If you are looking for a vegetable to grow in the autumn/winter consider peas.
Peas (Pisum Sativum) are part of the legume family which includes beans, groundnuts and clover. They are a cool season annual vegetable grown in autumn/winter. They are nitrogen-fixing plants, which means that they provide the soil with nitrogen, an important nutrient. This makes them a good cover crop. They are relatively easy to grow and need limited space making them ideal for emerging farmers like you.
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Peas are divided into three main classes: mangetout (snow peas), sugar snap and garden (shelling) peas.
Mange Tout (Snow Peas): These are flat pod types that are harvested while peas are barely formed and are eaten whole. Mange tout means eat all in French. Cultivars include 'Oregon Sugar Pod', 'Snowflake' and 'Oregon Giant'.
Sugar Snap: these have thick pods that are eaten whole. Sugar snaps are a cross between common peas and mange tout. They are used in salads and stir fry ( Asian cuisine). Some cultivars are 'Sugar Snap', 'Sugar Ann', and 'Cascadia'
Garden Peas (Shelling): edible podded peas that are small and round. They are typically referred to as common peas or shelling peas. Some cultivars are 'Onward', 'Alderman' and 'Green Feast'.
Site and Soil
Peas do best in a sunny, well-drained site. While they can grow in a wide variety of soils, they do best in sandy loam or clay loam soils. They do not thrive in heavy, waterlogged soils.
The ideal soil pH for peas is between 5. 5 and 7.0. Do a soil test to determine your soil's pH (alkalinity or acidity). The pH determines the level of nutrients available to your plants. Amend soil with dolomitic lime if the pH is below 5.
Plant peas (early, second early and main types) in the dry season from February/March to July/August (autumn/winter). It is important to plant on time to avoid problems from high heat or frost.
Peas are sensitive to heat and very low temperatures. They prefer temperatures between 15 and 25 degrees C. Temperatures above 26 degrees Celsius reduce germination, suppress flowering, are detrimental to sweetness and increase stringiness of pods.
High temperatures also lower crop yields and promote pest and disease such as powdery mildew and fusarium wilt. They also encourage pests such as Helicoverpa bollworm, leaf miner and thrips.
Although the plants are relatively frost tolerant, the peas themselves can be damaged by frost. Select growing sites with the lowest frost risk at all the times. Flower buds, flowers and pods are sensitive to very low temperatures and are damaged by frost. Young plants, however, are tolerant of light frosts.
Crop rotation is one of the best ways to prevent disease. Avoid planting peas after growing tobacco because soils may have a nematode infestation. Conduct a soil test to check for soil nematode levels.
Fungal infections are also common, particularly in early and late plantings, and it is, therefore, advisable to plant upwind from earlier plantings when plantings are being staggered. This will reduce the spread of disease. Dry hot winds cause flower drop and pod malformation, particularly from mid-September onwards.
Peas are sensitive to residues of some herbicides applied to previous crops, including Atrazine and Command. It is a common recommendation not to plant on lands treated with residual broadleaf herbicides.
Land Preparation and Planting
Clear the fields of any weeds and clumps well ahead of planting. Prepare soils to a fine tilth and good depth.
Pre-irrigate the field to field capacity. It is then very important to keep the soil moist during germination; this is not only important for germination but will also prevent capping.
Three weeks after germination the plants should be stressed for 10-14 days to harden them off. Do not stress quicker than three weeks as the roots will not cope. This also gives any un-germinated seed a chance.
Plant peas in beds to improve drainage, to keep the plants off the ground during picking, and pickers out of the rows. Make beds wider and flatter than tobacco ridges, and give them a top of about 90 cm. Make spacing 1.5 m (bed centre to bed centre) for the bush type varieties and 1.8 m for the trellis type varieties.
Apply fertiliser banded about 5 cm to the side and 5 cm below the seed or it can be broadcasted before making up the beds.
Seed Treatment and Sowing
Legumes such as peas have specific rhizobia requirements. If it is your first time growing peas in the field it is important to inoculate seed with a suitable rhizobium (Rhizobium leguminosarum).
