Applications in sustainable production

Abstract

Magnesium is the central element in the structural unit of chlorophyll but there appears to be a lack of awareness of the importance of magnesium in plant production and it has not always being given due recognition in fertilizer application considerations. To determine the balance between inputs and outputs of magnesium in a cropping system, a 12 month field study investigated its accumulation and distribution relative to calcium in taro (Colocasia esculenta), a staple food and cash crop in the Pacific Islands, grown on a Fluventic Eutropept. Magnesium and calcium inputs were accounted for through additions of fertilizer, irrigation water and rainfall while outputs were measured by crop uptake/removal. A partitioning of the biomass was made to trace magnesium and calcium distribution in the various parts of the plants (leaf, petiole, root and corm) during growth to maturity. During early growth, magnesium and calcium accumulation occurred mostly in the leaves and petioles. Towards maturity there appeared to be a decline in the leaf and petiole content with an increase in the corm suggesting a translocation of magnesium and calcium to the corm. At final harvest, magnesium and calcium removed from the system by taro harvesting was calculated at 6 and 15 kg ha‐1 yr‐1, respectively.