Coir, an Alternative to Peat—Effects on Plant Growth, Phytochemical Accumulation, and Antioxidant Power of Spinach

Abstract

The effects of four commercial substrates, a peat-based substrate, and three coir types (coir pith, coir chips, and coir pith + fibers) on yield, phytochemical accumulation, and antioxidant activity were evaluated in Spinacia oleracea L. cv. ‘Manatee’. Soil-blocked spinach seedlings were transplanted into Styrofoam planting boxes filled with the substrate. Each planting box was irrigated daily by drip with a complete nutrient solution, and the irrigation scheduling was optimized to the peat. Leaf area and fresh yield in coir pith and coir pith + fiber were similar to those obtained in peat. However, shoot dry weight accumulation and leaf chlorophyll were lower in plants grown in coir. Substrate type did not affect leaf carotenoids. Total flavonoid content was higher in plants grown in the different types of coir. Total phenols and antioxidant activity (DPPH) were higher in plants grown in coir pith. This indicates that the different coir types, mainly coir pith, may provide an alternative to peat since they allowed a high fresh yield to be reached and the total flavonoids to be increased. In contrast, the levels of other phytochemicals and antioxidant activity were usual for spinach. However, further research is necessary to analyze the effects of irrigation scheduling and the nutrient solution adjusted to each growing medium on yield and phytochemical accumulation.