Rhizobium promotes nitrogen fixing, legume nodulation, grain and biomass yield and post crop nitrate levels. Commercial inoculant formulations are available from the Zimbabwe Department of Research and Special Services. Purchase only what you need for one season.
When growing under contract the seed is supplied pre-dressed for the normal seedling diseases, but an extra Benomyl seed dressing can be made before planting.
Sow seeds directly in the field in rows. About 100kg of seed is needed per hectare. Sow seeds 2-3 cm deep with a spacing within rows of 10 cm apart. Seed germinate in about 1 and half weeks.
Vining/tall types (indeterminate varieties) of peas need some type of support as they grow. This allows the pods to develop with good air circulation and provides easy access for crop management. (fertilising, monitoring and harvesting).
The sugar snap trellis should consist of a stake (simple form for plant support) every 5-6m, to support wires and vegetable netting. Poles should extend 2.2 m above ground level with a 30cm gap between soil and bottom of the net (use 1.5m netting). The netting should be hung from 16 gauge wire and secured at the bottom with either 16gauge wire or baling twine. The height can be increased by strands of 16 gauge wire or bailing twine above the net.
Extending the trellising height will improve yield potential significantly. If you don't use netting, then three doubled strings should be attached to the stakes at 30, 60 and 90 cm above the ground. The plants must be trained in-between the strings. The plants are fairly heavy and need fairly sturdy stakes. The stakes should be anchored at the end of each row. Train your pea plants during the warmer part of the day to reduce damage.
Growers are strongly advised to have soil samples from their lands analysed regularly. The nitrogen, phosphorous and potassium (NPK) status of specific soils can only be reliably determined by soil analysis. The soil pH must at least be known, as this exerts a strong influence on the availability of nutrients, particularly the minor or trace elements. Excessively low pH is corrected by application of lime at the time of land preparation. Typically, the following fertiliser program is used for peas (given as “NPK”):
Basal dressing 500 kg/ha “6 17 6” (Compound S)
Or 500Kg/ha “8 14 7” (Compound D)
Week 3 100 kg/ha Ammonium Nitrate
Week 6 100 kg/ha Ammonium Nitrate
Flowering 100 kg/ha Ammonium Nitrate + 50 kg/ha MOP (Potassium Chloride) 7 to 10 days later
After 1st pick 50 kg/ha Ammonium Nitrate+ 50 kg/ha MOP
1 week later 50 kg/ha Ammonium Nitrate
Ammonium Nitrate (AN) should be applied immediately ahead of irrigation cycles to avoid burn.
Organic matter: adding well-rotted compost or compost to your beds will help improve soil structure, retention and nutrients. Add organic matter when preparing the soil at a rate of about 20t/ha.
Flowering and pod formation are the most water sensitive stages and a lack of soil moisture will seriously affect yield and quality. Good irrigation management is crucial at this stage. The pea plant is, however, reasonably drought resistant during the early stages of growth. Excess moisture during the vegetative phase causes rank growth, delayed flowering and promotes lodging and diseases.
Plants should then be given between 24 to 35 mm per week. It is particularly important to ensure sufficient irrigation during harvesting to avoid limp peas and dry calyxes. The maximum rooting depth of peas is between 40 and 45cm.
Peas are not very sensitive to weed pressure. Weeding can cause disturbance to surface roots. When you do weed use hand weeding and mulching.
Pest and Disease
Nematodes: The initial symptoms will be a reduction in plant vigour but a severe infestation will cause a rapid decline in plant health resulting in death. Feeder roots will be absent and root nodules will be visible on the remaining roots.
Control: Follow a suitable crop rotation (e.g. marigolds, Rhodes grass or maize) to avoid a build up in the nematode population. Where the risk of nematode infestation is high, e.g. on sandy soils or old tobacco lands, monitor plants for symptoms of nematode infestation. There are no nematicides cleared for use on export peas. Ploughing in of green manure such as tagetes or thymus vulgaris at least 3 weeks before anticipated planting date will assist. Select well-drained soils.
Cutworms: Field scouting for cutworm (Agrotis spp) should begin as soon as the first peas start emerging. Cut worm cut through the stem at ground level and can be found just under the ground near affected plant.
