Vegetable plants generally require much higher fertility than is usually available in most soils,
as we have bred vegetables over the centuries to produce large yields when soil fertility is high.
Most of the gardens that we manage as part of this RED Gardens project rely
primarily on compost with a few amendments to build and replenish this soil fertility.
The Extensive Garden, which is based on the advice of Steve Solomon,
uses a reasonable addition of compost to feed the soil each year,
but focusses on the use of a DIY mix of materials to feed the plants.
Steve refers to this mix as Complete Organic Fertiliser, or COF, and recommends that it
starts with a substantial amount of seed meal or seed cake, which is the remains of
the seeds grown for oil, such as rapeseed, after the oil has been pressed out of them.
This dry, leftover material is often used as an animal feed, as is still contains a
significant amount of nutrients, and is especially high in protein, which when
decomposed by soil organisms can provide a convenient supply of nitrogen for plants.
I have only been able to get seed meal on a few occasions in the past, as it just doesn’t seem
to be used as a common animal feed around here. So, in preparation for this season I have been
searching for a suitable substitute, which is more readily available in this area, in order
to ensure that I’m able to provide a substantial amount of nitrogen for the plants in this garden.
I think the approach that Steve has taken with this Complete
Organic Fertiliser, is quite interesting. It is a mix of materials that we can adjust so
that it contains a balanced supply of all of the nutrients that a plant would need, from the larger
quantities of nitrogen, phosphorous, potassium, and calcium right through to trace elements.
And the proportions of different ingredients can be adjusted to suit the type of soil, and
to slowly start to balance out any deficiencies or excesses that there might be in that soil.
Getting all of the ingredients took a bit of work and shopping around,
and I have tended to buy larger quantities that are a significant investment up front,
but much cheaper in the long run. I have enough of some of some of these ingredients
to last years or decades, or at least more than enough to share with friends and neighbours.
Steve’s recipe has everything worked out in easy to measure volumes,
and once mixed together it produces a stable, dry material that is easy to store,
and easy to spread onto the gardens when needed. Used in addition to a reasonable amount of
compost, it is supposed to provide an abundance of the balance of nutrients
that the vegetable plants need to grow quickly. But the main ingredient seed meal, which is
added primarily to provide a convenient source of nitrogen, has been quite difficult to get.
I was able to get a few bags of seed meal a number of years ago from a farmer who grew
organic rapeseed for producing oil, but it definitely wasn’t a convenient option, and
none of the producers I contacted in the past few years were able to provide me with any seed meal.
So I have been using chicken manure pellets as a source of nitrogen instead.
The chicken manure pellets have been my usual form of additional fertility for use in a
few of the gardens, and was a convenient substitute for the seed meal in providing
a reasonable amount of nitrogen, as well as phosphorous, potassium and other nutrients.
And I have been able to grow a lot of good quality vegetables with this mix,
but I have wanted to try to find a replacement that had more on common with the seed meal.
One of the key reasons that Steve Solomon recommends the use of seed meal
is that it is commonly available in animal feed suppliers in many places around the world,
but not here in Ireland it seems. Where it is available, a large bag can apparently
be purchased at a reasonable cost, and used as the basis of fertility in the vegetable garden.
And I think this idea is really quite interesting,
that a convenient and inexpensive fertiliser for the vegetable plants in our gardens
can be found in the stores that are supplying feed for livestock, horses and other animals.
Essentially, whatever can be used to feed animals, can be used to feed plants,
or more accurately, it can be added to the soil, where it is consumed by the worms and other soil
organisms, and the released nutrients are then available to be picked up by the plant roots.
I am based in a landscape dominated by dairy and beef farms, with a few poultry and pig operations,
and with a lot of people keeping horses, so naturally there are places in local towns
where different kinds of feed can be purchased. And I went looking for a suitably substitute
for seed meal, and wanted something that had similar characteristics.
It needed to contained a fair amount of nitrogen, but was minimally unprocessed
without a lot of unknown additives, was widely available and preferably from local sources,
and it would be great if it was the by-product or waste product of some other industry or process.
But I could not find anything that satisfied all these criteria.
Most of the feed was a mix of several different ingredients, often containing
substantial amounts of soya beans which was imported from Argentina, Brazil, and the USA,
which I definitely wanted to stay away from. And almost all of it was processed into a
pellet or kibble form with a range of different ingredients, with the aim of adjusting that
feed to better meet the requirements of different animals, at different stages of their development,
and being raised for different purposes. And it seemed that only rolled barley and
rolled oats, sold as a simple feed for horses, was the closest to what I was looking for.
