Introduction organic vegetable growing

Course notes classes held 24th May at Hopesay Glebe Farm

Intended as an introduction into organic vegetable growing on a small to medium scale

Soil & Site.

Soil testing

Soil texture and structure. The hand test will tell you which of the soil types you have, Sandy Loam, Medium loam, Heavy Loam. Although Soil Texture cannot be easily changed, knowing the make up of your soil will give indications on how to make the best use of what you have with cultivations and fertility management. In general heavy soils will hold onto nutrients better but will tend to water log in wet seasons. Lighter soils will be hungry well drained and will heat up quickly in spring. Both extremes will benefit from the addition of humus

Soil nutrients:,the test for NPK will inform decisions on what methods of fertility management are required and how best to plan the rotation.

pH and lime Test for acidity and recommend lime use. pH has a big influence on what nutrients are made available to the plant and on other soil fauna which are part of a healthy soil. In general terms alkaline soils are better for most vegetable crops whereas acid conditions give opportunities for ornamental plants. Rate of lime application can be calculated using the pH test results.

Site

Choice of site for vegetable patch usually limited,where possible avoid shade, water-logging and overhanging trees and tree roots. In general terms anything that will interfere with access to sun rain and nutrients.

Rotation and Planning.

Rotation,

Using a rotation of crops means that the same crop is not grown on a plot of land for two years running. Crops are divided into groups of related plants or crops requiring the same conditions and are rotated around pre determined plots within the growing area, so providing the opportunity to apply manures, lime and pest control measures according to the crops requirements. For example by keeping brassicas and potatoes on separate plots allows lime to be applied to brassicas to discourage club root while avoiding lime on potatoes which may encourage scab.
The movement of crops around the growing area limits the spread of some soil borne diseases although this is less effective on smaller plots.
The rotation can be changed according to need. A traditional rotation would be 4 or 5 years say:
Alliums followed by Brassica, followed by Roots followed by Legumes. If Green Manures are used extra years will be added to the rotation.
The rotation will depend on what quantities of each crop are to be grown and whether a green manure crop is to be grown or if fertility is to be added using FYM or compost.

Alliums,

Have need the highest nutrition due to primitive roots also respond to high nutrient levels. Must have high light levels. It is advisable to plant Alliums immediately after green manure or FYM if used

Brassica & Lime.

Brassicas respond well to lime and as it helps prevent the establishment of club root. Lime can therefore be applied if needed before planting. Brassicas can follow Alliums which have had an input from green manure or compost so there is residual fertility from the green manure and any lime applied will help to stimulate microbial activity so liberating more nutrients.

Legumes.

Legumes respond well to alkali soils and need reasonable nutrient levels to establish, thereafter they produce some nitrogen from their nitrogen fixing root nodules.Legumes can be flexible where they fit in a rotation as they have less soil associated problems.

Beets and Salads

These can fit with legumes or alliums, they respond well to high nutrient levels and do not have many soil borne problems.

Roots,

Potatoes, parsnips and carrots,Used late in the rotation so FYM and lime are broken down in previous plantings, so preventing forking of carrot or parsnip roots. Lime avoided for the roots part of the rotation as high lime content in the soil can increase incidence of common scab in potatoes.
Compost or FYM can be added for potatoes but should be avoided for carrots and parsnips. The quantity of potatoes grown will determine if they should have a rotation of their own or if they are included with roots or possiblly legumes.

Green Manure

Green manures will replace nutrients used by crop plants if legumes such as sweet or red clovers are used. They can be used to prevent nutrient loss through leaching when non legumes are used notably over winter. They also provide humus and encourage soil fauna activity.
If Green manures are to be used exclusively to replace nutrients and humus they will need to be grown ay least one in three years or more depending on the natural fertility of the soil and density of planting.

Compost

Making a compost heap: Garden style, square up to 2m square by about 2m high, this size ensures that oxygen can reach the inside of the heap while still being big enough to retain the heat needed for efficient working.
There are four factors in making a successful compost heap
1 Oxygen, make the compost no more than 2m wide so air can pass into the centre of the heap, also the heap should not be over compressed so to prevent the access of air to the centre.
2. Water, necessary for the bacteria to develop and to allow the heap to heat up. When high nitrogen is added to a heap the composting process can be so rapid that it uses up all the available water and stalls the composting process. In winter however the heap must be protected from too much water as this will push the oxygen out causing anaerobic conditions which will also stall the process. Water may have to be added to the heap in hot dry conditions.
3.Heat, this will be generated by the composting process but the design of the heap will help to retain it and kep the process going. The heap should be compacted so each layer is in contact with the next but so squashed as it removes all the air. Avoid water logging and drying out.
4. Carbon to nitrogen ratio: The nitrogen (leafy material) speeds up the process while Carbon (wood/straw lignified material) provides the material to turn in humus and slows the process. With too much N the compost will heat up quickly then stall. With too much C the compost will be cold and slow to start.

In the case of a stalled heap it can be restarted by turning the heap adding water, lignified (woody) material, leafy material as needed to get a proper balance.

