Monitoring soil moisture status

Moisture in nursery soils is monitored by estimating soil moisture content. Several methods used for this are:

Gravimetric method

Here, soil samples are randomly collected from the plough layer with a soil auger or sampling tube. Samples are then placed in per-weighted metal containers, weighed and tied to constant weigh in an oven at 105ºC for 12 hours. Samples are re-weighed after drying, and the percentage of total soil moisture content by weight(%TSMC) is computed. The gravimetric method works well in most nursery soils because of their homogeneity, however it normally takes too long for every day use.

Neutron probe

The neutron probe can indirectly measure%TSMC(wt)if bulk density is known. High energy neutrons are emitted into the soil from a radio active source contained in the probe. The neutrons are slowed down and thermalized by elastic collisions with other nuceaui. Because the slowing down or moderating of the neutrons is caused almost entirely by hydrogen nuclei in soil water, the number of thermal neutrons detected per unit time is directly proportional to the %TSMC (Wt). Though accurate, neutron probes are expensive and cumbersome and require highly trained, licensed personnel for their operation.


Tensiometer can only provide indirect inferences about internal seedling moisture stress. A Tensiometer is basically a porous cup filled wit water which is buried in the soil and connected to a vacuum gauge. This gauge registers the pressure drop on the water in the cup which is in equilibrium with the metric potential of the soil water. Tensiometer generate well in the 0 to 0.8 bar range and they are ideal for monitoring irrigation in forest-tree nurseries. However, when metric potential drops below-- 0.8 bar, air begins to enter the porous cup, and the Tensiometer becomes inoperative.

Electrical resistance

Sensors containing a pair of electrodes, usually in blocks or sandwiches made of gypsum, plaster of pairs, or fiber glass cloth are planted in the soil at specified depth to directly measure metric potential. As the water content of these blocks changes with soil moisture contents, the electrical resistance meter connected to these electrodes converts the resistance to an index of soil moisture content. Resistance blocks are sensitive over a –0.5 to –0.15 bar range of matrix potential and are therefore effective in dry soils.

The electrical resistance is calibrated against soil moisture content by the gravimetric method, and plotting a curve relating the true soil moisture content to the electrical resistance reading.

Soil moisture retention curves

Soil moisture retention curves which illustrate the relationship between the percentage of soil moisture by weight and matrix potential of a soil. These curves must be developed for each soil type at the nursery and can be obtained from most soil laboratories. Soil samples should be collected from the plough layer of the nursery field.

Monitoring irrigation

To monitor completely, managers must rely on:

Soil moisture retention curves for individual nursery soils

An effective procedure for rapidly assessing soil moisture status

An accurate means of monitoring seedling moisture stress

An understanding of seedling response to irrigation

Irrigation in the nursery is usually provided by an atomizer, watering can, percolation method, flooding, border/strip, furrow, sprinkling method, and drip method


It is a type of pump by which water is applied in the form of small droplets. This type of irrigation is very useful in species that have very minute seed, e.g. Eucalyptus, Adina etc. Irrigation by atomizer should be done till seedlings attain a height of 10 cm. This system delivers a very fine, uniform water coverage as long as strong winds do not blow the mist off designated beds. This type of mist irrigation is ideal for propagation beds because the fine drops do not pack germination medium or wash the seeds away. Mist systems require about 280 to 350 g/cm2 of water pressure for each nozzle.

Watering can

The use of watering can for irrigation is very popular in most of the nurseries. This method is useful for almost all species including those with very minute seeds. The method is useful both for the irrigation of beds as well as potted plants. In this method, the economy in the use of water can be maintained.

Percolation method

In percolation method water is allowed to stand around raised narrow beds so that, water percolates to the center of the beds from the sides.

Flooding method

This method is not good fro minute seeds. Flood irrigation systems can only be operated on land with very gentle topography because large areas must be uniformly supplied with water from irrigation ditches.

Border irrigation

This method is similar in many respects to flood irrigation expect that each strip is subdivided into sub strips. Water is then allowed to enter into each strip until the main strip is completely irrigated.

