Yellowing of leaves during the winter season

Yellowing of leaves during the winter season

by Mr. Hitoshi Kifuji, Maebashi-City, Gumma, Japan

Question

We have planted tomatoes in our greenhouse using original hydroponic system. The sowing date was September 10th and transplanting was on the 25th of same month. The harvesting started at the beginning of January. The problem, as you can see in the enclosed photo, is the yellowing of leaves during the winter season. Though leaves of some varieties have recovered as temperatures became warmer, other varieties are still yellow. Our local expert suggested that one of the reasons might be the low temperatures, as greenhouse temperature dropped to 10°C on several occasions. However, he thinks that fertilization might also be involved. I would appreciate your opinion as to what could have caused this problem and ways to avoid it. Continue reading