PCA recommends that growers obtain a complete nutrient analysis or soil test prior to planting their peanuts.

The ideal pH range for peanuts is from 6.0 to 7.0. Soils that are more acidic than this (below pH 6.0) should be limed.

Peanuts are regarded as good scavengers for nutrients but if any nutrients are lacking in the soil - including micronutrients - then yields will be reduced.

Potassium, phosphorus, calcium and sulphur are the most common nutrients applied to peanuts, but growers should also check magnesium levels as these are becoming depleted in many Australian soils.

Micronutrients must not be ignored as a deficiency can sometimes lead to major yield losses. Zinc, boron and molybdenum are commonly used. Copper is often deficient on very sandy soils. Many soils also have manganese deficiency.

Foliar applications of micronutrients are most commonly used, however soil applications are also applicable for some nutrients.

Peanuts also have a relatively high requirement for calcium. Calcium is not very mobile within the plant, so the peanut pod takes up its own calcium directly from the soil. Available calcium must be present in the podding zone (the top 2-10cm of soil).

Adequate calcium is essential for ensuring high quality kernels. Insufficient calcium may lead to smaller kernels and kernels with hollow hearts (not completely filled). Low calcium will also reduce the germination of seed peanuts. In larger seeded peanuts, low calcium levels can lead to kernel abortion, causing empty pods or "pops", splits and poor germination.

To provide an adequate supply of calcium, gypsum (calcium sulphate) is usually applied at early flowering over the peanut row. Gypsum is a relatively soluble source of calcium that is easily absorbed by the pods. Gypsum contains 18 to 20 percent calcium and is applied at rates of 600 to 1000kg per hectare.

Alternatively, fine lime can be applied four to six weeks prior to planting and lightly incorporated. Lime is less soluble than gypsum. It is usually applied at rates of two and a half to four tonnes per hectare and contains 35 to 40 per cent calcium.

High levels of nitrogen are needed for high-yielding peanut crops. However, like other legumes, peanuts fix nitrogen from the air via rhizobia nodules on their roots.

Growers must inoculate peanut seed with efficient strains of rhizobia prior to planting to ensure optimum nitrogen fixation occurs.

When the suitable rhizobia bacteria become established in fields, farmers do not need to add nitrogen fertilisers to peanut crops.

Peanuts also require relatively large amounts of phosphorous but the presence of a fungus on their roots makes them very efficient at absorbing any reserves in the soil.

To illustrate the importance of Vesicular arbuscular mycorrhizal fungi (VAM), experiments in Kingaroy showed that very high levels of phosphorous were needed when there was no VAM present.

Soils which had been sterilised required about 240kg/ha of phosphorus to achieve full growth potential.

But when the VAM was not destroyed, the rate was just 30kg/ha.

Peanut growers have traditionally used high phosphorous rates on alternate crops (eg maize) during crop rotation.

Peanuts respond better to fertiliser left over from the previous crop than to fertiliser directly applied to the latest crop.

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• Soil Preparation
• Peanuts and Fertilisers
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More information of specialist interest to peanut growers, including information and videos from the Best Management in Peanuts research, is available in the password-protected Insite area of this website. Contact us for more information.