Efficient Water Management Strategies for Higher Water Productivity Anurag Saxena Central Arid Zone Research Institute, Jodhpur, Rajasthan E-mail:
[email protected];
[email protected]
Environmental constraints of arid zone • • • • • • • • • • • •
Low and Erratic Rainfall < 400 mm (cv. 40- 80%) High Temperature (45- 48oC) Intense Radiation (15.12 to 26.50 MJ m-2 day-1) High Wind Velocity (20- 40 km hr-1) High Evapotranspiration (1800- 2200 mm yr-1) Deep and generally saline groundwater Presence of excessive fluoride nitrate- unsafe drinking water Over-mining of fresh groundwater Poor drainage network Sandy Soils with low WHC Overgrazing due to high Biotic Pressure due Frequent Drought (47%)
SPATIAL VARIATION OF RAINFALL • • •
Mean Annual rainfall - 1170 mm Maximum mean rainfall - 11000 mm (Cherrapunji) Minimum mean rainfall - 100 mm (Western Rajasthan)
Rajasthan India
Scenario/ Problem • Scarce water in arid regions • Fall in groundwater 0.5 – 1.0 m annually • Over exploitation of water led to 70 – 80% area under dark zone
Rapidly depleting ground Water- A major concern Safe Critical Nagaur
Nagaur
Rainfall in the west and east Rajasthan Meteorological sub-division
Monthly rainfall (mm) June
July
August
Sept
West Rajasthan
24
175
95
55
East Rajasthan
48
273
210
250
Total 237 blocks, Over exploited –140 (Dark zones), Rest critical
Water use Drinking Agriculture Industry Power generation • • • •
Water loss 04% 80% 10% 06%
Soil moisture Percolation Run-off ET
Groundwater main source of water Depleting at an alarming rate Need to produce more with less water Improving crop WP is must
10% Useful 9% 19% 40% Loss 81% 41%
The Problem • Demand of other sectors increasing • Share for in 2050 will be less by 15-20% • However, 1% of water productivity gain in agriculture means 10% increase of availability for other uses Water Consumption (Virtual Water)
•
We drink 2~3 litres/day (15-20 Glasses)
•
We eat 1500 – 10000 litres/day
Virtual water content of products Commodity 1 kg grain
Water (Litres) 1 – 2,000
1 kg cheese
5000
1 kg beef
16000
1 cup coffee
140
1 kg wheat bread
1600
1 kg rice
2500
1 Hamburger
2400
100 g Chocolate
2400
1 kg sugar
1500
1 kg tomato
180
Dryland-adapted system 200
150 mm
Runoff harvesting – additional 35% of annual rainfall
Type of water Green water: volume of rainwater evaporated or incorporated into product Blue water: High value (competition with other uses), don’t use in agriculture, water
has relative low value Grey water footprint: volume of polluted water In agriculture optimally use green water
Focus on: Rainfed Agriculture Water Harvesting Supplementary Irrigation
Technological Options/ Strategies • Increasing water availability
• Improved agronomic practices (Tillage, weeding, mulching etc. ) • Crop planning based on longest growing period: Choosing efficient farming systems • In-situ rainwater harvesting and management •
Deficit /Extensive irrigation
• Improving water use efficiency through micro irrigation (Drip/Sprinkler system)
Crop production depends on • • • • • • •
Rainfall & its distribution Crop & varieties Sowing Planting pattern & population Weeding & inter-culture Water management Fertiliser management
398 Better Husbandry
Hybrid, fertiliser & water harvesting
2433
Better Husbandry
1301
1544
Better – poor Tech Gap 2447
Hybrid fertiliser & water harvesting
2845
Integration of Management Practices & water harvesting improves pearl millet yield
Weeding influences WUE (Kg ha-1 mm-1 ) & yield (Kg ha-1 ) of Pearl millet Treatment
Good rainfall ( 548 mm)
Low rainfall (252mm)
Yield
WUE
Yield
WUE
Un-weeded
1672
3.1
1053
4.2
Weeded
1868
3.4
1521
6.0
Mulching improves Yield and WUE of Pearl millet Type of Mulch
Water Use (ET) mm
Yield (kg ha-1)
WUE (kg ha-1 mm-1)
Polyethelene
279
2900
10.4
Bajra husk
269
2300
8.5
No. Mulch
291
1740
6.0
Planting Arrangement improves water use and yield of pearl millet Planting Arrangement
Good rainfall (548 mm)
Low rainfall (252mm)
Yield
WUE
Yield
WUE