Control: Karate (lambda-cyhalothrin) can be used to control cutworm before 1 June or after 31 August.
Heliothis / American bollworm (Helicoverpa armigera or tobacco budworm): causes damage by eating buds, flowers and pods. It will often be found feeding on the pod with its rear end protruding outwards.
Bollworm can be responsible for large losses in yield and must, therefore, be swiftly and efficiently controlled. Scout buds regularly for eggs and spray at first sighting. Karate is effective against Heliothis, but should not be used between 1 June to 31 August to comply with local pyrethroid resistance management strategies.
Control: During picking, when PHI’s of most chemicals hamper picking, Biobit or Dipel (Bacillus thuringiensis toxin), Align/Neemix or Garden Insecticide Concentrate (natural pyrethrum) are useful options. Spraying Karate flares up thrips populations thus should only be sprayed as required, not as a routine spray. Always include 2l/100l molasses to thrips and worm sprays.
Web worm: The webworm is a small green caterpillar, about 15 mm long. It spins a fine web, which binds the leaf margins together causing the leaf to roll. It feeds on leaves in and around the webbed area. The same sprays used for bollworm will control webworm.
Leaf miner: The larva burrows through leaves leaving meandering trails of black excrement. When mature the larva exits the burrow leaving a hole in the leaf and drops to the ground where it transforms into a pupa and eventually a small fly about 2 mm long.
Two species occur in Zimbabwe, the American leafminer and the pea leafminer. American leafminer makes circular or “serpentine” mines and rarely causes economic damage and spraying is therefore not usually necessary. The pea leafminer makes straighter mines along leaf vines and margins and can make mines in the pod. Pods with mines are not marketable, and exported pods must be 100% free of mines (which may contain live larvae).
There are currently no chemical sprays that can be used while pods are being harvested due to the lack of tolerances for such products in the export country. Trigard (cyromazine) can only be used before pod formation.
Control: Use natural enemies (parasitic wasps) and trapping. Parasitic wasps occur naturally and must be conserved as far as possible.
Thrips: thrips are small, torpedo-shaped, highly mobile insects about 1 to 2 mm long. The immature thrips are wingless and yellow while the mature thrips are brown with wings. They lay their eggs in the pods leaving a small hole surrounded by a white halo. Nymphs pupate in the soil so tobacco scrap applied on the ground around the base of the plant will break the cycle of the thrips by killing the larvae and pupae in the soil. Thrips damage is often responsible for reduced pack outs.
Control: Sugar at 200g/100l or Molasses 2l/100l water will improve the efficacy of Malathion sprays. The increased rate of sulphur at flowering is also done to control thrips; sprays should be done in the late afternoon to avoid burn.
Aphids: pea aphids are the most common insects in field peas. These are tiny insects that are light to dark green and are prevalent in warm, dry spells. They settle on the underside of leaves and shoots causing distorted growth.
Control: aphids can be managed using beneficial insects (ladybugs and parasitic wasps), spraying with a blast of water from a hose to wash adults; use a recommended pesticide such Dimethoate 40 EC if an economic threshold is reached.
Fungal infections can be responsible for substantial losses in exportable yield and effective control is therefore vital.
Aschocyta : Aschocyta pisi is the fungus responsible for “black spot” or (more accurately) “brown spot” on peas. The disease is favoured by moist, cool weather. Overhead irrigation and pivot irrigation favours disease development. It causes lesions on both the pod and the leaves, as well as on stems. The lesions (or spots) are slightly sunken, tan and sharply delineated by a dark border.
Control: Ortiva (Azoxystrobin) (600ml/ha) is effective in preventing it. The spots are usually circular on leaves and pods. When spores are produced, the lesions have a concentric ring pattern, which is easily visible. Pods with Ascochyta spot cannot be exported, so the disease must be controlled at an early stage.
Preventative sprays of copper compounds (copper oxychloride, Kocide) and mancozeb (Dithane M 45) or metiram (Polyram) should be used every 7 – 14 days to suppress the disease. Ortiva is also an effective controlling (800ml/ha). Once lesions become severe or concentric rings become visible, curative products must be used.
