Adequate water supplies are critical for cranberry production. Water is used for irrigation, frost protection of fruit buds in the spring and berries in the fall, wet harvesting and winter flooding. Water requirements have been estimated at between 7 to 10 acre-feet of water per acre of cranberry bed each year ( 0.86- 1.23 ha-m of water per hectare of cranberry). This translates into a one acre of water storage, 7-10 ft deep for each acre of cranberry bog (assuming there is no recharge from natural watercourses or groundwater). Direct withdrawal of water from natural watercourses to supply the bog is permitted provided a Watercourse Alteration permit from the Department of Environment is obtained.
Sand is used in cranberry bog construction to ensure rapid water movement through the upper soil layer and prevent water ponding on the bed surface. Cranberries will not flourish under constantly wet soil conditions. Ponded water in the beds may cause problems with root rot and eventual death of the vines. A moist, well oxygenated root zone approximately six inches deep is preferred by the plants. Ideal sand texture is classified as 80% coarse sands (particle size from 0.2 & 2 mm) and 18% fine sand (particle size between 0.02 and 0.2 mm). This size distribution allows enough coarse material for good drainage and sufficient fine sand to provide adequate moisture and nutrient holding capability to supply crop requirements.
The quantity of sand initially required to supply a 6 inch layer (0.15 m) for planting new cuttings is 806 cubic yards per acre (616 cubic meters per acre). Once in production, the beds are re-sanded (0.5 - 1 inch) every 2 or 3 years. This is equivalent to 65-138 cubic yards of sand per acre (50- 106 cu m/acre). Sand does not have to be located on site however the cost of transporting sand will increase the initial development costs of the bog and subsequent annual operating costs.
The ability of the site to hold a flood is directly related to the soil type present and the natural groundwater hydrology. A comprehensive series of test holes should be dug on the site to map and evaluate soil characteristics and to determine the depth to the existing groundwater. The bog design should reflect these site characteristics. The pH of the native soil, sand and water source should be tested. Cranberries prefer pH's in the range of 4.0-5.5.
Other Parameters to Consider:
When selecting an area for cranberry development, the slope and vegetative cover are considered. Sites with a slope greater than 2.5% are generally avoided. Excessive requirements for site leveling (cuts and fills involved) will increase construction costs considerably. The site may be stepped (terraced) to minimize some of the cuts and fills. If that is the case then the size of the pump(s) required to move irrigation and flood water will increase because of the higher elevation lift from the water source to the beds.
Cleared and wooded sites have different associated development costs and challenges. Marketable wood should be cut and sold, but the stumps and waste must be burned or disposed. Roots and stumps are unsuitable for use in dikes or berms as they will rot and cause the structure to settle over time.
The overall size of the site should be considered since only 50-65% of the area will actually be planted in cranberries. The balance of the area is required for roads, berms, drainage ditches, ponds, buildings and any buffer areas in support of the development. The ideal production size will vary depending on site conditions. There is also some economy of scale associated with the purchase of equipment like harvesters, pruners, etc.
Site location and accessibility are essential considerations. Year round access to the site through the provision of good roadways is important. Existing access roads on the site should be evaluated to determine if they are capable of handling heavy equipment traffic. The cost of upgrading these existing roads or constructing new must be included in initial development cost estimates for the project. If the site is located on a floodplain, the predicted flood frequency needs to be examined and design features incorporated into the plans to protect the site. Access to electrical power, especially three phase power, would allow the developer to consider the use of electrical motors for pumps versus diesel or propane powered units.
Will the project impact a watercourse or a wetland? If a wetland is present on-site, the project needs to be registered for, and possibly undergo, an Environmental Impact Assessment. Environmental considerations must be accounted for when selecting a site. Initial designs may need modification to address issues or concerns. For example, a design consideration that has been requested to date in New Brunswick includes the construction or provision of a reservoir to store drainage water from the cranberry production area prior to release from the site. This reservoir acts as a sediment control basin and allows for the degradation of agri-chemicals.
The Department of Agriculture, Fisheries and Aquaculture strongly advises all potential cranberry developers to file their project with the Department of Environment and Local Government prior to initiating any construction. This will help ensure that all relevant permits are in place and the project can proceed without unnecessary delay. Site registration and compliance with regulations will benefit the developer if further issues or concerns arise.