Application of calcium targeted to flowers and fruits in the production, quality and nutrient content of okra seeds

The appropriate use of fertilizers is considered a prerequisite for obtaining high yields and seed quality. For okra, a species with great importance and potential to be explored in several areas, the quality of the seeds is one of the most limiting factors for obtaining uniform plant populations and, consequently, high yield. The aim of this work was to study the effect of applying calcium to flowers and fruits on production, quality, enzymatic activity and macronutrients content in okra seeds and fruits. Five concentrations of calcium were tested (0.0 (control), 0.25, 0.50, 1.0, 2.0 g L−1), using calcium chloride (27% Ca). Applications were made every 10 days, directed to flowers and fruits, starting as soon as the first floral buds appeared on most plants. There was no difference in the characteristics of electrical conductivity, accelerated aging, P, K, Mg and S content in fruits, N, K, Ca and S in seeds and lipid peroxidation. The higher the calcium concentration applied, the greater the activities of the POD and CAT enzymes in the seeds and of Ca content only in the fruits. The highest values for weight of one thousand seeds, seed (germination and emergence) and hydrogen peroxide content were estimated with concentrations between 1.2 and 1.3 g L−1. There was a linear increase in fruit and seed productivity the higher the calcium concentration, resulting in an increase of 27 and 25%, respectively, in relation to the treatment without calcium application. Despite being the second nutrient with the highest content in the fruits, after K, Ca was the macronutrient with the lowest content in the seeds.