Potash in fibrophos

Trials have shown that fibrophos is a very effective source of Potash across a wide range of soil types throughout the UK. Potash is an important nutrient for grass especially where the whole crop is removed by silage or hay cuts.

In grain, Potash is removed in proportion to the yield, e.g. 27 units per acre are removed in each tonne of grain and straw. 40 units per acre of Potash are removed in each tonne of hay.

fibrophos not only replaces the Potash removed but also replenishes the soil with important secondary elements and most of the trace elements. In particular, the levels of Magnesium in fibrophos help to reduce the risk of staggers in cattle.

Evaluation of fibrophos as a fertiliser

Objective And Method
S.J.Richardson1993ADAS Huntingdon
Ryegrass was chosen as the test crop because sequential cuts allow an assessment of how quickly nutrients become available as well as revealing their overall availability. Two soils were used with low K levels. The pH levels were 8.2 and 6.4 respectively.

Cuts were taken whenever the most advanced plants reached 10-12 cm in height on each occasion. Ashed Poultry Litter (fibrophos) was compared with Muriate of Potash
Low Potassium soil,
Herbage dry matter yield (g/pot).
TreatmentP2O5(kg/ha)Cut 1Cut 2Cut 3Cut 4Cut 5Cut 6Total
Muriate of Potash401.111.090.681.770.700.716.07
Muriate of Potash801.041.160.771.920.900.736.51
Muriate of Potash1200.991.130.781.980.950.846.67
Muriate of Potash1600.751.060.862.221.180.926.97
Muriate of Potash2000.821.190.711.991.191.006.90
Standard Error or Deviation0.15NS0.620.920.760.940.22
Coefficient of variation20.68.311.69.611.26.24.6

Response to potassium was both rapid and significant from Cut 1 onwards. At Cut 4, both yield and leaf potassium content showed the potassium in fibrophos to be very largely available.


On balance, the evidence from total yield and potassium uptake indicates that the potassium in fibrophos is 90 to 100% available within a few months of application.

It is likely that any residual potassium unused in the first season will remain or become available to plants in the longer term. Thus fibrophos is a very effective fertiliser for grass and it can be assumed with confidence that it would be equally valuable for cereals, oilseed rape, peas, beans, linseed and many other crops.

It would be appropriate to apply the ash either annually or in larger dressings every three years for nutrient maintenance purposes.

Since these early trials (conducted in 1994) over 100,000t of fibrophos has been sold nationwide for both cereal and grassland applications. Many of the sales made today are to farmers who have used fibrophos across their farms for the past 10 years – thus endorsing the work carried out by ADAS.