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The adoption of effective soil management practices, designed to achieve both high yield and product quality, are key for all horticultural crops, whether grown on owned or rented land. Under Cross Compliance, growers are required to maintain land in Good Agricultural and Environmental Condition (GAEC) by following management practices that maintain soil organic matter levels, reduce the chances of soil erosion by wind and water, and reduce damage to soil structure.
Soil Biology and Fertility
Yield/Quality
Slumping and Capping
Waterlogging
Compaction
Wind Erosion
Water Erosion
By following sound management practices, including the maintenance of organic matter levels, growers seek to maintain and enhance soil microbial activity by achieving a positive balance between water and oxygen availability. Well-prepared seedbeds improve drainage and soil aeration and thus crop development, and in horticulture many crops are grown on raised beds for this reason. Some growers seek to supplement and replace organic matter by carrying out on farm-composting or by buying in municipal compost or other organic manures. By carrying out in-field packing operations, crop residues can also be left in the field rather than being removed to the packhouse, which also enhances organic matter levels. Under intensive cropping systems where high yielding crops are produced, organic matter levels can reduce over time.
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Some crops such as brassicas, salads and cucurbit crops may be grown in modules or blocks by specialist plant propagators and then transplanted into the field by the grower. Others such as umbellifers and alliums, where seeds are small, are drilled at shallow depth directly into a prepared seedbed. Well- structured soils and seedbeds are vital for rapid plant development resulting in high yielding quality crops. Crops are programmed to meet the strict demands for timely supply to purchasers, such as the multiples. Poorly prepared soils with damaged structures are prone to compaction, capping and slumping resulting in unsatisfactory plant growth with reduced yield and quality of product.
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Adequate temperatures, combined with good moisture and oxygen availability, are required for satisfactory seed germination. Capping and slumping delay seedling emergence and subsequent growth. Any soil impedance will damage fragile seedlings and reduce seedling emergence, thus leading to reduced plant populations. Allium seeds in particular are slow to germinate and emerge after sowing. Capping restricts infiltration of water to around 1 mm per hour, so can lead to increased runoff and soil erosion.
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Waterlogged soils are damaging to good plant health, with drilled crops particularly prone to damage after drilling and as seedlings emerge. Roots die in waterlogged soils, crops become stressed and nutrient uptake is reduced. Damaging root diseases such as Phytophthera spp. develop in waterlogged soils.Well-structured soils high in organic matter are less prone to waterlogging. To promote good drainage and rapid root development through the soil profile, growers should aim to create a porous structure in the seedbed directly below and to the sides of the seeds or transplants. Effective field drainage systems are required and crop cultivations should be designed to minimise compaction. Raised bed systems help to reduce soil waterlogging. Irrigation should be managed to prevent over-watering.
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Compaction reduces soil porosity, restricting water and air movement in the soil profile. It affects seed germination, root development, plant growth, yield and quality. Plants in compacted soils are less resistant to crop diseases and pests and there is a reduced uptake of soil nutrients and response to applied fertilisers. Poorly-drained soils are more at risk of compaction, which in turn increases the risk of waterlogging. Investigation of the soil profile to identify areas of compaction is fundamental. The most important soil cultivation operations are those that minimise and remove compaction. Bed formers and powered cultivators should be set to run as slowly as possible to avoid over-cultivation and pulverising the soil more than necessary. Once soils have been loosened by cultivation they are prone to compaction. This can be minimised by use of low ground pressure tyres or cage wheels which can be fitted to tractors or other equipment, or tracked vehicles can be used. Timely subsoiling to break up soil pans will reduce the risk of waterlogging.
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Light soils such as peaty and light sandy soils are particularly at risk from wind erosion. Seedbeds can be eroded and, in extreme cases soil, blow can result in seed and seedlings in topsoil layers being blown away. Seedlings and young plant leaves can be abraded by soil particles. Where salad crops are grown on peaty soils soil can be blown into the hearts, affecting marketability. Growing crops in fields protected by shelter belts and the use of windbreak materials around crop areas can help to prevent wind erosion. The use of cover crops, straw or companion planting with cereals planted in between the rows in small seeded drilled crops such as carrots, parsnips and alliums as a barrier can prevent wind erosion. Crops may be grown through mulches and crop covers can also help to prevent erosion. Increasing soil organic matter levels can help to stabilise soils.
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Light soils are most at risk but all soils can be prone to water erosion in intense periods of rainfall. The leaching of pesticides and fertilisers and damage to soil structure hinders growth and affects crop yield and quality. Measures that can be taken by growers include:
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Planting crops along contours
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Increasing organic matter by the use of composted material
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Avoiding compaction
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Carrying out risk assessments of fields prone to water erosion prior to cropping
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Avoiding fine seedbeds where possible, if they will cap or slump
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Using cover crops (e.g. sowing cereals on pre-formed beds destined for salads to stabilise soils through the winter)
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Maintenance of field drainage systems
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For more information about horticulture visit the HDC website: http://www.hdc.org.uk/index.asp | 
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