# Design and Comparative Analysis of a Ground-Level Trellising Tool for Greenhouse Tomato Cultivation
## 1 Introduction
This technique consists of placing a main steel-wire trellising line that supports the weight of all plants at a crop height between 3 and 3.5 m. A hook or \"hanger\" is placed on it, where the plant is wound with a thread of plastic raffia [7] that has previously been placed in a spiral around the plant and that will support the crop. As the plant grows, the hanger must be unhooked and the raffia must be released and re-hooked, letting it fall as the plant grows, until the production cycle is finished, which is a fairly repetitive job [8]. The disadvantage of this is that more labor resources and time are required, resulting in higher production costs. Furthermore, this work is performed at a certain height from the ground, with the resulting danger that the farmer may fall from height [9]. Therefore, although this technique improves the profitability and productivity of crops such as tomatoes [10], it is still necessary to remove these safety-related drawbacks. Crop hangers that are commonly used in agriculture in southeastern Spain can be classified into two groups [8]: (i) traditional hangers, consisting of a steel-wire or plastic hanger around which the training thread is wound, and (ii) new-generation hangers, consisting of a coil with the thread attached to the body of the hanger, some of which may have a locking system to stop the training thread. Figure 1 shows an image of each type of hanger. The biggest drawback of the new-generation hangers compared with the traditional ones is their price, which may be almost double that of traditional hangers and, hence, traditional hangers are more often used in most greenhouses. Other systems to support crops in a vertical position in greenhouses are used to replace the practice of manually untying and retying the support ropes to lower the plant when it has reached the height of the greenhouse caves. This is achieved by establishing a modular division that allows the lowering of each plant or a complete row of plants by cutting the support ropes or ropes arranged appropriately so that they allow the continued growth of the crop [11]. Focusing on the trellising task, specifically the handling of the hangers, it can be observed that there are different devices that help farmers gain height to carry out the trellising activity on plants. The most common device is a traditional ladder, which has two main drawbacks: firstly, it must be moved sideways to reach each hanger and, secondly, the danger it presents because it is supported by a sandy surface that is not firm (Figure 2a). Some agricultural companies have designed manual scaffolding with wheels (Figure 2b), which is safe when the trellising activity is being carried out, but this has the drawback that, for every certain number of hangers, the scaffolding has to be moved and the farmer has to get off, move the scaffolding, and get back on, leading to a risk of falling when going up and down and a loss in efficiency. Motorized scaffolding (Figure 2c) has also been designed, which is quite efficient, but it still presents the danger of working from a height. Additionally, the action of climbing onto the platform presents a risk of falling and this approach implies a high economic cost. Finally, there are silts (Figure 2d), which are very efficient, but they present a great danger to the farmer due to their instability. The extreme severity of falls or accidents related to their use is also noted, which is why their use is prohibited in some places. Figure 1: Types of cultivation hangers: (**a**) traditional hangers; (**b**) new-generation hangers. Figure 2: Techniques for accessing the supporting wire to create a greenhouse trellising system using (**a**) manual ladders, (**b**) manual scaffolding, (**c**) motorized scaffolding, and (**d**) silts. The incorporation of robots or robotic arms to perform agricultural tasks, such as trellising, phytosanitary treatments, and harvesting [12; 13; 14; 15], is currently a developing line of work at commercial levels.