EFFECTS OF SCALE QUALITY ON PHYSIOLOGICAL PROCESSES IN ONION
The common picture of poor scale quality is that the dry scales are thinner than usual, they crack easily and eventually fall off during sorting, packing and transport.
Loss of the dry scales affect the external appearance and consequently the quality of the onions because only small defects of this kind are tolerated for onions of grade I. This is one of the reasons why we are working on this problem
According to the literature the same problem exists in other countries, The Netherlands, Poland and USA. Experimental results from these countries indicate that several factors might affect the skin quality (Knott, 1933; Chroboczek, 1936; Magruder et al., 1941; Van Doorn et al., 1962, Nieuwhof, 1965).
In 1966 a research programme was started in order to find out more about what cracking is and the factors involved.
Our investigations included experiments with fertilizers, varieties and growing methods. From the results reported elsewhere (Apeland & Balvoll 1969) we can mention that the effect of fertilizers, type of soil and growing method seem to be of minor importance, however, pronounced differences were found between varieties; the new Dutch variety 'Dura' being especially promising.
Another question which we did not find an answer to in the literature, was whether the skin quality affected the physiological processes in the onions. We found it important to get a better knowledge about this, and such studies were undertaken. Results from some of these experiments will be presented.