Irrigation Systems for Kiwifruit
Good irrigation is critical for good growth and production. Irrigate young plants enough to wet the root zone without keeping the crown too wet; otherwise, crown or root rot may occur. In young plants, the range between too wet and too dry is narrow.
Unfortunately, there is relatively little direct experience on water requirements of hardy kiwifruit in Oregon. The following information relates to Hayward production, but should be a good starting point for other cultivars as well.
Growers often irrigate by experience rather than irrigation scheduling tools. In kiwifruit, however, observing vines for trouble signs doesn’t work well, because by the time water stress symptoms are visible, damage has occurred.
Vines under mild or moderate water stress have a subtle off-color look, with the foliage turning blue-green. Other symptoms include poor shoot growth, wilting, small fruit, sunburn, and reduced yield in the current and following season.
There are various types of irrigation systems. Unfortunately, there is no single best system. Design a system that can supply an average of 25 to 35 gallons of water per mature vine per day during the growing season. Irrigate vines once or twice per week. Surface mulch may help conserve soil moisture.
Drip systems economize on water use, but on lighter soils often supply water to only a narrow cone of soil. Frequent irrigations are necessary, particularly to young plants with small root systems. However, as the crown tends to stay drier, risk of crown rot (phytophthora) may be reduced. You can’t use drip systems for frost protection.
Drip irrigation systems commonly are used in California in young plantings. At planting, one emitter is placed near each plant. The second year, two emitters are placed at 12-18 inches from the trunk, and the one near the trunk is removed (to keep the trunk relatively dry). When the plant is 4 years old, two more emitters are added 3 feet away from the trunk.
When plants are mature, California growers find it difficult to supply enough water with four emitters per vine, so they add more emitters or switch to minisprinklers. For larger vines, up to 10 emitters per vine may be necessary.
Under-vine minisprinkler systems, which produce a wetted area of greater size, often are preferred. In general, they wet more soil than drip emitters do, are easy to install, and tend to plug less frequently than drip emitters. They can be used to replace drip systems as vineyards age. In young vineyards, however, minisprinklers tend to over-irrigate.
These sprinklers spray water in a 6-18 foot diameter circle. One full-turn minisprinkler per vine, located equidistant between vines, should be adequate in mature plantings. Generally, they are allowed to run 6, 8, or 12 hours, two to four times per week.
Impact sprinklers also are used in kiwifruit vineyards, especially in more mature plantings. They can be placed over or under the canopy.
Overhead sprinklers are best for frost protection, but may spot or discolor the fruit when used in summer. They also may leach nutrients from the leaves and increase incidence of fungus diseases.
Some California growers use a T assembly on the sprinkler riser to switch from over-vine sprinklers to under-vine sprinklers. They use the over-vine positions for frost protection (shoots in the spring, fruit in the fall) and switch to the under-vine position in summer. (Note that only fuzzy kiwifruit are sensitive to fall frosts, because hardy kiwifruit mature earlier.)
Impact systems work well if the canopies aren’t in the way, but they tend to use more water. Under-vine sprinklers should be between vines in order to reduce impact on the trunk.
Over-canopy sprinklers can provide 6 to 8oF frost protection, whereas under-vine impact sprinklers can provide about 2 to 3oF protection. In California, 5/16″ sprinklers are used at a spacing of 30 x 40 feet (at 50 lb/inch pressure) to supply 0.1 inch/hour (50 gallons/acre/minute). Start sprinkler irrigation before temperatures fall below the critical level and continue until temperatures are above critical levels (see Kiwifruit Site Selection).
Bernadine C. Strik Extension Berry Crops Specialist, Oregon State University.
This fact sheet is adapted from Oregon State University Extension Publication EC1464, Growing Kiwifruit.