Managing and maintaining soil organic matter is important in small fruit production, as in vegetable crops. Managing properties that affect soil-water relations and root growth may be the primary challenge in sustaining soil quality during production of perennial small fruit crops. Small fruit crops require adequate available soil moisture for high total and marketable yields. However, the roots of small fruits such as strawberry, raspberry, blackberry, and blueberry are extremely sensitive to even short-term periods of saturated soil, so good drainage is also essential. Waterlogged soil restricts aeration, thereby damaging roots and promoting the growth of root pathogens.
Soils with optimum structure provide a balance of air and water in the plant-root zone. Soil structure refers to how soil particles are grouped and arranged. Well-structured soils contain voids or pore spaces of different sizes between soil particles. Small pores hold and store water that is readily available to plant roots. Large pores allow free air exchange with the atmosphere and rapid movement and drainage of excess water. While little can be done to alter soil texture (the size of soil particles), soil structure is strongly impacted by management.
Knowledge of soil structure is important because the perennial nature of small fruit production dictates that special care be taken in selecting a site for small fruit production. For example, some fields are prone to early spring flooding due to high seasonal water tables or poorly drained low spots; these fields are unsuitable for perennial small fruit crops. At the least, such fields will require costly and extensive modification before planting.
Small fruit are least tolerant of water-saturated conditions in the spring and fall when rapid root growth requires good aeration. Flooding during winter dormancy can break and damage roots by increasing soil heaving. While annual crops allow an opportunity for fertilizers and lime to be incorporated into the soil, this is difficult or impossible with small fruit. Small fruit growers must carefully consider soil management needs both before planting and during every phase after plant establishment.
Improvements in soil quality for small fruit production are easier to accomplish prior to planting, rather than after establishment. Ideally, soil preparation begins one to two years before planting is scheduled to occur as poor conditions are not easily changed after planting and are likely to result in crop failure.
Organic matter additions before planting from manures, other organic wastes, high-residue rotation crops, cover crops, and other sources can increase soil aggregation and improve soil structure. These same practices may also improve root penetration, water infiltration, permeability, and available water-holding capacity. Subsoiling can break up impermeable soil layers, increase rooting depth, and create passages for air and water movement.
Conservation tillage in the years before small fruit planting and between rows or beds of established small fruit maintains surface residue, limits crusting of the soil surface, improves infiltration, decreases runoff, and increases earthworm populations by providing a stable habitat. The channeling activity of earthworms and other soil organisms increases soil tilth and porosity.
Crop rotation before small fruit plantings can help control nematodes, weeds, and root diseases. Strawberries, raspberries, and blackberries are all susceptible to Verticillium wilt, which can be suppressed by avoiding the planting of Solanaceous vegetables before establishing small fruit crops. Some plant pathogenic nematodes are suppressed by cover crops of marigold, oat, Brassicas (mustards) like oilseed radish and forage turnip, rye, sudangrass, and sorghum-sudangrass hybrids. Plant residue also contributes SOM as it slowly decomposes.
Small fruit production on raised beds is increasingly common. Raised beds improve natural drainage and aeration and speed soil warming and early spring root growth. Building raised beds provides an opportunity to modify the soil environment by incorporating organic soil amendments, fertilizer, and lime during their construction. Raised beds dry out faster than plantings on flat ground, but this can be counteracted by applying organic mulches on the bed surface to increase water infiltration, reduce evaporation, and conserve water.
Practices to Help Maintain or Improve Soil Quality
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