Postharvest Fruit Quality Today’s market demands high quality fruit. and Storage Life in Mineral levels in the fruit as it grows and after Relation to Mineral it is harvested are highly significant factors Nutrients in producing and maintaining fruit quality. William J. Bramlage and Sarah A. Weis Clearly N, Ca, B, Mg Department of Plant and Soil Science and K have the most University of Massachusetts, Amherst, MA 01003 impact on fruit quality.

“ uality of fruit” means different Following storage, they are more likely to whatever stresses are producing the things to different people. In this develop scald, bitter pit, brown core, in- symptoms. Q article, we view it as the fruit ternal browning, and internal breakdown. Ca is often said to be related to fruit grower does: possessing the properties They are also more likely to develop rots. softening, with low Ca levels producing that yield a profitable price. These include Furthermore, research has shown that in softer fruit. Large increases in fruit Ca size, color, firmness, and freedom from Red Delicious apples, high N can reduce definitely increase firmness. However, defects. Of these, size and color will be the development of fruit flavor as they none of the practical Ca treatments are determined before harvest, and so we are ripen. likely to increase Ca sufficiently to result focused primarily on maintaining firm- Much attention has been given to the in firmer fruit. We have nearly 30 years ness and freedom from defects after har- form of N being applied. Are some forms of data on effects of Ca treatments, and vest, if we include loss of a “fresh appear- less damaging to quality than others? We significant differences in firmness have ance” as a developed defect. It shall be have conducted many experiments in- been rare. Our opinion is that a Ca treat- argued that taste should be included, and cluding different N forms, and rarely have ment might increase firmness slightly, we will comment on taste where there is we found N form to be a significant fac- but if so, you’ve received a bonus ben- relevant information available. tor. We believe that it is the total amount efit. Ca treatments should be applied to A long list of mineral nutrients are of N being applied during the growing reduce the occurrence of storage disor- essential for plant growth, but not all of season, not the form or the timing, that ders, not to obtain firmer fruit. them have been related to postharvest influences postharvest quality. fruit quality. Therefore, we will discuss Phosphorus (P) the effects of only nitrogen, calcium, phos- Calcium (Ca) phorus, boron, potassium, and magne- The significance of P in maintaining sium. Let’s look at how these elements are In 1936 bitter pit in apples was first fruit quality is hard to assess. In Europe, related to the growers’ task of delivering related to fruit Ca content. Since then, increased fruit P has often led to longer quality of apples to the consumer. awareness that Ca plays a central role in postharvest life, and periodically there postharvest fruit performance has become are reports in North America, especially Nitrogen (N) universal. In warmer growing regions from Canada of benefits from P treat- bitter pit is generally a big concern, but in ments. However, we have conducted To stimulate growth of young trees, cooler regions such as the Northeast we numerous trials with P-containing ma- N is commonly applied at high rates. are usually more concerned with more terials that have raised fruit P, and sel- These rates might continue as cropping subtle effects of Ca. Ca is one of the cellu- dom have they produced any benefit. begins since they can increase yield. But lar regulators of fruit ripening and dete- Others, especially in the Northeast, have even if they are reduced when trees be- rioration: when Ca is low, these processes had similar results. Thus we believe that, gin to bear (as they should be), the re- proceed more rapidly. We see this in the under our conditions, P treatments of es- sponse to lower rates will probably be susceptibility of the fruit to many prob- tablished trees are quite unlikely to im- slow because reserves of N can accumu- lems. When Ca is low, fruit are likely to prove fruit quality. late in the tree and the soil during the time ripen earlier and have greater pre-harvest of high N fertilization. It is not unusual drop, to have more watercore at harvest Boron (B) for harvested fruit, especially from and to develop more scald, browncore, younger trees, to be high in N. internal breakdown, internal browning, B deficiency in apples is a constant The consequences can be very seri- bitter pit, and rots during and after stor- threat on most Northeastern soils. Grow- ous. At harvest high N fruit tend to be age. Of these, only internal breakdown ers should apply B annually unless they larger, greener, softer, more subject to and bitter pit may be direct symptoms of have clear evidence that B level is suffi- preharvest drop and more likely to be af- low Ca. The others simply result from the cient in their orchard. B deficiency caus- fected with corkspot and/or bitter pit. fruit being “older” and less resistant to es corking inside fruit that can lead to NEW YORK FRUIT QUARTERLY • VOLUME 12 NUMBER 2 • 2004 11 misshapen and cracked fruit. Its effect Interaction of Elements Conclusion destroys visual quality of fruit. Grow- ers should be aware however, that ex- The above discussion has considered Today’s market demands high cess B treatment can cause earlier rip- mineral element effects as direct respons- quality fruit. Mineral levels in the fruit ening, preharvest drop, and poor stor- es. However, there is a great deal of inter- as it grows and after it is harvested are age quality. Thus, B treatments need to action among these elements that greatly highly significant factors in producing be made with great care, since either too influences their effects. fruit that will satisfy this market and little or too much can be very harmful. High N probably worsens the effects maintain financial viability. Clearly, N of deficiencies of all the other elements. and Ca demand careful management by Potassium (K) and The fruit are “weaker” and so more sus- fruit growers to achieve high fruit qual- Magnesium (Mg) ceptible to other problems. However in ity. B must be maintained within an the case of Ca, the consequence is clear: adequate range also. Mg and K are im- K is an important element in fruit high N increases fruit size, and as fruit size portant for tree productivity, but fruit quality. Fairly high K levels in fruit are increases fruit Ca directly decreases. Any- quality may be damaged if excessive often reported to increase red color and thing that increases fruit size will likely treatments are applied. P level in fruits to raise fruit acid level, which can im- decrease fruit Ca and increase storage does not appear to be related to prove fruit taste. We have never losses. postharvest quality in Northeastern worked with K treatments, so have no K and Mg can directly interfere with fruit. personal experience to add to what is the ability of Ca to slow down fruit dete- Growers today must produce larger said in the literature. However, K is a rioration. It has often been shown that sizes of fruit to satisfy market demand. difficult element to manage. It is the ratio of K + Mg : Ca is more closely Larger fruit have lower Ca and are in- present in fairly high concentrations in related to fruit quality than is Ca level herently more at risk of quality loss af- the fruit, so a large crop can deplete a alone. This means that if either K or Mg ter harvest. Futhermore, the longer fruit tree’s K reserves. In a low-crop year, is excessively high in fruits, the impact of is stored before marketing, the physi- however, the K in leaves is released to low Ca will be increased. This makes it ologically older they become and the the soil as leaves decay, and is quickly very important that K and Mg only be more susceptible to disorders they are. recycled to the tree. Thus, K applica- applied if leaf analysis calls for it, and then A slow market makes it harder to main- tions should be done judiciously and be only at the rate indicated by the levels in tain fruit quality. based on annual leaf analyses. the leaves. The challenges don’t seem to get Mg is an element frequently defi- Both P and B also interact with Ca. P easier! cient in Northeastern apple orchards, so apparently works with Ca to maintain it is often applied. There appears to be quality, so if it is low, Ca is less effective Bill Bramlage is an emeritus professor little direct relationship of fruit Mg lev- in maintaining quality. B is somehow in- at the University of Massachussets who els to fruit quality, so applications volved in movement of Ca to fruit on the specializes in factors that influence should be based on tree needs, as tree, so if B is low, it can cause fruit Ca postharvest fruit quality. Dr. Sarah Weis shown in leaf analyses deficiency to occur. is a research technician with Dr. Bramlage. .

12 NEW YORK STATE HORTICULTURAL SOCIETY