Starter fertilisers are an important part of the strategy to address low phosphate on one Cambridgeshire County
Phosphate indices on the deep-bodied, organic clay loam (10-12% organic matter) are typically one or below,
yet detailed Healthy Soils analysis shows a relatively large soil P reserve that is unavailable to crops.
“The soil is naturally high in iron and aluminium which is locking up phosphate,” says Hutchinsons agronomist George Baxter.
“There’s an estimated five tonnes per hectare of P in the soil, with less than 0.1t/ha (100kg/ha) available.”
The farm started using Primary P starter fertiliser on wheat, spring barley and peas, four years ago to kick-start early root growth.
“It’s much more efficient than broadcasting TSP fertiliser and we’ve seen a real benefit for establishment and crop growth,” says Mr Baxter.
This year, all 40ha of winter wheat and a similar area of spring barley received Primary-P, which is applied with seed using a Stocks applicator mounted on
a Weaving GD drill.
This is part of a wider strategy to improve soil nutrition and health. Five years ago the farm moved to shallower tillage, cultivating the top 5-7.5cm, and also uses multi-species catch and cover cropping.
“Stopping deep tillage was originally for black-grass control, but we’ve seen big improvements in soil biology, which is key to a healthy, productive soil, and for
converting phosphate into available forms,” says Mr Baxter.
Furthermore, catch crops before autumn drilling, and winter cover crops ahead of spring drilling provide an effective way of scavenging phosphate from the available pool at a time when no other crop is growing, preventing it becoming locked up. Both are in the ground for eight weeks before being terminated, when
phosphate is then released slowly in a plant-available organic form as residues breakdown.
“A healthy soil that works for us is vital to promote phosphate cycling, plus the many other benefits,” Mr Baxter adds.
TSP is still applied on a rotational basis, targeted at areas and crops where it is less likely to become locked up quickly.