canopy in April. These treatments were repeated each year until 1986, when the 

 100-lbs. application rate was discontinued. Each year leaves and fruit were 

 analyzed, and when available (the site is subject to frost), fruit were stored 

 in 320F air and assessed after long-term storage. 



Results are summarized in Table 3. Gypsum increased Ca concentrations in 

 both leaves and fruit, and decreased Mg concentrations in both leaves and 

 fruit. It did not affect fruit K and slightly increased leaf K. Gypsum ut 100 

 lbs. per tree was no better than 50 lbs. per tree in any of these measurements. 



Table 3. Effects of annual gypsum applications, 1980-84, on leaf and fruit 

 mineral concentrations. Delicious. 



Gypsum (lbs. /tree) Significance^ 



Factor 50 100 vs 50 vs 



50 + 100 100 



Fruit Ca, ppm 145 153 152 * 



Mg, ppm 263 258 255 ** 



K, Z 0.54 0.55 0.55 n.s. 



Leaf Ca, % 1.22 1.32 1.36 ** 



Mg, % 0.36 0.32 0.32 ** 



K, % 1.36 1.42 1.43 ** 



zsignif icance: ** = odds of 99:1; * = odds of 19:1; n.s. = not significant. 



In this experiment no consistent effect on fruit quality has been 

 measured. In part this probably is due to the large variability in cropping 

 among trees, and the consequent variability in fruit quality. For example, in 

 1986 a severe bitter pit problem existed but it was found only on the large 

 fruit that were produced on trees that had been damaged by frost. The large 

 effect of fruit size may have masked any possible benefit from the gypsum 

 treatments . 



These results indicate that soil applications of gypsum beneath the tree 

 can increase apple Ca concentrations and improve fruit quality after storage. 

 The effects are modest in size but can produce measurable benefit under 

 appropriate conditions. 



Use of gypsum can, however, create some problems. The obvious one is 

 suppression of leaf Mg levels. Mg deficiency is common in Massachusetts and 

 results in loss of vigor and productivity of trees. Our results have shown a 

 steady decline in leaf Mg in the Cortland block with continuing gypsum 

 application. Each year leaf Mg was lower than it was the previous year in the 

 gypsum-treated trees. Clearly, Mg levels would have to be monitored carefully 

 and corrective measures applied as needed if a gypsum program was adopted. 



