Growth and irrigation requirements of croton in substrates amended with pre-charged zeolitic tuff

Peatmoss-perlite (PP) was mixed with pre-charged zeolitic tuff (Z) at different ratios (Z, 3Z : 1PP, 1Z : 1PP, 1Z : 3PP, and PP) (v/v). Rooted cuttings of "Aceton" croton (Codiaeum variegatum Blume) were planted in the substrates and grown under controlled conditions. During the 4-month experiment, substrates were allowed to dry via evapotranspiration to 80% of container capacity before the plants were irrigated with a nutrient solution to target a 0.2-leaching fraction. In another 4-month experiment, rooted cuttings were planted in 1Z : 3PP and the substrates were allowed to dry via evapotranspiration to 55, 65, 75, or 85% of available water before the plants were irrigated to target a 0.2-leaching fraction. Results indicated that plants grown in 3Z : 1PP or 1Z : 3PP received the least volume of water (3.4-3.5 L) and amount of nitrogen (N) (514-529 mg). Plants grown in 1Z : 3PP were more vigorous than those grown in 3Z : 1PP and comparable to those grown in peatmoss-perlite. The highest tissue content of N (4.8%) was obtained with zeolitic tuff, phosphorous (P) (0.19-0.21%) with zeolitic tuff and peatmoss-perlite and potassium (K) (2.6%) with peatmoss-perlite. The highest concentrations of N (6944 ppm) and P (306 ppm) were detected in peatmoss-perlite substrate and of K (6594 ppm) and sodium (Na) (4385 ppm) in zeolitic tuff. Plants irrigated at a substrate moisture content equivalent to 55% of available water received the least volume of water (2.4 L). Plant growth and tissue contents of N, P, and K were not affected by substrate moisture content. The lowest Na concentration in the tissue (1.6%) and the substrate (3086 ppm) was recorded for the 85% moisture content. Irrigating at 55 or 65% moisture content resulted in the highest substrate content of N (1778-1841 ppm). The highest substrate content of Na (4031 ppm) was recorded for the 55% moisture content. It is apparent that a croton grower will be able to use around 29% less water and fertilizer if zeolitic tuff is incorporated into the commonly used peatmoss-perlite medium.