We do not know what effects long-term use of gypsum would have on soil 

 properties. These effects must be determined in future assessments. 



Likewise, we do not know what application rate is optimum. Since spread 

 of the trees was different in the Cortland and Delicious blocks, it is more 

 useful to consider applications in terms of lbs. per square foot. The Cortland 

 trees were treated with 0.2 lbs. per sq. ft. annually, and the Delicious trees 

 with 0.3 and 0.6 lbs. per sq. ft. Since the higher rate on Delicious was no 

 different from the lower rate, it appears that something less than 0.3 lbs. per 

 sq. ft. may be optimum. However, a comprehensive experiment needs to be 

 conducted to determine effective rates. 



Gypsum treatments are both laborious and expensive when applied as we did. 

 The material was evenly spread under the trees, a slow unpleasant task. Our 

 price for gypsum was approximately $0.08 per pound, and therefore the treatment 

 cost between $3 and $5 per tree per year using the rates reported here. 

 However, we do not know if gypsum needs to be applied annually. In 1986 the 

 100 lbs. per tree treatment under Delicious was discontinued, but fruit mineral 

 analyses showed that Ca level remained equal to that of fruit no longer 

 receiving gypsum. 



At this time, 1 view soil gypsum treatment as an effective way to raise 

 fruit Ca levels when it is applied as we have. Perhaps the best way to use 

 gypsum is in an orchard or a block that is known to consistently produce low- 

 Ca apples. We have another block of Cortland trees that is in very fertile 

 soil and which produces excessive vigor and large fruit, and these fruit are 

 always badly affected with bitter pit and breakdown. In 1986 we established an 

 experiment in this block to see if we can improve fruit quality through gypsum 

 treatments. Our data show that treatments did not influence mineral 

 concentrations in this first year. Fruit were not analyzed the first year in 

 either of the earlier experiments, so this is the first time in which we can 

 determine the rate at which fruit mineral levels change over time. Based on 

 the earlier studies, we should see improvements next year. 



1 have tried to emphasize that use of gypsum is still very experimental. 

 It will take a number of years before we can make recommendations with 

 confidence. However, it is obvious from the results shown here that soil 

 gypsum treatments can improve fruit Ca levels and quality under some 

 conditions. It is therefore a new weapon in the modern apple grower's arsenal 

 of techniques for coping with the ongoing threat of Ca deficiency in fruit. 



POMOLOGICAL PARAGRAPH 



Reducing Fruit Load on Tree Leaders 



Growers should avoid allowing too many fruit to develop on the leader of 

 young trees. It may be advantageous to remove fruit from the entire tree until 

 the fourth year. Then for the succeeding years, depending upon tree size, the 

 removal of fruit from the leader should be continued. 



