Outdoor food production

Outdoor production of vegetables or fruit, whether on a commercial or garden scale, depends on many factors such as cultivation, propagation, timing, spacing, crop protection, harvesting and storage, but success is diffi cult unless the right site is selected in the fi rst place.

Selecting a site
It is important that the plants have access to light to ensure good growth. This has a major effect on growth rate, but early harvesting of many crops is particularly desirable. This means there are advantages in growing on open sites with no overhanging trees and a southern rather than northern aspect.

A free draining soil is essential for most types of production. This is not only because the plants grow better, but many of the cultural activities such as sowing, weeding and harvesting are easier to carry out at the right time. Earliness and timeliness is also favoured by growing in light, well-drained soils which warm up quicker in the spring. Lighter soils are also easier to cultivate. For many crops, such as salads, where frequent cultivation is required the lighter soils are advantageous, but some crops such as cabbages benefi t from the nature of heavier soils. In general, heavier soils are used to grow crops that do not need to be cultivated each year, such as soft fruit and top fruit in orchards, or are used for main crop production when the heavier soils are suffi ciently dry to cultivate without structural damage. All horticultural soils should be well-drained unless deliberately growing 'boggy’ plants.

Many tender crops, such as runner beans, tomatoes, sweet corn and the blossom of top fruit, are vulnerable to frost damage. This means the site should not be in a frost pocket. Slopes can be helpful in allowing cold air to drain off the growing area, but too steep slopes can become subject to soil erosion by water flow. Lighter soils, and seed, can be blown away on exposed sites.

Shelter is essential to diffuse the wind and reduce its detrimental effects. It plays an important part in extending the growing season. This can take the form of windbreaks, either natural ones such as trees or hedges or artifi cial ones such as webbing. Solid barriers like walls are not as effective as materials that diffuse the wind. Complete shelter is provided in the form of fl oating mulches, cloches, polytunnels and greenhouses.

Extending the season
Many fruits and vegetables are now regarded as commodity crops by the supermarkets and required year round. It is therefore necessary for British growers to extend the season of harvesting, within the bounds of our climate, to accommodate the market. Traditionally walled gardens provided a means to supply the 'big house' with out of season produce, but commercially this is now achieved with a range of techniques including various forms of protected cropping.
Cultural operations
Soil pH (acidity and alkalinity) levels are checked to ensure that the soil or substrate is suitable for the crop intended. If too low the appropriate amount of lime is added or if too high sulphur can be used to acidify the soil.

Cultivations required in outdoor production depend on the plants, the site and the weather. Usually the soil is turned over, by digging or ploughing, to loosen it and to bury weeds and incorporate organic matter, then it is worked into a suitable tilth (with rakes or harrows) for seeds or to receive transplants. In many situations cultivation is supplemented or replaced by the use of rotavators. If there are layers in the soil that restrict water and root growth these can be broken up with subsoilers.

Bed systems are used to avoid the problems associated with soil compaction by traffi c (feet or machinery). On a garden scale, these are constructed so that all the growing area can be reached from a path so there is no need to step on it. These can be laid out in many ways, but should be no more than 1.2 metres across with the paths between minimized whilst allowing access for all activities through the growing season.

'No-dig' methods are particularly associated with organic growing. These include addition of large quantities of bulky organic matter applied to the surface to be incorporated by earthworms. This ensures the soil remains open for good root growth as well as, usually, adding nutrients. Freedom from weeds is fundamental to preparing land for the establishment of plants of all kinds. Whilst traditional methods involve turning over soil to bury the weeds several methods that use much less energy have become more common. Once planted the crop then has to be kept free of weeds by cultural methods or by using weed killers.

Propagation methods used for outdoor cropping include the use of seeds, cuttings or grafting.

Nutrient requirements are determined and are added in the form of fertilizers. They are usually applied as base dressings, top dressings, fertigation or a combination of methods.

Pest and disease control can be achieved by cultural, biological or chemical means according to the production method adopted. This is helped by having knowledge and understanding of the causal organisms that affect the crop.