1) WHEN TO IRRIGATE
The most efficient way to water is to apply water when it begins to show signs of stress from lack of water. It’s paramount to avoid water stress unless it’s by design to induce it; lest one may incur massive crop loss on both quantity and quality. The following signs are indications of water stress;
• Footprints or tire tracks that remain in the grass long after being made
• Many leaf blades folded in half.
• If a soil sample sought from a profile 1-2ft deep is not pliable and sheds into soil droplets upon dropping to the ground.
• Premature fruit drop and/or flaccid fruits on trees.
2) EFFICIENCY OF WATER APPLICATION
• An efficient watering does not saturate the soil, and does not allow water to run off.
• Avoid extremes in watering frequency and amount. If you apply too much water, it runs off and is wasted.
• On the other hand, light frequent watering is inefficient and encourages shallow/restricted root systems.
• Typically, 2-3 irrigation rounds per week in the peak irrigation periods is ideal. If rainfall occurs, irrigation should be suspended depending on the rainfall amounts.
3) TIMING OF IRRIGATION
• The best time to irrigate is in the early morning hours and /or late evening. Watering during the day can be wasteful due to evaporation.
• Avocados require 8000-9000m3 per Ha for the whole year, including water supply from rain.
• The avocado trees have varied moisture requirement in amount depending on the prevailing physiological stage.
• Aspects/stages directly influenced by optimal water regime on avocados include; Flowering, fruit set, fruit drop fruit sizing and fruit quality.
• In central region, 50-60m3 suffices to supply adequate moisture to 1Ha of avocados in a 2 week cycle of irrigation in dry periods.
• In a week, 50-75 litres being applied per tree will supply adequate moisture to support the tree during peak demands.
Below is a guideline on irrigation calendar for the small-holder farmer:
PERIOD PLANT PHYSIOLOGY IRRIGATION STATUS WATER VOLUMES AND ROUNDS COMMENT
DEC – MAR Fruit set and rapid expansion Irrigate fully until rain starts 25-35 liters per tree twice every week There must be no stress on trees
APR – MAY Fruit development Do not irrigate Rainy season
JUN – AUG Harvest Partially irrigate 5-10 liters per tree once a week Maintenance only
Sept-mid Oct Dormant period Do not irrigate Stress prior to flowering
Mid Oct-rains(Nov) Flowering and fruit set Irrigate fully 25-35 liters per tree twice every week There must be no stress on trees
4) IRRIGATION METHOD OPTIONS FOR SMALL-HOLDER FARMER
a) DRIP IRRIGATION
• Install a drip line in the orchard to be served by a tank through gravity. Ensure the tank is raised and/or installed on higher ground.
• 2 drip lines to serve a row of trees.
• The tank can be filled with water by manually pouring using jericans or through pumping.
b) MANUAL IRRIGATION
• Entails manually transporting water in 5, 10,15 or so liter containers sprinkling around the root zone.
• Care should be taken to avoid excessive water application that can lead to run-off.
• Water can also be applied using watering cans and these give a better distribution.
• This is important operation that helps retain moisture around the root zone.
• It’s important to maintain mulch around the tree always.