Influence of canopy formation on the productivity of immune apple cultivars

For an intensive apple orchard, it is crucial to choose the right canopy shape. It determines how much solar energy the leaves will absorb, how nutrients will be distributed, and what nutritional area each tree will require. Long-term trials (2001–2008) on trees planted in 1997 helped determine the optimal canopy formation system for the scab-immune apple cultivars Liberty (early-winter) and Florina (winter). The indicators were evaluated in six replicates, with one tree considered as a single plot.

• Rootstock — M9
• Planting pattern — 4×2 m
• Soil — leached chernozem
• Climate — moderately continental

Light regime and photosynthesis: how the canopy affects leaf performance

Apple productivity is directly related to leaf surface area. The Florina cultivar features the largest leaf area across all training systems — from 10.6 to 14.9 thousand m²/ha. At the same time, for both studied cultivars, the leaf surface reaches its maximum with the classic central leader (modified leader) system of canopy formation. However, for high productivity, not only leaf area is important, but also their illumination.

The best light regime occurs in the canopy of the Liberty apple cultivar. The "Russian spindle" training system allows for an increased influx of solar energy to the leaves inside the canopy for both cultivars. In August 2007, the illumination of the central zone under the "Russian spindle" system proved to be significantly higher, which was especially pronounced in the Florina cultivar — 30.2% of full open-field illumination against 20.5% in the central leader canopy.

Light intensity determines the net productivity of photosynthesis. The Florina cultivar shows high photosynthetic activity (up to 0.5 g/m² per day in June 2007) if the trees are trained in the "Russian spindle" style. With such a system, nutrients are distributed more balanced between tree growth and fruiting.

Tree dimensions and vigor: planning the nutritional area

The canopy shape directly influences the vigor of growth processes and the final size of the trees. The central leader system stimulates active vegetative growth. Trees with this training grow taller, with a maximum trunk diameter and a wide canopy both along and across the row. The maximum annual growth was recorded here: long branches provide the tree with productive wood (spurs, fruit-bearing wood) and large active leaves.

The "Russian spindle" training limits excessive growth, making trees more compact. Regardless of the chosen canopy, the Florina cultivar outperforms Liberty in all dimensions. Taking these varietal and training characteristics into account helps to correctly calculate the planting pattern and avoid orchard overcrowding.

Increased yields of fruit trees from the application of a particular canopy formation system can be caused by a number of factors. The most important of these is creating conditions for better setting and development of flower buds. Research data indicate that abundant flowering was observed on Liberty apple trees. When comparing the flowering intensity of trees with different canopy shapes, it can be noted that for both cultivars, it was more abundant on trees trained in the "Russian spindle" style. Trees with a central leader canopy were characterized by low flowering intensity. Thus, an increase in the growth activity of apple trees is associated with a weakening of their generative function and vice versa.

Orchard yield is one of the main indicators used to determine the profitability of using a cultivar and individual cultivation practices. It is noteworthy that in the experimental variants (Russian spindle) that stood out in terms of canopy illumination and photosynthetic productivity, a faster (compared to the control) build-up of apple fruit yield is ensured. t/ha

2001 2002 2003 2004 2005 2006 2007 2008 years central leader Russian spindle t/ha

2001 2002 2003 2004 2005 2006 2008 central leader Russian spindle

It should be noted that the low fruit yield in 2006 was associated with the negative effect of low sub-zero temperatures on plants, which are critical for the "apple" species.

However, if we consider the obtained data from the perspective of a rational balance between the two main functions of the plant: growth and fruiting, the preferred option is the one in which trees of both apple cultivars are trained using the "Russian spindle" type. Only in this case can the desired results be achieved: restrained plant growth and, simultaneously, moderate but regular fruiting, ensuring the production of high-quality market produce.

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