GROWTH DYNAMICS OF STEVIA CULTIVATED IN ORGANIC SUBSTRATES IN GREENHOUSE

Abstract

In Mexico there are many species of Stevia; however, there is little information on their growth and development. The dynamics and growth rates of plants of S. pilosa Lag. and S. tomentosa H.B.K. were evaluated in greenhouse grown on substrate with different proportions of coconut fiber:vermicompost (0:100, 25:75, 50:50, 75:25 and 100:0) based on volume. Dynamics and growth rates were evaluated six times between 42 and 82 days after seedling emergence. Results indicated that there were differences in the studied variables in relation to the amount of vermicompost. In biomass distribution, the stems of S. pilosa and S. tomentosa with 100 % of vermicompost assigned 54.7 and 48.1 %, respectively, while without vermicompost the assignation was 38.5 and 23.2 %, respectively. Plants of S. tomentosa with 75 and 100 % of vermicompost developed the largest leaf area (440.87 and 426.98 cm², respectively) at the final sampling. The relative growth rate was higher at the first sampling in both species; it was 0.954 g g^-1 d^-1 (50 % vermicompost) in S. pilosa and 0.657 g g^-1 d^-1 (25 % vermicompost) in S. tomentosa. The best mixtures were those with 75 and 100 % of vermicompost, which means that plants prefer highly humified organic materials, as it occurs in natural conditions. S. pilosa was the species with the best growth dynamics and efficiency indices.