An authentic "Mariscada" from Galicia.
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Decision time: Inorganic or Organic..?

Plants need appropriate amounts of essential nutrients if they are to grow fully and generate the yield of which they are capable. Quite often, however, one of those essentials – principally, nitrogen (N) – is in insufficient supply in the soil. To achieve maximum crop yields those missing nutrient(s) are added by humans. Traditionally, that has been achieved with expensive, natural-resource-depleting, environment-polluting, artificial fertilisers (also termed ‘chemical fertilisers’, inorganic, synthetic, manufactured fertilisers). So, if faced with a choice between those fertilisers and a clean organic fertiliser that is able to regenerate degraded soil caused by overharvesting, and which is biodegradable, insoluble and harmless to human health, does not pollute the environment, and can be used in lower amounts than other compounds, which would – or, rather, should – you choose?

The responsible decision is to go for the latter option. But does such a fertiliser exist?

Yes, according to a research partnership between the Universidad Politécnica de Madrid (Spain) and the University of Hamburg (Germany), and from a seemingly unlikely source – the exoskeletons (external skeleton, ‘outer shell’, carapace) of marine crustaceans (e.g. shrimps, crabs, langoustines, prawns, scampi, lobsters).

An authentic "Mariscada" from Galicia.
An authentic “Mariscada” from Galicia. Photo: Pedroserafin / Wikipedia.

The chitin (a N-containing polysaccharide composite) within those crustaceans’ carapaces has been used to generate a biodegradable N-containing fertiliser that has been shown to stimulate growth of several forestry and herbaceous plant species, with increases of up to 10% of N and C (carbon) content, and an increase in roots (which further enhances the nutrient-exploiting capacity of the plants into non-fertilised areas…). Now, whilst this sounds like an intriguing use for all of those discarded claws and legs after that fruits-de-mer feast, are there sufficient stocks of the oceanic creatures to fuel this source of fertiliser? I know not. But, in any event, a renewable (therefore more environmentally-responsible and sustainable) alternative source of the exoskeletons exists. For crustaceans to increase in size during growth, they must shed (‘moult’) the inextensible exoskeleton and develop a new one once their body size has increased. This presumably means there is a shed-load of carapaces on the seafloor – or marine aquaria throughout the world – waiting to be harvested (before they are exploited by other marine organisms!) and turned into plant food.

A whole new career path has just been created for enterprising individuals – commercial crustacean carapace collector. Let’s just hope that the fruit and veg produced by this fertiliser don’t taste ‘fishy’…

Nigel Chaffey

I am a Botanist and former Senior Lecturer in Botany at Bath Spa University (Bath, near Bristol, UK). As News Editor for the Annals of Botany I contributed the monthly Plant Cuttings column to that august international phytological organ for almost 10 years. I am now a freelance plant science communicator and Visiting Research Fellow at Bath Spa University. I also continue to share my Cuttingsesque items - and appraisals of books with a plant focus - with a plant-curious audience at Botany One. In that guise my main goal is to inform (hopefully, in an educational, and entertaining way) others about plants and plant-people interactions, and thereby improve humankind's botanical literacy. I'm happy to be contacted to discuss potential writing - or talking - projects and opportunities.
[ORCID: 0000-0002-4231-9082]

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