In this article we will discuss about:- 1. Introduction to Forest Nursery 2. Definition of Forest Nursery 3. Significance 4. Classification 5. Planning and Management 6. Site Selection 7. Rooted Cuttings 8. Plant Propagation Structures.
Introduction to Forest Nursery:
During the past century, the world’s land base has been subject to urban expansion, poor management practices and increasing pressure to provide resources for a growing population. As a result, tree seedling production has become a fundamental tool for addressing reforestation, restoration and conservation needs. Nursery practices for tree seedling production have evolved considerably over the past several decades in accordance with technological advances, increased understanding of seedling physiology and development, and changing customer demands.
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Considerable research into plant physiology and nursery practices has led to a much greater understanding of seedling responses to environmental conditions, nursery treatments and growing regimes over the past several decades. For example, early nurseries had limited understanding about soil physical and chemical properties, amending soils to achieve maximum seedling growth, optimizing soil/media properties for seedling development.
Now the scenario has changed and manufacture of chemical fertilizers and other products, as well as the ability to transport materials over great distances, have given plant growers more options for developing better planting stocks. Knowledge has also increased on the topic of seed management.
In addition to our better understanding of seedlings and the growing environment, technological advances in nursery equipment have greatly enabled forest nurseries to produce large volumes of high quality stocks. Now mechanical methods have replaced the manual labour works in transplanting seedlings, lifting of planting stocks, etc. Nowadays, there are custom machines for most nursery processes, from sowing to harvest, although smaller nurseries still rely on manual labour for many tasks.
Additionally, most nurseries, small or large, carry out much of their weed control via hand weeding. The basic concepts regarding density, fertility, irrigation, pruning, grading, storage, handling and other seedling production practices have always been considered in nursery management. Whether it is 1912 or 2012, the underlying driving force is based on the Target Seedling Concept: “Targeting specific physiological and morphological characteristics that can be quantitatively linked to out planting success”.
Because nursery production is expanding more and more to encompass a larger variety of species, there is an accompanying need to develop and refine nursery techniques for non- traditional native species. Until the past few decades, nursery production was primarily focused on commercial/ industrial species for forest regeneration or horticultural cultivars for urban landscaping and gardens.
The rise of the environmental movement in the late 20th century, the explosion of invasive non-native plants over the past century and increased land degradation has led to much attention being directed towards propagation and restoration of native or indigenous plants.
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Nursery management represents the greatest concentration of technology and investment in the forest growth cycle. On an area basis, any effect on subsequent seedling or tree growth brought by nursery decisions and investment is multiplied many fold. This extraordinary leverage given to nursery manager’s decisions not only makes those decisions the focus of land manager’s attention but also provides an unusual opportunity for using research to improve productivity.
Furthermore, because the nursery production cycle is short relative to many other forestry operations, the impacts of nursery manager’s decisions usually can be quickly seen and the effects of new research information applied to nursery operations can be rapidly evaluated.
The National Action Plan on Climate Change (NAPCC) and Green India Mission aim at afforestation of 6 million hectares of degraded forest lands and expanding forest cover from 23 to 33 per cent of India’s territory. The plantation forestry programmes viz. afforestation, reforestation and reclamation forestry, which focus on increasing productivity of forest, necessitates for production of quality planting stocks.
These large scale plantation programmes require huge quantity of elite planting materials supplied through forest nurseries across the country. The forest nurseries thus play an important role in meeting the national objective of keeping 1/3rd of the country’s geographical area under forest.
Definition of Forest Nursery:
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Tree seeds germinate and trees grow readily under natural conditions. These delicate young seedlings and young trees are exposed to adverse dry season conditions and intense competition from other plants in natural forests or plantations. Forest nurseries can provide optimum care and attention to seedlings during their critical juvenile stage, resulting in the production of healthy, vigorous seedlings. In many cases, successful reforestation requires nursery grown seedlings, since degraded areas have un-favourable conditions making natural vegetation or direct seeding not feasible.
Forest nursery is a managed area, designated to produce tree seedlings grown under favourable conditions until they are ready for planting. It can be an informal, small-scale arrangement or a large commercial enterprise. Nurseries vary in size, facilities (supplies, tools, equipments, etc.), types of seedlings produced and nursery operations. They also differ significantly in quality and quantity of planting stocks produced.
However, all nurseries primarily aim to produce sufficient quantities of high quality planting stocks to satisfy the needs of seedling users. Users include the nursery owners themselves, individuals, community organizations, farmer groups, government agencies, non-government organizations, corporate or private customers.
