Raspberries (Rubus idaeus) are the most important of the berryfruits in the Rubus genus produced commercially overseas. Consequently, most of the nutritional studies and fertiliser experiments have been conducted with this species. Despite the amount of research done on raspberries however, it is still not possible to provide definitive nutritional information on how the crop should be grown under our own conditions.

PLANT ANALYSIS
Samples for leaf analysis should be collected from primocanes during the December/January period. Approximately 50 youngest mature leaves (plus petioles) should be selected from 10 or more bushes to obtain a representative sample for plant analysis. Typical nutrient concentrations expected for this crop are listed in Table 1.

FERTILISER REQUIREMENTS
Rates of fertiliser suitable for established raspberries are presented in Table 2. The quantity of P, K and Mg required depends on the nutrient status of the soil. Consequently, reference should be made to soil test levels when determining the rate to be applied. Fertiliser may be aplied in bands 15-30 cm either side of the row to young plants, or broadcast once the crop is established. As for related Rubus species, a pH range of 5.8-6.5 is considered desirable.

There is general agreement that multiple applications of fertiliser through the season are beneficial. Jenner and Parminter (1981) suggest August and November applications at approximately ²/₃:¹/₃. Others suggest that P and K should be applied in autumn or spring. Side dressings of N in early summer are advantageous to ensure a constant N supply throughout growth. Multiple applications of N are not recommended however for autumn cropping raspberries in the Waikato where a single application of 100 kg urea/ha in September appears to be sufficient. Applications of fertiliser later in the season encourage growth of excessively tall canes which are difficult to harvest.

The rates in Table 2 are lower than those advocated by Jenner and Parminter (1981). It appears however that raspberries can reach optimum quality and yields on quite modest fertiliser applications. As fertiliser costs are becoming a significant proportion of total production costs, more consideration should be given to relating the amounts of fertiliser required to crop yield thereby avoiding over fertilisation. With careful monitoring of performance, a gradual reduction in applications should be possible.

Several compound high analysis fertilisers suitable for raspberries are available in New Zealand. Those based on chloride should be avoided. Other manufacturers supply mixes suited to berryfruit.

NUTRIENT DISORDERS
Providing a complete fertiliser programme is followed, it is unlikely that macronutrient deficiencies will occur. Work on the nutrition of Red Antwerp raspberries in the Nelson region during the early 50's showed that increased vigour and yield responses could be obtained following addition of micronutrient fertilisers containing Cu, Zn or Mo. Plants showed few, if any symptoms of deficiency however. Of all the micronutrient disorders though, B deficiency is probably the most important.

The typical symptom of B deficiency appears as a dieback with delayed budbreak, or complete budbreak failure (Askew et al., 1951). Some buds give rise to distorted leaves with unusually large petioles and a border of necrotic tissue. Leaves forming later do not show this. Less severely affected buds give rise to leaves with small deeply indented leaflets which persist throughout the season. Symptoms are rarely seen on the primocanes.

Concentrations of B in affected leaves of the Red Antwerp variety grown in the Nelson region ranged between 13-25 ppm. Responses to B and leaf concentrations associated with deficiency symptoms in other varieties may be different.

If specific deficiencies involving Mn, B or Cu have been identified, and confirmed by leaf analysis, correction with the following treatments should be sufficient to alleviate the disorders. For Mn deficiency 1-4 foliar applications containing 200 g MnSO₄ plus 300 g hydrated lime/100 i should be applied at intervals approximately 10 days apart until symptoms disappear. Black oxide spray deposits may occur on foliage and fruit with this treatment however. If it is necessary to continue the applications when fruit is present, spray concentrations of 100 g MnSO₄/100 i will avoid the problem. Soil applications of 9-36 kg borax/ha, or foliar applications of 5-20 kg Solubor® dissolved in water and applied at a rate of 100-400 i/ha, are recommended for correction of B deficiency in raspberries. Copper deficiency can be treated with foliar applications of copper oxychloride (1 kg/100 i) applied at a rate of 200-300 i/ha. A wetting agent should be used if it is not already included in the product.

FURTHER READING
Askew, H.O., Chittenden, E.T. and Monk, R.J. (1951). 'Dieback' in raspberries, a boron deficiency ailment. Journal of Horticultural Science, 26: 268-284.

Jenner, K.A. and Parminter, I. (1981). Raspberries. Management techniques. New Zealand Ministry of Agriculture and Fisheries AgLink, HPP 180.

Ljones, B. (1966). Bush fruits nutrition. In: Temperate to Tropical Fruit Nutrition (Childers, N.F., ed), Horticultural Publications, Rutgers - The State University, USA. pp130-157.

Turner, D.H. (1977). Raspberry Production. Bulletin 19, East of Scotland College of Agriculture, UK. pp96.

Wood, C.A., Anderson, M.H. and Smith, A.M. (1962). Quantities and composition of crop materials removed from an established raspberry plantation. Horticultural Research, 2: 85-95.