Furrow irrigation

It differs from both the flood and border systems. Here the water is run into furrows which are made either by cultivating the rows for the crop or by digging special shallow ditches between the crop rows.

In a flood, border and furrow systems water is allowed to enter the surface of the land from a nearby irrigation ditch. As a result they can only be employed on relatively flat terrain. None of these systems are particularly satisfactory for most of the water management objectives.

Sprinkling method

It is becoming popular in our nurseries. In most of the cases, water is still applied by the ditch with flood, border or furrow methods as in the past. With the development of highly efficient mechanical pumps and turbines in the 20th century, sprinkler irrigation systems came into common use for nurseries in the developing countries and are now universally used in nursery practice. The method involves greater costs but it is one of the best methods of irrigation as it affects the economy in water use and uniform water distribution. Sprinkler irrigation is completely different from the ditch methods in that, mechanical turbines or pumps are is used to pressurize a pipeline system that delivers water at a specific head pressure to sprinkler spaced so that their spray stimulates rainfall. Sprinkler irrigation is almost always used on bare root nurseries. It satisfies all the purposes of water management listed earlier. Sprinkler systems have a considerable advantages over all other irrigation systems because they can be calibrated for use on almost any soil type, can deliver the exact amount of water needed for any water management purpose, and can be used on uneven terrain. The main disadvantages are that their water distribution is readily affected by winds, their high initial capital cost and higher maintenance costs and power requirements than other systems.

Drip method

In this method, water is supplied through small tubes in drops. The flow continues throughout. The advantage with this method is that only a small area of surface soil is wetted and that soil is nearly always maintained at field capacity.

There is no regular prescription about the number of irrigation to be provided. It will depend upon the species, type of soil, season, climate, etc. Different species have different water requirements. Teak nursery requires a lesser number of irrigation compared to Eucalyptus, poplars, etc. which require more water than several broad-leaved species.

Sandy soils require more irrigation than clayey soils. Soils rich in organic matter absorb more water and therefore, less irrigation may be required in the soil. More irrigation is required in summer.. Normally, two irrigation per month during winter and three to five irrigation per month during summer may be considered good or best of the species. However, in arid areas, more number of irrigation is required during Summer

The choice of irrigation method depends upon the source of irrigation, size of the nursery, availability of the manpower, funds etc. Every method has its own merits and demerits. The selection of proper systems can be done by looking at these factors. Irrigation is usually recommended to be done in the afternoon but in a place where frost and damping-off are feared, it may be done in the morning.

An abundant source of water required to meet irrigation requirement is an important component of any nursery. This source must be able to meet the demand for all water requirement regardless of season, severe irrigation need and water requirements for other purposes. Water sources for bare-root nurseries are usually streams, rivers or wells on or near the nursery property. In order to estimate the quantity of water to apply in one month, the following formulae can be used.

Water quantity = Water lose factor x Area of seed bed x Monthly evapotranspiration

where water loss factor varies between 1.2 to 1.4, averaging 1.3.

Soil texture and depth, depth of root development and soil moisture content govern the amount of water to be applied in any irrigation. To irrigate a nursery crop scientifically, nursery staff may need the following information to compute the amount of water to be applied.

1. The average depth of the plant layer (Conventionally this has been 18 cm).

2. The bulk density (BD)

The BD of most of the bare root nursery soils averages 1.3 g/cm3, ranging from 0.9 g/cm3 in sands to 1.6 g/cm3 in clay loams. The soil moisture retention curve is the per cent total soil moisture content by weight (TSMC by wt) plotted over soil moisture tension per cent at field capacity (-0..1 bar) n=and upper limit of dryness between (-0.5 and -0.75 bar). From the information, the amount of irrigation required to maintain the soil within the optimum moisture range fro growth can be calculated.

