A peanut crop in Bundaberg

On this page:

• Climate and soil
• How peanuts grow
• Planning your crop
• Harvesting
• Marketing and finance
• Peanut growing problems

Climate and soil

Peanuts are a subtropical legume crop needing relatively warm growing conditions and 500 to 600 mm of well-distributed rainfall, plus stored soil water, to produce a high-yielding crop. Where rainfall is reasonably distributed through the growing season, peanut crops produce about 5 to 10 kg/ha of pods per millimetre of rainfall. Areas with high rainfall (over 90 mm annually) or consistently high humidity may have problems with leaf diseases. A well-managed fungicide program is needed in these areas to control leaf diseases.  Peanuts can be grown from southern New South Wales to northern Australia.

Contrary to popular belief, peanuts do not need red soil. The soil must be well-drained and friable with no large stones, sticks, stumps or chemical residues. Peanuts can tolerate a wide range of pH - from 5 to 8 - as long as it is not associated with nutrient disorders. Pesticide residues and heavy metals can contaminate peanuts. Organochlorines, such as dieldrin, endrin, BHC, heptachlor and DDT, are the most common problems. A soil test, along with the pesticide history, will give a guide to likely problems.

How peanuts grow

The peanut plant develops from an embryo embedded between the two cotyldons of the kernel and evetually grows to a bush about 50 cm tall and up to 100 cm wide. Small, yellow, pea-type flowers emerge at 30-40 days after planting (depending on ambient temperatures and on the variety) and, after self-pollination, the ovary's base elongates, bends downwards and penetrates the soil. The tip of this 'peg' then enlarges to form a pod containing one to three kernels. Depending on variety, location and seasonal conditions the growth period ranges from 14 to 26 weeks.

Planning your crop

The variety you choose to grow will depend on the market, soil type and time of planting.

Each stage of crop growth requires specific management decisions and inputs. Optimum plant population relies on careful seedbed preparation, looking after the seed, and planting at the right time, rate and depth with a planter capable of handling delicate peanut seed.

Peanuts have specific nutritional needs. For instance, the pods take most of their calcium and boron directly from the soil rather than through the roots. Calcium is often applied to the crop before flowering. Peanut roots depend on vesicular arbuscular mycorrhizal fungi (VAM) to take up phosphorus and are effective at using residual phosphorus from previous crops in the rotation.

As the crop develops weeds, pests and diseases can affect the yield and quality of the final crop. Managing the crop well through the various development stages takes experience and attention to detail.

Optimal irrigation can increase peanut yields, quality and crop profitability and also reduce the incidence of aflatoxin. To gain these benefits from irrigation more intensive management is required, particularly during the critical stages of germination, flowering, pegging, and pod filling. Sprinkler irrigation is the most common application method, but flood irrigation is suitable on some soils. Irrigation requirements for peanut crops range from 2.5 - 6 ML/ha. The Department of Employment, Economic Development and Innovation (DEEDI) has developed AQUAMAN, a web-based decision support tool to help growers make an informed decision about scheduling irrigation based on crop water demand.

Rotate peanuts with other crops to maintain soil structure and reduce the problems of soil-borne, and other, diseases.

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Harvesting

Harvesting a peanut crop is more complicated than for most other crops because the peanut kernels are underground and often mature unevenly. Correct timing is essential to avoid yield and quality losses. Harvesting is a two-part operation:

• the taproot is cut and the plant tops and pods inverted to partially dry
• a separate threshing operation is done.

The crop is often artificially dried to avoid losses from lying in the paddock too long. Drying peanuts starts with pre-cleaning to remove soil. Then strict guidelines for temperature, humidity, airflow and drying depth must be followed to ensure a high-quality product that will attract high prices. Two systems of drying peanuts operate in Australia:

• truck-back system used in North Queensland
• combination storage/drying system used in southern Queensland.

There is also a recent trend toward sending peanuts directly from the pre-cleaner to the processor where drying is done at much lower cost than using on-farm drying systems.

Marketing and finance

Peanuts are 'mother nature's positive nutritional snack food'. They are high in protein and fibre, and cholesterol free. Peanut products include:

• nut-in-shell
• salted or roasted kernels in many flavours
• peanut oil
• stockfeed
• garden mulch from the shells.

Peanuts can be a profitable crop, particularly with irrigation. Under rain-fed conditions variable yields and quality results in variable returns. Some irrigated crops have achieved better gross margins per hectare and per megalitre of water than cotton. The need for specialist machinery needs to be taken into account when considering the financial viability of peanuts as a new enterprise. The price received for different grades of kernels varies significantly and it is important to consider this variation when preparing budgets.

Growing peanuts as a seed crop for yourself or other growers is another option. Peanut seed is more delicate than most other seed and needs care and attention from planting of the seed crop through harvesting, curing, shelling, storage and seed preparation.

Making hay after the peanuts are threshed can provide extra income and peanut hay can be a good quality, palatable stockfeed. However, removing hay will reduce rotational benefits to the following crop by taking away additional nutrients from the field and these must be replaced. This practice is not recommended.

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Peanut growing problems

Weed control is one of the major objectives of successfully growing peanuts. Not only do weeds compete with the crop for nutrients and water, they make the digging and threshing operations very difficult, resulting in high pod losses. Peanuts can also be a problem weed growing in fallows and other crops.

A range of foliar and soil-borne diseases affect peanuts. Management practices such as crop rotation, variety selection and the use of fungicides, can minimise the effect of most of these diseases.

Peanuts generally have fewer above-ground insect problems compared to other high-value crops. Crops grown in cotton and lucerne growing areas may suffer more attacks from above-ground pests than crops grown in isolation. Soil insects such as whitegrubs and whitefringed weevil are significant pests in established peanut growing areas.