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Nutrient Dense Food and Carbon Sequestration using Local Sourced Fertiliser. Kay Closes The Loops – Part Two

July 25 2016

I put a roast in the oven tonight with Rainbow yams and red and purple potatoes, it looked so amazing. It never fails to amaze me and I always remember the old people who passed us these food plants and give thanks, then I cooked the purple mustard in the meat juice and ended up with purple gravy!

Spring is definitely in the air and I’m going to try to write something weekly over spring because having made the decision not to use EF custom made fertilser I have a big challenge on my hands and it feels like a great opportunity to share what is going through my head and how I handle that.

I do have to say to begin with though that I don’t think I would ever have made this decision if I hadn’t already spent several years building the humus in my soil and getting the minerals levels up as well as the cation exchange capacity..CEC.. it would have been a very long road without this..  During this process we took the humus level from 4 to 20…

So .. I spent the weekend preparing beds ready to plant my broad beans into, and to plant my garlic and shallots and potato onions,  as well as my peas.

I weeded them U barred them and then applied 5 x  20 litre buckets of compost to each bed. Ie 100 litres of compost to each 10 sq m. That is equivalent to 1cm of compost all over the surface of the bed… a good amount.

I forked that into the beds with home made biochar charged with urine. I was surprised that it was not really smelly or difficult/offensive  to handle. I added 3kgs per 10 sq m bed. I would have liked to have had enough to put 1kg per sq m but until we do another burn I won’t.

At that point I had a big decision to make. I knew from the test I had had done on my compost ( Reams test) that my compost did not have a good balance of calcium and magnesium. I had been adding calcium to the compost trying to get the levels higher and higher but did not add enough magnesium. That meant the calcium /magnesium ration was not 7:1 as it needs to be to get optimum growth.

I had already seen what happened when planting into that compost, very slow weak growth, poor plants with a low brix. I decided to add a common form of magnesium (magnesium sulphate .. Epsom salts) , in liquid form with added molasses ( carbon to hold the magnesium, bind with the magnesium so it is not so water soluble). I added 1 Tbspn of magnesium sulphate and 1 Tbspn molasses each 5 sq m in 10 litres of water.

If I put too much magnesium on it will lock up the nitrogen but if I don’t have enough the calcium/magnesium ration will be out and then I won’t have quality plants either. We’ll see how this goes!

Once the plants are up and growing I will then give them a boost with  liquid cow manure, I’m lucky the cows are just outside our housesite at the moment.

Ok so buying Epsom salts to use as a mineral supplement is easier and cheaper than bringing in custom fertiliser but it is still not my  ideal situation. Thinking ahead, I know I want to continue adding calcium to my compost heaps in the form of bone char and burnt bones, and plants selected as efficient accumulators of calcium in particular like oats and lupins, so I’m going to have to find a way way to know that I’m also adding something that contains significant amounts of magnesium… I’m thinking … which trees and plants are the best magnesium accumulators.

I’ve been working on this list for a while, not only in terms of designing plantings or collecting material for a compost heap but also in terms of designing forest gardens. It is easy to say that planting a diverse range of plants and having all 7 layers will create a system that is able to supply all  the needs of the heavy feeding fruit trees in the medium/long haul.. but to me it feels as though there needs to be some careful selection of at least the initial range of support trees going in to ensure we have enough legumes and potash suppliers, as Martin Crawford says, but it feels like good sense to ensure that when we plant our major minerals accumulators we make sure we get the basics covered.

The basics in terms of having the key minerals around for healthy cell growth initially are the major ones.. calcium, magnesium, potash and phosphate.

If the leaves falling to the ground each Autumn were from trees known as dynamic accumulators that concentrated these 4 major minerals then we could know that as they are broken down by the microbes and re enter the mineral cycle and be grabbed again by the feeder roots of the heavy feeding trees .. that the trees would have a good chance of growing to be strong and healthy and producing high quality food without the need to bring in fertiliser of any kind.

I have been researching for a while to find my ideal  list of trees/plants that can supply the forest garden with the minerals needed for the long haul, but now that I’m not buying minerals for the vege garden, it is obvious that the list is one and the same list.

Here is my current list.. it’s short because I think we’ve gotten too carried away and we should focus on what is very important first.. once we have the basics covered we can get more carried away.

For my compost heaps in the vege garden I will continue to grow lupins and oats which unlock sesquester both calcium and phosphate very well, but I’m also going to be adding oak, and dogwood ( the ultimate calcium accumulators that also bear very edible fruit), and linden,    leaves,   as well as alfalfa (an excellent source of calcium and phosphate and I’m growing it permanently around the vege garden now especially for harvesting to make compost and mulch beds).

To ensure I have adequate sources of magnesium, willow leaves, and bark, and alfalfa look to be my easiest bets, for potash I’ll use comfrey leaves, (it will have to be maple sin the forest garden because I have poultry  in there and they kill the comfrey)  also planted around the vege garden, for phosphate I will add loads of comfrey, alfalfa and oats and lupins again, and also collect linden, birch and  cassurina leaves.

For people in the cities many of these trees are in our parks, and easy to collect.

For those of you looking for support species to feed your forest garden check the Koanga website for forest garden support trees and seeds .  Our bundles are selected to cover the mineral bases and also to either be trees that like being coppiced (alders, tagasaste) or that only grow to 2-5m in height so they are suitable for smallish spaces.

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