2013 Volume 12 Issue 3 Pages 273-279
The effects of solution strength and fruit thinning were investigated on strawberries (Fragaria × ananassa Duch. ‘Nyoho’) grown in peat bags in an elevated CO2 environment (800–2,500 ppm in the day time, November 4 to April 7). Three strengths (low-80%, standard-100%, and high-120%) of nutrient solution (N: 8.85, P: 0.85, K: 3.90, Ca: 2.05, Mg: 0.93 mM; half strength of Ohtsuka A solution) were compared in combination with 2 × 2 levels of fruit thinning in primary (11 vs. 7 fruits) and successive lateral (7 vs. 5 fruits) inflorescences. For plants supplied with the 80% solution, nutrient supply was insufficient in November to December, and vegetative growth was less vigorous in December and January. No significant effect of the solution strength was observed on the fruit yield, but the concentration of total soluble solids (TSS) was significantly lower in fruits supplied with the 120% solution compared to the other 2 solutions. In the plants supplied with the 80% solution, nutrient uptake was lower than and almost equal to that in plants supplied with the standard solution, until late January and thereafter, respectively. Thus, the solution strength should be modified to keep the EC value of drainage around 50 mS·m-1. The highest fruit yield but lowest mean fruit weight were obtained in plants thinned to 11/7 fruits (primary and lateral inflorescences), and the highest fruit weight but lowest yield were obtained in those thinned to 7/5 fruits. The decrease in the mean fruit weight was caused by the increase in the number of inferior fruits of each inflorescence and also by competition for photosynthate, as fruit growth in secondary and tertiary inflorescences was significantly retarded in plants of which the primary inflorescence was thinned to 11 fruits than that of 7 fruits. TSS significantly decreased with an increase in the number of fruit left on lateral inflorescences. Thus, intensive fruit thinning was clarified to improve the growth and quality of strawberry fruit.
