| Reforestation in the Pacific Islands |
|5. Nursery development and practice|
Purchase the necessary nursery materials (fencing, construction material, tools, pots, plastic potting bags, etc.) well in advance of the planned start-up date. Early purchase of materials will avoid delays in planting or transplanting. Costs may be reduced and local acceptance increased by the use of local materials and labor and the integration of local knowledge into the design and construction work. Materials not available locally can normally be acquired from government forestry off ices or agricultural suppliers.
A list of materials could include the following: plow, hoe, rented draft animal or hand tractor, shovels, budding knife, pruning shears, pruning saw, pots (plastic bags, bamboo, clay), plastic sheets, spade, wood or wire fencing, construction materials for a shed, watering cans or hose, soil, sand, compost, and 55 -gallon drums. (See Illus. 5 -1.)
Timing is a critical factor in nursery development. Timing issues include the amount of time needed to set up, acquire materials, and make sure seedlings are ready for planting at the right time of year. An additional timing consideration is arranging labor and transportation for critical times (planting of seeds or stock, transplanting to planting sites, etc.). This planning should be done well in advance, since labor may be in short supply when workers are needed for other farming activities.
The most important time consideration is the timely planting of the seedlings. Since the survival chances of young trees depends directly on the maturity and size of the trees when transplanted, and upon transplanting at the right time of year, the timing of the project must be carefully planned.
The timing involved in seeding or placing open rooted stock or vegetatively propagated plants in the nursery must therefore be carefully considered in order to ensure that planting stock is ready at the correct time. Planting too late in the nursery will make for immature seedlings with lessened chances for survival.
Conversely, planting too early in the nursery will produce heavier seedlings that will be harder to move and transplant, and may become pot-bound.
To time the planting, the forester must know how long each species must remain in the nursery and plan nursery time to coincide with the rainy season. For the recommended age of transplanting for species covered in this manual, see Appendix C. Further information is available from the government extension service and agricultural schools.
Other planting considerations that must be taken into account are the overall location of the nursery, soil, sunlight, and local climate. All of these can speed up or slow down the development of seedlings. To avoid having a project ruined by these factors, it is necessary to consult local experts and records of other projects. It is important to keep good records--for yourself and for those who follow.
As stated, long-range planning is crucial for successful nursery operations. It avoids shortages, waste, and lost opportunities. Along with materials, record-keeping, and timing, other considerations for nursery development include soil, water, labor, space, design and layout, light and shade, protection and maintenance, propagation methods, care of nursery plants, records, and other activities.
Good, rich soil promotes healthy development of seedlings. Before a nursery is established, the soil should be tested for its suitability with the trees to be used. Factors to be tested for include pH, nutrients (nitrogen, phosphorus, others), and overall composition. (For more information on soil fertility, see Tisdale and Nelson, 1975.)
Adjust the soil according to the needs of the plants, if possible. Adequate fertilization is especially important to open-rooted stock. For open-rooted stock, cultivate the nursery soil to the expected depth of the roots. Add nutrients and any other elements the soil is lacking at this point.
Nutrient -rich soil should be developed for nursery use by the mixing of compost (see Appendix D), sand, and soil. A standard mix is 1/3 sand or loose soil, 1/3 clay, and 1/3 compost (see Illus. 5-2). This soil is loaded into pots or plastic bags, or used to make nursery beds. When planting in beds, it is necessary to supplement the soil mixture with additional nutrients: add a generous amount of composted animal and plant debris. A general rule is 90 kg per hectare. Continual addition of compost w ill ensure good soil structure.
Inorganic commercial fertilizer can be used to improve the fertility of the planting medium. However, it is expensive and may not be available. Where it is available, add commercial fertilizer containing nitrogen and phosphorus to the soil, clay, and compost mixture during preparation, or after placing the soil in the pots, plastic bags, or beds. (For additional information on the use of commercial fertilizers, see the Western Fertilizer Handbook written by the Soil Improvement Committee, California Fertilizer Association, available from ICE.)
It is very important not to leave the soil exposed to the sun, rain, and heat of the tropics for very long, as all of these elements will deteriorate the quality of the soil. Sunlight will bake the soil, dry it out expose it to wind erosion, and kill exposed microorganisms important to plants, such as mycorhizzae. Rain will leach out important nutrients and, if sufficiently strong, will wash away precious soil. Tropical heat speeds oxidative reactions in the soil, further weakening the soil's ability to nurture seedlings. Protect soil at all times, especially after tilling, by mulching with grass cuttings.
The cost, quantity and amount of water are important considerations in the development of the nursery. Projects can be seriously hampered if source of water becomes polluted, dries up, or is diverted for another project. To ensure the financial and technical feasibility of the nursery, the forester must assure that adequate quantities of clean water are available at a reasonable cost.
