RESULTS OF PLANTING SYSTEMS AND DENSITY TRIALS WITH DWARF AND SEMI-DWARF APPLE TREES GRAFTED ON MALLING (M) AND POLISH (P) ROOTSTOCKS
In 1990–91, apple trees of 'Elstar', 'Gloster', 'Idared', 'Jonagold', and 'Sampion' (some grafted on very dwarf rootstock P.22, dwarf M.9, and semi-dwarf M.26, M.7. MM.106, P.2 and P.60) were planted at densities ranging from 800 (semi-dwarf) to 5,700 (dwarf) per ha. Trees planted at the moderate densities (up to 3000 trees per ha) were trained as spindle, central axis or V system. Trees planted at densities higher than 3000 trees/ha were trained as super spindle system. All the trees produced commercial yields (a few tons per ha) within 2–3 years after planting. Tree quality at planting time influenced the yields more than rootstock or training system. Heavily feathered trees produced 3–6 kg of apples in the second year whereas unfeathered trees below 1 kg. On light sandy soils semi-dwarf trees were as precocious in cropping as the very dwarf P.22 or the dwarf M.9. Trees on P.22 and M.9 produced smaller apples than on semi-dwarf rootstocks and showed symptoms of the water deficit. Drip irrigation installed in the 3rd year improved growth and fruit quality. Trees planted in very high densities over 3000 per ha were affected by mutual competition within 2-3 years of planting. Tree growth was weaker, the yield low and less regular, and fruit quality depressed. In the most cases the optimum planting distance was 3.5 × 1.5 m for dwarf trees and 4 × 2.5 m for semi-dwarf trees.
Mika, A., Krawiec, A. and Krzewinska, D. (1997). RESULTS OF PLANTING SYSTEMS AND DENSITY TRIALS WITH DWARF AND SEMI-DWARF APPLE TREES GRAFTED ON MALLING (M) AND POLISH (P) ROOTSTOCKS. Acta Hortic. 451, 479-486
Malus domestica, planting systems and density, tree training