Forestry & Forest Sciences · Silviculture · also Nursery and Planting Technique, Nursery Management, Reforestation Practice
Raising planting stock and getting it established in the field: nursery layout, containers and media, seedling quality, site preparation, planting and early care.
In the exams: IFoS Forestry Paper I Section A (nursery and planting techniques, grading and hardening, water budgeting); ICAR AICE-JRF 59 Unit 2; ICAR AIEEA-PG Group 09 (nursery and planting technique)
A plantation succeeds or fails in its first two years. The work that decides this happens in two places: the nursery, where planting stock is raised, and the planting site, where the ground is prepared, the plants are put in, and they are kept alive until they can fend for themselves. This subject covers both. It begins with choosing and laying out a nursery, the kinds of nursery and container, growing media and sowing, and the daily operations of shading, watering, feeding and weeding. It deals with the pests and diseases that can destroy a season's stock, and with how seedlings are graded and hardened before they leave. It then moves to the field: site preparation, planting patterns, spacing and pits, planting methods and timing, conserving moisture, and assessing survival and replacing failures.
The subject draws on others and does not repeat them. Silviculture principles explains when artificial regeneration is chosen over natural regeneration; tree seed technology covers seed collection, processing, storage and pre-sowing treatment; forest biotechnology and propagation covers cloning and tissue culture; stand tending covers weeding and cleaning after establishment. Here the focus is the practical sequence from seed to an established young plantation.
The subject is examined in the UPSC Indian Forest Service Forestry optional, which names nursery and planting techniques, grading and hardening, and water budgeting; in ICAR's AICE-JRF and AIEEA-PG forestry papers; in state forest service and range officer examinations, which often ask about nursery layout, bed types, pit sizes and planting patterns; and in professional examinations elsewhere that ask about seedling quality, site preparation and planting practice. Because nursery and planting practice depends heavily on climate, species and local tradition, this manual gives the principles and common practice and says where values vary.
A forest nursery is an area set aside for raising planting stock. Permanent nurseries are large, well-equipped and used for many years, often supplying a whole division or company; temporary or flying nurseries are small and set up close to a planting site for one or a few seasons, saving transport over difficult terrain. The choice of site affects cost and quality for the life of the nursery.
The main criteria are a reliable supply of good-quality water throughout the raising season, because water is the nursery's most critical input; nearly level or gently sloping ground that drains well without eroding; a well-drained, workable soil, usually a sandy loam or loam, if seedlings are raised in beds; freedom from waterlogging, frost hollows and strong winds, with a windbreak where needed; good road access for bringing in materials and dispatching plants; nearness to the planting sites so that plants travel short distances; availability of labour; and protection from grazing animals, theft and fire, usually by fencing. Sites previously used for crops prone to soil-borne diseases, or with heavy weed infestation, should be avoided or treated.
A nursery is laid out so that work flows logically from seed to dispatch. A typical layout includes a seed store and office; a potting shed and an area for mixing and storing growing media; germination or mother beds; standing beds or container areas where plants grow on; a shade house or shade-net area; in clonal nurseries, a mist chamber or propagation house and hedge gardens of stock plants; a hardening-off area in full sun; a compost or vermicompost unit; water storage and an irrigation system; paths wide enough for carts or vehicles; drainage channels; and a dispatch area near the gate. Beds and container blocks are usually oriented and spaced so that workers can reach every plant from the paths.
The area needed is calculated from the number of plants required. The number of plants to raise equals the area to be planted times the number of plants per hectare, plus an allowance for culls in the nursery and for beating up in the field. To plant 50 hectares at 2 m × 2 m (2,500 plants per hectare) with a 20 per cent allowance, the nursery must produce 50 × 2,500 × 1.2 = 150,000 plants. The net bed area follows from the number of plants that fit per square metre, and the gross nursery area adds space for paths, channels and buildings, using a factor set by local experience.