Different water quality levels will determine the uses and species that can be successfully used. Drinking quality is not necessary for plants, although a drinking supply should be allotted for workers (unsafe water will cause sickness and absenteeism, which can disrupt the schedule). Overly dirty or organic water should be avoided or filtered, as slimes will gum up nozzles and valves.
The most important considerations when locating a water supply are the salt content and hardness. Water hardness is the result of excess minerals in the local groundwater. If hard water is used for long periods, the pH of the nursery soil tends to rise (become alkaline). If water is so hard that this cannot be avoided, then rainwater may have to be collected. This will require rainwater catchments and storage facilities, which must be incorporated into planning (along with considering rainfall patterns and supply).
Although some plants are tolerant of low levels of salt in water, most species will die if exposed to high concentrations. Even low levels of salt can be detrimental to seedling development in some species. Salt can come from many sources, including wells and surface water. Salt may have accumulated in ponds that previously evaporated away, making them unusable for water storage.
A shortage of water is a serious problem that adds to salt crystal development. For sites with limited water, use water sparingly. Occasionally flush seedlings with large amounts of water to remove as much salt as possible. This over-irrigation is one solution, although it may also leach nutrients out of the soil. If the needs of the community are compatible, saltresistant trees such as Casuarina may be grown where no method of reducing salt exists. There are salt levels so high that no trees w ill grow. If this is the case then a different site should be chosen for the nursery. See Appendix C for salttolerant species.
While planning the nursery, it is important to calculate how much water will be needed on a daily basis. This will determine all water supply plans and activities. Once the daily amount is known, it is possible to determine the pumping rates and water storage needs for the nursery.
An easy and reasonably good method for determining daily needs is to measure the area to be watered (the planting beds) and multiply this by 0.02 m. This w ill give the amount of water in cubic meters to cover the area with a sheet of water two centimeters in height. For example, if a bed is 1 m x 5 m, the amount of water needed per day will be: 1 m x 5 m x 0.02 m= 0.1 cubic meters, or 100 liters of water. (See Illus. 5 - 3.)
If the nursery has ten beds, it will require 1000 liters of water a day. This means the nursery will need 365,000 liters of water a year, if it is producing seedlings on a continual basis. Fluctuations in this number will occur depending on number of beds in production and maturity of the seedlings.
This calculation should show the amount of water adequate for most trees under most conditions. It can be less if:
o There is adequate humidity, shade, and protection from wind;
o Available water is used during the cooler parts of the day; and
o There is good water retention in the soil.
Under these circumstances, it might be possible to reduce water needs by up to one half. Other strategies to conserve water include sinking the pots in the ground, mulching, and constructing shade devices.
Water can become a limiting factor to nursery development. It may be necessary to carry out ground, surface, and rainwater schemes to assure an adequate supply. (For additional information on methods of collecting or extracting water, see ICE publication" Appropriate Technology in Developing Countries." The bibliography lists other sources of information for these types of projects.)
Labor requirements are extremely variable and depend on methods used, species, and sites. A large, permanent nursery requires more initial preparation and long-term maintenance then a temporary nursery. This means a large work force is needed for site preparation, and small staff for continual maintenance. Usually a wider variety of species are cultivated in a permanent nursery, which requires additional labor and a more knowledgeable work force.
Labor needs are not as great for a temporary facility. It is advantageous to site the facility near the project site, yet as close to the beneficiaries as possible. By placing the facility near a residence, it is possible to provide 24-hour surveillance, and better yet, a caretaker.
Regardless of the type of nursery, sites located on marginal lands need many days of laborious preparation in order to clear trees, rocks, and work the soil.
It is possible to calculate labor needs by referring to previous records of similar jobs and consulting local experts. Plan ahead to ensure that an adequate workforce is available at critical times. Whenever possible, use local volunteer labor to assist in the early phases of construction. Periodically, request their assistance to perform general maintenance such as weeding and general construction activities. Hold training sessions on the same day so the participants can take some knowledge home with them. If you are applying for a grant, many organizations will require the beneficiaries to contribute some form of assistance, whether it be money or labor However, make it perfectly clear to the participants that they are volunteering. Too many foresters have found themselves without a labor force once workers realized there was no pay.
If the nursery is permanent, provide enough money in the budget for a full-time live-in worker. One way to ensure high-quality work, as well as ensure the continuity of the project, is to recruit a recent graduate from an agricultural school to assist in managing the project. Enroll the manager in a short training program with the national extension service. It may be possible to make an arrangement in which the manager spends several weeks at a government nursery assisting in daily operations.
