Abstract
The present experiments tested the effects of root zone substrates consisting of coir and peat mixture (peat moss : vermiculite : perlite = 6 : 1 : 1, v/v/v) on the growth, yield, and water relations of the strawberry ‘Akihime’. Treatments consisted of four different ratios of coir and peat mixture as follows: 3 : 7, 5 : 5, 7 : 3, and 10 : 0. The liquid phase in the substrate at −1.5 kPa of matric potential decreased with increasing coir ratios, whereas the gaseous phase increased. The marketable yield of strawberries decreased with increasing coir ratios during the whole experimental period which is attributed to the significant reduction in water absorption and stomatal conductance during February and March. There is a high correlation between the marketable yield and the liquid phase in substrates during the February–March period (r = 0.74) and also during the whole period (r = 0.69). In January, the marketable yield, water uptake, and leaf water potential of strawberry plants decreased in all treatments compared with other periods. As a result, it was considered that the significant reduction of marketable yield during the February–March period was caused by restricted water absorption and transpiration from the substrate with low liquid phase, when the root growth and water absorption ability were inhibited by the previous excess fruit load.
