Runoff in cultivated hilly areas as influenced by crops and land management

Runoff is one of the major causes of soil loss in the hilly areas of Italy. It is possible to successfully prevent the phenomenon by an adequate drainage of water in the agricultural areas, via the modelling of soil surface, and choosing the proper tillage and crop. The best soil management is selected by a deep knowledge of the chemical and physical properties of the soil, of the topography and the land use. In order to study the problem in detail, a field experiment was carried out in the hillside next to Bologna, Italy (Ozzano dell’Emilia, 44°24'N, 11°28' E, 185 m a.s.l.) for a 17-year-long period (1992-2009). In this experiment the effect on runoff of field crops (wheat, sorghum, rye-grass and alfalfa) and orchard (cherry trees), with different slopes and land modelling was evaluated. The crops were cultivated with various field modelling, in 5 plots 1000 m2 large . The soil was sandy-loam and the tillage management was performed as in the common practice of the area. Precipitation was continuously measured thanks to a meteorological station next to the area and each plot was equipped by runoff ditches and measurement gauges. The results show that, between the permanent crops, cherry trees was always more efficient than alfalfa in minimizing runoff, independently from slope and management of the alfalfa. As an average of the entire period, the number of runoff events was the highest in the plots diagonally cultivated and was the lowest in the plot cultivated following the contour lines. The up-and-down modelling gave good results in controlling the runoff. A significant relationship was evidenced between the total amount of rainfall during the farming year and the mean number of runoff events, irrespectively of the crop.