2019 Volume 88 Issue 2 Pages 232-244
An excess or lack of soil moisture are significant abiotic stresses that reduce the average yield for vegetable crops worldwide. The responses of ‘Natsunoshun’, a processing tomato cultivar, to water stress at three growth stages, first flower differentiation, first flowering, and fruit development, were investigated over a two-year period. The year effect on yield was not significant; however, the growth stage and the type of water stress at a particular growth stage affected yield significantly. Either an excess or lack of soil moisture after the first flowering stage were significant in reducing yield. The decrease was related to the average weight of the fruit rather than the number per plant. Under dry conditions, fruit number was the same as control plants, but there was a decrease in the reddish mature fruit ratio. On the other hand, under wet conditions plant biomass decreased, especially in the roots, even if there was a transition from wet to dry conditions. We conclude that excessive soil moisture during the first flowering stage produces slower CGR and decreased biomass in the roots, which we believe is the reason for the yield decline.