Nursery beds are of three main types. Raised beds, built up above the surrounding ground, drain well and are used in high-rainfall areas and on heavy soils, where waterlogging would otherwise rot roots and favour damping-off. Sunken beds, dug below ground level, conserve water and are used in arid and semi-arid regions, where they collect irrigation water and reduce evaporation and wind damage. Level or flush beds, at ground level, are used where drainage and rainfall are moderate.
Beds are commonly about one to 1.2 metres wide so that workers can reach the centre from the paths on either side without stepping on the bed, and around ten to twelve metres long, though sizes vary with local practice. Beds are separated by paths and, in irrigated nurseries, by channels. Container nurseries use level, well-drained standing areas, often covered with gravel or weed mat, on which containers are placed in blocks, or raised benches and frames that keep containers off the ground so that roots are air-pruned at the base.
In a bare-root nursery, seedlings grow in open beds of nursery soil and are lifted with their roots exposed for transport and planting. Bare-root production is cheap per plant, suits large volumes and is the traditional method for temperate and boreal conifers such as pines, spruces and Douglas-fir, and for many broadleaves. Roots are shaped in the bed by undercutting (cutting the roots horizontally below the seedlings with a blade drawn under the bed) and wrenching (loosening the soil and roots with a tilted blade), which encourage a compact, fibrous root system and harden the plants.
Bare-root stock is vulnerable once lifted: fine roots dry and die within minutes in sun and wind. Lifting is done when plants are dormant, roots are kept moist and cool in bags or boxes, and plants are planted as soon as possible or stored in cold stores under controlled conditions. The planting season is therefore limited to the dormant period or the start of the rains.
In a container nursery each plant grows in its own container filled with a growing medium, and is planted with its root plug intact. Container stock tolerates handling and short delays better than bare-root stock, extends the planting season, and suits dry sites and species with sensitive roots. Polythene bags (polybags) are the commonest container in tropical forestry; they are cheap and widely available. Their drawbacks are serious: roots reaching the smooth inner wall turn and spiral round it, and these coiled roots may persist after planting, leading to poor anchorage, girdling of the stem base and toppling years later; filled bags are heavy to transport; and plastic must be removed and disposed of at planting. Shifting the bags periodically, so that roots that have grown through the base are cut, and pruning spiralled roots at planting reduce some problems.
Other containers include paper pots, biodegradable pots, blocks of compressed medium, and rigid plastic trays of cells of many sizes.
Root trainers are rigid containers, usually moulded plastic cells held in trays or racks, with vertical internal ribs and an open base. The ribs guide roots straight down instead of letting them spiral, and the open base, held above the ground, causes air pruning: root tips that reach the air dry and stop growing, which stimulates the formation of new lateral roots higher up. The result is a compact, fibrous plug without coiling that establishes quickly after planting. Root trainers use a light growing medium, such as composted organic matter, coir pith or vermiculite mixtures, so the plants are light to carry, and the trays are reusable for several seasons.
Root trainer cell volumes are chosen by species and planting site, with larger cells for slower-growing or drought-site stock; specific sizes vary between manufacturers and programmes. Root trainers are used widely in India and elsewhere for eucalypt and other clonal stock and increasingly for native species. They need more careful watering than polybags because the small volume of light medium dries quickly, and they require an initial investment in trays and stands.
Some species are planted as stumps (root-shoot cuttings): a seedling grown in the nursery bed is lifted, and its shoot and root are trimmed to leave a short shoot above the root collar and a longer section of tap root. Teak is the classic example; stumps are made from seedlings about one to two centimetres thick at the collar, with a root portion of roughly 15 to 25 centimetres and a shoot of a few centimetres, though local specifications differ. Stumps are cheap, light, easy to transport and plant with a crowbar, and resist drought because the thickened root stores reserves. Other forms of planting stock include cuttings and sets (unrooted stem cuttings of poplars and willows planted directly), wildings (naturally regenerated seedlings collected from the forest), and clonal plants produced from rooted cuttings or tissue culture, covered in forest biotechnology and propagation.