Nurseries may often provide income generating opportunities for the operators and enhance social capital and technical capacity and leadership skills of communities. Smallholder tree nurseries also serve as important training and research ground for many smallholder farmers.
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Forest nurseries are defined in a numerous way:
i. An area or place where forest seedlings are grown.
ii. An area where tree seedlings and plants are raised for eventual planting out.
iii. An area where trees, shrubs, or plants are grown for transplanting, for use as stocks for budding and grafting.
iv. A production unit that grows planting stock (seedlings and saplings) of forest trees and shrubs.
v. A plot of land where young trees can be raised under more or less controlled conditions.
Forestry projects and large scale afforestation and reforestation programmes spawn the establishment of self-help and self-sustaining local nurseries, which remain functional even after project termination. These local nurseries may be linked in a network to meet project, community or market needs. Government and non-government agencies often provide modest support to enhance the development of local nurseries, in recognition of the spontaneous growth of local nurseries.
These efforts strengthen local livelihood development and sustain public reforestation initiatives. In many areas, where nursery development has flourished, farmers also developed keen interests in collecting and propagating diverse species, including indigenous trees. Such forest nurseries have become rich repositories of tree biodiversity.
Significance of Forest Nursery:
Good nursery operations incorporate the selection of the best quality seeds and seedlings, thus initiating tree improvement. Forest nurseries are advantageous in propagating recalcitrant seeds, dormant seeds and tree species with irregular flowering. Nurseries are also good venues for vegetative propagation operations. Some important species do not need seed every year.
Plantation of these species can be raised annually only by collecting all available seed in years and sowing it in nursery to raise seedlings to be planted out in various years. Some species grow very slowly and if the seed of these species is sown directly in plantation, the seedlings are most likely to be swamped by weeds and killed. Therefore, slow growing species are generally raised in nursery and planted only when the seedlings are not liable to be damaged by weeds.
Success of roadside avenue plantations depends largely on planting tall and sturdy plants which can only be obtained from nursery. Plantations of some species when raised by direct sowing are not so successful as when raised by planting. In such cases, nursery is an essential part of artificial regeneration of those species.
The best method of introduction of exotics, viz. tropical pines, poplars, eucalyptus, etc. is only by planting and therefore nursery is very essential for them. Planting of nursery-grown plants is surest method of artificially regenerating poor and barren sites. Causalities in plantations have to be replaced either in the year of formation or in the next year.
Sowing done in the gaps are liable to be unsuccessful as a result of suppression from weeds and cannot catch up the plants from original sowing. Therefore, replacement of causalities is always done by planting nursery-grown plants or stumps and so nursery is very essential for causality replacement.
Classification of Forest Nurseries:
A. On the Basis of Area Size:
Based on size of area, forest nurseries are classified into:
i. Small Nursery:
Nurseries with an area of less than 3 ha
ii. Medium Nursery:
Nurseries with an area of 3-10 ha
iii. Large Nursery:
Nurseries with an area of more than 10 ha
B. On the Basis of Irrigation Facility:
Based on the water availability, forest nurseries are classified into:
i. Dry Nursery:
It is a nursery that is maintained without any irrigation or other artificial watering.
ii. Wet Nursery:
It is a nursery that is maintained by irrigation or other artificial watering during the dry periods.
C. On the Basis of Planting Stock:
Based on the planting stocks produced, forest nurseries are classified into:
i. Bareroot Nursery:
In bareroot nursery, plants grow directly in the nursery soil and the roots are separated from the soil at the time of lifting. The lifted planting stock is further handled and planted without soil surrounding the roots.
ii. Container Nursery:
In container nursery, plants are grown with roots in a growing medium held in a container. Roots of lifted plants are covered by the adhering growing medium.
D. On the Basis of Size of Seedlings:
Based on the seedling size, forest nurseries are classified into:
i. Seedling Nursery:
A nursery which has only seedling beds i.e., in which seedlings only are raised, no transplanting being done is called seedling nursery.
ii. Transplant Nursery:
A nursery which has only transplant beds, in which seedlings are transplanted for preparation for forest planting, is called transplant nursery.
In general, separate seedling and transplant nurseries are seldom made.
