Organic Substrates Differentially Affect Growth and Macronutrient Concentrations of Lulo (Solanum quitoense Lam.) Seedlings

We tested the effect of varying percentages (v/v) of peatmoss and compost (60/40, T1; 40/60, T2; and 20/80, T3) on growth and macronutrient concentration of lulo (Solanum quitoense Lam.) seedlings in a completely randomized experiment with ten replicates under greenhouse conditions. Lulo seedlings displayed higher plant height and stem diameter when grown in T1 and T2, as compared to T3. In root tissues, N concentration was higher in plants grown in T1, and the same trend was observed in leaves, though differences were not significant in the latter. All other nutrient concentrations analyzed in root tissues were higher in plants under T3. These results are directly related to a higher biomass production in roots as compared to shoots (52.5% higher) found in T3. In leaf tissues, however, significant increases in plants exposed to T3 were only evident for Ca and S concentrations (i.e., 10.6 and 2.6 g kg−1 DBW). Considering dry biomass weight (DBW), lulo plants exhibited a significant and positive correlation between shoot (ShDBW) and total dry biomass (TDBW), whereas low and negative correlations were observed between root DBW and ShDBW. Therefore, a peatmoss/compost ratio of 0.66 (40/60, T2) results in a better plant growth performance, ensuring a good plant nutrient status for lulo seedlings.