ANTHURIUM PRODUCTIVITY IS LIMITED BY WATER AND NUTRIENT AVAILABILITY IN VOLCANIC CINDER MEDIUM

Volcanic cinder is a standard medium for Anthurium production in Hawaii because it is inexpensive, biologically and chemically inert, and provides good drainage for plants. However, low water holding capacity of the medium imposes con¬straints to the availability of water and nutrient for Anthurium production. The daily water consumption was measured in Anthurium growing in 100% cinder with either limited or unlimited availability of water. Water consumption of Anthuriums was low and measured as half of the reference evapotranspiration (ET_o). Despite the low water demand, water uptake of Anthuriums was 40% higher when plants had easy access to water, and consequently resulted in higher yield. When four production methods were examined for comparison, fertigation treatment produced the highest yield with greater flower size throughout a year compared to the farm practice. However, either additional irrigation or P supplement to the current farm practice also increased productivity. Our study shows that field grown Anthuriums better perform when water is not limited even in an area with high rainfalls, which is partly due to the limited water holding capacity of cinder medium and partly due to Anthurium root characteristics. Efficient water and nutrient management should be achieved to optimize production of Anthuriums when cinder is used as a substrate.