Pedohydrological case study of two apple-growing locations in South Tyrol (Italy)

Abstract

Abstract South Tyrol in northern Italy is the biggest coherent apple growing area in Europe. Intensive orcharding is practised there within an area of about 18,000 ha. Irrigation represents a central factor of production in this region because of the local climatic situation (only about 500 mm precipitation per annum). But the way irrigation is applied there follows mostly subjective criteria. At many locations much more water is used for irrigation than the apple trees actually need. The consequence is that irrigation in this region is a very cost-intensive factor of production which is increasingly being discussed and criticized for both economic and ecological reasons. In the context of the current discussions about climate change, the question of protection of resources and the saving of water is becoming more and more relevant. This paper presents the results of soil-physical and soil-hydrological studies, which were done in summer 2008 on two neighbouring locations in the Etsch-Valley of the Vinschgau (South Tyrol). The studies were done to detect pedo-hydrological differences at irrigated orchards which are in immediate vicinity to each other. Because of rainy weather for a few weeks before there was no irrigation at both locations during the period of this study. This made it possible to observe both locations and their pedo-hydrological differences under the influence of a natural water supply. Mostly these differences are neglected in the irrigation practice. It turned out that not only the adjacency of the groundwater table of valley floor soils but also the substrate-specific differences have a crucial influence on the dynamics and the availability of soil water for the plants. Furthermore differences in the compaction of the soil surfaces may cause prolonged infiltration rates and thereby create longer time lags between the start of the irrigation and the resulting water supply in the rootzone. To optimize the irrigation practice in this region it is essential to provide an objective basis for the irrigation process. Accordingly, the term “precision irrigation” is increasingly discussed. But precision irrigation must be based on objective and quantitative criteria which focus primarily on the physical soil properties.