Agresol Limited

Phosphate

This element is related to the production of roots and stems within the crop. It is relatively insoluble and thus requires a gradual build-up within the soil profile to at least Soil Index 3 for crops to achieve their full potential. This build up is more readily achieved in well-worked soils with a significant organic matter percentage, where cropping and fertiliser regimes are correctly managed.

Despite over 100 years of research, the behaviour of Phosphorus in the soil is still not well understood. This is largely due to the numerous organic and inorganic forms of the element that occur in the soil, and the wide variation of activity according to soil type. There are also wide variations between different crops and their ability to metabolise different forms of Phosphate.

Generally, cases of visually apparent Phosphate deficiency are rare in the UK, mostly due to the use of Phosphate fertilisers. Where deficiency does exist, the crop displays classical symptoms of stunted growth, and some discolouration of leaves may occur. These symptoms are most likely to be seen in crops of spring barley and maize, and occasionally in grass, particularly in cold springs.

Crop uptake of Phosphate can be related to the extent of the root system in the enriched topsoil layers. The greater the root system, the greater the potential for uptake by diffusion. Soil temperature is also an important factor. It has been noted that a supply of available Phosphate is necessary throughout the growing season, but particular importance is attached to availability during the early growth stages of the crop.

Analyses often quote the result of tests as Phosphorus. In this situation, to calculate the PHOSPHATE value, multiply the number by 2.291. To calculate the application down from kgs / Ha to units per acre, multiply the kgs/Ha number by 80%.