MINERAL NUTRITION OF CACAO (THEOBROMA CACAO L.).COMPARISON OF PLANT GROWTH AND NUTRIENT CONTENT OF LEAVES OF SIX C.R.I. VARIETIES GROWN IN OPTIMUM AND DEFICIENT CONDITIONS IN SAND CULTURE

摘要

The early growth of six cacao varieties important in the breeding program of the Cocoa Research Institute was investigated in sand cultures supplied with optimum and deficient levels of plant nutrients. The varieties tested were the Amazon selections Nanay (Ny) and Parinari (Pa), West African Amelonado (A), and their hybrids, NyA, PaA, and NyPa. Varieties Ny, NyA, and NyPa had similar growth patterns and were the fastest growing; varieties PaA and Pa were similar and the next best; and A was the slowest growing. In the control solutions variety Pa was larger than variety A, but in all deficient nutrient treatments except the calcium-deficient one, the two varieties grew to equal size.Nutrient levels in the leaves did not vary greatly between varieties, and apparently were not correlated with plant growth. The larger, more vigorous varieties had a higher percentage of small lateral absorbing roots than did the less vigorous varieties.The Amazon varieties Ny and Pa grew significantly less in the potassium-deficient nutrient solution than did the Amelonado variety A when compared with their controls. In addition, the symptoms of potassium deficiency exhibited by the Amazon varieties were more severe than those of the Amelonado variety.