Fertilization of Established Kiwifruit Vines
Most of the research and experience on kiwifruit production is with Actinidia deliciosa, particularly Hayward. Unfortunately, there is relatively little direct experience with hardy kiwifruit production. The following information should, however, provide a good starting point for production of hardy kiwifruit as well as the fuzzy types.
It is relatively easy to burn the roots of kiwivines, so apply fertilizer cautiously. When applying granular N, be sure to broadcast it over the entire root zone area; concentrating it near the trunk can burn roots. Leaf necrosis is a symptom of fertilizer root burn.
Mature vines, of 5 to 7 years and older, use about 1 pound of actual nitrogen (N) per vine per year or about 190 lb N/acre/year (with 15′ x 15 foot rows).
Apply about two-thirds of the nitrogen in March at bud break as a broadcast application under the canopy. This provides the nitrogen needed for early season growth and fruit set in May-June. A second application of granular N, the remaining one-third, is recommended in May-June.
Plants should have good soil moisture when they are irrigated. Irrigate first, wait 1 to 2 days, then fertilize; or fertilize after a good rainfall.
You can substitute liquid fertilizer applied through the irrigation system for dry fertilizer. When applying liquid fertilizers containing N, use about 10 pounds of actual N in each application from April through July. Higher rates of liquid N, 20 lb per application, have injured roots on lighter soils.
Base fertilization with other nutrients on tissue and soil analysis. Critical levels for leaf samples taken in late August in California and for New Zealand are given in Table 1. (recommendations from both areas are combined). It is not known if species differ in nutrient needs or if critical levels vary by region. However, these values can be used as a guide.
Table 1. Kiwifruit leaf sufficiency levels for nutrients
|Nutrient||% dry weight||Nutrient||ppm|
Based on experience in New Zealand and California, growers typically apply the following as a maintenance application: 55 lb/acre phosphorus in February-March; and 80 to 130 lb/acre potassium split between February-March, April, and May.
Maintain soil pH at about 6.0 with lime application in the fall.
Kiwifruit seem to be sensitive to chlorine, so avoid any fertilizers with chloride.
Bernadine C. Strik, Extension Berry Crops Specialist, Oregon State University