A growing medium must hold enough water, drain well enough to keep air in the root zone, supply or retain nutrients, support the plant, and be free of pathogens, pests and weed seeds. In tropical polybag nurseries the medium is traditionally a mixture of forest or field soil, sand and well-decomposed farmyard manure or compost in proportions set by local experience; soil gives body and nutrients, sand improves drainage and aeration, and organic matter improves water holding. Heavy clay soils compact in containers and should be avoided or improved.
Root trainers and other small containers need lighter, soil-less media because soil compacts in small cells: mixtures of composted bark or organic matter, coir pith (the fibrous waste of coconut husks, widely used in South Asia), vermiculite and perlite, sometimes with a slow-release fertiliser. Peat has been the standard medium in temperate container nurseries, but because peat extraction damages wetlands and releases carbon, many nurseries are moving to alternatives. Media and soil can be disinfested by solarisation (covering moist soil with clear plastic in hot sun for several weeks), by steam or by approved chemicals, to reduce damping-off fungi, nematodes and weeds.
Seeds are sown by broadcasting over a bed, by sowing in lines or drills, or by dibbling individual seeds into the medium. Large seeds are often sown directly into containers, one or two per container, with surplus germinants thinned out later. Small seeds are usually sown in germination beds or trays and the young germinants are pricked out, that is, transplanted carefully into containers or standing beds at an early stage, typically when they have their first pair of true leaves. Pricking out uses seed efficiently and allows selection of vigorous germinants, but must be done in the shade with minimal root damage.
Seeds are covered to a depth related to their size; a common rule of thumb is to cover them to about one to two times their own diameter, with very fine seeds left barely covered. The covering may be sieved soil, sand or a fine medium. Many species need pre-sowing treatment to overcome dormancy, such as soaking, hot-water treatment, mechanical or acid scarification, or cold moist stratification; these are covered in tree seed technology. The sowing season is timed so that plants reach plantable size at the planting season.
The quantity of seed is calculated from the number of plants required, the germination percentage and the expected survival in the nursery. The number of seeds needed equals the plants required divided by the product of germination fraction and nursery survival fraction. To produce 10,000 plants from seed with 60 per cent germination and 80 per cent survival through the nursery stage requires 10,000 ÷ (0.6 × 0.8) = 20,833 seeds. If the species has 5,000 seeds per kilogram, the seed needed is 20,833 ÷ 5,000 = 4.2 kilograms. Germination percentage should come from a recent test of the actual seed lot, because it falls during storage. Purity, the proportion of the seed lot that is pure seed of the species, is applied in the same way when it is below 100 per cent.
Germinants and young seedlings of many species are damaged by full sun and high temperatures, so they are shaded in the early stages with shade nets, thatch or lath screens. Shade nets are rated by the proportion of light they block. Shade is reduced gradually as plants grow and removed completely during hardening, because plants raised in deep shade are soft and suffer badly when planted in the open. Light-demanding species need little and brief shade; some shade-tolerant species need more. Shade also reduces watering needs and protects seedlings from heavy rain.
Watering is the most frequent and most critical nursery operation. Seedlings need enough water to keep the medium moist but not saturated; overwatering leaches nutrients, starves roots of air and encourages damping-off, while underwatering stunts growth and kills germinants. The amount and frequency depend on the weather, the stage of growth, the medium and the container: small root trainer cells with light media dry far faster than polybags of soil. Watering is best done in the early morning or late afternoon to reduce evaporation and leaf scorch, using fine roses or mist for germinants and sprinklers, booms or drip systems for larger stock. Water quality matters: saline or alkaline water damages seedlings and should be tested before a nursery is established.
