Farmers who want to increase soil organic matter and health – while also reducing their CO2 footprint – should consider fermenting their manure rather than composting it, according to crop nutrition experts, Agriton.
Independent trials commissioned by Agriton have shown that fermenting waste in a similar way to ensiling grass significantly reduces carbon and organic matter losses, making more nutrients available to the growing crop.
Carried out by Feed Innovation Services, Wagenigen, Netherlands it found composting grass cuttings in windrows led to 60 per cent losses in weight – from 13,400kg to 5,070kg over six weeks.
In contrast, fermented cuttings – known as bokashi – lost just 3 per cent from the same starting weight. In addition, the bokashi had a higher carbon/nitrogen ratio, at 19.5 versus compost at 10.1 – an important indicator for soil organic matter content and fertility.
Overall, from the original 13,400kg of grass cuttings, the resulting compost contained just 882kg of organic matter and 441kg of carbon.
Bokashi contained 2,080kg, and 1,040kg, respectively, with more nitrogen, energy, ash, protein and cellulose, too.
Mineral levels were also considerably higher, from potassium, sodium and magnesium to sulphur and most micronutrients.
The trial also considered the CO2 footprint of the compost and bokashi. In total, the compost required 3391kg CO2 equivalent to produce, compared to 350kg for the bokashi.
“Farmers are under increasing pressure to reduce their greenhouse gas emissions – and many are seeking to improve soil health at the same time,” says Andrew Sincock, commercial director at Agriton.
“Soil health and carbon sequestration are very likely to form part of the new Environmental Land Management scheme.”
Following the initial trial, Agriton commissioned a second independent trial with SPNA Agroresearch to look at the impact of bokashi on both the soil and end crop. Replicated over three years, the bokashi-treated winter wheat averaged 8.9t/ha against compost at 8.74t/ha, with similar protein levels and bushel weights.
After three years, soil analysis revealed that nitrogen content was significantly higher in the bokashi treated plots, at 2402mg N/kg versus compost at 2,298mg/kg.
Sulphur, phosphate and potassium levels were also significantly higher, with organic matter content rising from 4.6 per cent in the control to 4.7 per cent with compost and 5.2 per cent with bokashi.
Biological life in the soil was generally higher when treated with bokashi than compost, with reduced levels of harmful nematodes, while weed and disease pressures were not statistically different.
The process ferments organic waste without aeration. Seashell, lime, clay minerals and Actiferm (80 species of effective micro-organisms like lactic acid bacteria, yeast and photosynthetic bacteria) are added to the windrow, which is then sealed with plastic wrap.
After six to eight weeks the bokashi (Japanese for fermented organic matter) is ready, similar to the process for ensiling forage crops.