Substrates for the production of lettuce seedlings

Abstract

High-quality alternative substrates are essential to ensure adequate conditions for the emergence and development of lettuce seedlings. The effect of different proportions of termite mound and bee nest materials on emergence and initial growth of lettuce seedlings were tested in this study. The experiment was arranged in a randomized block design, using three lettuce cultivare (Grandes Lagos Americana®, Crespa Grand Rapids - TBR® and Simpson Semente Preta®) and six substrate combinations formulated from different proportions (v:v) of bee nest material (BNM) and termite mound material (TMM) or commercial substrate (CS) (Click Mudas®), considering a factorial arrangement (3 x 6) with four replicates. The following substrate combinations were tested: S1 = BNM100%; S2 = BNM75% + TMM25%; S3 = BNM50% + TMM50%; S4 = BNM25% + TMM75%; S5 = TMM100%; and S6 = CS. The emergence rate, emergence speed index, root collar diameter, leaf number, relative chlorophyll index, root length, root dry mass (RDM), shoot dry matter (SDM), total dry mass (TDM) and morphological index (SDM/RDM) were measured. The 'Crespa Grand Rapids' cultivar was the most responsive to the use of different substrate combinations formulated with BNM and TMM when compared to the commercial substrate. For the production of lettuce seedlings, the substrate composed by 100% of bee nest material (SI) is the most adequate, since it results in a higher emergence rate, emergence speed index, root length, leaf number, shoot dry mass and total dry mass.