The effect of spent mushroom substrate enriched with selenium and zinc on the yield and photosynthetic parameters of lettuce (Lactuca sativa L.)

The aim of the study was to investigate the influence of Agaricus bisporus spent mushroom substrate (A-SMS) enriched with selenium (Se) and zinc (Zn) on the yield and photosynthetic parameters of lettuce (Lactuca sativa L. var. capitata) of the ‘Skindel’ cultivar. The growing medium for the cultivation of lettuce consisted of A-SMS (10%) and commercial peat (90%). It was further enriched with Se and Zn concentrated at five levels, i.e. 0.1, 0.2, 0.4, 0.6, and 0.8 mmol·L–1 to obtain six growing medias. Se was added to the growing medium in the form of sodium selenite and sodium selenate at a 1:1 ratio, whereas Zn was added in the form of zinc nitrate hexahydrate. Lettuce was grown under controlled conditions in growth chambers. The experiment was conducted in a randomised complete block design in three replicates. The results indicated that the A-SMS added to the growing medium increased both the yield of lettuce and its biological value by increasing the content of Se and Zn. Consumable percent recommended daily allowance and safe hazard quotient for lettuce biofortified with Se and Zn were achieved. The experiment also showed that the addition of Se + Zn did not negatively affect photosynthesis and chlorophyll fluorescence parameters, which proved that these elements did not have toxic effect on lettuce in agronomic perspective.