Abstract
Compost tea is a liquid fraction extracted from composts, and it is of great interest in sustainable agriculture because it reduces the unsustainable use of chemical-based pesticides and fertilizers. In this study, during two spinach field cycles, we evaluated the potential beneficial effect of the foliar application of a compost tea made from onion and vineyard composts either by itself (CT) or implemented with the beneficial microorganism Trichoderma harzianum T78 (CT + Th) on the “healthy quality” and yield of baby spinach. Results showed that both the CT and CT + Th treatments produced a higher spinach yield than the control, but these treatments did not result in an increase in soil dehydrogenase activity (DHA) or soil nutrient content. Furthermore, CT + Th treatment showed the highest yield, phenolic content, antioxidant capacity and flavonoid levels. Nitrate levels were below legal amounts, and they were significantly (p ≤ 0.05) lower in the CT and CT + Th treatments than in the control. Data suggest that compost tea extracts from onion waste and vineyard compost and/or enriched with T. harzianum can be used in a sustainable agriculture to increase yield and quality of baby spinach.
Highlights
Spinach is one of the healthiest vegetables in the human diet due to its high concentration of phytonutrients and health-promoting compounds [1]
The spinach yield was significantly higher in both composts either by itself (CT) treatments (CT and CT + Th) than in the yield was significantly both CT1a, treatments than in the control inThe bothspinach experimentsin(Figure
Applying CT produced a higher spinach yield and foliar area than the control treatment. This improvement corroborates previous studies, such as those conducted by Hargreaves et al [28], Marin et al [29] and Bernal-Vicente et al [26]. This fact could be attributed to a combination of factors, including beneficial plant microorganisms like biostimulants, biofertilisers, biopesticide microorganisms and/or growth promoter compounds like phytohormones that can be found in compost teas [30,31]
Summary
Spinach is one of the healthiest vegetables in the human diet due to its high concentration of phytonutrients and health-promoting compounds [1]. It is a good source of vitamins and mineral elements, such as calcium, iron, phosphorus, sodium and potassium [2]. Composts teas (CTs) are oxygenated compost water extracts obtained through a suitable liquid-phase blowing process. The application of CTs benefits plant yields, mainly by improving the physiological status of the plant and/or enhancing protection from pathogens [3]. CTs have been found to stimulate root and vegetative growth [4], showing behavior close to that of biostimulants [5]
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