Phosphorus (P) – Soil and Crop
Availability of phosphate in the soil
Phosphate (P) in the soil is not always available to the plant. Several complex soil processes play a role in this. Calcium, iron, aluminum, soil texture, pH and organic matter all have an impact.
Fertilisation and moisture supply during the growing season influence the phosphorus content in grass and silage. Adequate moisture in the soil causes phosphate to dissolve. In that form, the grass can absorb the nutrient.
On average, a spring silage contains four grams of P per kilogram of dry matter. On plots where phosphorus extraction is structurally higher than the supply, a decline in the phosphate status of the soil – and subsequently also in the crop – can be expected over time.
Phosphorus content in feed and crops
Compound feed ingredients normally contain more phosphorus than roughage. The growth stage also affects the content: the older the crop, the lower the P content. Types of roughage with a relatively high phosphorus content include brewer grains, grasses and grass silage, while silage, straw (in a later growth stage than grass and grass silage) and potato products are again very low in phosphorus.
Phosphorus content in different roughages (g/kg DM)
Eurofins Agro, data 2009–2013
| Feed type | Average | Target range |
| Fresh grass | 4.1 | 3.0–4.5 |
| Grass silage | 3.9 | 3.0–4.5 |
| Maize silage | 1.9 | 1.8–2.5 |
| Lucerne | 3.4 | 3.0–4.0 |
