Investigations on the nutritional status of <em>Hevea brasiliensis</em> plantations in the humid forest zone of CameroonPart 2: Establishment of macro nutrient norms

Abstract

Standard nutrient values are needed for the assessment of optimum nutrient concentrations for improved and sustained yields. The aim of this study was to establish optimum soil and plant nutrient values for Hevea brasiliensis in the humid forest region of Cameroon. A nutrient survey was carried out during August 2010 and August 2011 in some rubber growing zones of Cameroon. Both soil and leaf samples were collected for the determination of their macronutrient contents. Using the macro­nutrient concentrations and yield data, boundary lines were calculated. These boundary lines were described by second degree polynomials. Equating the first derivative of the second degree polynomial equations to zero, the following optimum nutrient values 3.5%, 0.31%, 1.53%, 0.28% and 0.83% were obtained for N, P, K, Mg and Ca, respectively, for Hevea leaves. On the other hand, the optimum soil nutrient levels were 3.1% for organic carbon, 0.18% for N, 5.9 mg/kg for P, 262. mg/kg for K, 432 mg/kg for Ca and 16 mg/kg for soil Mg. The optimum soil and plant nutrient ranges were obtained by solving the boundary line equation at 95% of the optimum yield. The optimum nutrient values for Hevea brasiliensis obtained in this study were to a large extent different from those obtained in studies elsewhere. This is an indication that for effective nutrient diagnosis, locally derived norms should be used. Those local nutrient norms will be used for nutrient assessment in Hevea plantations in Cameroon.

Keywords

• Boundary line
• Hevea brasiliensis
• Humid forest
• optimum nutrient levels/ranges