Evaluación de grados brix como herramienta para determinar el punto óptimo de cosecha con dos aplicaciones de k en tomate (Solanum lycorpersicum M.), en San Antonio de Pichincha, Quito, Ecuador

Abstract

One problem in tomato (Solanum lycopersicum M.) production is the postharvest losses (PPC) due to the extremely high maturity stage (EC) at which the tomato reaches local markets. Determining an optimal harvest stage (POC) based on Brix measurements (°B, an indirect measure of the total dissolved solids (SST) content) helps to decrease tomato losses, but it have not been evaluated in Ecuador yet. Furthermore, it is possible to increase tomato productivity through K foliar sprays (KF). The purpose was to determine a tomato POC with the use of °B measurements as an estimative of the SST in four EC and identify whether the KF have any effects over the ripening process and total weight. Four EC were selected and two levels of KF (0 and 12 kg K ha-1) were applied to them six times. A divided parcel (four plant per plot) with four replicates in a randomized complete block (RCB) arrangement design was used. It was evaluated the average tomato weight, equatorial and polar diameters, Brix degrees, acidity, and total yield. The °B and the productivity of tomato did not have a relation because the highest °B was obtained at red maturity stage (p = 0.03). Nevertheless, this is not useful to tomato growers because the EC is very high, and it increases the PPC. However, the application of KF increased in 6% the average tomato weight, and it also increased in 11% the total yield (p < 0.10). It could be presumed that K enhanced the activation of several enzymes which promoted photosynthesis, increased sugar flow, and regulated water efficiency on the plant. Additionally, it was determined that the tomato POC was at light red EC because at that stage were obtained the highest results of tomato weight and diameter. In economic terms, the application of KF in addition to harvest the tomatoes at light red EC provided a profitability to tomato growers of US$ 1.35 for each US$ 1.00 invested. Thus, the application of KF and harvest the tomatoes at light red EC could be an alternative to maximize the total yield of the crop and minimize the PPC of tomato.