Field Preparation for Cranberry Growing

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Once a suitable site has been selected for a large-fruited cranberry plantation, if it is in operation, it is essential to prepare it properly by grubbing out the top layer (10-30 cm) of perennial weeds and the waterlogged areas. After clearing, the site should be leveled, with a slight slope from the middle to the edges, so that it does not collect in the middle of the site after a downpour or a spring flood, but runs off into the ditches. For this purpose, ditches are cm deep around the whole plot. Perennial weeds are completely destroyed by herbicides.

After leveling the plot, the fields are shaped. The topsoil from the fields is used to form a berm, which will later be used as a road for machinery to enter the field.

The fields are usually about 55 m wide and 150-200 mil wide, so one field of a cranberry plantation covers about 1 ha. Fields: smaller, about 0,4 ha, depending on the shape of the plot. In larger areas, two shallower grooves are dug along the length of the field, leaving the cranberry patch of the same width. For the larger cranberries, the planting site is prepared in the autumn.

It is cheapest to set up plantations of large cranberries on cleared upland peat bogs, as there is no need to remove the topsoil, which is full of perennial weeds, and no need to dig ditches (perhaps only to repair them), as the remaining channels, are still in place from the period of intensive peat bog exploitation. In the excavated peat bog, the peat layer for cranberries should be at least 70-80 cm and the peat fragmentation rate should not exceed 30%.

For cranberries to grow well, the soil must also have the right texture, i.e. a sufficiently permeable soil to allow the thin and fine roots of the cranberry to develop well. Therefore, on sandy and sandy loam soils, where the conditions are not quite right for cranberries, it is best to dig deep furrows (trenches) and fill them with a prepared acidic soil mixture before establishing the plantation. It is not recommended to make embankments from a prepared substrate.

If the soil is loam or clay, the sides of the trench should be lined with thicker polythene sheeting, boards, or other materials. The bottom of the trench shall not be covered with plastic sheeting.

Cranberries
Cranberries

Tillage

The soil must be plowed to a depth of 20-25 cm, milled several times, harrowed, leveled, and given a slight slope of about 1 %. Tillage is used to kill or severely eradicate weeds and to prepare the soil (if trenching is not necessary) for planting the cranberry. The use of herbicides is prohibited when establishing organic cranberry plantations. Herbicides are not prohibited on conventional farms and should therefore be used during tillage.

Knowing the characteristics of each soil and the importance of cranberries can help to improve and adapt them for berry production. When the pH of the soil is much higher than that required for large-fruited cranberries, the soil is acidified with sulfur powder or granulated sulfur. The powder shall be spread evenly over the entire plantation and mixed well with the soil. The soil can also be acidified by irrigation with water, sulphuric acid, or nitric acid, but never with hydrochloric acid, as cranberries are very sensitive to chlorine compounds. Acidification should be carried out before planting and later, during the growing season, on the basis of agrochemical soil tests.

Digging (for amateurs)

If the soil is sandy loam, it is recommended to dig a trench up to 40-50 cm deep and of the desired length and width for successful cranberry cultivation, and to fill it with high moorland peat or an acidic soil mix. The trenches shall be dug at intervals of 1-2 m in a north-south direction. Preparation of the acid soil mixture

The soil mixture is made up of acid peat from the raised bog, standing (non-fresh) conifer sawdust, and coarse, non-alkaline sand free of lime particles (3:1:1). The soil mixture shall be prepared in advance and stirred several times with machinery. This substrate is the most suitable for the formation of mycorrhizae. Then, when the prepared mixture has been poured into the trenches, compacted and top dressed, and the surface is smooth and free of depressions, the cranberry plants can be planted.

field preparation for cranberry growing
field preparation for cranberry growing

Planting (on the plantation)

Cranberry shoots are planted in May to mid-June, rather than in autumn, as this is the year in which the plants are able to take root and overwinter better. It is recommended to cover the surface of the leveled fields with a 5-8 cm layer of coarse, non-alkaline sand, free of stones and clay particles, if planting on peat, to improve substrate aeration, reduce evaporation, improve water filtration, protect against weeds and plants in winter, and to reduce temperature fluctuations at the soil surface.

In large plantations, fields are planted mechanically: the cranberry shoots are spread over a predetermined area by means of special shakers. Between 1,5 and 1 tonne of cranberry, shoots are scattered per hectare and incorporated into the soil at a depth of 8-10 cm. After 3 weeks, the cranberry shoots take root and start producing new shoots.

Large-bearing cranberries planted in shoots start to fruit in the fourth year and produce a good crop in the fifth year. If the planting is made with shoots from a continuously cut cranberry plant, some of the generative shoots that have already formed flower buds from the previous year may continue to produce berries in the plantation in the first year.

Planting in the amateur garden

Cranberries are ornamental plants and are therefore suitable wherever a creeping ‘mat’ is needed. It is a good idea to separate this ‘mat’ from the rest of the non-family with a plastic fence 20 cm high or other materials that do not rot quickly and are not harmful to the environment or the plants.

The planting area should be about 30-50 cm deep and about one meter wide (wider is more difficult to harvest). Fill the hole with raised bog peat, which is friable, so it should be poured in batches and compacted to prevent it from sinking in later. Cover the surface with a 5-8 cm thick layer of coarse, non-alkaline sand. For small cranberry groves in the home garden, it is recommended to plant 2 or 3-year-old seedlings. The bushes should be planted at a density of 30×30 or 30×20 cm (or 6-10 pieces per m2), 2-3 cm deep. When planting the shoots, very long forks are shortened. If planting in spring, the cuttings are cut into 8-15 cm cuttings and planted in the nursery or in the same area.

In the case of cranberry introductions, if planted as an annual, the bushes will start to produce after 2 years and cuttings after 3 years.

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