The Value of Phosphorus

What does phosphorus actually do for cereals?

Tom: It supports establishment and root development, and it powers energy transfer inside the plant. The net result is quicker growth, better fertility and stronger yield potential.

What about potatoes and veg?

Don: It is just as critical. In potatoes, available P influences tuber initiation and starch storage. In veg crops, it underpins rooting and the development of storage organs. If P is short, crops rarely hit their ceiling. Without enough phosphorus, plants simply do not reach their potential.

Fertiliser use has fallen. Is that an issue?

Tom: Efficiency has improved, but long-term grain analysis shows P levels are slipping. That suggests crop demand can outpace supply. Soil tests matter, yet a grain test at harvest reveals whether P or N limited the crop in reality.

What is new in improving P use efficiency?

Tom: We are evaluating a suite of approaches:

• Release® to unlock bound P in soil.
• Coated fertilisers that keep P available and reduce lock-up.
• Microgranules and liquid P for accurate placement at drilling.

Glasshouse work shows these methods can increase root mass, which supports better nutrient uptake.

How does this translate to potatoes and specialty crops?

Don: Precision placement near the root zone at planting pays. We also combine P strategies with biostimulants and look at carbon reduction while keeping nutrition optimised. Precision placement is especially important in potatoes. Get P to the roots quickly.

Is throwing everything at the crop ever worthwhile?

Tom: Our “kitchen sink” trials stacked cost without proportional return. A medium input strategy was consistently the most profitable. Focus on ROI rather than headline yield.

What is the key timing in potatoes?

Don: Early work wins. What you do in the seedbed and up to tuber initiation sets potential. Later inputs rarely match the payback.

How do I check what my crops really need?

Tom:

• Run soil tests for P, K, Mg and pH.
• Add a grain test at harvest to confirm uptake and limitations.
• Match P strategy to soil type, pH and crop demand.

Any potato-specific pointers?

Don: Use precision placement so roots access P fast. Work with your agronomist to tailor nutrition and cost to your system.