Much of New Zealand's kiwifruit is grown in a number of regions in New Zealand and on a wide range of soil types. In general, kiwifruit yield best on soils that are well drained, not prone to waterlogging and do not dry out too quickly in the summer. However, many orchard blocks have been extensively "contoured" prior to planting to remove the worst topographical irregularities and to allow better access for machinery. The application of gypsum in orchards with the poorly drained soils or contoured land will have beneficial effects on soil structure. The improvement in soil structure is also likely to improve the general health of kiwifruit vines and to reduce the chances of root diseases such as phytophthora. Gypsum can be applied at any time and with other fertiliser applications.
Fruit calcium
Calcium uptake by by kiwifruit (fruit) occurs mostly in early spring during the first 6-8 weeks after full bloom. It is best to apply gypsum in late winter and early spring to ensure the calcium reaches the roots before flowering.There is still some debate concerning the role played by fruit calcium deficit in predisposing kiwifruit to postharvest disorders such as premature softening. However, more research is required before clear conclusions can be reached regarding the relationship between kiwifruit calcium and kiwifruit quality.
Unless soils are notably calcium deficient (some are), improving the calcium status of the fruit is unlikely to be simply a matter of applying more calcium on the orchard floor. Low fruit calcium status has more to do with the calcium transport physiology of the plant, than with calcium uptake by the vine.
Because of kiwifruit's genetic diversity, relatively little is known about the individual calcium requirements of the individual kiwifruit varieties. Therefore, with the knowledge that most fruit crop species suffer from specific calcium-deficiency disorders and, in the absence of more detailed information for various kiwifruit varieties, it makes good sense to maintain the highest possible soil-calcium levels when growing them. Annual gypsum applications is an excellent way to do this.
Applications of gypsum will be determined by the soil type and results of a recent soil lab test.