Irrigation systems

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

Atomizer

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.

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

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