THE POSSIBILITIES AND LIMITATIONS OF ORGANIC FRUIT PRODUCTION

In this review, direct and indirect technological elements of organic production are discussed. Today, there is a growing interest in production prepared without chemicals. We discuss the following issues: site selection, soil, rootstock and cultivar requirements, plant material, planting distances, crown formation, phytotechical operation, irrigation, soil tillage, soil covering and muchning, nutrition supply. Separate section deals with methods of plant protection.


INTRODUCTION
Today, there is a growing interest in production prepared without chemicals. This is partly due to the proliferation of healthy diets -which is very welcome, but on the other hand, unfortunately, cancer rate is very high, which is due to pesticides used in large quantities, and food contamination during processing. In recent decades, a numbers of technological approaches developed which were aimed to reduce pesticide pollution of the environment, production area, and consumers. The best known of the bio, which is officially known as organic farming. The wider spread of this environmentally friendly technology though is last long, because production is limited by strict roles and the profitability is only modest. Production success is much easier; however, if environmental conditions are fully satisfy the needs of the orchard. The most difficult area of organic production is plant protection. Plant pathogens and pests can impair significantly the possibility of successful cultivation. However, several factors may play a major role in technology which may further increase these negative effects or, conversely, positive benefits. The performance in orchards largely depends on the fitness of the trees. Taking into account the strict standards we note that organic production resulted in weaker tree fitness. However, there are factors which determine the success or the total failure at the begining. Succesfull production requires the knowledge direct and indirect technological elements.

Soil
The higher the soil nutrient capacity and uptake, the more easy the compensation for decreasing tree fitness coming from production technology. The best for this criteria is a deep soil layer with good water and air capacity. 1.5-3% of humus is optimal.

Rootstock
The rootstock provides the necessary nutrients and water for plant uptake. Synthetic foliar fertilizers are not used. Rootstocks with medium-strong or strong growth features are more suitable for selection. The deeper rooting ensures larger soil coverage and can provide a more equal water and nutrient uptake (Hrotkó, 1997). The stronger use of rootstocks will result in stronger growth in the above-ground parts, thus the prolonged shoot growth could help to promote the regeneration process. Cultivar General requirements for cultivars are the high yeild productivity and low tendency for yield alternation. The balanced fruit bearing charateristics from year to year is essential in this production system, because yield loss can occur for several years after an overloaded year It is possible to use cultivars with a certain level of disease or pest resistance (Soltesz, 1997b;Holb, 2000aHolb, , b, 2002Holb, , 2007. Growth characteristics of the cultivar is also an important issue, as pruning, spraying and harvest are much easier in a breezy, loose crown compared to a type of strongly growing up crown.

Plant material
Novadays is more and more difficult to buy a virus-free plant material, which is basis for strong inital growth, better vegetaive and generative production, and for early fruit bearing. We should not forget that fruit thining is an essential task in the first years as if we do not use it the tree fitness can be seriously reduced mainly for young trees.

Distance between trees and rows
Distance between trees and rows can fundamentally determine the success of production. Neither too narrow and nor too broad distances are good. Narrow distances will cause a lot of labour cost while broad distances will cause low land use capacity as trees will not fill the area available for them. If the trees are planted in the right distances, crown reach a better sun-light, and they become airy and a positive climate can be inside the crown.

Crown form
Reduction of tree fitness can be reached by using the best rootsocks. Larger crown must apply with a larger distances between trees and rows as well as the crown has to be breezy. In order to maintain their rates within the crown of the principles of Zahn has to be applied (Zahn, 1986(Zahn, , 1994. To keep the dominance of central axis, the thickness of later twigs can not be larger than 50% of the central axis. Similar rates have to be taken into account in the one above branches as well.

Phytotechical operations
Dormant pruning Dormant pruning has to be done int he dormat stage of the tree due to weaker fitness of the trees. Late pruning reduces nutrition capacity of the tree, and therefore, shoot growth and fruit setting are influenced negatively (Gonda, 1977).

Methods and intesity of pruning
A more diverse methods of pruning is needed for weaker trees. The cutting back methods have to be used which will increase fruit set and fruit quality. Disverse pruning will results in more smooth water and nutrition supply and the fruit setting will also improve (Gonda, 1979(Gonda, , 1991.

Summer pruning
Pruning is applied 3-4 weeks before havest and we remove all those tree parts that are planned to cut during winter. In this crown, the sunlight and fruit colouring are better and bud production is also more favourable under these circumstances (Gonda 1984).

Fruit thining
Fruit thinning can be eliminated according to experiences in the past decades. It can be stated that fruit thining is a central technological element (Soltész, 1997c). Fruit thinning has to be done as arly as possible as large yield can cause large negative effect. During fruit thining, infected fruits also have to be removed which will reduce the possibilities of furher infections (Soltész, 1997c;Holb, 2005). Today, there are no plantations, which could operate profitably without irrigation. It also reveals that irrigation has to be started 10-15 days before as usual in oredr to achieve the necessary quality by harvest (Ligetváry, 1997). In plantations without irrigation, not only yield can be questionalbe but tree fitness may decrease, which can lead to high level of tree die.

Soil tillage
Basically, 3 different forms are used in organic farming. In case mechanical removal of weeds in the rows, works with mashines and spraying are more difficult. Using grass alley in the row, the best if we use natural weed population and mow it several times in a year. Grass alley will help works with mashine and also ensure natural habitat for natural enemies.

Soil covering, mulching
There are also possibilites for artifical soil covering of the soil. Hovewer, this can only be succesfull, if the plant growth can be ensured by irrigation. This plants can compete with the trees buti f we cut these plant they can be used as a mulch and they can prvide a natural nitrogen source for the trees (Ames & Knepper, 2000;Haynes, 1980). Advanges of artificial plants are as follows: • Roots helps the soil microbial activity and provide nutrition if we plug them into the soil in spring • Legumes improve nitrogen capacity • Liveing hiding habitat for beneficial organisms (spiders, spider mites) • Larger honey bee population which will increase pollination • Reduce erosion in hilly areas and help maschine work and lower the deterioration of soil structure Disadvantage of artificial plants: • Larger labour • Larger amount of water and nutrition are needed • Lager risk of spring frost • Larger damage caused by voles especially if much is close to the trees.

Nutrition supply
Natural manure has an essetial role in organic farming. Sythetic fertilizers are banned (Anonymus, 1997). In order to reach a good nutrition supply, natural manure have to be used properly and we have to ensure good soil microbial activity and mineralisation of nutritions have to be helped. Planning nutrition supply, the basis is the nutrition extracted by fruits and plant parts but nutrition supply is more accurate if we plan it on soil and foliage analyses. The harmonic nutrition supply has to be done though the soil and root system as nutrition disorders seriously reduce resistance to pests and pathogens as well.

Direct elements of organic production
Plant protection which contains mechanical, physical, biological, biotechnological and chemical control options. Mechanical and phyiscal control methods are the followings: •  Pheromone, fragrance and colour traps. There are also plant and animal extracts than can alarm pest sor can reduce propagation or feeding. These compounds are: kvassia, neem, natural piretrins, plant extracts such as extracts form stinging nettle, wormwood, garlic and onion. Mineral dusts, soaps, plant and mineral oils and methylated spirits can also be used. Fig. 11. Larger amounts of pheromone capsules can offer complete protection against pests Several technical factor can play an important role in organic farming. Reduction of abiotic disorders can be done by using hail netting systems or rain protecting foil but irrigation system can also be applied to avoid frost damage. Timing of control is more accurate if agrometerological or specific measuring station is available which can predict the timing of damage. However, technical factors can not replace grower knowledge on plant protection..