Seedlings in containers depend on the nutrients in the medium and in added fertiliser. Nitrogen, phosphorus and potassium are supplied by incorporating fertiliser or manure in the medium, by top-dressing, or by fertigation, applying dilute soluble fertiliser with the irrigation water. Slow-release fertilisers supply nutrients gradually. Nitrogen promotes shoot growth in the active growth phase; in the hardening phase nitrogen is reduced so that shoots stop elongating and tissues lignify, while potassium and phosphorus support root growth and hardiness. Symptoms such as yellowing, purpling or stunting indicate deficiencies but can also arise from poor drainage or root disease, so diagnosis should be careful.
Many tree species depend on mycorrhizal fungi. Pines and other ectomycorrhizal species raised in sterile media or in areas without suitable fungi grow poorly; they are inoculated with soil or litter from established stands of the same species or with commercial spore or mycelium inoculum. Many tropical broadleaves form arbuscular mycorrhizas, and legumes form nodules with nitrogen-fixing rhizobia, which can also be supplied by inoculation.
Weeds compete with seedlings for light, water and nutrients and harbour pests. They are controlled by using weed-free media, by hand weeding while weeds are small, by mulching beds, and by approved pre-emergence herbicides where they are permitted. Other routine operations include thinning crowded germinants, shifting containers so that roots growing out of the base are cut and do not anchor in the ground, root pruning, grading plants into size classes so that small plants are not suppressed by larger neighbours, and keeping a nursery register of sowings, treatments, stock and dispatches.
Damping-off is the commonest and most destructive nursery disease. It is caused by soil-borne fungi and water moulds, chiefly species of Pythium, Rhizoctonia, Fusarium and Phytophthora. In pre-emergence damping-off, seeds or germinants rot before they appear above the surface, which can be mistaken for poor germination. In post-emergence damping-off, young seedlings develop a water-soaked, shrunken lesion at the stem base at soil level and collapse; patches of the bed die outward from a centre. The disease is favoured by wet, poorly drained, compacted media, overwatering, crowding from dense sowing, high humidity, heavy shade, warm temperatures and alkaline media.
Control is mainly preventive: well-drained, disinfested media; clean containers and tools; sowing at the correct density; moderate watering; adequate ventilation and light; and removal of infected seedlings with their medium. Seed treatment and drenches with approved fungicides are used where the disease is persistent and products are permitted. Once seedlings have developed woody stems, they are no longer susceptible.
Root rots caused by Fusarium, Phytophthora and other fungi kill older seedlings, especially in waterlogged media. Leaf spots, blights, powdery mildews and rusts attack foliage; in eucalypt nurseries in India and other tropical countries, leaf and seedling blight caused by Cylindrocladium (now also placed in Calonectria) is a major disease in warm, humid conditions, controlled by spacing, ventilation, avoiding wet foliage overnight and approved fungicides. Clonal nurseries must also guard against spreading disease through infected stock plants and cuttings. Healthy stock, hygiene and good growing conditions prevent most nursery disease.
Soil insects are serious nursery pests in many regions. White grubs, the larvae of scarab beetles, eat roots and can destroy beds; termites attack seedlings, especially in dry areas and in organic media; cutworms sever stems at night; crickets and grasshoppers eat seedlings. Foliage feeders include caterpillars, beetles, aphids, mites and scale insects, and nematodes damage roots in some soils. Birds and rodents eat seeds and germinants, and in many places cattle, goats and wild animals browse nursery stock if fencing fails.
Integrated pest management combines prevention (clean media, fencing, netting of seedbeds, removal of weeds and debris), regular inspection to detect problems early, physical and biological controls, and chemical control with approved products only when needed. Pesticide use in nurseries is regulated nationally, and certification standards restrict some products.
A good planting stock survives and grows well after planting on the intended site. Quality is judged first by morphology. Height should be adequate to compete with weeds but not so great that the shoot outgrows the root's ability to supply water. Root collar diameter, the stem diameter at the junction of root and shoot, is one of the best single predictors of survival and growth. The sturdiness quotient, height in centimetres divided by root collar diameter in millimetres, measures how stocky the plant is; lower values indicate sturdier plants, and values below about 6 are often recommended, though targets vary by species. A seedling 30 cm tall with a 4 mm collar has a sturdiness quotient of 30 ÷ 4 = 7.5, which is somewhat spindly.
