Productivity and economic evaluation of apple orchards on rootstock M.9 depending on crown pruning practices and terms

Abstract

Canopy-pruning is of particular importance in modern fruit growing with high tree density as one of the main agro-technical factors that prevents the periodicity of fruiting and ensures efficient fruit production. Traditional pruning methods of the fruit orchard are associated with the significant cost of manual labor and do not ensure the annual high yields of quality fruits. In the situation when labor costs rise and there is a difficulty in providing skilled workers, mechanical (contour) pruning is introduced, which optimizes the size of crowns, light conditions and fruiting of the orchards.

High stable productivity is achieved with the optimum term of mechanical (contour) pruning, so it is important to study this operation in intensive apple orchards. Since mechanical pruning has not been sufficiently studied in Ukraine, the aim of this reserach is to increase the efficiency of fruit growing by optimizing the method and timing of canopy pruning of winter apple-tree cultivars on dwarf rootstock.

The article presents the research results of the effect of pruning practicess and terms on the productivity and cost-effectiveness of apple production of cvs. Gala (Mitchgla), Golden Delicious (clone B) and Jonagold (Wilmuta) in the irrigated orchard on dwarf rootstock M.9 T337. The experiments were conducted in the intensive apple full fruiting orchard. Non-virus young-trees of Dutch production were planted with drop irrigation according to the scheme 4x1 m and formed according to the type of slender spindle. Soil management system was: sod-humus – between the rows, herbicide fallow – in the around-trunk strips.

The experiment with pruning terms and practices was laid out in triplicate replication with five accounting trees per plot. The trees were pruned in the rest phase (winter), a pink bud, during flowering, in the early summer period (10 leaves per shoot), as well as within two weeks after harvest. Pruning practices were traditional manual and contour (mechanical, modelling) with manual correction of the space between the trees in a row.

To form a crown shape, the first mechanical pruning of all variants was done in winter with a fixed width of 80 cm in the lower part and 50 cm in the upper one of a tree, and further the shoots on the outside were annually shortened. The spaces between the trees were pruned manually, highlighting the thickened areas and removing drooping, old and excessively thick branches.

It has been found out that mechanical pruning with manual correction of the space between the trees helps increase the productivity of orchard with a higher crop load by 20%, and under such pruning immediately after the harvest – by 17%. On the average during the experiment, the maximum value (23.1 kg / tree) was obtained for cv. Jonagold with mechanical pruning after harvest, whereas for Gala cultivar with manual winter pruning it was almost twice less. The crop of Golden Delicious trees with mechanical pruning after harvest (with manual correction) was by  38% higher than that of Gala cultivar, but by 5% lower than that of Jonagold variety.

The yield capacity of the orchards depended significantly on the factors studied and was lower on the manual pruning areas. The areas with mechanical pruning and manual correction were by 19% more productive and the yield capacity was higher by 17% for post-harvest pruning. A maximum yield of 54.3 t / ha was obtained on mechanically pruned Golden Delicious trees in the pink bud phase and after harvest, as well as for Jonagold (57.6 t / ha) after mechanical post-harvest pruning. On the average, over the time of the experiment, the yield of more vigorous Jonagold trees was by 9% higher than that of cv. Golden Delicious and it was by 37% larger than the yield of cv. Gala (the last two with average growth).

As compared with manual winter pruning, under mechanical pruning and manual correction, the fruit weight was by 8% larger, it was 10% higher after pruning in the pink bud phase and 12% higher on post-harvest pruning. The tendency to increase the fruit weight in the areas with mechanical pruning at a later time was revealed.

Mechanical pruning (with manual correction) does not reduce the amount of quality fruits. As compared with traditional manual pruning in winter, after mechanical pruning, the yield of marketable fruit is higher by 20% and this indicator is 13% higher in the areas pruned after the harvest. The output of commercial apples of Gala cultivar is slightly smaller than that of cvs. Golden Delicious and Jonagold, and the performance of all cultivars is significantly lower after manual winter pruning. The marketable quality of Jonagold apples was 4% higher than that of Golden Delicious and 10% higher than the quality of Gala cultivar.

Manual correction after mechanical pruning requires significantly lower labor costs in the plots of all the cultivars studied. However, due to higher crop and more manual labor to harvest additional crops, the total number of man-hours differed from traditional manual pruning slightly. In general, despite some increase in production costs, mechanical pruning immediately after harvest (with manual correction) provides a better price of fruit sale, higher profitability and high economic efficiency.

Due to better marketability, the price of selling apples was higher in the areas with mechanical pruning after harvest (with manual correction of space between trees). Due to higher yields, the cost of production turned out to be lower in the plots with mechanical pruning.

Mechanical pruning (with manual correction), carried out immediately after the harvest, provides a higher price of sales and a level of profitability, high economic efficiency of fruit production. As compared with manual winter pruning, mechanical pruning of the trees after harvest (with manual correction) requires 2.5 – 3 times less labor costs, it provides 2.0 – 8.5% lower production costs and 1.5 times higher profits annually. In this case, the profitability of the production of Gala apples is higher by 28% points, Jonagold – by 35% and Golden Delicious – by 27% points, as compared with manual winter pruning.