Wheat and rye grass crops treated with co-composted rock phosphate and farmyard manure have been found to have a higher phosphate concentration than crops on which they were applied separately.

A group of south west farmers, working together as an Innovative Farmers field lab group, have been exploring how co-composting GAFSA (reactive rock phosphate) with farmyard manure may improve soil biology, yield and phosphate availability for cereal crops since autumn 2016.

From samples of rye grass, leaf phosphate concentration treated with co-composted rock phosphate and farmyard manure was found to be around 20% higher (mg P g-1 Dry weight) than plots treated separately. The effect was most observed where co-composting process had been at least four months.

Timing of GAFSA application may also have an effect. There were also positive indications of greater biomass and flag leaf P concentrations in wheat plots on two of the three trial sites (where they had co-composted longer). Although the results were not statistically significant, the group think it is worth repeating the experiment. They hope to expand the number of sites and see if this effect can be observed again.

The study is a great example of farmers leading the way in research and development. It is being funded by its members and co-ordinated by one of the participants, Adrian Hares.

Mr Hares farms 130 acres of mixed beef and combinable cereals in Wiltshire, and as an independent soils adviser was keen to understand the potential effects on soil health.

He said: “Doing this kind of research individually gives you a single outcome, but working together we have multiple representations on different soil types and crop varieties, which means the results can be useful to a wider network of people.”

The group is collaborating with Dr John Hammond from the University of Reading, who said: “The results suggest that co-composting can have an influence on phosphate availability to the crop, especially on these alkaline soils. Co-composting for a minimum of four months and applying ‘little and often’ appears to have the best results, so we can use this to inform our trials going forward.”