PERFORMANCE OF Calendula officinalis L. IN SUBSTRATES DEVELOPED WITH SOLARIZED SEWAGE SLUDGE AND AGRO-INDUSTRIAL WASTES

ABSTRACT Efficient products can be developed for the ornamental plant sector using agro-industrial waste. This study evaluated the agronomic performance and ornamental quality of calendula plants (Calendula officinalis) cultivated in substrates formulated with solarized aerobic sewage sludge (SASS), rice husk ash (RHA), and sugarcane bagasse (SB). Five additive rates were used: S2: 33.33% SASS + 33.33% RHA + 33.33% SB; S3: 16.65% SASS + 41.67% RHA + 41.67% SB; S4: 12.48% SASS + 43.76% RHA + 43.76 % SB; S5: 8.32% SASS + 45.84% RHA + 45.84 % SB; S6: 4.16% SASS + 41.07% RHA + 54.76% SB; and S1: commercial substrate (reference). Raw materials and substrate formulations were characterized and agronomic and ornamental aspects were evaluated in calendula plants cropped in all substrates. The lowest agronomic performance was observed in S6 (lowest SASS rate), while the highest occurred in S3 compared to the other treatments. Regarding the ornamental potential, S3 and S4 and the commercial substrate (S1) were classified as excellent. This study highlights the successful use of organic raw materials (SASS and agro-industrial waste) to compose substrates for calendula production in pots, with the recommended proportions ranging from 12.48 to 16.65% of SASS combined with RHA and SB.