Safe and toxic application rates of boron for cocoa (Theobroma cacao) seedlings

Abstract

In a preliminary study to ascertain the safe and toxic rates of boron for cocoa seedlings, the F3 Amazon and the Amelonado varieties were treated in the glasshouse by foliar spray with 0, 5, 10, 25 and 50 ppm B as solubor. It was observed that 5 ppm B was required to raise the leaf-B of six-month old cocoa seedlings from the deficiency to the sufficiency level. The critical levels were 32.5 ppm B for Amazon and 36.3 ppm B for Amelonado. B rates in excess of 5 ppm caused chlorosis, necrosis, and in extremely high rates, the death of the seedlings.