E. On the Basis of Ownership:
Based on ownership, forest nurseries are classified into:
i. Institutional Nurseries:
They are commonly established, operated and maintained by research institutions, academic institutions, corporations and international organizations. They are permanent in nature but may be larger, medium or small, based on purpose.
ii. Government Nurseries:
They are established and operated by national or local government to support reforestation and community tree planting programmes. They are large in size and are permanent in nature.
iii. Industrial Nurseries:
They are commonly established and operated by large integrated wood based industries. They are large in size with high production capacities and permanent in nature. Seedling production complies with rigid quality standards or specifications.
iv. Project Nurseries:
They are established and managed by projects and nongovernmental organizations (NGOs) or development organizations to promote tree planting culture within target communities. The intended lifespan of project nurseries is usually 3-5 years, but may continue for longer periods.
v. Community Nurseries:
They are established by communities to support tree planting programmes for social benefits.
vi. Group Nurseries:
They are also established to build technical and leadership capacities of group members and expand the number of species and quality of germplasm available to group members.
vii. Individual Nurseries:
They are also known as household nurseries or backyard nurseries and are generally established and managed by individual farmer or household. These nurseries are usually initiated to produce seedlings for planting on operator’s personal farms. The house compound or farmland provides the planting sites. They are normally small in size.
F. On the Basis of Duration of the Use:
Based on the duration of their use, forest nurseries are classified into:
i. Temporary Nursery:
It is a nursery that is maintained for supplying stock for a short period after which it is abandoned. Normally, it is constructed in the plantation area and usually small in size. It is suitable for hilly regions.
ii. Permanent Nursery:
It is a nursery that is maintained for supplying nursery plants for a long time on a permanent basis. It is intended to meet the requirements of one or more ranges and it is relatively larger in extent.
Characteristics of Temporary Nursery:
i. Features:
Temporary nurseries are constructed for a short period of time and smaller in size. Manuring is not necessary and mostly located near/inside the planting area which is appropriate chiefly for casualty replacement. Elaborate soil preparation is not necessary and cost of transportation of seedlings to the planting sites is low. Seedlings of different species for mixed crops are raised. Gap between lifting the stock from the nursery and actual planting is less.
ii. Advantages:
Temporary nurseries are usually constructed in newly cleared sites fairly rich in humus and so, manuring is not required. Eucalyptus nurseries are an exception to the general rules. Minimum trouble with the weeds, destructive insects and diseases are observed. It enables raising of species in their optimum altitudinal zone in hills. Cheap transport of planting stock without any serious damage or shock.
iii. Disadvantages:
They are comparatively costly and difficult to supervise. Proper supervision is not possible as it is made out of way places. Due to lack of irrigation facility, the growth of seedlings is usually slow and heavy mortality is observed.
Characteristics of Permanent Nursery:
i. Features:
Permanent nurseries are fit for large and intensive work and intensively managed areas. It is established where all the facilities are available i.e., easy supervision, communication facilities, labours, etc. Intensive manuring and soil working are done in perpetuity.
It is used for large scale afforestation works, or distribution to the villagers under community and private forestry programme. Large labour forces, tools and equipments are needed. Initial cost of formation is high but is cheaper in the long run. Regular skilled supervision is mandatory.
ii. Advantages:
It supplies varieties of planting stocks such as root-shoot cuttings, grafted plants, layering, budding, container seedlings, etc. Duration of service life is long and production cost is reasonable. It meets the requirement of larger areas/ranges/divisions. Supervision cost is low and can be easily supervised. Plants are raised year after year for a long time on same site.
iii. Disadvantages:
Transportation of seedlings is difficult and costlier and establishment cost is high. Manuring of beds annually and intensive soil working are essential. It requires large labour forces throughout the year which is difficult during agricultural seasons.
Seedling Quality:
The end user and the environmental conditions at the site where the seedlings will be planted determine what kind of seedling is needed. A researcher will require planning stock raised under uniform conditions to ensure that the research results are not confounded by the status of the seedlings. On the other hand, farmers will require seedlings that can survive under hard, dry and nutrient-deficient conditions.
The good looking seedling at the nursery is worthless if it does not survive and grow after planting out. Targeting seedling production to the anticipated field site is important in producing strong healthy seedlings.
Seedlings need to be hardened off and gradually prepared for real-life harsh conditions by withholding water from time to time after they have developed a strong and healthy root system. Insufficient care in the nursery leads to weak and retarded plants with small root systems that will not survive in a harsh environment.
Quality seedlings produced for different sites may look different from each other but they all have one thing in common: a well-developed root system with many root tips from which new roots can quickly develop. In areas with adverse environments such as dry, flooded, saline or nutrient-deficient sites, only well-developed plants have a good chance of survival. Seedlings with deeper root system are preferred for dry areas and larger plants are preferred for weedy sites so that they can outgrow weeds quickly. Many studies have proved that field survival and productivity are related to the quality of the seedling used.
