Yield per unit of trunk cross-sectional area (or yield 

 efficiency) is a way to relate yield to tree size and pos- 

 sibly compare commercial yield potential. Using this 

 measurement (Figure 4), trees on Mark or 0.3 yielded 

 the most and those on M.26 EMLA yielded the least in 

 Massachusetts. In Maine, trees on B.9, Mark, or 0.3 

 yielded similarly and significantly more than those on 

 M.26 EMLA. In Massachusetts, the four scion culti- 

 vars in the study yielded similarly. Mcintosh appeared 

 to yield less, although it is not directly comparable. In 

 Maine, Golden Delicious trees yielded significantly more 

 that the other scion cultivars. 



Clearly the best way to compare yield performance 

 would be to compare actual yields per acre. In a study 

 such as this one, per-tree yield and per-trunk-cross-sec- 

 tional-area yield can be measured directly; however, suf- 

 ficient land and labor is not available to establish and 

 maintain an experiment that could be used to compare 

 actual yields per acre. Therefore, per-acre yield 

 must be calculated from per-tree yield and an esti- 

 mate of tree density per acre. Table 1 gives esti- 

 mates of tree density based on canopy spread, 

 assumingthat in-row spacing should be approxi- 

 mately 80% of the canopy spread after five years 

 and that seven feet should be added to in-row spac- 

 ing to obtain an appropriate between-row spacing. 

 Clearly, this is an imperfect measure of yield be- 

 cause it is based on estimates of density rather than 

 trees actually planted at those densities, but it al- 

 lows comparison of an actual performance mea- 

 sure. Using this measure (Figure 4), trees on Mark 

 and 0.3 yielded the most and those on M.26 EMLA 

 yielded the least in Massachusetts. In Maine, trees 

 on Mark outyielded the others and trees on M.26 

 EMLA yielded the least. In Massachusetts, Rome 

 tree yielded the most and Empire trees yielded the 

 least. In Maine, Golden Delicious trees yielded 

 more than all others. 



Tree size and yield are not the only measures 

 of tree performance. Fruit size also is a very im- 

 portant parameter. Fruit size was measured each 

 fmiting year of this study. These data are presented 

 in Table 2 as counts per 42-lb box. Rootstock did 

 not affect fruit size; however, cultivar differences 

 were dramatic, as would be expected. Rome and 

 Jonagold trees produced the largest fruit and Em- 

 pire trees produced the smallest. 



Another interesting comparison that we have not 

 yet discussed is the difference between the two sites. 

 As we have seen with other plantings, trees in Massa- 

 chusetts were larger after five years (Figures 1 , 2, and 

 3 and Table 1). They also yielded more (Figure 4). 

 Overall, trees in the Maine planting appear to be one 

 year behind those in Massachusetts. 



Conclusions 



This article presents only the preliminary results 

 from this study. The study will continue for another 

 five years, giving a detailed picture of these scion culti- 

 vars on these rootstocks. After five years, however, it 

 is possible to make some generalizations about root- 

 stock performance. Specifically, the largest trees among 

 these rootstocks will be on 0.3 or M.26 EMLA. The 

 smallest trees will be on B.9 (or possibly Mark). Trees 



Table 2. Size of fruit (as counts per 42-lb box) from 

 trees on five rootstocks or with five scions in 

 Massachusetts and Maine.* 



Within rootstock or scion and within column, 

 means not followed by the same letter are 

 significantly different at odds of 19:1. 

 Mcintosh data from Massachusetts were not 

 compared statistically, since trees were not 

 replicated within the experiment, but were 

 planted as part of a guard row. 



Fruit Notes, Spring, 1995 



21 