Space considerations are determined by the needs of the plants and the community, how much time and money is available, and how easy it will be to acquire written consent and permission for use of the land. Consider sites that allow expansion if extra room is likely to be needed or desired.
Estimating the Amount of Space Needed. First, the number of trees required by the project is determined by considering the overall project design and the capabilities and needs of the community. After determining numbers, the total space for the nursery can be calculated. As a general rule, when estimating the area needed for a nursery, use the following guidelines: for open-rooted stock, 1,000 trees need 10 square meters of space; for potted stock, 1,000 trees need 7 square meters of space. (See Illus. 5-4.)
After calculating the area, add 15-25% of the above figure to account for the miscellaneous needs of the nursery, such as extra nursery beds, walkways, roads, work sheds, firebreaks, and research areas. It may be tempting to add even more space, but doing so w ill add to the overall cost of the nursery because additional fencing, maintenance, and other items will be necessary.
A sample calculation to estimate the amount of space needed would take the following form:
A community forester decides that 800 keucaena trees per year would best suit the community's needs, resources, and capabilities. Pots are not locally available, but a good site with good loose soil is available and will be suitable for open-rooted stock.
For 800 trees, using the open-rooted method, the initial calculation is 800 x 10 sq. m = 8,000 sq. meters; added to this figure is 15-2596; 8,000 sq. m x 0.15 = 1,200 sq. meters, or 9,200 sq. m total, 8,000 sq. m x 0.25 = 2,000 sq. meters, or 10,000 sq. m. total. The size of the nursery should range between 9,200 and 10,000 square meters.
Nursery Design and Preparation
Good design and preparation will increase the efficiency and productivity of a nursery operation. Unnecessary deaths of seedlings can thus be avoided, which is crucial when a project requires a specified number of trees in order to be economically efficient.
Nursery design depends on the site. Some general guidelines exist that can help in the initial stages. Draw out your design so that the best overall nursery plan can be developed, and so that alternative plans can be easily formulated. (See Illus. 5 - S.)
The size, orientation, and location of the nursery beds are important considerations. Beds should be 1.2 m in width for ease of weeding; their length will depend on the shape of the nursery. Orient the beds with the long dimension of the bed running from east to west. This orientation allows even exposure throughout the day for the trees on both the inside and outside of the bed. If the area is level create a slight slope to facilitate surface runoff.
The beds should be separated by walkways that are at least 45 cm wide, allowing people with wheelbarrows easy access for weeding, pruning, and other treatment. Beds should be slightly raised above the walkways, at least 15-20 cm. This allows good root penetration and easy maintenance. A slightly concave shape is recommended for the top of the bed. This controls erosion of the sides and enhances water retention.
If the nursery is permanent and the budget allows, lay a concrete pad as a base for each of the beds. The pad will deter roots from penetrating too deeply, as well as facilitate surface runoff. Another option is to line the bottom of the beds with plastic sheets. Large fruit tree plantations use plastic bags to cover the fruit during crucial periods. When split they make excellent liners, and plantation managers are often willing to provide them free of charge. (See Illus. 5-6.)
Space should be made available for a driveway and turnaround so that trucks, tractors, and carts can drive right up to each bed. This access will avoid long carries and allow quick loading of seedlings for transport. Other items to work into the design include supervisor's quarters on the site, a work and storage shed, a soil compost pile, a water supply or well, a research area, and germinating beds. The space allotted to each of these will depend on their importance to the project, their size and the size of the project, and on the availability of space. Another important item needed is a firebreak surrounding the entire nursery. This should be 3-4 meters wide to prevent nearby bush fires from destroying seedlings. The firebreak should be wider in fire -prone areas.
Light and Shade
Seedlings tend to be fragile following sprouting and transplanting. This is due to the immaturity of the root system, which is unable to support the seedling during times of stress. The harsh tropical sunlight can be a serious threat to these young plants. On the other hand, seedlings require increased light as they mature in order to maximize the rate of growth. For this reason, it is best to pick a site with both shade and open areas. Protect the seedlings until they are hardier, and then move them into direct sunlight. A site with carefully placed shade trees is a good idea, although too much shade will slow the growth of seedlings, (See Illus. 5-7.) It may be possible to thin out tree cover, but no large sections of tree should be cut out if the objective of the nursery is tree conservation.
If no trees exist, shading for young seedlings may have to be constructed, especially in hot, dry areas. Use local resources, materials, and labor for the reasons listed above. Spread raised woven mats and banana and other leaves across seedlings as shading. (See Illus. 5-8.) Prior to planting, sow fast-growing tree species around the perimeter of the site.
