Farm-made fertiliser

Bags of fertilizer. Photo by Colin (chuckoutrearseats), used under CC BY-SA 2.0 licence.
Bags of fertilizer. Photo by Colin (chuckoutrearseats); licensed under CC BY-SA 2.0

One Kent farmer, Doug Wanstall, hopes to beat the economics of pricey factory-made fertilisers, by using what he can do and make on the farm. He farms 485ha at Aldington, including 74 head of beef cattle and 12,000 laying hens. Starting in 2015 after receiving a Nuffield scholarship, his ‘on the farm’ project of experimenting to use less factory-made fertiliser has taken seven years.

“Here’s some I made earlier”

He grows milling wheat and needs to get 8t/ha. So far he now achieves this with only 120kg of nitrates, spread little and often, rather than the extravagant 270kg he used to buy. Overuse of artificial fertiliser by farmers is one of the causes of river pollution, as it leaches into water courses, causing algal blooms such as the eutrophication of Stodmarsh. It is also the duty of the Environment Agency (now facing cuts) to monitor the incidence of this, and ensure that farmers comply with regulations.

Farmer Wanstall has five ways of increasing the fertility of his wheat fields:

  1. He grows lucerne on 80ha in rotation (this puts nitrogen back into the soil).
  2. He has a ‘straw for muck’ deal with a neighbouring beef farmer. He composts this for three years before spreading it. He proved its worth by comparing a control field (with no muck spread) which yielded 6t/ha with an experimental muck-spread field which yielded 8.5t/ha.
  3. He uses frass from incubating that black soldier fly larvae, which are eventually fed to the chickens. The frass (some 120–150m3 of it, from their poo, presumably) is made into a tea which contains NPK (nitrogen, phosphate and potassium, the standard ingredients of fertiliser) in proportions 7:5:5. When this is spread on cultivated plots it also has the merit of repelling the cabbage fly pest.
  4. He has eight large containers of wormeries using wood chip, leaf mould and chicken poo.
  5. He also uses fish emulsion, which is a waste product of local fisheries, mashed and fermented with molasses, and spread at the same time as the frass.

All this with the help of researchers at the University of Kent.

However, as a precaution, he is still keeping a load of bagged fertiliser in reserve, just in case of failure. If he succeeds, he will show the way for other local farmers to become more self-sufficient and less dependent on increasingly threatened global markets.

The cost of war

The Ukraine war both increases the price of wheat (because less of it can be grown and exported from that war-torn land), and the price of fertiliser, much of which used to be imported from Russia.

Food and Agriculture Organization expert Máximo Torero, talking about how the Ukraine War affects world food supply, commented on Russia’s exports of fertiliser:

“Even without an export restriction, international companies have been hesitant to purchase fertilisers from heavily sanctioned Russia, which is the world’s top exporter of soil additives containing nitrogen, as well as those with phosphorus and potassium — all by-products of the vast Russian energy industry.  

“In 2019, Russia exported 5.5 billion kilograms of these fertilisers, more than double the amount of the second biggest exporter, the European Union, and nearly four times as much as third biggest exporter, Belgium, according to figures from the World Bank.”

So while Europe scrambles to find substitutes for Russian oil and gas, stories that are well covered in the international Press, the farmers’ need to find substitutes for Russian fertiliser is not so much in public awareness. This Kent farmer’s experiments may yet show us the way towards food self-sufficiency.

Intensive farming

However, although his experiment is for localisation of fertiliser inputs, the inputs of feed is not in the spotlight. Fresh from reading Limbery’s book Dead Zones, I can’t help wondering about those 12,000 hens. They are probably reared intensively* (certainly indoors just now with avian flu precautions) and fed pellets made 80% from soya grown on land, probably in Brazil, which has been cleared from the Amazon, thus making climate change worse.

Free range hens at Bank Farm, Aldington
Free range hens at Bank Farm, Aldington

The beef cattle, with all that mucky straw, may also be confined rather than spread out on grazing pastures, so again needing feed consisting mainly of imported grains. So most British farmers have a long way to go before farming can be de-industrialised, and inputs of both feed and fertiliser can again be truly localised in a circular economy.


*Photos of Bank Farm, Aldington however, do show cattle and hens together on grass.


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