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EFFECTS OF MINERAL NUTRITION ON KEEPING QUALITY 

 OF CA McINTOSH IN MASSACHUSETTS 



W.J. Bramlage, M. Drake and S.A. Weiss 

 Department of Plant and Soil Sciences 



In the previous issue of FRUIT NOTES (Fall Issue, 1983) 

 we reported results from a four-year study showing relation- 

 ships of mineral nutrition to keeping quality of Mcintosh apples 

 kept in air storage. We now have the results from this study 

 showing how mineral nutrition is affecting keeping quality after 

 CA storage. 



As described previously, 172 orchard blocks were sampled 

 over a 4-year period. One bushel of apples from each block was 

 stored in CA at 31 Oj, S% CO2, and 36°F for approximately 8 mon- 

 ths, then kept 70-80 degrees F. After 1 day firmness was measured 

 and after 1 week the apples were examined for the occurrence of 

 breakdown, rot, scald, and bitter pit. However, scald and bitter 

 pit were too infrequent on these samples for any relationships to 

 mineral concentrations in the fruit to be established. 



Maintaining fruit firmness is vitally important to quality of 

 Mcintosh after storage. In these tests firmness was measured at 

 harvest and after storage. As we reported previously for air 

 storage, mineral concentrations had no relationship to firmness 

 after CA; all correlation coefficents were non- significant . Fruit 

 maturity at harvest and postharvest conditions, not mineral concen- 

 trations, are what regulated fruit firmness in these tests. 



Although the fruit were stored 3 months longer in CA than in 

 air storage, the CA samples generally developed less breakdown and 

 rot than did- the air-stored samples because CA greatly slows down 

 changes in apples. Therefore, with smaller amounts of these problems, 

 relationships of minerals to them tended to be lower than were the 

 relationships to the same problems after air storage. This is 

 illustrated in Table 1. Correlation coefficients express these 

 relationships in such a way that the larger the number (whether it 

 is positive or negative), the closer is the relationship. It can 

 therefore be seen that in nearly every case, the relationship be- 

 tween a mineral and a problem is somewhat less for CA-stored than 

 for air-stored samples. 



Table 1 shows that mineral concentrations affected the occurr- 

 ence of rot after storage. In this relationship, P concentration 

 was more important than that of Ca. However, rot can generally be 

 controlled by use of fungicides in postharvest treatments, which 

 were not used in these tests. 



