September 2017 issue of the Cornell Flower Bulb Research Program Research Newsletter:
Last forcing season we were presented with an interesting case of potted tulips with essentially no root growth. It looked like the roots had started to grow, but then when they were less than 1” long, the tips of the roots died and stopped growing. There were several possibilities, but a quick soil test showing the pH at 3.9 pointed to the fact these plants were suffering from severe calcium deficiency.
Read the whole article. Starts on page 4.