Of all the berry crops, highbush blueberry has the highest demands for soil chemistry and moisture. However, one bush grown under optimal conditions can provide fruit for up to 50 or even 60 years! The reasons for such demands lie in the anatomophysiological peculiarities of highbush blueberry. Let’s consider the main components of high yields of blueberries that are established before the fruiting period.
Location
When choosing a site for planting highbush blueberries, prefer an open area with maximum sunlight access. Plants can also grow in semi-shade, but as the shade increases, the flower coverage per unit area decreases, and consequently, the total yield. It is necessary to avoid areas surrounded by trees, which also create competitive conditions in the struggle for soil moisture.
Soil solution, substrate, and pH
The fine fibrous root system of highbush blueberries is often colonized by mycorrhizal fungi. Glucose secreted by the plant’s root system attracts symbionts. The fungi penetrate the blueberry roots with their hyphae and obtain nutrients from them, but in turn, provide the plant with essential nutrients, particularly phosphorus. Additionally, mycorrhizae improve plant water uptake by increasing the coverage area and enhance resistance to pathogenic microorganisms by stimulating the plant’s defense mechanisms. Favorable conditions must be created for the full development of mycorrhizal fungi: a pH range of 3.5-4.5 (up to 5) for the soil, moderately moist and well-drained soil.
The required pH level is achieved by using fertilizers with a pH range of 3-5. These needs are met by using Novalon 3-7-37+МЕ, Novalon 13-40-13+МЕ, and Novalon 19-19-19+ME fertilizers, with parallel acidification using Hydroponica UP (urea phosphate), which is also an excellent source of phosphorus.
The proper selection of soil or substrate during plantation formation is an essential component of intensive growth and good yields. Soil with low pH and high organic matter content is an ideal choice for forming blueberry plantations. Adding Kekkila professional peat to the soil will help create the necessary conditions since it has an acidic pH level and, due to its mechanical composition, creates optimal air regime conditions for the root system. Due to periodic leaching and mechanical erosion of the peat substrate, it is necessary to replenish the substrate of the beds to maintain favorable conditions for the soil solution.
General preparation of the site for planting highbush blueberries begins with the formation of a ridge with the addition of substrate and sulfur-containing fertilizers, according to the recommendations of the agrochemical laboratory, and should be done in advance – at least 6 months. The presence of a ridge is a guarantee of intensive growth and development of the root system of the blueberry plant. Peat, when added to the ridge during planting, should be moist to retain soil moisture for the plant. Dry peat will draw moisture away from the planted plant.
Nitrogen – what is it for?
Nitrogen is a structural component of several important parts of plants and compounds, including chlorophyll (the central magnesium atom is connected to 4 nitrogen atoms), nucleic acids (DNA, RNA) in every cell, and all proteins.
The blueberry is not able to efficiently utilize the nitrate form of nitrogen (NO3) because it evolved in soil conditions where nitrate nitrogen is not present in large amounts in nature. Blueberry plants are dependent on the availability of nitrogen in the ammonium form (NH4). The plant can uptake both forms of nitrogen but has limited nitrate reductase activity and therefore cannot efficiently use nitrate forms of nitrogen. Nitrate reductase is an enzyme that is necessary for the conversion of nitrate to nitrite ions and later to amino acids and proteins. Excessive fertilization with nitrates on blueberries results in leaf scorching.
When creating a bed mulch with peat moss, it is important to use only material that has been composted for 2-3 years. If fresh peat moss is used, the mineral nitrogen in the soil will be used by microorganisms to decompose the peat moss and will not be available to the plant.
The annual nitrogen requirement can be divided into two or three equal portions for application in May and June, using Novalon 19-19-19 fertilizer products with parallel application of Hydroponica UP (urea phosphate) for fertilization, supplemented with foliar feeding of Novalon Foliar 20-20-20+ME and Speedfol Amino Vegetative. The application of a large amount of nitrogen during the fruiting period stimulates late shoot growth, which will be prone to winter kill.
Magnesium
The maximum level of magnesium bioavailability at pH 5.0-7.5 soil is beyond the optimal conditions for the development of highbush blueberry root systems. Therefore, there is a need for fertilization with complex fertilizers containing magnesium by applying a range of Novalon 19-19-19+ME and Novalon 3-7-37+МЕ, combined with magnesium sulfate. The physiological role of magnesium in the plant organism is diverse:
- It is a component of chlorophyll;
- It activates enzyme systems;
- It is essential for respiration;
- It significantly increases carbohydrate formation in plants;
- It enhances cell turgor.
Therefore, it is impossible to neglect magnesium root nutrition. The visual manifestation of magnesium deficiency is the reddening of the leaf blade edge.
Iron
Highbush blueberries are sensitive to iron deficiency. Symptoms of such deficiencies include chlorosis on mature leaves and interveinal chlorosis on young leaves, which turns from pale yellow to white. The plant gradually ceases to develop and withers. Among other functions, iron is involved in respiration and metabolism in plants, as well as in nitrogen fixation. The limited absorption of micronutrients, associated with the pH level of the soil solution, is the cause. Low pH of the soil solution leads to excessive availability of manganese, which in turn blocks the absorption of iron. A preventative measure to combat iron deficiency is the application of iron to the leaves, rather than the roots.
Zinc
Highbush blueberries are sensitive to Zinc deficiency. Symptoms of such deficiencies include chlorosis on mature leaves and interveinal chlorosis on young leaves, which change color from pale yellow to bleached. The plant gradually stops developing and withers. Among other functions, Zinc participates in respiration and plant metabolism, as well as nitrogen fixation. The reasons for limited assimilation of micronutrients are associated with the pH level of the soil solution. Low soil pH causes excessive availability of Manganese, which, in turn, blocks Zinc absorption. An effective tool for combating Zinc deficiency is preventative foliar application of Zinc.
One of the features of the fruiting of highbush blueberry plants is the fruiting on last year’s growth shoots. Therefore, it is extremely important to preserve these shoots during the winter and early spring periods. To take care of this, it is worth focusing on adding Zinc in the autumn and early spring periods. Under the influence of Zinc, the synthesis of sugars and starch increases, the overall content of carbohydrates, proteins, ascorbic acid, and chlorophyll increases, and drought, heat, and cold resistance of plants increase. The role of Zinc in the formation of auxins and its effect on the growth rates of plants lies in increasing the activity of tryptophan synthetase (Zinc determines the synthesis of the amino acid tryptophan (a precursor of auxin)).
Quality of irrigation water
Highbush blueberry plants are sensitive to the pH of water, salinity of soil solution, chlorides, Boron, and Sodium. Before laying out the plot, it is necessary to check the quality of the irrigation water according to the indicators (the maximum permissible values of water are indicated):
- Electrical conductivity (EC) – 0.45-1.02 mS/cm.
- Bicarbonates – 925 ppm (mg/L).
- Boron – 1 ppm (mg/L).
- Chlorides – 70 ppm (mg/L).
- Sodium – 46 ppm (mg/L).
The key to a good harvest is prevention. Leaf diagnostics during the growing season and soil analysis will help achieve the maximum result.