finiit in these larger trees. We should have a better 

 picture of effects when 1989 samples are analyzed. 



A key experiment for us is the one in which differ- 

 ent rates of gypsum are being applied, as it will help 

 considerably in determining practical treatments. In 

 only the second year of application to these young trees, 

 results have begun to emerge (Table 1). Both leaf and 

 fruit Ca levels were higher in the gypsum treatments 

 than in the controls, vdth the hint that 16 lbs. per tree 

 might be as effective as 48 lbs. per tree. Both leaf and 

 fruit Mg were suppressed by gypsum, and neither leaf 

 nor fruit K was affected by it. It will require several 

 more years of data to establish response levels, but 

 these results suggest that much lower rates of gypsum 

 application than we have used in our previous experi- 

 ments may be just as effective. These results also add 

 to our view that tree size influences response time: 

 fruit on these small trees responded in two years, while 

 on the large Cortland trees, fruit did not respond in 

 even the third year of treatment. 



Effects on Soil Properties 



It is important to know what effects the treatments 

 are having on soil properties in order to judge long- 

 term effects of gypsum applications. 



In 1988, we analyzed soil samples taken to hardpan 

 in April in both the Delicious block and the mature 

 Coitland block. Only the results for the Delicious block 

 are presented here (Figure 4), since the results from 

 the mature Cortland block were nearly identical. 



Gypsum greatly increased the exchangeable Ca in 

 the soil throughout the entire soil profile. Thus, a huge 

 reservoir of exchangeable Ca has been created on the 

 treated soil. However, a shocking reduction of ex- 

 changeable Mg and K also occurred. It is surprising 

 that the suppression of leaf and fruit Mg has been so 

 small (Figure 1), and even more surprising that neither 

 leaf nor fruit K has been affected by gypsum treat- 

 ments. Apparently, in this soil, before treatment there 

 was much more exchangeable Mg and K than was 

 needed to feed the apple roots, but less Ca than is 

 desirable for optimum Ca uptake. 



There was no consistent effect of gypsum treat- 

 ments on soil pH beneath the Delicious trees (Table 2). 

 Similarly, there was no effect on pH beneath the ma- 

 ture Cortland trees (data not shown). 



Discussion 



In 1987 we cautiously concluded that gypsum 

 treatments could improve fruit Ca levels and fruit 

 quality. Two more years of data remove some of the 

 caution from our conclusions. 



It is evident that under our soil conditions, gypsum 



Depth (cm) 



2 4 a 8 10 



meq Calcium/100 g soil 



Depth (cm) 



0.2 a4 oj as 1 



meq Magnesium/ICO g soil 



Depth (cm) 



02 0.4 0.6 OJ 1 



meq Potassium/lOO g soil 



Figure 4. Effects of 8 years of annual applica- 

 tions of gypsum (501bs./tree) on exchangeable 

 Ca, Mg, and K at different depths of Scituate 

 fine sandy loam soil. 



Frmt Notes, Fall, 1989 