The shoot-to-root ratio, usually on a dry-weight basis, compares transpiring shoot with absorbing root; a balanced ratio, often in the range of about 1 to 2 for many species, is preferred for dry sites. The Dickson quality index combines these measures: total dry weight divided by the sum of the sturdiness quotient and the shoot-to-root dry-weight ratio. A seedling with a total dry weight of 6 g, a sturdiness quotient of 7.5 and a shoot of 4 g on a root of 2 g has an index of 6 ÷ (7.5 + 2) = 0.63; higher values indicate better quality. Root form matters too: a fibrous root system without coiling, kinking or J-shaped tap roots, and a straight single leader, healthy foliage and terminal bud.
Plants that look similar can differ greatly in physiological condition. Root growth potential, the ability to grow new roots in a standard test environment over a set period, indicates how quickly the plant can establish contact with the soil after planting. Cold hardiness, measured by freezing tests or electrolyte leakage, is critical in temperate and boreal nurseries. Plant water status, carbohydrate reserves, nutrient concentrations and dormancy status also affect performance. Physiological tests are used routinely in some large temperate nurseries and in research; in many tropical nurseries quality is still judged mainly by morphology and experience. The target seedling concept defines the morphological and physiological characteristics that give high survival and growth on a particular planting site, so that nursery practice is tailored to the site.
Before dispatch, plants are graded: each is inspected and sorted into grades, and culls (plants that are too small, spindly, deformed, diseased, with damaged or coiled roots, or with multiple leaders) are discarded. Grading standards, such as minimum height and collar diameter for each species and stock type, are set by nursery programmes. Culling seems wasteful but planting poor stock wastes far more, because poor plants die or grow slowly and must be replaced. Graded plants are counted, packed and labelled with species, seed source or clone, and date.
Hardening off prepares nursery plants for the harsher conditions of the planting site. Over several weeks before dispatch, shade is removed, watering is reduced in frequency, nitrogen is reduced, and plants are exposed to full sun and wind in a hardening area. The plant's growth slows, the terminal bud forms, the stem and roots lignify, the cuticle thickens and carbohydrate reserves build up, so the plant tolerates drought, sun and handling better. Hardening must not go so far that plants are damaged or that roots die from drying. Plants that have not been hardened, especially soft, shade-grown, heavily fertilised stock, often fail in the first dry spell after planting.
Site preparation is the treatment of the planting site before planting to give the young plants the best start. Its aims are to remove or reduce competing vegetation; to deal with logging slash and debris that hinder planting or add to fire risk; to improve the physical condition of the soil at the planting spot by loosening compacted layers, improving drainage on wet sites or water capture on dry ones; to raise soil temperature and nutrient availability at the planting spot; to reduce populations of pests such as root-feeding insects; and to make planting faster and easier. The intensity of preparation is matched to the site: too little leaves the plants to fail, too much wastes money and can cause erosion, nutrient loss and damage to soil structure.
Slash and vegetation are treated by manual clearing, cutting and lopping, chopping or crushing with machines, piling into windrows, or controlled burning, which removes fuel and releases nutrients but can damage soil organic matter and is restricted in many places. Herbicides may be applied before planting where permitted. Soil is worked manually by hoeing, digging pits or cultivating patches, or mechanically by ploughing, disc harrowing, ripping or subsoiling (breaking compacted layers or hardpans with a tine drawn deep through the soil), mounding (creating raised planting spots on wet or cold soils), bedding (forming continuous raised beds on poorly drained flat sites, as in parts of the south-eastern United States), and scarification (exposing mineral soil in patches or furrows, as with disc trenchers in boreal forests). Each method suits particular soils and climates, and mechanical methods need slopes gentle enough for machines.
