Hand out for phosphate fertilization

Standards mean that phosphate fertilization is restricted for a grower. This is awkward because it is precisely the yield from shallow rooting crops which respond favourably to a plentiful supply of fresh phosphate. The plentiful supply of manure/fertilizer also makes it an attractive option for covering the requirement for organic matter and other nutrients using this manure/fertilizer as far as possible. Here are some of our own practical tips.

Apply phosphate in the spring.

A phosphate fertilizer should be applied in the spring. The soil temperature is then relatively low and the soil phosphate is less readily available. Also, the plant has only a limited root development. Test results confirm that spring application of phosphate produces the highest yield. Although late summer application of manure is possible, an application in spring is preferable provided that (certainly on clay) this is done with a system that does not cause any structural damage.

Placement of phosphate

Phosphate is not particularly mobile in the soil. For crops such as potatoes, onions and leaf vegetables (crops which are cultivated in rows) the phosphate must be placed directly next to the roots. Row fertilization with animal manure is therefore the recommendation for maize and potatoes, for example. Mineral fertilizers can more easily be placed close to the root, as can liquid fertilizers. Via placement (row fertilization) approximately half as much phosphate is required in comparison with scattered spreading. In other words, the functioning coefficient of phosphate is twice as great via row fertilization compared with full area application.

Dry weather and phosphate fertilization

Dry weather greatly restricts availability of phosphate. However, there is no point in fertilizing with extra phosphate; precipitation will quickly eliminate any temporary phosphate shortage in the spring.

The best way to deal with phosphate

Here are a few tips below. These tips make a contribution towards limiting emissions and ensure optimum phosphate use, i.e., reduce costs.

Tips for the best ways to deal with phosphate in agriculture

• Ensure that you know what the phosphorous status of your soil is. It would be a good idea to have a sample taken as soon as possible before cultivation (every four years minimum).
• Create a fertilization plan per plot of land or crop. It is hard to readily detect a lack of phosphate and additional applications in the season are ineffective. Consult with an adviser to check your own opinion and to optimise fertilization wherever possible.
• Apply phosphate in the spring shortly before sowing or planting. Where suitable in the form of animal manure, and top up with chemical fertilizer (if legally permissible / derogation). Phosphate (in manure or chemical fertilizer) applied late in summer is less effective than an application in spring. The optimum time is two to three weeks before soil preparation.
• The most needy crops are potatoes, onions and leaf vegetables. Give these crops the most manure/fertilizer.
• Application of manure/fertilizer in the spring requires proper planning, at the right time, in the right amount and with the right equipment. This is to avoid structural damage, amongst other things.
• Because phosphate is not mobile you must ensure that it is close to the young roots. Preparing the land is generally the only time that you work the soil in the spring, so apply before this time!
• Row fertilization ensures better usage and means less phosphate is needed. The young plant can get sufficient food easily because placement means a high concentration next to the root.
• Choose a fertilizer containing phosphate and nitrogen in the right ratio. Having a custom blended fertilizer is a solution.
• In case of chemical fertilizer, use phosphate fertilizers which are highly water-soluble.
• Adding humic acids in combination with phosphate improve the phosphate availability for the plant. Adding humic acids can be done in full area applications before or during sowing (liquid). Fertilizers coated with humic acids are the most practical solution (a single operation, less structural damage).
• Loose soil (good structure) with a good ratio between soil, air, water, nutrients and organic matter ensures optimum rooting. Good rooting is crucial when it comes to the absorption of phosphate.
• Foliar application using phosphate is ineffective.

Tips which lead to an emission neutral method

• Prevent leaching. Leaching from the phosphate-rich soil layer is an important route through which phosphate can get into the surface water. Therefore, keep the surface of your soil “unworked” after the main crop has been cultivated.
• Prevent the fertilizer from getting into the surface water through correct use of fertilizer spreaders or side spreaders.
• Drainage pipes must be at the right depth. Shallow drainage pipes remove water with phosphate from the phosphate-rich top soil.
• Avoid fertilizing when the ground is cracked. This leads to direct leaching of fertilizers via the preferential flow paths to the drainage pipes and so to the surface water.

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