Líquido da casca do coco verde como fonte de potássio no crescimento e na taxa fotossintética da melancia ‘Sugar Baby’

Abstract

Potassium (K) is an essential macronutrient for plant growth and physiological performance, acting in osmotic regulation, stomatal control, enzyme activation, and photoassimilate transport. Given Brazil’s high dependence on imported mineral fertilizers and the need for sustainable alternatives, this study aimed to evaluate the use of green coconut husk liquid (GCHL) as an alternative K source in the growth and physiology of watermelon (Citrullus lanatus), cultivar ‘Sugar Baby’. The experiment was carried out in a greenhouse under a completely randomized design with five treatments: T1 – 100% of K supplied as GCSL; T2 – 75% GCSL + 25% KCl; T3 – 50% GCSL + 50% KCl; T4 – 25% GCSL + 75% KCl; and T5 – 100% KCl, with six replicates. At 15, 35, 50, 65, and 78 days after sowing (DAS), biometric growth parameters, biomass partitioning indices, and variables related to gas exchange and photosynthesis were assessed. Partial or total replacement of KCl by GCSL did not result in significant differences among treatments, indicating similar physiological and morphological responses. The results demonstrate that GCSL showed comparable efficiency to mineral fertilizer as a K source, suggesting its agronomic viability and environmental sustainability for watermelon nutrition.