Stonefruit have been grown successfully on a wide range of soils (pH 5.5 to 7.5) but yield best on land that is not prone to water-logging. Most of New Zealand’s stonefruit is grown in the Hawke’s Bay and in Otago. Here, sites are usually chosen which enjoy good drainage through a combination of their soil characteristics and a sloping topography. In Otago, a slope also offers some protection from radiation frosts.
Even top-class horticultural land will contain areas that have less-than-ideal drainage caused by local irregularities in topography or in soil properties. Also, even top class land can contain areas having low organic content or suffering from compaction. Local applications of gypsum can help to remedy these problems and will bring about significant improvements in both yield and fruit quality in the affected trees.
The improvement in soil structure obtained by adding gypsum is likely to improve the general health of stonefruit trees and to reduce the chances of their suffering ‘wet feet’ related problems.
Plumcots After harvest, stonefruit store for shorter periods than do many other fruit types (such as apples and kiwifruit). In stonefruit, premature softening, increased ethylene production and elevated respiratory rates have all been associated with calcium deficits. Storage of stonefruits can be improved by increasing fruit calcium status and this can be achieved in a calcium deficient soil by the addition of gypsum.
A stonefruit orchard requires between 250 and 500 kg/ha of calcium each year. A substantial part of this can be supplied in the form of gypsum with other calcium-containing fertilisers accounting for the balance. Commonly with stonefruit, nitrate is applied in the form of calcium ammonium nitrate (containing 27% of nitrogen and 8% of calcium) at the rate of around 300 kg/ha. This supplies only 24 kg/ha of calcium so that most of the balance of calcium can be supplied in the form of gypsum.