Our new series, Answers to Your Questions, collects questions from Wicked Leeks readers and presents them to our team of expert writers and contributors. Submit your question for consideration by commenting on this article.
What do you primarily use as fertilizer on Riverford farms? I am concerned that using sewage slurry is considered organic fertilizer when most humans don’t eat well enough that there is a lot of good in it.
Unappreciated, via wickedleeks.com
Sewage sludge actually has quite a few benefits to replenish the soil and is used regularly on non-organic farmland. That said, you’re right, there are some health concerns, particularly around heavy metal and microplastic contamination, but these generally come from the sewer system, where human waste combines with other waste streams, such as runoff. of roads, before being treated. and then used on agricultural land. If human waste is used from composting toilets and does not pass through the sewer system, after a period of time it becomes usable on the land, and if it passes regulatory contamination tests, it can even be used on farmland . You can read more about the pros and cons of sewage sludge in this article.
Organic soil has strict controls, and the Soil Association, the UK’s largest organics certifier, bans man-made waste, including sewage sludge, due to the risk, albeit slight, of contamination. Instead, organic farmers, including Riverford, use a combination of grass and clovers in their fields to add different nutrients to the soil, slowly and naturally increasing fertility. The so-called green manures are crops such as clover, rye or pea that are grown specifically for their ability to store (or release) nitrogen, which they release when they are plowed into the soil again.
Fertilizers on non-organic farmland are also a major climate problem, as the main component of artificial fertilizers is nitrogen, made in an energy-intensive process that releases nitrous oxide once it is used. Many farmers are already trying to reduce the use of artificial fertilizers, mostly to save money, but as it is one of the biggest climate impacts of agriculture, it is likely to gain momentum. Crop rotation, green manure, and compost are the most common organic substitutes right now, but alternative options like ‘humanure’ should perhaps not be ruled out either.
Regarding the Riverford farms specifically, I asked the farm manager, John Richards, for his expert insight and his comment was as follows.
“The main underlying fertility comes from a rotation that includes grass and clover meadows. [field scale crops]. We also use ‘green manures’ that add organic matter to the soil, fix nitrogen and prevent it from leaching, including pea, grass-fed rye, crimson clover, crow’s foot, etc.
“Vegetables receive an application of free range manure (mainly cattle / horse) at 15 tons / acre. Sometimes we use green manure, which is an excellent source of organic matter as well as a good source of potash and phosphorous. At the beginning of the season, we use a fertilizer called Law’s High N, which helps supply much-needed nitrogen at a time of year when natural soil levels are low. It is made from plant products, including waste sugar beets. We also use a granulated poultry manure fertilizer, which is approved by the Soil Association. “
Nina Pullman, editor of Wicked Leeks
Do you have a question about food, agriculture, ethics or the environment? Comment on this article to join the conversation and sign up for our newsletter so you never miss an update: www.wickedleeks.com/#join.