The aim of our two year study is to research the effect of nutrient supply on apple fruit quality, and to explore the relationships between selected fruit quality parameters.
Observations were made in Kálmánháza (in the eastern part of Hungary), on a commercial apple orchard. In this experiment, we studied the nutrient supply reaction of
The research results showed that N fertilization has a great effect on fruit quality. This is shown in the cases of increase of fruit size (fruit diameter, fruit height, fruit weight). The increase is proportional with the N doses, accordingly the highest positive difference was observed by using 100 kg/ha N doses. It is important to note that moderate N doses (75 kg/ha) plus P and K additions also had positive effects. There approached the values of 100 kg/ha N, and even exceeded its values in the cultivar Golden Reinders. The increased N doses enlarged the standard deviation, on the other hand, this parameter was low in the cases of balanced NPK fertilization. The nutrient supply increased the vegetative area (density of foliage) in addition to the generative parts, in particular only N fertilizer. However the denser foliage hindered the growth of fruit weight and colour-coverage, and also decreased the fruit quality and the flesh firmness of cultivars, which have a negative effect on storageability.
A linear correlation was demonstrated between the fruit weight and colour-coverage, or between fruit weight and flesh firmness. The character of their relationship was similar, but the direction differed: high fruit weight was with high colour-coverage, but with low flesh firmness.
On seven apple cultivars (Gala Must, Gloster, Granny Smith, Idared, Jonagold, Jonathan Csány 1, Mutsu), the authors studied the influence of N-phenyl-phthalamic (PPA) acid and fertilization on flowering, fruit set and fruit quality in the years 2003-2004. The research results showed that PPA application extended the flowering time of the most...cultivars. Fruit set of apple cultivars increased in many cases when regulator was applied. The additional nutrient supply could increase the fruit set too. The increase of fruit set increased the number of fruit per tree. Quality parameters determined by fertilization and fruit number per tree. For example, when N-phenyl-phthalamic acid was applied without fertilization the fruit number per tree increased considerably however, it caused a considerable frittering away. The reason for this is that fruit set was high and fruit received not enough nutrition for growing up. The skin colour of fruits was decreased in several cases by the treatments. In one respect the enlarged fruit number was shaded the others and the fertilization increased the vegetative shading leaf area.
The authors studied the effect of rootstocks with different growing vigour on fruit quality of different cultivars. Research results shows that best fruit diamter and fruit weight of all cultivars are for M9 rootstock. Similar tendency was found in skin colour, but in the case of Granny Smith, MM106 rootstock is more favourable because the gree...n skin colour is necessary for the consumers’ acceptance. Seedling rootstok has some unfavourable effects on fruit quality, thus its usage is not expedient.
Crop load, a quantitative parameter used by industry, is generally defined as the number of fruit per tree. It is often expressed in terms of number of fruit per trunk cross-sectional area (fruit/TCSA). Crop load is the most important of all factors that influence fruit size, and the removing of a part of the crop is the most effective way to i...mprove fruit size.
The potential size of a given pome fruit is determined early in the season and growth proceeds at a relatively uniform rate thereafter. This uniform growth rate permits the accurate prediction of the harvest size of the fruit as early as mid-summer. The growth rate, once established, is not easily altered, and fruit numbers, therefore, can affect fruit size only within definite limits and maximum effectiveness requires adjustment in fruit numbers relatively early in the season. It was established, that „thinning does not change a potentially small fruit into a large fruit, but rather insures that a potentially large fruit will size properly.” Emphasis should be on estimating fruit numbers rather than fruit size.
Fruit thinning can quickly reach the point of diminishing returns. Rather than a high percentage of large fruits, the objectives of thinning should be the elimination of the smallest fruits, improved fruit quality and annual production. Fruit thinning is accomplished by hand or chemical thinning. Chemical thinners are separated into categories as bloom thinners and post-bloom thinners. Early removal of potential fruit (blossom thinning) is currently used in many apple producing areas to enhance flower initiation for next year’s crop and thus, return bloom. It also results in reduced competition for photosynthates. Blossom thinners usually have a caustic effect on floral parts.
The amount of fruit left on a tree should be determined by the vigor and general condition of the tree. Leaf area per fruit affects the number of spurs flowering the following season. It can be difficult to separate timing and fruit number effects in crop loading studies, as abscission rates after hand thinning of retained flowers/fruitlets tend to very with the time of hand thinning.