Composting Process in the Production of Lettuce Seedling Substrates: Effect of Covering and Turning Frequency

Abstract

The composting of waste from a broiler chicken production chain (BCPC) promotes the mitigation of environmental impacts and allows the commercialization of compost as an agricultural input. Both the characteristics and the potential for use of the final compost depends on the operational conditions during composting. The objective of this study was to evaluate the use of organic compounds generated from composting BCPC residues and the pruning debris of urban trees in the germination and initial growth of lettuce seedlings. Six organic substrates obtained under different coverage conditions (presence and absence) and number of turns (8, 12, and 16) were evaluated using the germination index (IG) and Dickson quality index (DQI) for the production of seedlings in trays and compared with a commercial substrate. Principal component analysis demonstrated that the IG is not related to the DQI. The compounds produced without coverage showed lower levels of electrical conductivity (p < 0.05) and potassium (p < 0.05) due to the leaching of soluble salts during composting. These substrates did not inhibit seed germination (IG ≥ 75%), but resulted in less robust seedlings, mainly in relation to the aerial portion. BCPC residues were viable for composting treatment and the DQI of the organic compounds (0.0125) used as substrates for the initial growth of lettuce seedlings were, on average, 14% higher than that obtained from the commercial substrate (0.090), indicating that the organic compounds were of better quality.