The experiments were conducted in fall/winter and spring/summer seasons, respectively, using expanded clay (grain sizes 4-10, 4-13, 10-13, 13-20 mm) saturated twice or three times a day with nutrient solution N-P-K (1-0.3-2.5) plus conventional production system. The plants grown in expanded clay in fall/winter seasons had dry matter production and N-P-K content significantly higher than those grown in conventional production system. These characteristics improved when planting occurred at the three smallest expanded clay grain sizes and saturation with nutrient solution was done twice a day. The plants grown in expanded clay in the spring/summer season had dry matter production and N-P-K and Ca contents similar to those grown in conventional production system. These characteristics were not affected by frequency of saturation with nutrient solution and expanded clay grain size. Factors, as planting season, temperature and moisture may have limited absorption of nutrients by the plants grown in hardened expanded clay. All treatments showed adequate levels of macronutrients in upper leaves.
circulant nutrient solution; mineral nutrition; dry matter production