Determining nursery water requirements

Before a new nursery is established, it is essential to estimate or calculate the water requirements for all potential water-management purposes. This can be done either by consulting tables showing the average water requirements in various regions or by obtaining climatic data from a station at or near the proposed nursery site and computing seasonal and annual water requirements.

Water requirements from table

The average amount of water needed to produce forest tree nursery in any region is approximately similar to that needed for agricultural crops, so the tables giving the average annual irrigation requirements of agricultural crops may be obtained from local agricultural extension agencies.

Water requirements from climatic data

Computing the water requirements of a bare root nursery from climatic data recorded at or near the nursery site is preferable to relying on annual tables used for agricultural crops. To do this, it is best to obtain due monthly means of precipitation and temperature for as many previous years as possible, or at least for mean and extremely dry years.

The amount of water required to maintain nursery soil is within an optimum range of available soil moisture levels throughout the growing season each year. The irrigation needed for a given bare root nursery can readily be estimated by water balances for all years in the past by the Thornthwate method.

Thornthwate formulae = 1/6 (10 t/I)a

Water quality is defined in terms of the elemental composition and concentration of salts dissolved in the irrigation water. The ratio of precipitation to potential evaporate-transpiration varies seasonally in arid and semi-arid climates. Salinity is a common problem in poorly managed container nurseries when fertilizer salts are allowed to build up in the medium without adequate leaching, but is not usually a problem in bare-root nurseries. Salts injure bare rootstocks in the following ways.

  1. by increasing the osmotic pressure of the soil solution, causing stress and drought
  2. by decreasing soil permeability owing to lose, soil structure and aggregation caused by the deflocculation of soil colloids (particularly in clays)
  3. by direction toxicity from sodium, chloride, borate, other ions and
  4. by the change in nutrient availability owing to changes in pH

Osmotic stress

The following values are often used to access the effects of salts on growth

Salt hazard

Conductivity (micro mhos/cm)


< 250





Very high



PGS is a quality assurance initiative that is locally relevant, emphasizing the participation of stakeholders, including producers and consumers and operate outside the frame of third party certification. A group of farmers agrees to practice organic farming in conformity to a set of locally adopted organic standards with accepted procedures for documentation, review, certification, and marketing.

Basic Elements of PGS

  • Participation
  • Shared vision
  • Transparency
  • Trust
  • Horizontality
  • National Networking

PGS National Standards for Organic Production

General requirements

  • Habitat management
  • Habitat management is an important part of organic management
  • Diversified plants/trees on bunds and other non-cultivated areas of the farm
  • Planting of nitrogen-fixing trees
  • Creating rainwater harvesting pits and farm ponds


  • Ensure a balanced nutrition of the soil
  • Combination of mixed cropping, intercropping, relay cropping and rotation with legumes
  • Use of trap crops and barrier crops

Integration of animals/livestock

  • Integrate crop production with livestock rearing

Conversion period it is the time required by the conventional farm to attain PGS organic status

  • The whole farm including the crop production and animal husbandry shall be converted to organic management
  • Parallel or part conversion is not allowed under PGS
  • The conversion period shall be not less than 24 months for seasonal and annual crops
  • It shall be not less than 36 months in case of perrenial and permanent crops from the last date of use of prohibited inputs or from the date of taking the pledge, whichever is later
  • Regional controls may allow conversion in phases, but the entire farm holding of the group members must be brought under PGS organic management within 24 months of joining the group
  • The duration of the conversion period can be reduced to 12 months if no prohibited substances have been used for the last three years.
  • Conversion period for animals provided they are fed with fully organic feed and fodder.

Contamination control

  • All organic production units shall have effective measures to check accidental contamination with prohibited substance through drift
  • All organic farms shall be either protected with a biological fence or maintain a buffer zone
  • Organic farms also need to be protected from contaminated water flow from adjoining non-organic fields by adopting proper measures

Soil and water conservation

  • Measures should be taken to prevent soil erosion, salinization of soil, excessive and improper use of water and the pollution of ground and surface water
  • Clearing of land through the means of burning organic matter eg. Slash and burn, straw burning shall be restricted to the minimum.

