Optimum Substitution of Commercial Substrate with Moinha as an Alternative Biodegradable Agricultural Waste Substrate in the Production of Beet Seedlings

This study aimed to evaluate the effect of increasing concentrations of residues from the drying of coffee beans (moinha) in substrates composed of varied proportions (0, 10, 20, 30, 40, 50 and 100%) of commercial substrates (CS), fixed proportions (20%) of coconut fiber (CF) and carbonized rice husk (CRH) on beet seedling quality production. The experiment was carried out in a completely randomized block design, with seven treatments including control and ten replicates. The treatments were T1: 100% CS (control); T2: 10% moinha (MO) + 20% CRH + 20% CF + 50% CS; T3: 20% MO + 20% CRH + 20% CF + 40% CS; T4: 30% MO + 20% CRH + 20% CF + 30% CS; T5: 40% MO + 20% CRH + 20% CF + 20% CS; T6: 50% MO + 20% CRH + 20% CF + 10% CS; and T7: 60% MO + 20% CRH + 20% CF + 0% CS (all percentages were by volume). The variables evaluated were electrical conductivity of the substrates, seedling height, number of leaves, stem diameter, and dry matter of roots and above-ground parts. Substrate treatments containing 30 and 40% of MO presented the highest values for the growth variables analyzed. However, proportions of MO at up to 50% can be incorporated into the soil nutrient substrate containing 20% of CRH, 20% CF and 10% CS, replacing the exclusive use of the CS, without losing any quality in the beet seedlings produced.