SOIL APPLICATIONS OF GYPSDM CAN IMPROVE 

 APPLE FROIT CALCIOM LEVELS 



William J. Bramlage 



Department of Plant and Soil Sciences 



University of Massachusetts 



Calcium (Ca) deficiency in the fruit is a chronic problem in modern apple 

 production. If this deficiency occurs, it causes poorer keeping quality of the 

 fruit . 



There are 4 possible approaches available for dealing with potential Ca 

 deficiency in apples. These are cultural practices, soil treatments, foliar 

 sprays, and postharvest dips or drenches. These approaches were addressed 

 recently (Proc., Mass. Fruit Growers' Assn. 93: in press). 



Of these approaches, soil treatments are generally the least effective due 

 to the poor ability of apple roots to absorb Ca from the soil solution. We 

 have tried numerous treatments and have obtained marginal benefits at best. 

 However, recent results from applications of gypsum (CaS04-2H20) have been 

 better than any from earlier studies of soil treatments and will be described 

 here . 



We have conducted 2 major trials with gypsum. The first trial was 

 initiated by Dr. Mack Drake in 1976 in a block of mature, seedling-rooted 

 Cortland trees. Half of these trees received 80 lbs. of gypsum spread under 

 the canopy in April and half received no gypsum. Otherwise, the trees were 

 fertilized and cared for in an identical manner. These applications were 

 repeated annually through 1986. 



During this period leaves and fruit were sampled and analyzed for mineral 

 concentrations, and fruit were usually stored in both air and controlled 

 atmosphere (CA) and their quality was assessed after long-term storage. 

 Results for analyses from 1977 through 1984 are summarized in Table 1. It can 

 be seen that gypsum treatments increased Ca concentrations in both leaves and 

 fruit. In addition, they suppressed magnesium (Mg) in both leaves and fruit, 

 and suppressed potassium (K) in the fruit but not the leaves. Treatment had no 

 effect on phosphorus (P) levels in either fruit or leaves. 



The increased fruit Ca levels improved keeping quality of the apples 

 (Table 2). Both bitter pit and senescent breakdown were significantly reduced 

 after both air and CA storage. In the case of bitter pit, the reduced levels 

 of both Mg and K in the fruit should enhance the benefit from increased Ca, 

 since it has long been known that high Mg and K worsen the effects of low Ca in 

 causing bitter pit development. It should be noted that in 1985 there was a 

 severe bitter pit problem in the fruit on the trees. As we walked through this 

 block it was very clear which trees had and had not been treated with gypsum, 

 as the appearance of the fruit was markedly different. In contrast, little 

 bitter pit occurred in this block in 1986 and no difference was apparent at 

 harvest time . 



The second gypsum experiment was established in 1980 in a block of 

 Delicious trees planted on MM. 106 rootstock in 1972. This experiment was set 