Standard requirements for crop production

Selection of seed and planting material

  • Seeds and planting material varieties should be well adapted to the soil, climate conditions
  • Suitable for organic management, resistant to pests and diseases and preferably of organic origin
  • In case organically grown seeds are not available then, chemically untreated conventional materials shall be used
  • Genetically engineered seeds, pollen, transgenic plants or planting material are not allowed.

Manuring or fertilization

  • On-farm bio-degradable material of microbial, plant or animal origin
  • Green manuring, intercropping or crop rotation with legumes shall be an integral part of cropping system
  • Off-farm/purchased bio-degradable material of microbial, plant or animal origin
  • Microbial preparations such as bio-fertilizers, bio-dynamic preparations, EM solutions, etc.
  • Off-farm /industry produced inputs approved by NPOP accredited CB as approved input for use in organic farming can be used
  • Mineral fertilizers shall be used in their natural powdered form as a supplementary source of nutrients
  • The use of synthetic fertilizers is strictly prohibited in any form, directly or indirectly.

Pest, disease and weed management including growth regulators

  • Selection of pest and disease-resistant varieties, suitable crop rotations, green manure crops, balanced fertilization
  • Early planting, mulching, cultural, mechanical and biological control measures
  • Thermic weed control or thermic sterilization of soils
  • Microbial pest control formulations such as bio-pesticides
  • Use of synthetic herbicides, fungicides, insecticides and other chemical preparations including synthetic plant growth regulators are strictly prohibited.
  • Use of genetically engineered organisms or products are also prohibited

Equipment/implements and storage containers

  • All farming equipment, implements, and tools, etc., must be washed and cleaned before use on the organic farm.
  • Bags and containers used to harvest, store and transport organic produce must be clean and free from any chemical contamination.
  • Should not be used for storage of conventional produce

Storage and transport

  • Organic products must be protected at all times from co-mingling with non-organic products.
  • Use of synthetic or chemical storage pesticides/fumigants are prohibited
  • Use of carbon-di-oxide, nitrogen or any other such inert gas is permissible
  • Mineral fertilizers shall be used in their natural powdered form as a supplementary source of nutrients.
  • Use of synthetic fertilizers is strictly prohibited in any form, directly or indirectly

The seeds/planting material selected for planting must be most suited for the local production situation and conditions.

1.1 The producer should choose the variety of crop that is most suited for the geographical location and climate

1.2 The producer should choose the variety of crop that is pest and disease resistant.

1.3 The use of genetically engineered seeds, pollen, transgene plants or plant material should be avoided.

1.4 The producer should maintain records of the seeds/planting materials purchased.

The certified farm must develop a clear and visually identifiable system for avoiding the mixing of certified products with non-certified products.

2.1 Records of the volume of certified products harvested should be regularly available and maintained

2.2 Records of the volume of certified sold products should be regularly available and maintained

2.3 The producer must follow a clear and visually identifiable label while transportation

2.4 The producer must have records of product flow including the balance stock of each certified product.

Conservation of soil and minimising soil erosion and degradation

3.1 The producer must use techniques to prevent soil erosion. In the case of new planting, vetiver grass or other suitable plant species should be planted around the erosion-prone areas

3.2 The producer must use techniques to maintain and improve soil structure and fertility.

3.3 In sloppy areas, planting on contour lines should be followed. Whenever possible, contour bunds must be constructed for soil and water conversation.

Need for appropriate choice and use of recommended fertilizers.

4.1 The fertilizer application should be made on the basis of nutrient availability of the soil

4.2 Fertilizers should be selected and used as per the recommendation of Kerala Agricultural University and other research institutions.

4.3 Records should be maintained for the purchase of fertilizers, storage, and application.

4.4 The fertilizers must be stored safely in facilities that are dry, well ventilated and do not have access to children and unintended people.

