Relationship among the planting density, tree growth and fruit quality of columnar-type apple tree 'Tuscan'

The relationships among planting density, tree growth, and fruit quality spaced 'Tuscan' apple grafted on Marubakaido (Malus. prunifolia Bork. var. ringo Asami) rootstock were studied. The percent instantaneous incident photosynthetic photon flux density decreased at the middle and bottom canopy; this decrease was more pronounced in the higher density planting. The foliar volume of shoots at the middle and bottom of the canopy decreased with tree age. Likewise, fewer flower buds differentiated in the lower, shady portion of the canopy. It was clear that the relationship among tree growth factors, yield and plant density (p), could be represented by the following reciprocal equation: 1/X = Ap + B (where X depends on tree growth factors, whereas A and B depend on cultivation practices). Moreover, fruit weight (W), Brix % (B) and fruit acidity (A) and p could be represented by the following equation; W = K(1)p(-al), B = K(2)p(-a2), A = K(3)p(-a3). In conclusion, we belive that the canopy expansion and fruit quality decreased because of the worsening light environment in proportion to the high planting density. Thus, it is important to balance planting density with a good light environment in the canopy to accrue benefits from the columnar growth habit of 'Tuscan'.