The Levels of Manganese, Sodium, Aluminium, Iron, Boron, Zinc, and Copper in the Leaves of Cacao (Theobroma cacao L.): As Affected by Shade, Fertilizer, Irrigation, and Season

The results are given of chemical analyses of leaves collectedover a period of one year from cacao trees in a field trialreceiving fertilizer, shade, and irrigation treatments. Thegreatest variation in concentration of the elements under studywas found to be due to the time of year at which the leaveswere collected. The lowest concentrations of zinc and copperwere found in the leaves collected during the peak of the mainseason crop. The lowest concentrations of manganese, aluminium,and iron were found in leaves collected about a month afterthe end of the main harvest. The levels of most elements rosesharply after the end of the main harvest. The levels of mostelements rose sharply after reaching a minimum, and the maximumlevels were usually reached before completion of flowering forthe next main season crop. The effects of the treatments onthe nutrient levels in the leaves were generally small. Thefertilizer treatment tended to increase the levels of manganese,aluminium, iron, sodium, and zinc and to decrease the levelof boron. The shade treatment tended to increase the levelsof sodium, copper, and zinc and to decrease the levels of manganese,aluminium, and iron. The irrigation treatment had no substantialeffect on the level of any element. The levels of iron, manganese,and boron, were found to be positively correlated with the levelof aluminium.