optimal yields per acre would not be obtained if 

 trees were spaced 13 ft apart on the SED soils. 



Regardless of soil moisture level, trees on 

 M.7A were the largest, and those on M.26, M.9/ 

 MM. 106, andM.9/MM.lll were similar in size 

 and significantly smaller than those on M.7A. 

 In a practical sense, growers can assume that 

 the relative vigor of rootstocks will be the same 

 on most soil types. 



The effects of soil moisture on tree growth 

 are not as important as effects on yield. Figure 

 2 presents the cumulative yields (1986-88) for 

 each rootstock in the 5 soil groupings. In 

 general, trees yielded the most on the WD and 

 MWD soils and the least on the SED and PD 



soils. The interesting result, however, was the 

 relationship among the rootstocks. On the dri- 

 est soils (SED and WD) the largest trees, those 

 on M.7A, outyielded trees on M.26, M.9/ 

 MM.106, or M.9/MM.111. On the wetter soils 

 (MWD, SPD, and PD), however, trees on M.7A 

 yielded similarly to the smaller trees, those on 

 M.26, M.9/MM.106, or M.9/MM.111. 



Yield per tree is only part of the picture. 

 Yield efficiency (lbs of fruit per square inch of 

 trunk cross-sectional area) relates yield per tree 

 to tree size and is a way to compare relative yield 

 potentials per acre, the much more important 

 determinate of performance. Figure 3 presents 

 the cumulative (1986-88) yield efficiencies of 



Yield per tree (bu) 



SED 



WD MWD 



Drainage class 



SPD 



PD 



Figure 2. Cumulative yields per tree (1986-88) of Marshall Mcintosh on M.7A, M.26, M.9/ 

 MM.106, and M.9/MM.111 planted in 1982. Drainage class: SED = somewhat excessively 

 drained; WD = well drained; MWD = moderately well drained; SPD = somewhat poorly 

 drained; and PD = poorly drained. 



Fruit Notes, Summer, 1991 



1 1 



