EFFECT OF IRRIGATION AND SOIL MANAGEMENT PRACTICES ON FRUIT PRODUCTION AND QUALITY IN CHESTNUT ORCHARDS OF NORTHERN PORTUGAL

Chestnut orchards have an important role in the rural economy and landscape patrimony of Northern Portugal. However, there is a great concern about those systems, especially related to the management practices, in order to improve its productivity and sustainability. The traditional management system involves several annual surface tillages, being cited as main reason the soil water conservation. Different studies developed over the last ten years, involving measurements related to soil moisture, leaf water potential, soil quality indicators, orchard productivity and plant health, have shown that frequent tillage provides no advantages to the orchard productivity and sustainability, when compared with less intense or no-tillage practices, such as the maintenance of natural ground vegetation or seeded pasture under tree canopy. Also producers are questioning the utility of annual soil tillages and new solutions related to the soil management have been envisaged, e.g., no tillage with control of vegetation and seeded pasture, irrigated or droughted. Thus, following the previous studies, a new experimental set was established since 2001 in order to study the effect of no-tillage management with natural vegetation cover, or with seeded pasture (irrigated and droughted), on fruit production and quality. The obtained results during 2003 and 2004 are reported and the following conclusions are allowed: (i) soil water content is an important factor to obtain satisfactory fruit production and quality; (ii) however, irrigation does not increase fruit production and only the fruit dimension was lightly improved, which questions the need of irrigation to increase productivity; (iii) No-tilled plots, covered with natural vegetation, controlled by grazing or cutting, seems to be the most favourable management practice concerning fruit production, sustainability, and the costs-benefits rate.