Open access publications in the SLU publication database

Vaccinium corymbosum and hybrids between V. corymbosum and V. angustifolium are the blueberry types cultivated in Sweden today. Blueberries contain high amounts of antioxidants and their popularity as dessert berries is increasing. Vaccinium-species are adapted to light soils with high organic matter content, acid pH and ample water supply. In commercial blueberry cultivation, the crop is often established on mineral soils with a higher pH. As establishment costs are high and the crop will continue to develop and yield for many years under good conditions, it is important to adapt the growing substrate after the plants' requirements. If the soil organic matter content is low, soil amendment with organic matter like sawdust or peat is recommended. Mulching with sawdust, bark or peat also commonly has a positive effect on plant growth and yield. The recommended soil pH-range for blueberry cultivation varies but is commonly between pH 4,0 to pH 5,2–5,5. At higher pH, there is a risk for micronutrient deficiency, in particular for iron. If pH is too low, high amounts of aluminium or manganese may damage roots and retard growth. The sensitivity for iron deficiency and for aluminium and manganese toxicity varies between cultivars. For lowering of soil pH before crop establishment, soil amendment with elementary sulphur the year before is commonly recommended. Soil amendment or mulching with peat or sawdust or bark from pine trees may be used for smaller pH reductions, and may also increase iron availability. Most Vaccinium-species are adapted to grow at low nitrogen availability, and blueberries generally have a low nitrogen requirement. High amounts of nitrogen may reduce plant growth and young plants may die. Too much nitrogen may also increase winter injury. For a fully yielding crop, a nitrogen amount of 50-60 kg per hectare has been reported to give good growth and yield from many experiments For younger plants, the amount of nitrogen should be lower. If the plants are mulched with organic matter, the amount of nitrogen should be increased in accordance with the amount of nitrogen that will be immobilized when the organic matter is decomposed. Both ammonium and nitrate may be used as a nitrogen sources as long as the total amount of nitrogen supplied is low and pH is not too high. However, blueberries do have a lower ability to utilize nitrate than many other plant species, and several experiments have shown better growth of blueberries with ammonium, or with a mixture of ammonium and nitrate, than with nitrate only as a nitrogen source. Nitrogen fertilizer should be applied when plant uptake is high. Splitting the nitrogen application on two or three occasions is often preferable to a single application. Addition of high amounts of nitrogen may negatively affect the occurrence of ericoid mycorrhizas in blueberry roots. Potassium may also need to be added and the potassium requirement of the plant increases when fruit production is high. Published data indicate that the relationship between the amount of nitrogen and potassium in the plant varies from 100:40 to 100:75 for young and older plants, respectively. The relationship between nitrogen and phosphorus is approximately 100:10, and the need for phosphorus fertilizer is often low. Blueberries efficiently acquire calcium and deficiency is uncommon. In some experiments, however, calcium addition has had a positive effect on berry firmness. The nutrient status of the crop should be followed by leaf analysis and mineral nutrients added when risk of deficiency is indicated. Blueberries are sensitive to high amounts of salts and addition of too much sodium and chlorine should be avoided.