Trunk cross-sectional area (in 2 ) 



SED 



WD MWD 



Drainage class 



SPD 



PD 



Figure 1. Trunk cross-sectional areas after 7 growing seasons of Marshall Mcintosh trees 

 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. 



trained to central leaders utilizing minimal dor- 

 mant pruning. Yield and tree size data were 

 collected annually through 1988. 



Soils were grouped by their drainage class 

 for presentation of the results. One soil was in 

 the somewhat excessively drained (SED) cat- 

 egory; three soils each were in the well drained 

 (WD) and moderately well drained (MWD) cat- 

 egories; two soils were in the somewhat poorly 

 drained (SPD) category; and one soil was in the 

 poorly drained (PD) category. This grouping 

 provides an approximation of the soil moisture 

 levels present among the sites. 



The effects of soil and rootstock on tree size 



were significant (Figure 1). Trees grew best on 

 the WD and MWD soils and poorest on the SED 

 and PD soils. This result suggests that tree 

 growth is affected dramatically by soil moisture, 

 with the driest and wettest soils producing the 

 least growth. To obtain maximum productivity, 

 a grower must be aware of the size potential of 

 trees in their soil. On sites where growth is 

 expected to be low, trees should be planted close 

 together, and on sites where growth is expected 

 to be high, trees should be planted farther apart. 

 The spread after the 1988 growing season of 

 trees on M.7A, for instance, varied from 13 ft on 

 the MWD soils to 8 a on the SED soils. Clearly, 



10 



Fruit Notes, Summer, 1991 



