Study: soil 1.2

What did I once read about sunflowers pulling poisons out of earth?

I know it was on paper and in my school days so I suspect it was in New Scientist or Scientific American, but a search for ‘sunflowers toxins earth’ gives me the keywords phytoremediation and (specifically for metals) hyperaccumulator.

“Hyperaccumulating plants can contain more than 1% of a metal in their dry biomass. For example, the hyperaccumulating plant Berkheya coddii was found to contain as much as 3.8% of Ni in the dry, aboveground biomass, when grown in contaminated soil. It is possible to extract metals from the harvested biomass in a process termed phytomining.” DUDE. THIS HAD NEVER OCCURRED TO ME AND I LOVE IT.

What does too much ‘organic matter’ do to a plant is pretty clear on the matter: it’s about the NPK ratio. Many plants need less phosphorus than the other two, and phosphorus doesn’t wash away like the other two but sits around year on year while you add npk after npk.

But wait. We mine phosphorus. From rock. It’s a limited resource.

ttps:// says so. “Perennial vegetation, such as grassland or forest, is much more efficient in its use of phosphate than arable land. Strips of grassland and or forest between arable land and rivers can greatly reduce losses of phosphate and other nutrients.”

And in case you weren’t already getting a headache: “the current system of manure management is not logistically geared towards application to crop fields on a large scale. At present, manure application could not meet the phosphorus needs of large scale agriculture.”

What’s wrong with that compressed coir stuff? says not much is wrong with it at all. It’s renewable because it’s made from shaved coconuts, it’s light and fluffy so seedlings and growing roots don’t have to work too hard to shove it aside. It doesn’t, of itself, have much nutrition in it, and because it’s so light a liquid fertilizer would probably drop straight through it like prunes through a short grandmother. But it’s great for starting seeds, because they already contain the energy they need to throw their first leaves and after that they can make sugars, obvs.

Why is it N for leaves?

How neat! This is a perfect segue: they need nitrogen to make chlorophyll! And as they make more chlorophyll, they make more leaf surface area to use it in.

Excess nitrogen gives excess green growth at the expense of flowers (and therefore fruit). It will also “increase the soil’s mineral salts; excessive elemental nitrogen takes water away from the plant while leaving the salts behind. As a result, the leaves take on a burnt look from dehydration.” –

Why is it P for roots and flowers?

It isn’t, and gosh, these people feel strongly about the sales pitch that it is:

I massively don’t understand the details of this page but phosphates are involved at every stage of complicating sugars, and P is in fatty acids?

Why is it K for stems?

Hmm, this may have been another oversimplification: “The main role of potassium is to provide the ionic environment for metabolic processes” And then I add the word ‘phloem’ into my searches and everything suddenly gets a lot more polysyllabic: I very suddenly stop understanding the abstract of this paper between the sixth and seventh sentence. 

Find a summary of crop rotation.

Phew, this is easier. brassicas and beans AFTER roots and potatoes, is the main point. If you have more time or more space, roots after brassicas after beans after potatoes. The site assumes you’ll be adding a lot of soil modifications in, though, which I genuinely thought rotation was instead of. 

Find a summary of organic certification. send you through an unusual number of links and pages and I very uncharitably think that it might be in order to make it seem more difficult than it needs to be so that you pay a professional to handle it for you, like tax. I naively expected it to be ‘no synthesized treatments or interventions’ or something simple like that.

I did find this: “In the UK you do not need certification if you only sell organic products directly to the final consumer or user provided that you do not produce, prepare, store organic products other than in relation to the point of sale or import such products from outside the EU or have not contracted out such activities. In other EU countries certification may be required for these activities.”

And this: is THE complete list of seeds supplied by companies that have acquired organic certification for those seeds. 

What connects those answers?

Plants have been managing themselves long, long, long before cave people decided to grow them in places that were convenient for us. Plants will compensate their growth in ways that make it more likely that they’ll outlive the unfavourable circumstances: they’ll wait out excess heat or cold or water or, I dunno, deer. It’s the minimal intervention principle, innit.