50X50 cm(RR)
2914
5.3
2235
8.9
25X75X15 cm (DR)
2732
5.0
2724
10.8
Yield : kg ha-1
WUE: kg ha-1 mm-1
Performance of intercropping systems under two rainfall situations Planting system
Rainfall 409 mm Paired row Alternate row Rainfall 152 mm Paired row Alternate row
Base crop plant population (000 x Plants ha-1)
Yield (Kg ha-1)
Grain
Stover
166 100 166 100
3098 2880 2989 2947
6505 5760 6336 5890
166 100 166 100
475 590 381 506
192 1334 872 1138
1:2
2:2 1: 2
2: 1
2: 2
Rainwater conservation practices A) In-situ Rainwater: Conservation water is stored in soil profile itself B) Ex-situ Rainwater: Conservation Water is stored in a reservoir on pond for recycling
Inter plot/ row water harvesting
Pit and trench method for vegetable and fruit crops
Bench terrace water harvesting
Micro Catchment Farming
In-situ water harvesting system Pearl millet yield was almost doubled
Circular catchment for water harvesting
Plastic gave 95% Run off
Micro Catchments for horticulture crops Ring Pit
Saucer
Trench and Mound can be made mechanically and economically viable
5 times
4 times
Productivity enhancement and economic benefit Water harvesting prevent runoff losses by 30-50 % and maintain higher soil moisture regime Enhanced soil moisture storage by 42% in the upper 75 cm layer alone after mild shower of 27.5 mm Facilitate better crop production due to better development of root system Improved water use efficiency by 4-7 times
Runoff Water Conservation
Sowing on specially created furrows
Pearl millet crop
Comparison of conservation of run off water in pearl millet fields
Laser Land Leveling: A water-wise technology Laser Leveler- productivity gain & water saving Yield (kg ha-1) Crop
• • • • •
Increases irrigated area ~ 2% Improves crop stand and yields Increases water productivity Increases nutrient use efficiency Improves farm profitability
Water saving over without laser leveled field (%)
Laser leveled field
Without laser leveling
Potato
11000
8250
25
Onion
10000
8000
20
Check - basin
Land quality degraded by irrigating low quality water
Management of limited irrigation water In arid region water is limited and land is vast, hence water management should aim to maximize production per unit of water rather per unit of land • Water Harvesting is capturing and storing rainfall to irrigate plants or to supply people and animals • Water harvesting will help in reducing dependence on ground water
Techniques in water saving Rainwater conservation Extensive irrigation Deficit irrigation
Runoff efficiency of different sealants Sealant Plastic Pond sediments Compacted earth catchment Flat Surface
Runoff efficiency ( %)
Pearl millet Yield (kg ha-1 )
95.7 88.9 65.9
883.5 557.5 532.5
-
383.5
Pond sediment to improve water retention
Water Use, yield and WUE of Pearl millet by water harvesting System Conventional In- situ Water Harvesting
Yield : kg ha-1
Good rainfall Water use Yield WUE 440 2320 5.3 630
2425
WUE: kg ha-1 mm-1
Low rainfall Water use Yield 143 400
3.9
Water use: mm
212
1240
WUE 2.9 5.9
In-situ water harvesting: Efficient use of limited rainfall & N-fertiliser in pearl millet System
Added Water (mm)
N- levels (kg ha-1) 0
40
Rainfed
0
210
400
In –situ water harvesting
69
660
840
Seasonal rainfall 143mm
Deficit irrigation • Avoid irrigation at less critical stages of crop growth and apply less water at the end so as to eliminate water stored at harvest Extensive irrigation • Apply a small quantity of water over a large area rather than large quantity over a small area
Extensive irrigation maximise production for given water supply
Crop
Water use (mm)
Wheat
840
Mustard
250
Pearl millet
250
Area (ha) 1 3 1 1.5 1 4
Yield (kg ha-1) 5500 9100 1100 2000 4.2 10.3
WUE kg ha-1 mm-1 6.5 10.8 4.4 8.0 16.8 21.0
Increased Area under S-IRR Enhances Pearl millet Production Low Rainfall (143 mm) S-IRR Area Yield
Medium Rainfall (266 mm) S-IRR Area Yield
Good Rainfall (331 mm) S-IRR Area Yield
341 209 117 0
292 145 73 0
190 76 38 0
1.0 1.6 2.9 1.0
