Chemical thinning in apple trees using innovative means

apple orchard

Apple tree is one of the most important crops due to the high nutritional value of the apples intended for human consumption. The apple tree cultivation is of high importance for farmers and especially for those who are in areas with very low temperatures, as in order to create apples of excellent quality it needs exposure to bitter cold. These climate conditions make it impossible for other crops to survive. Thus, apple trees are a way for farmers to stay in their hometown and prosper. By nature, a healthy apple tree can produce hundreds of apples, but according to plant physiology, only a percentage of 7-10% of initial flowering is needed to achieve satisfactory yield. Therefore, farmers must keep only the best apples and as a result, cut the rest. This purpose is accomplished by thinning, which is an annual cultivation task and is carried out a few weeks after full flowering. Initially, thinning was done by hand, but because it required a lot of time and cost, mechanical thinning took its place. However, the development of agrochemicals and spraying machines led to chemical thinning. 

Currently, chemical thinning is the most efficient work, as it has the least cost and time to carry out, it does not require specialized knowledge from the farmers nor workers. The next step that needs to be taken with the widespread adoption of precision agriculture by the farmers is chemical thinning with innovative means. This need has been raised through the weaknesses of conventional sprayers. More specifically, spraying as performed according to existing agricultural practices, includes horizontal spraying which means that spray volume is the same in every field area independently of the tree foliar area and density. This inevitably leads to excessive use of chemicals and many times to undesirable results, such as excessive reduction or even loss of production. This also works in conjunction with the fact that mist blowers do not have the ability to target the active substances to each tree according to its needs, due to their lack of interconnection with intelligent crop monitoring systems. Moreover, mist blowers are responsible for spray drift due to high spraying pressure and the very fine spraying droplet size which is easily air-borne even hundreds kilometers far away and may end up in aquatic recipients, food, animals or humans. 

The solution lies in innovative devices, such as the Eden Library Viewer, which, using computer vision and artificial intelligence models and knowledge from domain experts, can identify the apples that need to be thinned. Actually, models are the result of training neural networks in images taken from the field which have been annotated by domain experts in order to be distinguishable from the computer. As a result, all this information is translated into specific spray volume and specific locations in each tree, which is consequently transferred to the sprayer. The innovative sprayer is equipped with hardware and software to perform variable rate spraying, in specific locations in trees and independent nozzle operation. 

The outcome is a great benefit in chemicals that are not sprayed indiscriminately, but only where and as much as needed, which result in money savings for the farmer. Also, bearing in mind that innovations bring knowledge from domain experts, the farmer can feel confident about the decision making by the device. Sometimes, chemical thinning by conventional sprayers is unsuccessful, forcing the farmer to repeat spraying, which contrary to his expectations can lead to a loss of production. Finally, a very important benefit of the innovative chemical thinning is the protection of the environment and the subsequent avoidance of soil and underlying water table pollution.