Seedling quality depends on the following parameters:
i. The ability of plant to produce new roots quickly
ii. The speed with which seedlings get anchored in the ground and start assimilating and growing after planting out
iii. A well-developed root system
iv. Sun-adapted foliage
v. A large root collar diameter
vi. A high root: shoot ratio
vii. Good carbohydrate reserves
viii. An optimum mineral nutrition content
ix. The establishment of adequate mycorrhizal or Rhizobium infection
Nursery Planning and Management:
Quality seedling production depends on a sound understanding and implementation of the key principles of nursery planning and management. As with the operation of any forest nursery, planning is essential for a successful and productive nursery. Factors to be taken into account are efficient use of inputs and resources, identifying problems and potential solutions, monitoring progress and working towards nursery objectives.
Nursery plans vary in detail and in implementation. Nursery plan may be formal written documents or a list of informal management guidelines. Generally, project and group nurseries engage in participatory planning, working with stakeholders and members.
Recommended elements of a nursery plan include: site selection, objectives, demand forecasting and target seedling production, inputs and scheduling, contingency plans to respond to unexpected problems, documentation, staff training, promotion and marketing and networking.
Nursery Site Selection:
The selection of an appropriate nursery site is the most important decision affecting the efficient production of good quality plants.
The following are some of the technical factors which need to be considered while setting a nursery:
i. Water Supply:
In order to have the good irrigation facilities, it should be situated near or slightly below the source of adequate water supply. Reliable and adequate water supply is essential. Water source should be near and at the higher level than nursery site. Water should be available throughout the year.
ii. Availability of Suitable Soil:
For raising seedlings in polythene bag (tube), soil of the actual nursery itself is not important. There should be suitable source of soil preferably forest topsoil and sand within easy reach of the nursery. Clayey soils should not be selected as their aeration and drainage is poor and they are liable to crack during summer.
The symbiotic organism (Mycorrhiza and Rhizobium) should be present in soil because most of the trees grow best if their roots are associated with certain symbionts, which help in their nutrition. Mostly these organisms are found naturally but in some cases artificial inoculation are needed.
iii. Access:
Nursery should be situated as centrally as possible with reference to the area to be planted. It should preferably be near residence area for close and regular supervision. Nursery should be near to the plantation site to facilitate easy transportation of seedlings and access road should be usable at all seasons of year.
iv. Aspect:
Slope with South aspect is much warmer and chosen for hill nursery at high elevation while in low elevation north facing slope is chosen.
v. Slope:
The ideal slope is about 5 degree which is steep enough to allow proper drainage. Complete flat land should be avoided; it is likely to become water logged during monsoon rains. Steeper slopes will have to be terraced and very steep slopes should be avoided as it may be difficult to make a nursery bed and path on each side to allow access to the beds.
vi. Exposure to Frost, Strong Winds and Flooding:
At high altitudes, sites which are particularly liable to frost damage should be avoided. Sites exposed to strong winds and with danger of flooding or landslides should be avoided.
vii. Labour Availability:
Labour should be available without difficulty preferably near a village so that labourers need not walk much distance for work.
viii. Availability of Land:
There should be enough land to raise the number of seedlings needed and if possible room for expansion. Legal enquiries should be made about the legal ownership of the land.
Rooted Cuttings in Forest Nursery:
Cuttings rooted in a nursery are commonly set in raised, well-drained beds of friable soil. Before planting cuttings, the lower end may be cut again to ensure that the cut surface is clean. This cut at the base is made just below a node, because generally root formation is best at the nodes. If the bark is thick, it may be sliced or scraped off the base of the cutting to make it easier for new roots to break through.
Push the cuttings into the soil until about 2/3 of the length of the cutting is covered. For cuttings of trees, two buds are allowed above-ground. If they both grow out, the weaker one is removed so that the most vigorous one will form the tree trunk. In the case of shrubs 3-5 buds may be left aboveground and all emerging shoots are allowed to grow. The cuttings may be set at an angle.
A vertically placed cutting tends to produce one dominant shoot, whereas a more horizontally inclined cutting is likely to produce several more or less equivalent shoots. Hence a vertical position is generally preferred for trees and a slanted position for shrubs. The cuttings should not be planted upside down. The cuttings are planted in rows about 25 cm apart with a spacing of about 20 cm in the row. After planting, the bed is watered again.
Cuttings can also be set in pots, but this requires close attention to watering. The soil must be kept moist all the time, but if it becomes too wet the young roots quickly die because of lack of oxygen. In a bed, it is easier to keep the soil moisture between these limits. Shade helps to reduce moisture loss and is essential for cuttings that retain some leaves, also because shade reduces air temperature.
