Coffee Seedlings in Forestry Tubes

General - The aim of the project was to develop seedlings meeting or exceeding the criteria of success established for the current plastic bag system. Simultaneously, the new system had to overcome the limitations of the old in production and environmental costs, and agronomic deficiencies.

Overall, the tube container system was found to be superior to the bags in complying with the stated aims of the experiment. Though growth to maturity took longer than expected due to the factors mentioned previously (i.e. faulty watering regimen), tube seedling health and conformation were as good as the bagged trees. While the aerial part of the tube trees was less developed, as had been expected due to crowding, the tube product reached the same height of the bag seedlings. Leaf size was not as restricted as had been prognosticated, but caliper measurements of the trunks were smaller than hoped, though still acceptable. Most likely, this was caused by excessive nitrogen application which should have been reduced once the decomposition of the rice hulls had been achieved. Density of roots per volume unit of growing medium was superior in the tubes but perhaps would have been greater if the excessive nitrogen would not have prioritized the development of stems and leaves. On the date of the submission of this report only a limited number of trees had been planted. So far, survival rate has been 100%. The superior root system of the tube seedlings made for faster establishment of the plantation if sufficient soil moisture was present. The first flush of leaf and stem growth was faster with the tube than with the bag. In the following, the performance of the tubes will be compared to the problems they sought to resolve.

Production Costs:
Problem - Substantial tracts of land are needed to establish bag nurseries. This involves expenditures in constructing lots and access roads in mountainous locations and creation of infrastructure (irrigation, electrical, drainage, shade cloth houses) over a wide area.
Solution – Tube containers reduced planting area to one eighth of the bag nurseries. The size of vehicle entryways and the head house space were greatly reduced. Germination boxes were eliminated. Utility infrastructure was shrunk in proportion to the diminished planting area.
Problem – The bag growing medium must be prepared on-site using topsoil and organic materials, both which are expensive and hard to procure. Manufacture of the growing medium requires heavy equipment and special machines which must be housed in large structures.
Solution – Soil was substituted by a light weight, organic, non soil medium. As opposed to manures and composts, these materials require no government permits to process or transport. The small volume of medium needed by the tube containers required less investment than the soil mix. Reduced medium weight and volume allowed for fast manual preparation in a small area.

Problem - Transportation costs within the nursery, and to and within the farms are high because the bags are fairly large and heavy. The average weight of each filled bag is 6 pounds; its volume is 113 cubic inches. A planting worker can only carry 9 bags, weighing 54 pounds total.
Solution – Tubes decreased container weight in a 40:1 ratio or better depending on the growing medium used, each filled cell weighing no more than 2.5 ounces. Cell volume is 10 cubic inches each; volume decreased by an 11:1 ratio. 2500 tube seedlings, enough to plant 2 acres, weigh no more than 400 pounds, and can be carried in a 4’x 4’x 3’ cardboard box. An identical number of bag seedlings, arranged on 2 levels, require an 18’ flatbed truck for transport due to combined weight (15,000 pounds) and volume. A planting worker can now carry 100 or more tube seedlings weighing less than 20 pounds total.

Problem - Heavy use is made of expensive agricultural chemicals because of the large area involved and because the soil in the bags must be treated as well and its volume is high. As the growing medium is not sterile and the bags are placed directly on the ground the rate of application and variety of agricultural chemicals is increased.
Solution – The use of all agricultural chemicals, except for soluble fertilizer, was eliminated. This was made possible by lifting the crop off the ground where many pests and pathogens are concentrated; reducing the volume of growing medium thereby diminishing the volume of chemicals needed to treat pests and disease found in the medium; augmenting planting density in order to reduce the area where chemicals would have to be applied; and utilization of a sterile growing medium so as to eliminate herbicides, soil fungicides and sterilants. These factors, rather than the chemical reduction that had been hoped, allowed for complete elimination of chemicals, and consequentially, significant expenditure on these inputs.

Problem - The bag system is labor intensive in all phases of production. This is by far the greatest cost of production in coffee nurseries.
Solution – Maintenance was reduced to less than 2 hours a day, 1 hour of which was spent on hand watering. Non maintenance operations dropped from 2 months to a few days. Distribution of the seedlings to clients took minutes rather than hours.

Problem - There is a considerable expenditure in fuel and utilities. Most bag nurseries use long-throw impact sprinklers which by nature are imprecise and wasteful of water. Fuel and electricity are relied upon for machine operation involving the preparation of the growing medium, transport, etc.
Solution – Water costs were reduced by increasing planting density and by the use of efficient, fixed-head micro sprinklers having a more even water distribution than impact sprinklers. Machine and equipment use in the manipulation of the medium was cut down; one worker rapidly mixed the medium using nothing more than a shovel, the characteristics of the medium and containers permitted fast filling of tubes and economical transport.

