Orchard Management (1+1)

EXERCISE 15

EXERCISE 15: LAYOUT OF IRRIGATION SYSTEMS IN FRUIT ORCHARDS-SUB-SURFACE IRRIGATION

Aims:

• Saving of water by its judicious use
• Avoid weed growth
• Increase yield and fruit quality

Applying water to the plants from below the soil surface is referred as subsurface irrigation. Trenches of suitable width and about 3 feet deep can be dug at suitable intervals for the required length. Plants are planted in between two trenches. Water allowed in to trench will be available to the roots from below. The same trenches will act as drainage channels during rainy season.

As an alternative, a network of perforated pipe line to be buried in the soil at the required depth. Water let into these pipes will be made available to the roots from below. An improved version of this system is the drip irrigation, which has gained popularity all over the world.

Drip irrigation: This is one of the effective systems of irrigation where in water allows falling from drip nozzles near to the root zone of plant. A net work of drip nozzles are laid using suitable pipe lines covering total areas of the orchard.

Advantages:

1. This system saves water up to 30-70%.
2. This system saves labour - 60 – 90%
3. Increase in plant vigour and yield.
4. No interference with cultural operation.
5. Very useful in hilly terrain and problematic soils.
6. Reduced weed growth.
7. Saving of nutrients – 30-60%.
8. No problem of soil erosion even at step slopes.
9. Retain of soil structure in good condition and better aeration.
10. Fertigation is possible.

Disadvantages: 1. Initial cost is high & 2. Clogging of drippers

Drip irrigation system.

A drip irrigation has four basic components:

1. Suction
2. Regulation
3. Control and
4. Discharge

These components are accomplished by water lifting pump, hydro cyclone filter, sand filter, fertilizer mixing tank, screen filter, pressure regulator, water meter, main line, lateral and dripper. After lifting, the water passes through hydro cyclone filter, sand filter, fertilizer mixing tank and screen filter and ultimately through dripper. Coarser sand particles, relatively finer particles and very fine particles are filtered through hydro cyclone filter, sand filter and screen filter, respectively. These filters are essential for smooth running of water through laterals and drippers otherwise chocking of laterals may takes place.

Types of drip irrigation systems:

• High pressure drip system. This operates at more than 30 psi pressure.
• Low pressure drip system. This operates at less than 30 psi pressure.

Fig. 15.1: Drip irrigation system

Water requirement of crops
Water requirement in litres per plant per day = r x f x k x c
Where- r = Evaporation pan reading (mm)
f = Plant spacing (m2)
k= Canopy constant
c= crop factor

Spreading canopy (m2)
Canopy constant K ---------------------------
Plant spacing (m2)

Crop factor for some crops are
Grapes---0.70; Citrus---0.60; Banana---0.85 ( 0.8 as an average for all plants)

Water requirement for different crops
add

For example Mango with 8.0x8.0m spacing taking 75 lit./plant/day on an average

Length of irrigation with 2 } Water requirement
Drippers of 4 litres discharge/hr. } = No. of drippers x dripper discharge

ie. 75 = 9.375 = 9.4 hrs.
2x4

Total water requirement per ha. = 75x 156 ( No. of plants /ha) = 11700 lit./ha.

Maximum area that could be covered with } Pump discharge x hrs of pumping
a pump discharge of 10,000 litre/hr. for 9.4 hrs.} = Water requirement / ha.

= 10000 x 9.4 = 8.03 ha.
11700

Observations to be recorded:

Record evapo-transpiration loss of water in the orchard by pan evaporation method and work out water requirement of fruit crop under drip irrigation system.