4.5 All the applications of organic and inorganic soil and foliar fertilizers are recorded. It should include:

date of application

product brand name, type of fertilizer and chemical composition-quantity or volume per hectare, plot or field

field identification

method of application and equipment used

Minimise the use of CPP’s and safe application and disposal of CPPs

5.1 Integrated pest and weed management programme may be adopted, which promotes the use of physical, biological, mechanical and cultural control methods, and the least possible use of agrochemicals

5.2 CPPs should be selected and used as per the recommendation of Agricultural University

5.3 Documented records for the use of CPPs must be available, including:

pre-harvest interval

date of application

product brand name, type of fertilizer and chemical composition-quantity or volume per hectarre, plot or field

field identification

method of application and equipment used

5.4 The registered pre-harvest intervals should be strictly followed by the farm

5.5 All the plant protection product applications should be recorded including the pre-harvest interval.

5.6 Adequate visual warning signs must be used to inform people on re-entry time.

5.7 The certified unit must have an adequate plan for safe disposal of the CPP empty containers

5.8 Emergency facilities and procedures must be available in the vicinity of CPP storage to deal with spillage of CPP

5.9 Obsolete plant protection products should be securely maintained and disposed off in a safe manner.

5.10 Material Safety Data Sheet (MSDS) must be available with the farmer to deal with accidental poisoning.

To ensure water conservation and use of water from sustainable sources

6.1 The best possible irrigation method that minimises the wastage of water must be used.

6.2 Sewage water must not be used for irrigation

6.3 Rainwater harvesting or infiltration may be practiced, for example from roofs or retention ponds built-in run-off areas away from streams

Avoid contamination through the processes

7.1 Good hygenic practices should be ensured in packing and labeling

7.2 Product integrity should be maintained during packing and transportation of certified products

7.3 Certified products should be separated from non-certified product during transport with clear labeling.

7.4 Cleaning agents, lubricants, fuel, CPP and fertilizers should not be stored along with the packing materials, finished products, etc., to prevent chemical contamination of produce.

7.5 Transport vehicles should be maintained clean to avoid contamination.

7.6 Rejected produce and waste material in the packing environment should be stored in designated areas.

7.7 Packing materials should be clean and stored in clean and hygenic conditions.

Ensure appropriate waste management Practices

8.1 The farm must implement an integrated waste management program for the wastes it generates

8.2 The farm must appropriately use the crop residues and bio degradable wastes from farm and processing as manure, compost or mulch.

8.3 The use of open waste dumps and open-air burning of waste is prohibited.

8.4 The waste deposit areas on the farm must be managed to reduce the risks of environmental contamination and damage to human health.

8.5 Plastic items, PVC and other toxic items should never be burnt in the farm.

8.6 The farm must be clean and free of non bio-degredable waste products in order to maintain a positive image of the farm.

Training programmes

9.1 Training must be provided to farmers on GAP standards

9.2 Farmers and workers must be trained on the safe use of crop protection products and other agrochemicals.

9.3 Farmers and workers must be trained on use of personal protective equipment while applying the crop protection products.

9.4 Training must be provided to farmers and workers on the safe and appropriate application of fertilizers.

9.5 Farmers and workers should be trained on appropriate on-farm processing and handling activities.

9.6 Farmers and workers should be trained on-farm management activities including maintaining proper buffer zone, water management, waste management.

9.7 Records of training must be maintained for verification.

Conservation and protection of natural ecosystems and biodiversity

10.1 The farming activity must not cause any type of contamination or pollution to the environment.

10.2 No solid waste must be discharged into the farm

10.3 Conduct activities to restore degraded ecosystems

10.4 No destruction of threatened or endangered plant/animal species

Health and safety of workers/farmers in the workplace at the farm

11.1 All workers and or farmer himself who apply, handle, transport or come into contact with agrochemicals must be trained by a qualified trainer.

11.2 The unit shall provide free access to clean and safe drinking water for all workers.

11.3 The production unit should make available first aid boxes

11.4 Farmers/Workers who apply hazardous crop protection products should wear suitable protective clothing and equipment that is in good condition.

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