Preliminary Diagnosis and Recommendation Integrated System (DRIS) Norms for Hevea brasiliensis Grown in the Humid Forest Zone of Cameroon

The main source of natural rubber is the Hevea brasiliensis, an important crop to the Cameroonian economy. In order to improve yields in a sustainable manner, nutrient norms must be derived for proper nutrient and sustainable soil fertility management. The aim of this study was to derive Diagnosis and Recommendation Integrated System (DRIS) norms for Hevea brasiliensis grown under the ecological conditions of Cameroon. A survey of 130 Hevea brasiliensis fields was carried out to collect leaf samples and yield data. The leaves were analysed for N, P, K, Ca, Mg, S, Fe, Mn, Mo, Na and Zn. Using the yield data, the sampled population was divided into high- and low–yielding sub-populations. The DRIS norms were derived from a high-yielding sub-population (fields yielding >1, 486kg/ha) following standard procedures. Some of the DRIS norms obtained as ratios of nutrients presented significant differences between low- and high- yielding sub-populations. The DRIS norms were made up of ratios of macro nutrients, ratios of micro nutrients as well as ratios of macro and micro nutrients. Some of the obtained norms were different from literature reports that locally derived norms can be more accurate for nutrient diagnostic purposes. The DRIS indices were calculated and used for the assessment of the nutrient status of a low- yielding sub-population of Hevea. The results showed that most macro nutrients were deficient. The obtained nutrient norms will be used for nutrient assessment in Hevea plantations in Cameroon.