Shelter is also important because it protects the cuttings against drying wind and tends to raise the humidity of the air. Whereas seedlings have a dominant taproot, cuttings form so-called adventitious roots which are basically all equal. In due course some adventitious roots may become much stronger than the others, but the root system does not become as strong as that of a seedling with a taproot.
Stumps:
They are root shoot cuttings of seedlings. Cutting root and shoot is known as stump. Plants with a collar diameter of 1.5-2.0 cm and taproot with a length of not less than 30 cm are selected. Shoots are cut off at 3 cm and all the lateral roots are pruned.
The tap roots should be cut at a distance of 20-30 cm from the collage region. It is most common for propagating teak (Tectona grandis) and gamhar (Gmelina arborea). They are easily planted in the field and are very easy for handling and transportation.
Plant Propagation Structures and Forest Nursery:
The need for enclosed structures varies greatly with the climate. In humid locations, structures may be needed only to provide shade or to keep pests out, whereas under arid conditions enclosures are needed to maintain higher humidity for germinating seed, rooting cuttings and successful grafting.
Although automated misting systems may be desirable, simple structures enclosed in polyethylene, such as polypropagator or polytunnel are low cost and sufficient in most cases where small number of plants are produced.
Some of the important plant propagation structures are presented below:
1. Greenhouse/ Glasshouse:
A greenhouse (also called glasshouse) is a propagation structure in which plants are grown. These structures vary in size based on the purpose and size of plants grown. Greenhouses allow for greater control over the growing environment of plants. Depending upon the level of greenhouse, key factors which may be controlled include temperature, light, water, fertilizer and atmosphere. Greenhouses may be used to overcome the poor growing qualities of a piece of land, such as poor light levels, seasons, or soil infertility. Greenhouses allow certain plants to be grown throughout the year.
A greenhouse is a structure with different types of covering materials, such as a glass, fibreglass, double sheets of polyethylene (PE) film or plastic roof and frequently glass or plastic walls. Several new polycarbonate and acrylic materials are now made for greenhouse coverings. It heats up because incoming visible solar radiation (for which the glass is transparent) from the sun is absorbed by plants, soil and other things inside the building. Air warmed by the heat from hot interior surfaces is retained in the building by the roof and wall.
2. Mist Chambers:
Nursery plants propagated by cuttings are grown in mist chambers and sometimes for germinating seeds. In mist chamber, relative humidity is maintained artificially at high level (95 per cent) with the help of mist installations, which spray water under pressure. Artificial microclimate and high relative humidity facilitates better root initiation and development whereas cooling effect prevents the cutting from drying out.
Higher success rate are found in propagation of hard wood cuttings under mist chamber conditions. Nowadays, mists chamber with fully automatic system and timers are installed which maintains temperature and humidity even in unfavourable environmental conditions.
3. Net Houses:
Net houses are widely used as propagation structure in tropical areas, where artificial heating is not required and artificial cooling is expensive. The roof of net house may be covered with gunny cloth or even with live plant creeper to cut off the solar radiation and to keep the house cool. Different types of shade nets are available in the market for shade purpose. Net houses can be constructed as per need of propagation and therefore size of net houses varies.
4. Poly-Houses:
Poly-house is widely used for propagating off season seedlings which fetch better price in the market. Modern poly-houses are automated for temperature and humidity control to assist propagation. In poly-houses, plants are propagated using pro-trays or poly-bags on ground or benches. In Poly-houses, thermostat, hygrometer, automatic ventilation system is maintained to facilitate microclimate. Irrigation and fertigation systems in poly-houses are automated to provide measured quantity of water and nutrients to plants.
5. Plastic Tunnels:
Plastic tunnel is a simple but effective method of protective cultivation, used by many nurserymen throughout the world. The three feet wide loops which support the polyethylene are made from 0.2 inch diameter wire and are erected at 30 inches intervals. A white translucent polyethylene sheet of 6 feet wide is then stretched over the loops and is fastened to the frame of the tunnel. Plastic tunnels prove effective for seed germination as well as vegetative propagation of nursery plants in winter season.
6. Walk-In Poly Tunnels:
It is constructed for larger operations or larger plants. Walk-in structures like tunnel is made from semi-circular steel rods and covered with polyethylene sheeting.
7. Propagation Boxes:
For small operations and small plants, propagation boxes are sufficient. These boxes can be made to varying specifications according to the purpose. A recommended size is 2 m long, 1 m wide and 0.5-1.5 m high, with a slanting lid. Layers of stones, gravel and rooting substrate are arranged inside the box. The box is completely enclosed in polyethylene, i.e. including the bottom, depends on the conditions and the main use. For propagating cuttings, a complete enclosure is recommended to guarantee very high air humidity.