Environmental Costs:
Problem - The heavy use of agricultural chemicals has been mentioned. The large areas taken up by the bag nurseries make containment of pollution difficult. Controlling runoff is not easy with the many streams present and typical rain levels reaching 80 to 120 inches in the mountains where the nurseries are established. Puerto Rico has one of the highest population densities in the world and virtually all nurseries are located next to homes and communities, augmenting the potential for chemical harm.
Solution – Under the conditions of the experiment, no chemical application was necessary. There was no special weather or other atypical situation which could account for this unexpected result, so it is felt that the result is reproducible for the next seedling harvest. Though the nursery location is nearly ideal for temperature and other weather related factors, it is surmised that the high density of the crop and its associated humid micro atmosphere played the determining role in controlling the coffee’s main pest, the coffee leaf miner. The sterile growing medium prevented soil insects. Soil fungi were avoided through the use of the sterile, aerated medium but the effect was counteracted somewhat by the untreated irrigation water. Mollusks did not invade the crop because it was raised off the ground and the tar coating of the tables repelled them. Nutrition, self shading, and plentiful watering kept down leaf fungi to a minimum.

Problem – In the conventional system there is extraction of precious topsoil in mountain areas in a small island possessing a delicate ecosystem, increasing the potential for erosion and land slides. The bulldozing and excavation of lots on slopes averaging 40 to 60% is detrimental to environmental and aesthetic values.
Solution – The tube nursery was established on a long narrow lot excavated on the mountain contour. This minimized the creation of tall, unstable back slopes and mitigated negative aesthetic impact. Extraction of topsoil was, of course, not necessary for the formulation of the growing medium.

Problem – Conventional nurseries are wasteful of water. Ironically for such a well watered land, usable water is scarce and expensive in Puerto Rico, due to pollution, inefficient infrastructure and management. All water resources in Puerto Rico are owned by the central government and franchised to the nurseries. With the mounting pressures from a growing population, inefficient use of water in agriculture is no longer acceptable.
Solution – Because of the concentrated planting area and small container volume, the overall water use for the tubes is similar to the most water thrifty system, that is, drip irrigation. This is so despite the windy conditions of the locality which often interfered with the settling of the droplets.

Problem - All operations within the bag nursery and seedling transportation rely heavily on the use of fossil fuels.
Solution – Cutting back on high energy operations and equipment curtailed the wasteful use of fossil fuels. Reuse and recycling of containers and trays keep the hydrocarbons spent in producing plastic in the production chain rather than in a dump or in an incinerator. By eliminating agro chemicals, whose production and make-up is based on the burning and refining of petroleum and coal, the harmful effects of these practices on the environment are also avoided.

Agronomic Deficiencies:
Problem - The combination of germination in sand beds, replanting of germinates into plastic bags, and the bags themselves promote the development of root abnormalities. These include L, J, and spiral roots and multiple tap roots.
Solution – The root systems of hundreds of tube seedlings were observed. Spiral and J roots occurred in none. Almost all cases of L and multiple tap roots were related to seed that had floated to the surface of the medium and took root or was then replanted. Multiple tap roots frequently spread out in a shallow “crow or cock’s foot” pattern which is said to cause weak anchoring of the trees in the field. In the tubes, all multiple roots were trained downward. Only field observation will reveal if this positive behavior will continue after transplant. Some of these abnormal root conditions have been vaguely ascribed to genetic factors by coffee specialists. The experiment’s results support the contention that the deformations are largely caused by mechanical and heat damage of various sorts. Because of the high germination rate of fresh and properly stored coffee seed, direct seeding was a success, both from the speed at which it was carried out and from its agronomic benefits. A source of multiple tap roots that could not be controlled in the experiment was mechanical damage to the seed embryo in the removal of the coffee rind or pulp by the seed processor.

Problem - The growing conditions and unsterile growing medium promote pests and disease.
Solution – As was discussed, placing the crop on tables and eliminating the soil component prevented contact with pathogens and water logging of the bags during occasional flooding.

Problem - The soil based medium, particularly its clay component, does not provide sufficient porosity and related root aeration, leading to losses to damping-off disease in the early stages of seedling development. Soil porosity is 50%. A soil, peat, and sand mixture in equal parts has 55% porosity. Thus, the inclusion of soil as a major ingredient (20 to 30%) in a container mix reduces porosity to unacceptable levels, when proper levels should be in the order of 80 to 90%. Most manures and composts have fine particles which act in the same negative manner as soil within containers.
Solution – In the conditions of the experiment, the control peat mixture as well as the rice hull mixtures dried out too quickly. Good results were obtained with a fine peat and vermiculite mix similar to those used to germinate in very small containers. Fine mixes can increase the danger of damping-off. Obviously, a finely tuned balance between the antagonistic properties of aeration and water retention will have to be worked out for tube grown coffee, though the results obtained so far have been encouraging.

Problem - Some losses occur in the conventional system because of over dosing of fertilizers and burning from uncomposted organic materials incorporated into the soil mix. Slow release artificial fertilizers are difficult to incorporate evenly into the growing medium and decompose too quickly under humid tropical conditions, leading to waste.
Solution – The combination of fertigation and an infertile growing medium proved to be problem free and ideal in controlling fertilization at all stages of growth.