Greenponics as a strategy for successive vegetable cultivation in an ecologically based system

Greenponics is an innovative technique in which non-composted plant biomass is used as a substrate and source of nutrients for cultivation in pots, seedling trays and in soil. The objective of this research was to evaluate the successive cultivation of kale (Brassica oleracea L. var. acephala), cambuci pepper (Capsicum baccatum var. pendulum), and okra (Abelmoschus esculents) in a greenponics system using mixtures of elephant grass (Pennisetum purpureum) and gliricidia (Gliricidia sepium) biomass as substrate and nutrient source under organic management. The sequence of experiments was kale (experiment I), cambuci pepper (II), okra (III), kale (IV), and okra (V), all grown at the same location. For the field cultivation, cradles (pits) were dug in the soil, which functioned as pots that were locally enriched. In experiments I-IV the treatments consisted of: plant biomass with 100% elephant grass (T1); 75% elephant grass +25% gliricidia (T2); 50% elephant grass +50% gliricidia (T3); 25% elephant grass +75% gliricidia (T4); 100% gliricidia (T5). In experiment V (okra), mulch doses composed of 50% elephant grass +50% gliricidia were tested. In kale and peppers, there were no significant differences between the three treatments that received 50%, or more, gliricidia, with average marketable yields of 33 Mg ha−1 for kale and 14 Mg ha−1 for peppers. For the okra there were no significant differences between the treatments, with an average marketable yield of 18 Mg ha−1. Greenponics using gliricidia mixed with elephant grass as a fertiliser source could be recommended as a potential alternative for successive cultivation of vegetables in the field.