In the hills and on erodible land, all soil working should follow the contour so that it catches water and soil instead of channelling them downhill. On steep slopes, preparation is restricted to small patches or pits around planting spots, and the vegetation between is left to protect the soil.
In dry regions and on degraded land, site preparation is combined with structures that harvest rainwater and conserve soil. Contour trenches, continuous or staggered, intercept runoff and store it in the soil beside the planting line. V-ditches and contour bunds serve the same purpose. Saucer-shaped basins and crescent-shaped bunds (half-moons) around individual plants collect water from a small catchment above them. Micro-catchments, such as the diamond-shaped Negarim catchments used in arid zones, direct runoff from a larger area to a planting pit at the lowest point. Narrow terraces cut across steep slopes, sometimes called gradoni, provide level planting strips. These works are chosen by rainfall, slope and soil, and their dimensions are set in local soil conservation manuals.
The planting pattern is the geometric arrangement of plants on the site. In square planting, plants are at the corners of squares, with equal distances between and within rows; it is simple to lay out and allows cultivation in two directions. In rectangular planting, the distance between rows is greater than within rows, allowing machines, intercrops or agroforestry crops between rows. In triangular planting, plants are at the corners of equilateral triangles, so every plant is the same distance from its six neighbours; this uses space evenly and fits about 15.5 per cent more plants per hectare than square planting at the same spacing. In quincunx planting, a square pattern has an extra plant at the centre of each square, often a temporary filler or nurse species that is removed later. Contour planting follows the contour lines on slopes, with spacing measured along the contour, and is combined with contour trenches and bunds. Line planting places plants in lines through existing vegetation, as in enrichment planting, and cluster or group planting places several plants close together at each planting point.
Spacing decides the number of plants per hectare and influences survival, early growth, crown closure, branch size, stem form, the need for weeding and thinning, and cost. For square spacing, the number of plants per hectare is 10,000 divided by the square of the spacing in metres; at 3 m × 3 m it is 1,111. For rectangular spacing it is 10,000 divided by the product of the two distances; at 4 m × 2 m it is 1,250. For triangular spacing with distance s between neighbours, the number per hectare is 10,000 divided by 0.866 s squared; at 3 m it is about 1,283, compared with 1,111 for a 3 m square. For quincunx planting at a square side of 4 m, there are two plants per 16 square metres, or 1,250 plants per hectare.
Close spacing gives early canopy closure, which suppresses weeds and promotes natural pruning and straight stems, but costs more to plant and needs earlier thinning. Wide spacing is cheaper and suits fast-growing species, agroforestry and dry sites where water is limiting, but gives larger branches and longer weed control. Spacing is chosen according to species, site, product, management intensity and cost; local plantation manuals give recommended spacings for each species.
In tropical and dry-zone planting, plants are usually set in pits. Pit size depends on the stock and the soil: small pits, such as 30 cm × 30 cm × 30 cm, for small container plants in good soils; larger pits, such as 45 cm or 60 cm cubes, for larger stock, hard or compacted soils, arid sites and avenue planting. A 45-cm cube pit contains 0.45³ = 0.091 cubic metres of soil; 1,111 such pits per hectare involve moving about 101 cubic metres of soil, which shows why pit size drives planting cost. Pits are dug ahead of planting, often some weeks before the rains, so that the soil weathers, and are refilled before planting with the topsoil, sometimes mixed with manure, compost or fertiliser, and with the subsoil placed at the surface or used to make a bund. Augers dig pits quickly where the ground allows. In temperate and boreal forests, small seedlings are often planted in notches or screefed patches without pits.
