulk densities (cores). Nevertheless, the effect of management was observed for root distribution as a function of depth, where roots explored larger portions of soil in OR profiles. Regarding tillage, the order plw, chp, dsh was characterized by an increase in soil penetration resistance and number of earthworms. Moreover, a relationship with time was found for earthworm abundance, where the OR system exhibited a higher and constant population. Organic management seems to achieve a long-lasting soil fertility. In the MoLTE experiment results suggest that available P2O5, bulk density (clods), aggregate stability, soil penetration resistance, time-related earthworm abundance, root distribution and yields are the most informative on the impact of management and tillage options. Furthermore, results of physical and biological fertility indicators support the hypothesis that significant differences between OR and CO management, even if not observed in topsoil, might be detected in deeper soil layers, below 30cm.