3540 4528 5829 1080
1 2 4 1
S-IRR in mm ha-1, Area in ha, Yield in Kg ha-1
3620 5380 7560 1400
1.0 2.5 5.0 1.0
3660 7225 12950 2280
Effect of furrow irrigation on yield and water use Crop
Maize Saving of water (%) Yield (q/ha) Water Use Efficiency (kg ha mm-1)
Irrigation in Irrigation in alternate each furrow furrows 41.3 25.8
30.0 40.6 36.7
Pressurized irrigation systems
Improved conveyance and application efficiencies on coarse & shallow soils Low discharges used Reduced labour requirements Suited to all range of topographies & field dimensions and Easy to operate High irrigation efficiency: Uniform distribution Accurate and easy measurement of water applied Application of fertilizer through irrigation system Mobility, enabling the exploitation of one unit for irrigating other plots
Effects on micro-climate protection against frost Weed growth is minimized since only desired portion is wetted
Comparison of water movement in different irrigation systems
Sprinkler
Drip irrigation
Alternate furrow sub surface drip irrigation
Uniformity of application tests: Irrigation water collected in containers laid out in the plot. The size of the containers and their layout depend on the type of the sprinkler. Coefficient of Uniformity of Application (Cu)
Cu (%) = 100 1 − Cu (%) = 100 1 −
𝑥𝑖 −𝑥 𝑥.𝑛 𝑆𝑢𝑚 𝑜𝑓 𝑑𝑒𝑣𝑖𝑎𝑡𝑖𝑜𝑛𝑠 𝑆𝑢𝑚 𝑜𝑓 𝑟𝑒𝑎𝑑𝑖𝑛𝑔
Cu (%) = Coefficient of uniformity of application Σ = Total xi = Individual reading – catch can 𝑥 = Mean readings – catch can N = Number of containers (readings) Minimum Cu (%) requirement for sprinkler and drip irrigation in field crops 84 and 90%.
Single sprinkler Sprinkler system operating at too low pressure
too high pressure
Normal pressure
Overlapped sprinklers
Uniform Application: Overlap 50% of sprinkler wetted diameter
Non-uniform Application: Overlap urea > KNO3) • Soil & Water Salinity : (Avoid Na and Cl salts use NO3 salts) • Ca content of water : (Avoid Sulphates) Amount of water required for irrigation Amount of irrigation water =A * B * C * d * E * F • A: Evaporation from open pan (mm/day) • B: Crop factor
• C: Area (m2) • D: Percent area to be wetted • E: Treatment • F: Pan factor
(Litres per day)
Operation time Operation time (Hrs) = Volume of water to be applied per tree/ Total dripper discharge Rate of fertigation • Rate & concentration is calculated to avoid over fertilization • Fertilization schedule of drip irrigated crops is site specific • Primarily depends on concentration of soluble fertilizer & desired quantity of nutrients to be applied during irrigation
Rate of fertigation Qc = Fr * A/C *tr * Ta Qc = Rate of injection of soluble fertilizer solution in to the system (l/h) Fr = Fertilizer rate per application (kg/ha) A = Area to be irrigated/fertilized in Ta Ta = Irrigation application or set time C = Concentration of actual nutrients in the soluble fertilizer (kg/I) Tr = Ratio between fertilizer time and irrigation application time
Micronutrient fertigation
Micro nutrient fertigation should be separate from macro nutrients If micronutrients are added to high acidic solution of NPK there will be interaction of Fe with P, Zn and both element will not be available to the plant
Effect of planting configurations on crop yields Yield (metric t ha-1) of
Plant arrangement Cabbage
Tomato
Turnip
Cauliflower
Rectangular
35.5
68.4
19.5
20.0
Square
33.2
73.1
20.3
23.8
Hexagonal
16.9
55.1
11.8
13.2
Equilateral
33.0
78.4
22.9
26.0
Drip Improves yield (t ha-1) & WUE (Kg ha-1 mm-1) of Vegetables Crop
Furrow
Sprinkler
Drip
Yield
WUE
Yield
WUE
Yield
WUE
Ridge Gourd
11
1.3
10
1.2
12
1.7
Long gourd
38
4.6
39
4.6
56
8.1
Round gourd
30
3.7
34
4.2
41
5.4
Water melon
67
8.3
75
9.3
82
11.0
Check-basin vs. Drip in Chilli
Yield (t ha-1)
WUE (kg ha-1 mm-1)
Check-basin + 180 kg N
1.93
2.05
Drip + 180 kg N
2.94
5.17
Drip + 135 kg N
2.79
4.90
Drip + 90 kg N
2.06
3.64
Drip + 0 kg N
1.14
2.03
Method
Effect of Water and N on Yield and WUE of chilli Treatment
Yield (t ha-1)
WUE (kg ha-1 mm-1)