Pit planting is the standard method in the tropics: the container plant is placed in the refilled pit so that the root collar is at or slightly below ground level, the polybag or other non-biodegradable container is removed carefully without breaking the root ball, soil is firmed around the plug, and a slight depression is left to collect water. Notch planting is used for small bare-root seedlings, especially conifers in temperate and boreal forests: a spade or planting bar opens a slit (with variations such as T-notch and L-notch), the roots are inserted to the correct depth, and the slit is closed by heeling in. Container plugs from root trainers are planted with a dibble or tube planter that makes a hole of the right shape. Stumps are planted in holes made with a crowbar, with the soil firmed around them. Mound planting places plants on prepared mounds on wet sites, and mechanical planters are used on large, level sites.
Good planting depends on details: roots must not be bent upward into a J or L shape, exposed or crowded; the plant must be upright and firm; the root collar at the right depth; and roots must never dry out between the nursery and the planting hole. Planting quality is checked by inspectors who lift a sample of plants to see root placement and depth.
Plants are most vulnerable during transport and the few days before planting. Container plants are watered thoroughly before dispatch, transported in shaded, ventilated vehicles, unloaded carefully, and kept in shade and watered at the site until planted. Bare-root plants are kept in bags or boxes with moist packing, out of sun and wind, and planted the same day or kept cool. Plants should be carried in trays or buckets, not by the stem, and roots should never be left exposed to the air.
The best planting time is when the soil is moist and will stay moist long enough for roots to grow into it, and when temperatures allow root growth. In monsoon climates planting is done after the onset of the rains, once the soil has been thoroughly wetted to a good depth, and early enough in the season that plants can establish roots before the dry season; planting late in the monsoon gives plants too little time. In regions with two rainy seasons, planting may be done in either. In temperate and boreal regions, bare-root stock is planted while dormant, in spring after the soil thaws or in autumn, avoiding frozen, waterlogged or dry soil; container stock allows a longer season. Planting on hot, dry or very windy days, or into dry soil, should be avoided. Planting schedules are planned backwards to set sowing dates in the nursery.
In dry regions and in the first dry season after planting, water is the main cause of failure. Moisture conservation reduces losses by evaporation and competition and increases the water that reaches the root zone. Weeding around plants, especially of grasses, is the single most important measure, because weeds transpire soil water that the plant needs. Mulching the planting spot with cut weeds, crop residues, stones or sheets reduces evaporation and soil temperature and suppresses weeds. The water-harvesting works described under site preparation, such as saucer basins, half-moons, contour trenches and micro-catchments, increase the water stored in the soil around plants. Water-absorbing polymers (hydrogels) mixed into the planting pit are promoted to hold water, but field results vary and their cost-effectiveness depends on site and product.
Where rainfall is inadequate or unreliable, and in urban, roadside and high-value plantings, plants are irrigated during establishment. Life-saving irrigation supplies water during the first dry season or during drought spells to keep plants alive until their roots reach deeper moisture. Methods include watering by hand or from tankers into the basin around each plant; pitcher or pot irrigation, in which a porous clay pot buried beside the plant and filled with water releases it slowly; deep-pipe irrigation, in which a vertical pipe delivers water to the deeper root zone; and drip irrigation, which supplies small amounts frequently through emitters and is efficient but needs investment and protection. Irrigated plantations of fast-growing species on farms and industrial sites may be irrigated for several years.
Water budgeting estimates how much water establishment will need and whether it is available, so that the plantation can be planned within the water supply. The total requirement is the water per plant per application times the number of plants times the number of applications. If each of 1,111 plants needs 5 litres a week for a 20-week dry season, the requirement is 5 × 1,111 × 20 = 111,100 litres, or about 111 cubic metres per hectare. The calculation is compared with the water available from tanks, wells or tankers, its cost and transport, and the labour needed. Budgets also consider losses in delivery, the timing of rains, and how the requirement falls as plants root deeper. Where the water budget cannot be met, species choice, spacing, planting time and moisture conservation works must be adjusted, rather than planting more than can be kept alive.
