Although the bramble group (Rubus hybrids) constitutes a significant proportion of the national berryfruit area, surprisingly little is known about their nutritional requirements. Virtually no controlled work has been carried out in New Zealand on either application, responses, or leaf tissue analysis for brambles and the overseas literature in this area is frequently inconsistent.

PLANT ANALYSIS
Samples for leaf analysis should be collected from primocanes during January and February. Each sample should contain approximately 50 youngest mature leaves (including petiole) selected at random from 10 or more canes. There is little published information on chemical analysis of leaf tissue for these crops. The data presented for boysenberries (Table 1) is based on a compilation of results recorded at the Soil Fertility Service plant analysis laboratory at Ruakura over a number of years, hence is only an indication of the sorts of concentrations anticipated.

Values for youngberries are not considered to differ markedly from those of boysenberries.

FERTILISER REQUIREMENTS
To date fertiliser applications in New Zealand have been made to ensure adequacy, rather than based on crop data or plant needs. No nutrient removal figures are available for this group, and fertiliser recommendations from various sources are widely divergent. NPK rates for example range between 28-160 kg N/ha, 35-112 kg P/ha and 28-160 kg K/ha. Despite the variation, these rates are still considerably less than those many New Zealand growers are presently applying. Boysenberries in California and Oregon have shown little yield response to the level or timing of fertiliser applications. This suggests New Zealand growers could, with careful monitoring, reduce the rates being used here.

For this group of crops applications of N should be based on plant vigour, soil type and rainfall, with P, K, and Mg application based on soil test levels (Table 2). A pH range of 5.8 - 6.5 is considered satisfactory. Where Ca, or pH levels are below those suggested, lime should be applied in autumn or early winter. If this is coupled with low Mg levels, lime and magnesium oxide (which is less expensive), or dolomite should be used.

On young plants banding of fertiliser on both sides of the row is accepted practice, however, by the third years this is usually broadcast.

Applications of N throughout the growing season are advantageous, but there appears to be no disadvantages in applying P and K in single applications in either autumn or spring. As the plants continue growing well into the autumn, post-harvest applications of water and nutrients should continue into this period.

Proprietary mixes suitable for berryfruit are available in most regions. Experience with chloride based fertilizers in the Nelson region has shown no deleterious effects on boysenberries, but this should be watched particularly in areas without irrigation or very low summer rainfall. Blackberries, which are amongst the least tolerant of the berry crops to excess chloride, should receive sulphate based potash fertiliser until experience suggests otherwise.

FURTHER READING
Anon (1975). Canefruit Reference Book. Publications 156, Agricultural Development and Advisory Services, Ministry of Agriculture, Fisheries and Food, UK, pp.40

Langford, G.I. (1985). Berryfruit. Varieties and culture for commercial production. New Zealand Ministry of Agriculture and Fisheries AgLink, HPP 86