P. Voroney, C. Kessel, J. Gardner, H. Martin
Over the past several growing seasons, a number of organic apple producers in southern Ontario have observed a decline in apple yields and reduced tree vigour in their orchards. Observations included lack of shoot growth, development of chlorotic leaves during the season, smaller fruit production and early defoliation. The objective of this research was to determine if there were any significant soil nutrient limitations to organic apple production, based on soil and leaf analyses. During the 2005 growing season soil samples were collected from 18 affected organic orchards and 2 conventional orchards of varying ages. At one of the organic orchards where there were significant observable differences in tree growth due to sod management, leaf tissue analysis was conducted for determination of tree nutrition status. Soil tests indicate that some of the organic orchards (and one of the conventional) have nutrient deficiencies requiring significant annual additions; about half the organic orchards sampled were P and K deficient. Nitrogen, calcium, and iron levels were low in leaf tissue sampled from weak trees growing where sod was dominant, compared to that sampled from strong trees growing where sod growth was minor. The problems observed in the organic apple orchards appear to be related to orchard floor management. Competition between the apple trees and the sod for available nutrients, particularly nitrogen, is most likely the limiting factor affecting tree growth and production.
Voroney, P., Kessel, C., Gardner, J. and Martin, H. (2007). SOIL FERTILITY SURVEY OF ORGANIC APPLE ORCHARDS IN SOUTHERN ONTARIO. Acta Hortic. 737, 79-85
DOI: 10.17660/ActaHortic.2007.737.10
orchard floor management, leaf tissue analysis

Acta Horticulturae