Estimate Of Macronutrients Uptake By Arracacha At Harvest

In Puerto Rico, arracacha or apio is a minor crop planted for its yellowfleshed corm. The climatic requirements of this crop restrict its commercial production to high elevations where ultisols are common. Previous studies did not examine the amount of nutrients that must be supplied by the soil-fertilizer combination for optimum crop development and yield. The objective was to estimate arracacha's macronutrient uptake in a soil typically used for its production. The experiment was planted on a Humatas soil (Typic Tropohumults) under rain-fed conditions. Three levels of Κ fertilization were used (45, 90 and 135 kg/ha). Yield and plant fresh weight were recorded at harvest; then the plant parts were oven dried. The nutrient concentrations in the tissues were obtained to estimate nutrient uptake. Neither yield, plant parts fresh and dry weight nor nutrient concentrations in tissues were affected by the level of Κ fertilization. Fresh corm yield was 4.8 t/ha. On a dry weight basis, the crop harvest index was 0.81. Except for K, the nutrients were more concentrated in the leaf lamina. Uptake of Ν and Κ were the highest, whereas Ρ and Ca uptake tended to be intermediate between the N-K group and Mg uptake. Nutrient harvest indexes exceeded 0.35.