The most common berryfruit crops in New Zealand are strawberries, blackcurrants, boysenberries, raspberries and blueberries. Individual berryfruit groups have their own special (and diverse) production requirements – some require very good drainage (e.g. strawberries) while others are naturally bog plants (e.g. cranberries).
Drainage
All berryfruit require adequate water to size the fruit but since they are all shallow rooting, poor drainage and associated anaerobic conditions are not tolerated by any of them. Blackcurrants and boysenberries are more tolerant of wet conditions than are blueberries and cranberries. Strawberries and raspberries are both very sensitive to water logging and its associated diseases, the use of gypsum to remedy poor drainage in heavy or compacted soils is particularly recommended.
Calcium
Specific calcium deficiency storage disorders are not as familar in berryfruit. However, berryfruit has a limited shelf life and there is evidence that inadequate fruit calcium is associated with reduced shelf life, reduced firmness and more rapid softening in storage. There is also some evidence that good calcium nutrition can enhance fruit size. Lime or dolomite can be used to raise soil pH and to provide soil calcium but where pH adjustment is not required (most berryfruit like acid soils) gypsum is the better calcium source.
Strawberries
Strawberries are best grown in a soil pH between 5.0, for finer textured soils, and 6.5 for sandy-textured soils. Their shallow feeder roots do not tolerate waterlogging and the root diseases associated with wet conditions. Because lime raises soil pH, it should not be used on strawberries except in cases of extreme soil acidity. Gypsum is ideal both to improve soil structure, thus reducing wet-feet problems, and to provide a source of calcium.
Blackcurrants, boysenberries and raspberries
Blackcurrants, boysenberries and raspberries are surface rooting, prefering a moist, well-drained, fertile soil that provides free root-run with a soil pH between 5.4 and 7.0. The soil must have adequate water holding capacity to cope with dry periods. Raspberries are more susceptible to wet-feet problems than boysenberries or blackcurrants. Again, gypsum is ideal for use on these crops.
Blueberries and cranberries
Blueberries and cranberries are closely related species having shallow root systems that are very fibrous and devoid of root hairs. This characteristic makes them very sensitive to fluctuations in soil water. Blueberries and cranberries are typically grown on peaty soils with very high organic matter, but may be poorly drained due to a high water-table. For this reason, the addition of gypsum to improve or modify soil structure is unlikely to be beneficial.
The growing of blueberries on mineral soils is relatively new. Where mineral soils are used, they are usually modified by the addition of organic matter such as sawdust. Growers are well advised to avoid clay soils where drainage problems might arise, but on marginal soils gypsum is a valuable amendment to address structure and drainage issues.
The optimum soil pH range for blueberries is 4.5-4.8 and 4.0-5.0 for cranberry. The calcium requirement of these plants is generally met by the calcium content of other fertilisers. Sulphur requirements are usually met by fertilisers such as sulphate of ammonia, or compound materials.