## 2 Thinning Methods
### Pruning  
Pruning is one of treatments supporting the thinning of fruit. Its primary purpose is to control the tree size and improve the distribution of light in the crown; however, proper pruning can also regulate the number of flower buds and reduce the need for thinning in the next growing season [32]. Different pruning systems are used depending on the species, cultivar, spacing, machine size, and agronomic treatment. In addition, pruning intensity and precision can vary, and in some systems precise pruning is carried out to remove individual spurs or buds [54; 55]. However, pruning must always take into account the age of trees. When the orchard is young, the priority is to form a crown (shape and topological structure of a tree) to ensure continuity of production in subsequent years. At this stage, the type of growth and fruiting should be taken into account. Spur-bearing cultivars grafted on dwarf rootstocks have weak vigour and form few new shoots with a large number of fruit already in the first years of production. Such trees require more intensive thinning in the initial years to allow better and faster crown formation. Pruning during the dormancy period may limit the number of flower buds, so it can be treated as the first stage of thinning. The advantage of pruning before the start of the vegetation season is that it enables the tree to maintain the assimilates accumulated in the branches, trunk, and roots for the remaining buds, thus ensuring their better nonishment, which allows obtaining fruit with better quality parameters [9]. Pruning is often divided into two stages. In the first stage, the whole longest shoots are removed. This does not affect the yield in the event of temperature drops and the risk of damage to flower buds in the early spring period. The second cut is made when the risk of frost damage to flower buds has already passed. If only part of the flowers or flower buds freeze, it will cause them to thin out naturally, which can improve the quality of fruit and allow obtaining a crop of higher commercial value [9]. The method and intensity of cutting is also determined by the rootstock used. Trees on vegetative rootstocks, such as Gisela(r) 6 or Gisela(r) 12, require different pruning compared to trees on strongly growing generative rootstocks, such as Mazzard (_Prunus avium_). Growers producing cherries on trees grown on a generative rootstock must limit tree growth and maintain or even increase fertility. However, when trees grow on dwarf vegetative rootstocks, a stronger focus should be placed on reducing too high a yield and, at the same time, on stimulating tree growth. The removal of cherry shoots of small diameter during the dormant period allows the reduction of the total yield and obtaining larger fruit. This can be achieved by cutting 20% of all fruiting shoots each year. Shoots are not removed completely, but only shortened so as to leave stubs, because the best fruit is obtained on the youngest spurs at the base of last year's shoots. The length of stubs varies from 7-8 cm to 60 cm and depends on the location \begin{table}
\begin{tabular}{c c c} \hline \hline
**Method of** & **Chemical Substance** & **References** \\ \hline \multirow{4}{*}{Other} & rapeseed oil & [6] \\  & whey & [16] \\  & vinasse & [16] \\  & Mechanical & \\  & removal of buds & [6; 12; 32; 33; 34; 35; 36; 37; 38] \\  & Removal of flowers & [15; 16; 33; 35; 39; 40; 41] \\ Pruning & removal of short shoots & [42] \\  & removal of spurs & [33; 40; 42; 43; 44] \\  & Removal of fruit & [16; 45] \\  & Removal of fruitlets & [35] \\ Mechanical & & [46; 47; 48; 49] \\ Hand-held & & [15; 16; 50; 51; 52; 53] \\ \hline \hline \end{tabular}
\end{table} 
Table 1: _Cont._on the tree--the shortest stubs are near the tree top with their length increasing towards the bottom of the canopy. Strong apical dominance in cherries hinders the formation of lateral branches, which are necessary to produce the right number of leaves responsible for proper photosynthesis. Leaving stubs when pruning stimulates branching.