High relative air humidity from the stage where the tuber diameter has reached 8 mm is strongly stimulating the cracking of radish tubers. Especially in winter, radish is very sensitive to this phenomenon. This was found in a study financed by the Product Board for Horticulture and carried out by Wageningen UR Greenhouse Horticulture.
Especially in the winter period, radish tubers can crack quite easily, during cultivation as well as in the post-harvest stage. Wageningen UR Greenhouse Horticulture has investigated in which stage radish is sensitive as well as the conditions under which the problem occurs.
An experiment with high and low relative air humidity (RH) has been set up for this purpose. A cracking-sensitive cultivar was sown on three dates in November in containers filled with sand mixed with some coconut fibre. The effect of RH and the time of climate change on cracking could be established by transferring the radish three times from a low to a high RH, and vice versa.
Especially the radish tubers of the first harvest at the end of January were very sensitive to cracking. At harvest the percentage of cracked tubers ranged from 4 to 16%. Emptying of the picking container, washing and packing was then mimicked by a sort of ‘bouncing test’. This resulted in a further strong increase in number of cracked tubers during cold storage. In the end, the total percentage of cracked tubers in January ranged from 28% at continuous low RH to 67% at continuous high RH. The number of cracked tubers increased with an earlier high RV.
From a tuber diameter of about 8 mm, i.e., in winter about four weeks before harvest, the tubers are sensitive to cracking. It is therefore important to avoid a high RH as much as possible in this phase. This can be achieved by not letting the temperature drop too much and, if possible, slightly stimulating evapotranspiration. This will reduce the crop tension resulting in less cracking of the tubers.