Co-composting rock phosphate and farmyard manure

An Innovative Farmers field lab has found higher phosphate concentration in plants from wheat and rye grass crops that were treated with co-composted rock phosphate and farmyard manure, compared to crops where they were applied separately.

Adrian Hares

The Soil and Root Innovators, a group of farmers in the South West, have been exploring how co-composting GAFSA (reactive rock phosphate) with FYM may improve soil biology, yield and phosphate availability for cereal crops since autumn 2016, with these first annual results encouraging them to continue their research into 2018 and 2019 harvests.

From samples of rye grass, leaf phosphate concentration treated with co-composted rock phosphate and FYM 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.

Adrian 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: “We’re really pleased with the results and we’re confident that we can repeat and improve in the next year of research. One of the best things about doing research in this way – when it’s practical, in-field and replicated across several farms – is that we have a genuine representation of the influence co-composting has, both on our own land and on a wider scale. 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 are 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. We’re also hoping to use larger trial plots to get an even more conclusive set of results next time around. This has been an interesting and valuable process so far, so I’m very pleased we are able to carry on with these trials and refine our research.”

You can follow the trial progress at

Adrian Hares will be speaking at the Innovative Farmers Network Day on Wednesday 9 May 2018. Open to members and non-members, this Innovative Farmers event will discuss past, present and future field labs and look at what the future of farmer-led research could look like. What are the biggest challenges facing farming, and how can ground-level research and development help tackle them? The event will take place at Sheepdrove Farm, Berkshire. Find out more, see the full event schedule, and book your place at

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