Using compost

Plant Cycle.

The normal cycle for a vegetable plant is as follows
1.Seed sown either direct in growing area, in module trays, seed trays or in see beds for later transplanting.
2.Transplanting were applicable either bare root or a module into final cropping area. All transplants are watered after planting
3.Weeding watering and staking and protecting from pest and disease as needed
4. Harvesting

Seed sowing and Transplant production.

Methods of sowing include manual placing seeds either into modules or direct into drills (braodcast sowing used for some spp).
There are push seed sowers which will sow and cover a drill much quicker than by hand.
generally thogh most seed sowing on a garden scale will be manually placing the seed in the drill or tray.
Some still sow seed into seed trays then prick of seedlings into pots or larger trays but with the advent of module trays this practice is seen less.

Pest and Disease Control.

Rotation.

Avoid diseases especially white rot onions, nematodes in potatoes and club root brassicas

Beneficials.

There are various beneficial organisms that will control pests some can be purchased and released deliberately. this method is most useful in an enclosed area like a greenhouse.

Knowledge of which predators are in your area will give the opportunity to encourage them with cultural methods. e.g. Beetle banks for ground beetles

Crop covers,

Effective against most larger pests including Rodents, Cabbage White and aphids
Fleece, mesh and polythene are the three main options.

Organic sprays,

There are various materials which can be used under an organic system, these include soft soap, Ferramol for slugs and copper for potato blight. Although the organic grower would have to apply for a derogation for the use of some of these.

Cultivation methods, Weed Control and Tools.

Site clearance.

If there is a significant covering of weeds these should be first be mown off and either collected then the soil inverted to bury annual weeds. Perennial weeds and roots should be removed by hand before inverting the top soil.
Alternatively a heavy gauge polythene or woven plastic sheet can be laid over the area to exclude light and kill weed growth. this can take up to 2 years if there is a heavy load of perennial weed.

Surface cultivation.

Regular cultivation used prior to planting or sowing. Generally it is advisable to cultivate a shallowly as possible to avoid damaging beneficial soil organisms.
Hand tools: single digging with spades, forking over the surface
Mechanical methods: using rotary cultivators, plough.

Sub surface cultivation.

Hand tools double digging, Bastard trench which can be used as initial site clearance or to break up a pan.
Mechanical methods using deep tines or sub soiling prior to rotary cultivating or shallow ploughing.

Weed Control after initial establishment.

Soil covering using polythene or woven plastic membrane prior to sowing or planting:Using this method the soil covering sheet is removed prior to planting or sowing. The objective is to exclude light so preventing germinated weed seedlings from growing.If the ground is covered for six weeks in early spring this can give four weeks before weed seedlings start to grow.

Weed control Mulches. bio degradable and reusable. Laid by machine hand tools or by hand. The crop plants are planted through the mulch so significantly reducing competition from weeds and incidentally reducing soil moisture loss during a dry summer.

Stale seedbed.

A method which involves allowing weeds to germinate to seedling leaf stage then hoeing off all the weed leaving a clean bed. The concept is to encourage germination of weed seed in the top layer of soil then hoe off to give a weed free plot for about 2 to 3 weeks.

Weed control tools mechanical

If weeds are being controlled using mechanical methods, hoeing should be done before weeds are established.
Wheel hoe
Hoes dutch, draw and push pull hoes.

Planting tools.

Dibber, hand trowels

Seed sowing tools.

Seed sower push
Wolf sower

Protective structures.

Artificial Lighting/Growing Room

Can be useful early season transplant production to give reliable light and heat when its not available outside. Blue light spectrum needed to produce seedlings

Polythene tunnels,

Larger the better, not normally heated for frost protection, used for soil grown crops, module production. A proper rotation should be used to prevent rotation needed to prevent deterioration of the soil.

Greenhouse,

Can be kept frost free, used to raise modules, also useful for growing tomatoes, as due to dry conditions blight is reduced.

Frames/raised beds.

Useful for soil grown crops and can be used to bring on transplants. There is the option of changing the cover: polythene to increase temperature, mesh to keep out pests or shade to reduce temperatures.

Loose crop covers fleece and Mesh.

Theses are laid directly over the crops, usually with no supporting structures.
Fleece will raise the temperature of the soil and will prevent ingress by pests. They are however very light and can damage easily and get blown about letting in pests which then can breed unimpeded by predators.

Gardening year.

Rough guide to jobs through the year

Jan Feb.

Seed sowing Alliums& early Lettuce
Sowing Carrots in tunnel or frames
Harvesting winter and tunnel crops

March April.

Cultivations and incorporating compost
Mulches laid
Planting
seed sowing
weeding, important to weed down now before the rapid growth stage in May

May June.

Weed control
Planting, main season for planting, ideal to get most completed by June
Harvesting early crops
Seed sowing

July Aug.

Weed Control, weeds are seeding by now so important to remove before seed matures
Harvesting
Planting Late crops tunnel and frames
Sowing wintering crops, salads, spinach
Sowing Green Manures