As an intermediate step between shading and full sun, seedlings in pots can be half-buried in trenches dug in the shape of nursery beds. This step limits the amount of water lost--the major form of stress caused by excess sun--yet allows full exposure to the sun much earlier, for faster growth. (See Illus. 5 - 9.)
Protection and Maintenance
Besides drying out, harsh sun, and the dangers to seedling growth cited above, other problems exist of which nursery managers must be aware. These include dangers from livestock, people, pests, and fires.
Seedlings have no chance for survival if they are trampled on or eaten by livestock. To protect the area from livestock, 24-hour surveillance or fencing is required. This may not seem to be so important where few livestock roam, but it may only take several animals to wipe out months of work. A combination of fencing and surveillance may be necessary if other problems include theft and pedestrian traffic.
For surveillance, people must be available and willing to work regularly. In the case of a permanent nursery, a worker may be willing to live at the site. The cost of paying workers must be considered, as it is unrealistic to hope that people will volunteer to watch the nursery for the entire time it will be operating. Food, money, shelter with land, or any other locally acceptable form of payment should be used.
Fencing is the best alternative to hiring a full time worker The type of fencing used will depend on availability and purchase and construction costs. Cost and availability are usually linked: the cost of the fencing often depends on the type of material available.
Before deciding on the type of fencing, determine the local land use patterns. Be aware that fences may cut off a walkway or traditional grazing area of which you are unaware. Plan around customs, and ensure that change will not adversely affect area residents.
Local materials may be used entirely or in part to save money. Bamboo, wood stakes, layered branches from thorn trees, and other structurally sound materials are adequate assuming they are maintained regularly. (See "Appropriate Building Materials" by Roland Stulz, and "Tools for Agriculture: A Buyer's Guide to Low Cost Agricultural Implements" by John Boyd, available through ICE.) Another option is to purchase wire fencing from an agricultural supply store. A live fence, which can provide fertilizer, seed, and rooting stock, is also viable if there is sufficient time to wait for the trees to mature. (See Illus. 5-10 for examples of fencing materials and Appendix C for species that have been used as live fences.)
Design the fence to keep out all types of animals. Several wires strung four feet ok the ground may keep out large animals such as cattle and mature pigs, but it will not deter piglets or chickens. It is necessary to add thick brush or additional wire at the base of the fence to keep out piglets. Chickens are almost impossible to discourage if it is not a local practice to clip wings at birth. In this case only surveillance will work.
Construction costs are another consideration in the type of fencing to be used. A wire fence or fence constructed from local materials requires digging holes and setting posts. A live fence is easier to install, as all it takes is shallow plowing, planting, and periodic maintenance. Whenever possible, train and use local volunteer labor in fence construction.
Maintenance is an absolute necessity for fences, and its cost must be considered. Without maintenance, the fence might as well not be erected, for it will soon come down. Maintenance will be especially important when fragile items such as twigs and sticks are interwoven into the fencing to keep smaller animals out. Without constant monitoring, they w ill eventually work loose and fall out.
Fire can ruin a nursery in short order. Check sites for history of fire. Know the dry season months and plan accordingly. Encircle the nursery with a firebreak, and conduct regular patrols to prevent build-up of materials that will allow the fire to pass into the nursery. If available, water
should be kept on hand during dry periods to fight any small, controllable outbreaks.
Wind can dry seedlings out entirely or damage them to a point where their chances of survival are lowered. If possible, choose a site with a natural windbreak such as forests or hill slopes, or construct a windbreak. The general rule is that 2.25 times the height of the fence is the distance from the fence that is protected from the wind. Therefore, a 1 m fence will provide 2.25 m protection downwind.
Infestations can come in many forms, but the most serious ones involve insects, nematodes, fungi, and bacteria. The range of possible pests is beyond the scope of this book. Insects and diseases specific to particular species are listed in Appendix C. Local forestry extension agents can provide more information on specific insects and diseases in the area. If an infestation is suspected, institute the following procedures.
o If possible, isolate affected trees and burn the infected parts. This will limit the spread of the problem.
o Identify the pest as best you can. Drawings of insects (or photos) will help extensionists identify problems if they cannot visit the site. Most government forestry services have manuals to help identify common insects and diseases. If the pest cannot be seen, a drawing or photo of the effects on the tree(s) can also help in identification.
o Enact controls. Consult extensionists, local people, and other foresters working in the same area for information on possible controls for infestations. All possible techniques should be considered before decision(s) are made. It may be advantageous to use a powerful control, such as pesticides, or a less risky and less expensive technique such as integrated pest management. Other forms of control include wider spacing, plant diversity (this is more difficult with nurseries than in the field), and companion planting.