Orchard Management (1+1)

DRIP IRRIGATION SYSTEM

Drip irrigation system.

• In this system of irrigation, water supplied to the plant is equivalent to its consumptive use. This is a highly water use efficient (WUE) system of irrigation having very less water requirement.
• This is an outstanding irrigation technique especially for arid region, where there are two basic constraints for surface irrigation, namely undulating land terrain and less water availability.
• A drip irrigation has four basic components: suction, regulation, control and discharge, which 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 (Figure 8.4 & Plate 8.3).
• 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.

Figure 8.4: Lay out plan for drip irrigation system for horticultural crops

Plate 8.3: Drip irrigation in papaya (left) and kiwifruits(right)

Advantages:

1. Water saving to the tune of 30 to 70 per cent.
2. Increase yield and fruit quality.
3. Higher returns per unit area and time.
4. It saves labour cost.
5. Improved water penetration.
6. Eliminate soil erosion.
7. Reduced weed growth.
8. Saving in fertilizers and chemicals (40-60%).
9. Poor quality water can be used more safely.
10. Even undulated land can be irrigated.
11. Better pest and disease management.
12. Eco-friendly technology.

Scheduling Irrigation:

• Orchard is irrigated to supplement the deficit in soil water storage.
• Proper scheduling of irrigation involves the use of soil, plant and climatic parameters, so as to achieve maximum productivity.
• It is essential to determine the field capacity and permanent wilting point of the soil by gravimetric method.
• Set up tensiometer in the field to monitor changes in moisture level to determine the time of irrigation.

Soil parameters

• Root zone soil profile moisture give fair account of the irrigation requirements.
• Moisture in the soil between FC(field capacity ) and PWP (permanent wilting point)is the available water to the plant and this moisture content varies with soil texture, and structure, rooting depth and water extraction capacity of plant species.
• Depletion of available water is replenished with irrigation.
• The appearance and feel of the soil at different profile depths also indicate its moisture status.
• Irrigation requirement can be calculated by adding the moisture deficits of each profile and giving allowance for irrigation efficiency.
• The state of water in the soil can be more precisely expressed by its content or energy status. The moisture content can be measured by gravimetric (drying samples at 105o) or volumetric (ratio of volume of water to bulk volume of soil) measurement.
• Estimation of water extraction from soil can be made from the pre-calibrated relation between the difference in evaporation from black and white atmospheres and water extraction from soil for use in irrigation practice.
• The component forces which influence energy status and make up total soil water are:
• gravitational (Z), Matrix (M) and osmotic (O) given by  =Z+ M+ O.
• Since osmotic potential in most normal soil is negligible, matrix potential is usually measured by techniques, such as pressure plate apparatus, pressure membrane apparatus, thermocouple psychrometer, tensiometer, electric resistance meter, neutron scattering etc.

Plant parameters

• Though wilting is the most common sign of water deficit but, at this stage, there is a significant adverse effect on the growth of plants.
• Visual plant symptoms such as change in foliage colour, leaf angle; reduced growth, etc. provide fair indication about the irrigation requirement of trees.
• However, measurement of plant water status is the most practical approach for scheduling of irrigation.
• Leaf water potential is considered a good measure of plant water status for scheduling irrigation.
• Transpiration rate from the leaves is also correlated with the plant water status.

Climatic parameters

• Climatic factors, such as rainfall, temperature, relative humidity and wind speed determine the pattern of water loss from soil through evaporation and from plant surface through transpiration.
• While the loss from the soil surface gets progressively decreased with the spread of canopy cover with the tree age, that from plant surface depends upon the crop coefficient (Kc), a ratio between evapotranspiration (ET) under a crop and the potential evapotranspiration (PET) or potential evaporation (Ep) or pan evaporation (PE).
• This evaporative demand mainly determines the amount and frequency of irrigation, keeping in view the incidental soil moisture condition.
• The PET can either be estimated by mathematical computations from weather data or can be evaluated by standard evaporimeters.
• The ET is insignificant.
• The cumulative pan evaporation (CPE) data are used for scheduling irrigation.
• Since the irrigation water depth (IW) varies with tree age, fruit crop and soils, the IW/CPE ratio is commonly used for this purpose.
• In fruit crops, critical stages of growth/developmental stage should also be considered.
• In full bearing fruit trees, growth flushes, fruit set and fruit developmental stages are considered critical for irrigation.

Water requirement:

WR = Wa + Ws + Wm or Wi + Wr +Ws + Wg + Wd
Where, Wa = Non avoidable losses in run-off, seepage, deep percolation, weed
growth, etc.
Ws = losses through transpiration
Wm= Quantity of water needed for metabolic activity
Wi = Irrigation water
Wr = Contribution of effective rainfall
Wg = Ground water
Wd = Stem flow

• Water requirement for individual fruit crop (Table 8.1) would, thus depend on its irrigation needs besides the several factors which contribute to losses and gain of water in the orchard.
• However, optimum water requirement is that which results in maximum yield. This varies with stages of growth and development of fruit plants.

Table 8.1: Water requirement for different crops:

Sl. No.	Crops	Spacing(m)	Water requirement (ltr./pl/day
			Minimum	Maximum
1	Mango	8.0x8.0	50	100
2	Banana	1.8x1.8	04	11
3	Coconut	8.0x8.0	55	120
4	Cashew	7.5x7.5	40	95
5	Oil Palm	7.5x7.5	40	95
6	Ber	6.0x6.0	30	70
7	Sapota	10x10	80	175
8	Citrus	5.0x5.0/6.0x6.0	20	65
9	Guava	6.0x6.0	25	70
10	Grapes	3.0x3.0	25	70
11	Pomegranate	5.0x2.0/5.0x3.0	20	65
12	Arecanut	2.7x2.7	07	18
13	Rose	0.75x0.75	01	08
14	Jasmine	1.5x1.5	03	05

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 ltrs discharge/hr.} = No. of drippers x dripper discharge

ie. 75
2x4 = 9.375 = 9.4 hrs.
Total water requirement per ha. = 75x 156 ( No.of pl. /ha.) = 11700 lit./ha.

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

= 10000 x 9.4= 8.03 ha.
11700