Fish Eye rot: is a severe form of blackspot which develops in storage and is typically associated with tobacco farms. Careful disinfection of lugs and storage areas using chlorinated water is advisable to prevent the spread of infection within the farm and across the network of farms.
Control: Rovral (can be used as a protectant with some eradicant action up to flowering. Rovral makes a useful rotational partner to other recommended fungicides.
Once flowering has started, azoxystrobin (Ortiva) can be used. This is a highly effective (if used early enough) but expensive product, and should not be used more than 3 times per season.
Mycosphaerella – Mycosphaerella pinoides causes long brown lesions on the stem and brown angular leaf spots with a halo. The fungus will often come in late in the plant’s life. A Benomyl seed dressing is recommended at 300g/100 kg of seed to give early protection.
Powdery mildew: A whitish, powdery fungal growth that appears on leaves and stems. The disease is a problem in the warmer months when the days are hot and dry and the nights cool enough for dew formation. Avoid watering the foliage if possible and water at the base. Frequent rain or overhead irrigation causes wet foliage. Crops grown under pivot or overhead irrigation will require greater protection by spraying and cultural practices. Powdery mildew forms a whitish-purple mycelium under the leaves and small green pimples on the pods. The green pimples turn black after storage making the peas un-exportable. Preventative sprays of Dithane, Polyram and Sulphur (2000g/100l) will help to suppress powdery mildew. As a curative, Ortiva can be used (600-800ml/ha)
Integrated Pest Management
- Plant at the right time and location
- Use disease-free, resistant varieties
- Practice crop rotation
- Give plants plenty of light and air
- Use drip irrigation to minimise wetting foliage.
- Practice good crop monitoring to identify pest early
- Attract beneficials (natural predators)
- Keep plants well-watered during critical stages (flowering and pod formation)
- Remove and discard diseased plants
Harvesting and Post-Harvest Handling
Peas are hand harvested between 8 to 11 weeks after planting depending on the time of year and the location. A pack out of about 70% should be aimed for which should result in exportable yields between 3 to 6 tons per hectare.
Yields are lower early and late season when it is warmer and mange tout yields slightly higher than Sugar snap. Picking mange tout usually spreads over 4 weeks in the warmer months to a maximum of 6 weeks in the cooler months while sugar snap can be reaped for up to 8 weeks.
Mange tout should be picked as the pods reach their full length but before the seeds start to enlarge. The pods should, therefore, be flat at picking. The right harvesting stage is about 10 days after flowering. The ideal length of mange tout at harvest is between 6 to 9 cm. The ideal length for sugar snaps is between 5 to 9 cm.
Sugar snaps seeds should be slightly enlarged resulting in an oval pea. It only takes two to three days for the seeds to enlarge and consequently, it is very important to keep on top of the picking. Failing to do so can result in large volumes being dumped (rejected).
Overgrown pods left on the plant will suppress the growth of younger pods. Twenty pickers per hectare should be sufficient during peak picking. After picking the peas must be placed in the shade immediately and covered with clean wet hessian. The peas must then be placed in a cold room at 0-2 degrees C as soon as possible and should preferably reach the packhouse within two days from picking.
After harvesting is complete, the stover (the leftover leaves and stalks) can be fed to dairy cows.
Pods should be sorted and graded based on size, uniformity of pods. High quality is required for premium price.
Your pods should be free of mildew and insect damage to avoid rejections. If your peas are rejected you could use them as animal feed.
Snow peas and snap peas are typically grown for export to the EU where demand is high. The high demand period for peas is during the EU off-season (winter). Get the appropriate accreditation for export, the basic requirement is Global G.A.P certification. GAP stands for 'Good Agricultural Practices.'
Zimtrade is a good resource for export information and identifying markets. Identify markets before production, especially for export markets.
If there is a contracting company in your area work with them if you are getting started. Do your due diligence to make sure that they are a good partner. Follow the guidelines to produce the right quality and yields.
Average local market prices for peas (fresh and shelled) are available through eMkambo.
Further readingThe Winter Harvest Handbook: Year Round Vegetable Production Using Deep-Organic Techniques and Unheated Greenhouses
About the Author
Kevin Jena has experience with commercial horticulture production. He is passionate about feeding the nation!