Analysis and application of soil and plant chemical concentrations in hevea brasiliensis nutrition
Soil and plant chemical analysis have been applied in nutrient management. However, for soil analysis, there is a need to use multinutrient extractants for timely analysis results to be obtained while making use of the modern multinutrient analysers. Application of soil and plant chemical analysis for fertilizer recommendations entails the establishment of standard values (norms). These norms for Hevea brasiliensis in Cameroon have however, not been established. In order to choose an appropriate soil extractant and develop fertilization standards for Cameroon, a survey was carried out in some industrial Hevea brasiliensis plantations during which yield data as well as some soil and leaf samples were collected and analysed for their elemental composition. The pH of the soil samples was also determined. The acidic ammonium acectate – EDTA extractant was preferred for the extraction of soil P, K and Mg because it saved time, cost and labour. The nutrient status of soils and plants ranged between low (deficient) and high (excess) values. From leaf analysis and yield data, critical leaf nutrients were derived and there were no significant differences in the values of critical nutrients derived using different methods. The nutrient levels were further assessed using the Diagnosis and Recommendation Integrated System (DRIS) and the Compositional Nutrient Diagnosis (CND) to identify those that were most limiting to yields. Mean values of nutrient ratios and the coefficient of variation for a high-yielding sub population, calculated as the Diagnosis and Recommendation Integrated System (DRIS) norms, were not exactly the same like those in the literature, emphasizing thereby need for locally derived standards. Preliminary Compositional Nutrient Diagnosis norms (CND) were associated with higher yields (> 1,687 kg/ha dry rubber), while the low-yielding populations presented both macro- and micro-nutrient deficiencies based on the DRIS and CND indices. These indices in turn were highly correlated indicating that they can both be used for Hevea brasiliensis nutrient assessment.