One factor that has a direct influence on the success of the coffee crop formation is the quality of the seedling. All care should therefore be taken to ensure the conditions favoring the development of the roots and the balance between the root system and the aerial part - characteristics of a good coffee seedlings. In the conventional system, the seedlings are produced in polyethylene bags with their own dimensions and a minimum of 36 holes in the lower half to drain excess water. The substrate composition consists of a mixture of soil, corrective acidity, organic fertilizers and minerals. Since the mid 1990s, however, a new system of coffee seedlings production began to be used in the region of Marília, SP, Brazil, based on works presented by the technical staff of the Cooperative of Coffee Growers of the Region of Marília (Coopermar). The traditional polyethylene bags were replaced by plastic tubes, which are conical in shape, open at the lower end for drainage, with internal grooves to direct the roots downwards, preventing them from rolling. The production of seedlings in tubes has a number of advantages over the conventional system.
The higher initial cost of the pipe system, however, is diluted during the seedling production process, by a number of operating advantages over the conventional system. The handling of the tubes in suspended screens is much more practical and requires less labor; the selection of seedlings for the planting and reorganization of less developed ones - laborious and time-consuming operations in the conventional system - are easier and more economical procedures, as well as the planting itself. Without contact with the soil, it reduces the contamination of the roots of the seedlings by pests, mainly by nematodes. This isolation of the soil, coupled with the fact that the tubes are opened at the lower end, causes the main root “pivot” to cease its development upon contact with the atmosphere, which acts as a natural pruning that eliminates the "crooked pivot" - a common defect in plastic bag seedlings, caused by the folding of the roots, when they reach the bottom of the container, a problem responsible for a large number of failures in plantations formed with seedlings in bags. The filling of the tubes is faster than the bags, the difference in volume between the two packages and also because it is made in compacting machines, and the yield is much higher than the filling of the manual bag. Those who opt to work with the plastic trays have the possibility to build a support site or can place them directly on the floor, reducing the implementation costs. The trays have feet that do not let the seedlings stay directly in contact with the soil.
The bags are filled with a mixture of soil, organic fertilizers and chemicals prepared by the greenhouse, a mixture that generally needs to be chemically purged to control soil pests, mainly nematodes, in complex, time-consuming and expensive operations. The tubes are filled with commercially prepared substrates made from pine bark or coconut fiber, enriched with complete fertilizers, an easy-to-handle substrate that does not need to be purged because it does not contain soil in its composition. The use of weed-free substrates is another factor that reduces labor, dispensing with common cleaning operations in the production of seedlings in polyethylene bags. In tube greenhouses, although the substrate is enriched with macronutrients and micronutrients, as in conventional greenhouses, a supplementary supply of nutrients, mainly micronutrients, via fertigation, foliar spraying, or the provision of fertilizers of gradual release. This is very important for a good development of the root system and for the maintenance of the vigor of the seedlings, until planting in the field.
The area required for production of tube seedlings is also smaller than the conventional greenhouse area by the difference in size of the two containers; thus, the consumption of water, pesticides and the labor used will be much smaller in the greenhouse of seedlings in tubes.
The transport of tube seedlings for field planting presents important advantages over conventional seedlings, since the operation is cheaper, since the tubes occupy less space and can be placed in plastic boxes, both the lying seedlings and standing seedlings. Typically, it is possible to increase the load capacity of the tube seedlings by up to four times. It is also possible to use plastics for rolls, where the seedlings are removed from the tube and wrapped in plastic, containing from 25 to 50 seedlings each, so that the producer does not need to return the tubes to the nursery, making it much easier for those who plant. In fact, a serious defect of the conventional seedlings is precisely the movement of the substrate during transportation, causing mechanical damage to the roots and even the removal, which, when it happens, increases the possibility of losses in the field. The planting operation itself is more practical and yields more with the tubes, which are smaller, easier to handle and to remove the packages, not requiring root pruning, different from what happens with seedlings in a polyethylene bag. The advantages in planting are greater also because there are machines used in the forestry branch that realize the mechanized planting of the seedlings.
Edson Gil de Oliveira – coffee-growing autonomous consultant