Spinach production in cocopeat: Effects of soil block number and the number of emitters on plant growth, nitrate concentration, and antioxidant activity

Abstract

Currently, the interest in the use of coir dust (or cocopeat) as a growing medium has increased. The aim of this research was to evaluate the effects of plant density and the number of emitters per Styrofoam box on plant growth, nitrate (NO3-) concentration and antioxidant activity in spinach (Spinacia oleracea L. cv. Manatee) cultivated in cocopeat. The experiment was carried out with four treatments, including two plant densities (160 and 280 plants/m2) and two number of emitters per Styrofoam box (4 and 8 emitters). The crop was irrigated and fertigated daily with a complete nutrient solution, in which NO3-/NH4+ ratio decreased through the crop cycle. Shoot dry weight was not affected by plant density or emitter number. However, the yield (kg m-2) increased significantly with plant density and with the number of the emitters by Styrofoam box. The yield in treatment 280 plants/m2 and 8 emitters reached 5.4 kg m-2. Leaf-blade and petiole NO3- concentration was not affected by plant density, number of emitters and the interaction between treatments. Leafblade and petiole NO3- concentration was low, ranged from 0.49 to 0.56 and 0.94 to 0.96 NO3- mg g-1 fresh weight, respectively. These results indicate that cocopeat is a very suitable growing medium for spinach production.