The success of planting is measured by survival and early growth. Survival is assessed by counting live and dead plants, either on every planting point in small plantations or on sample lines or plots in larger ones, after the first rains and growing season and again before the next planting season. Survival percentage is the number of live plants divided by the number planted, times 100. If 2,500 plants were planted on a hectare and 1,950 are alive, survival is 1,950 ÷ 2,500 = 78 per cent and 550 plants must be replaced to restore full stocking. Assessments also record the condition of survivors (healthy, browsed, diseased, suppressed by weeds), the causes of mortality where they can be identified, and the height of a sample of plants. The results are entered in the plantation journal, which records the history of every plantation from site preparation onward.
Stocking surveys, which record whether each of a set of small plots contains at least one acceptable plant, are used in some countries to judge regeneration success, because survival percentage alone does not show how evenly the plants are spread over the area.
Common causes of failure are drought and late planting; poor planting stock (unhardened, spindly, coiled-root or diseased plants); poor handling (roots dried in transport); poor planting (J-roots, wrong depth, loose soil, polybag left on); weed competition; termites, white grubs and other pests; browsing and grazing by livestock and wild animals; fire; frost; and waterlogging. Identifying the cause matters, because simply replanting without correcting it repeats the failure.
Beating up, also called casualty replacement, filling or gap filling, is the replacement of dead or missing plants to restore full stocking. It is usually done at the start of the next planting season, or later in the same season if early rains allow, using healthy plants of the same species and, where possible, of a size that can catch up with the survivors; for this reason nurseries raise a reserve of plants for beating up. Beating up late, after the surviving plants have grown well ahead, is often wasteful, because the replacements are suppressed. Where survival is very low, the area may need complete replanting, and where it is high and the missing plants are scattered, beating up may be unnecessary because the survivors will occupy the space. Many forest departments set survival standards that a plantation must reach before it is considered established; their values differ between agencies and regions.
A student should be able to lay out a small nursery on paper, choose bed types for wet and dry sites, prepare a growing medium, sow and prick out seedlings, and recognise damping-off. Practise the calculations: plants to raise with allowances, seed quantity from germination and survival, plants per hectare for square, rectangular, triangular and quincunx patterns, pit soil volume, sturdiness quotient and Dickson index, water budgets and survival percentage. In the field, plant container seedlings and stumps correctly and check planting quality by lifting plants.
A range or plantation officer five years into service runs nurseries and planting programmes: estimating stock needs, scheduling sowing so plants are ready for the rains, managing watering, shading and pest control, grading and hardening stock, organising site preparation and pit digging ahead of the season, training planting crews, inspecting planting quality, budgeting water for dry-season irrigation, assessing survival and arranging beating up, and keeping the nursery register and plantation journal.
A senior forester with twenty-five years' experience plans planting programmes at division or company level: deciding stock types and nursery capacity, investing in root trainers or clonal facilities, setting grading and survival standards, choosing site preparation methods that balance cost, establishment and soil protection, and reviewing survival records to find and correct systematic causes of failure. The senior forester also negotiates with communities over grazing and fire protection, on which plantation success often depends.
A researcher with long field experience studies how nursery practice and planting affect field performance: seedling quality and physiology, root development in different containers, media alternatives to peat, nursery nutrition and mycorrhizas, site preparation effects on soil and growth, water harvesting and irrigation efficiency, and the causes of establishment failure across sites and climates. Such work produces target-seedling specifications and planting guidelines.
This manual gives nursery and planting principles and common practice; it does not give species-by-species sowing seasons, seed rates, container sizes, grading standards, spacings or pit sizes, which belong to silviculture-of-species and to local nursery and plantation manuals. Seed handling and pre-sowing treatments are covered in tree-seed-technology, and cloning and tissue culture in forest-biotechnology-propagation. Fungicide, insecticide and herbicide products, doses and approvals are national and label matters and are not given. Dimensions of soil and water conservation works are left to local manuals. Survival standards for plantation acceptance differ between agencies and are not tabulated.
Original practice questions written to the syllabus and pattern of the exams named in each question's examTags. They are not past papers and do not reproduce any board's questions.
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