CHLORINE - AN ESSENTIAL ELEMENT IN THE MINERAL-NUTRITION OF HYBRID COCONUTS IN LAMPUNG (INDONESIA)

At the P.T. MULTI-AGRO-Corporation plantation in Central Lampung (Sout h Sumatra), 90 km from the sea, water stress is the major factor limit ing tree crop production. In fact, a long dry season recurs at least o nce every five years, on relatively shallow loamy sand soils with a lo w water reserve. Experiments on hybrid coconut mineral nutrition have revealed that chlorine has a predominant effect on both yields under s light water stress conditions and resistance to high water stress, on young and adult coconut palms. The Cl critical level is 0.42-0.45% for young PB 121 hybrids (leaf 4) and 0.5% for adults (leaf 14). NaCl fer tilizer is very effective and much cheaper than KCl, but it cannot be used alone because of K-Na antagonism. In order to maintain good K and Cl contents at the same time, it is necessary to use a combination of KCl and NaCl, whose ideal proportions for local conditions are determ ined through experiments.