S21 - Session O2 - How to solve the problem of lack of foliar nutrient thresholds for other than conventional production systems?

Authors: Luiz Teixeira *, Edson Nomura, Erval Damatto Jr, Eduardo Fuzitani

The evaluation of the nutritional status of banana plants is an essential tool to optimize the use of production factors and plays a key role in production sustainability. Nutritional diagnosis based on plant analysis requires critical leaf nutrient thresholds (CLNs), such as critical levels or sufficiency ranges, to detect nutritional deficiencies or excesses. However, banana production systems that involve any changes from conventional cultivation lack specific CLNs to enable reliable diagnostics. The introduction of new genotypes, cultivation under very peculiar edaphoclimatic conditions, or the shift from conventional to organic production are some of the situations which may demand new CLNs to be generated. The classical approach to obtaining these CLNs involves extensive and costly field experimentation that may not always be feasible for new farming scenarios, such as the transition from conventional to organic production. This paper presents a methodology for generating specific CLNs for a given crop condition from a database comprising leaf nutrient concentrations and fruit yield. Using this method, we generated CLNs for a 'Grand Naine' banana (Cavendish, Musa AAA) grown on a tropical soil of low natural fertility in Vale do Ribeira, Brazil. Initially, DRIS norms were generated from a database of 180 entries of leaf nutrient concentrations and fruit yield collected from six demonstration areas during two production cycles. The CLNs were derived using multiple linear regression relating the foliar nutrient concentration with DRIS indices of all nutrients. Finally, the CLN for K commonly used in the region was compared with the sufficiency range generated specifically for local conditions. This validation was done in a fertilization experiment conducted under similar soil and climatic conditions. The new sufficiency range for K generated specifically for Grand Naine grown on a tropical soil of low natural fertility provided a more accurate diagnosis of the nutritional status of the plants than the CLN commonly used in Brazil.