Water on Area Basis + N kg ha-1 Total + 180
3.03
4.52
Canopy + 180
2.94
5.17
Wetted +180
1.50
4.54
Check basin
1.93
2.05
High yield potential with drip irrigation (t ha-1)
Method
Tomato
Cabbage
Cauliflower
Drip
78
36
26
Conventional
50
30
20
Drip Provides Gainful use of saline water Method Conventional
Salinity (d Sm-1)
Potato (t ha-1 )
Tomato (t ha-1)
Sweet
20
50
3
26
-
10
-
44
Drip
Drip economises water in potato
Method
Water Use (mm)
Yield (t ha-1)
Furrow
366
20.2
Drip
183
20.5
Drip economizes fertiliser in tomato
Fertilisers (kg ha-1)
Method
Yield (t ha-1 )
Broadcast
N 224
P 88
K 168
72
Fertigation
56
22
42
60
Drip irrigation Vs. conventional irrigation
Crop
Water requirement (L day-1 plant-1)
% increase in
Drip
Conventional
Yield
Water saving
Grape
25-45
90-100
23
48
Pomegranate
20-40
60-130
61
45
Lemon
10-20
25-65
40
40
Papaya
5-8
18-26
75
68
Banana
8-12
30-40
52
45
Tomato
1-2
4-6
50
39
Chillies
1-2
3-6
44
62
Gourds
1-2
3-6
39
53
Saving in fertiliser & water
Vegetable
Fertiliser saving (%)
Water saving (%)
Bulb crops
30 – 40
30 – 35
Cole crops
40 – 50
40 – 45
Solanaceous crops
40 – 50
45 – 50
Cucurbits
60 – 70
60 – 70
Okra
40 – 45
40 - 45
Top problems with drip
o
o o o
o o o o o
System not matched to available flow rates Insufficient pressure & Inadequate filtration Improperly sized main lines & manifolds No or insufficient no. of pressure gauges No flushing manifold Improper or inadequate chemical injection program for clogging control Insufficient water supply for the crop Insect and salt clogging occur regularly Unrealistic expectations
Drip system maintenance • • • •
flushing of filters frequently flushing of laterals and sub-mains running the system at required pressure acid treatment against the salt deposits
• chlorine treatment against the algae
Drip Irrigation Systems - Crops FRUIT CROPS : Almond, Apple, Arecanut, Indian Gooseberry, Ber, Banana, Cashew, Custard Apple, Cherry, Fig, Guava, Grape, Litchi, Lemon, Sweet Lime, Mango, Orange, Papaya, Pomegranate, Pear, Peach, Strawberry, Jack Fruit, Water & Melon VEGETABLE CROPS : Brinjal, Cucumber, Lettuce, Pepper, Potato, Pea, Tomato FIELD & OTHER CROPS: Corn, Cotton, Sugarcane, Tobacco, Betel vine
OIL SEEDS : Groundnut, Sunflower, Jojoba, Castor FORAGE CROPS : Lucerne, Pastures, Turfs, Fodder PLANTATION CROPS : Cardamom, Coffee, Tea, Rubber, Spices, Oil Palm, Coconut
ORNAMENTALS : Rose, Gerbera, Carnation, Gladioli, Poinsettias, Chrysanthemum FOREST TREES : Eucalyptus, Casuarinas, Teak, Acacia, Bamboo, Neem, Dalbergia
Drip Irrigation: Saves 40-45% water
Low cost drip irrigation systems
Conventional drip irrigation systems
Irrigation methods Surface irrigation
Piped system
Furrow
Water flows through furrows over the field
Border strip
Water flows over strip of land
basin
Water is hold in a small basin until irrigator decides
Sprinkler
Spraying water over the soil surface
Drip
Emitting water to top soil at low flow rates
Sub-surface
Control of groundwater
Water Savings - Comparison • Conveyance efficiency
:
Open field channels
70%
Piped distribution
80 - 85%
• Field application efficiency: Surface methods (Irrigation Efficiency) Sprinkler Micro-Irrigation
50 70% 80 - 90%
• Overall efficiency
35% 57% 70%
: Surface methods Sprinkler Micro Irrigation
Polyhouses/ Shade houses • Cultivation under controlled environment for massive yields from small area and faster crop rotations.
• Useful in raising off-season, high value vegetables, floriculture and grafting, nursery raising activities.
• Available in different types with cladding by PE film, Poly carbonate, Poly shade nets
Polyhouse Technology
• Protection from wind current, scorching sunlight & extreme cold conditions • Maximum production from minimum space, labour & minimum use of water • Diseases and pests can be controlled easily
• Protection from birds, animals and human activities • Best quality production of crops throughout the year
Protected cultivation
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