I think any of these other types of feed supplies could be used in the gardens if that’s all I could
get, or if I had a few bags lying around, and it would be interesting to try, if I wasn’t concerned
about the origin of some of the ingredients. For use in the vegetable gardens, it is the
protein content that is listed on the side of each bag that is the key thing to look for, as
the higher the protein content the more nitrogen will eventually be made available for the plants.
This is one of many things that I learned from Steve Solomon, that essentially
protein is nitrogen, or more accurately nitrogen is a key component of all proteins.
From the standpoint of the garden, the nitrogen is simply stored in a more complex molecule of
proteins and amino acids, which will be consumed by the soil organisms when it is added to the
soil, and the nitrogen will then be released in a from that can be absorbed by the plants.
Apparently the main way protein content is typically determined in feeds like this
is to measure the nitrogen content and multiply that by 6.25,
to get an approximation of the protein content.
So we can do the reverse, divide the listed protein content by 6.25 to
get an approximate percentage of Nitrogen that we would expect to be made available.
This is one of the reasons that Steve Solomon recommends seed meal,
as it is so high in protein, often exceeding 30%, which would translate to about 5% nitrogen.
The recipe for COF lists everything in volumes required to cover a certain area,
but because the other ingredients have different densities and protein content, I used the typical
density of seed meal to calculate that about 100g of nitrogen would be added to each batch of COF.
So that is the very approximate target of the amount of nitrogen
that I am looking for in each batch. The rolled oats in my local supplier
are listed as having 9% protein, which would translate to almost 1.5% nitrogen.
Dividing the 100g of Nitrogen that I am looking for by 1.5%, this works out at just under 7kg
of oats, which is conveniently about 1/3 of a 20kg bag of rolled oats per batch of COF.
And with the layout of the Extensive garden into 8 beds, each of which is
about the size that Steve recommends applying a batch too, I would need 8 batches in total.
So three of the 20kg bags of rolled oats would be enough to supply the full garden
with a generous amount of nitrogen at the beginning of the growing season,
with enough left over for another batch of COF which could be used to side dress
the plants during the growing season. These three bags of rolled oats cost me
just over €20, which is a reasonable amount compared to the 300-400kg of vegetables
that I could grow in this garden in one season, and rolled barley would be similar.
Some of the other types of feed would be cheaper as a source of nitrogen,
and it is possible to get nitrogen from a lot of other sources that are less expensive and
potentially even free, but there are usually issues and potential problems with all of them.
And it is interesting that the rolled oats are approximately the
same price as the chicken manure pellets that I have been using,
at least when comparing the amount of nitrogen that they contain.
I like that these oats are minimally processed, simply rolled to crush the seeds,
which will make them much faster to decompose in the soil, and prevent them from sprouting.
I also like that they don’t contain any other additives, and that they come from
a processing facility that is not so far away, so transportation will not be much of an issue.
And it is likely from oats were grown on farms in the same region or at least in Ireland,
though that is not guaranteed, and these bags of rolled oats are available in
feed suppliers throughout the country. So rolled oats have a reasonable amount
of nitrogen, are minimally processed, don’t contain additives or ingredients
that I would rather stay away from, are widely available, and from a relatively local source.
But they are not a by-product or waste product from another industry or process.
Unlike the chicken manure pellets which are made from the waste streams of large scale facilities
that raise chickens, these oats are grown specifically for feeding horses and humans.
And this is the key issue that I have with using
oats directly as a source of fertility in the soil.
I like the idea that waste by-products that would otherwise need to be disposed of,
can be used in the gardens as a source of organic matter and fertility.
For those of us who don’t have access to a convenient supply of uncontaminated manure,
and don’t have the capacity to produce the abundant quantity
of high quality compost that our vegetable gardens would require,
buying in fertility and organic matter is a reasonable alternative.
And there are lots of possibilities, though they all have issues.
For example with the chicken manure pellets that I have been using, I wonder about the
energy and infrastructure needed to dry the manure and process them them into the pellets.
I have also bought in another type of fertility in a pellet form that is higher in nitrogen,
and perhaps more suitable ingredient to the COF, as but it is processed and packaged
far away from where I am located. And like many of the other forms of
concentrated fertility that we could buy in for our gardens these pellets make use of
the waste streams that come from large scale industrial facilities that process livestock,
something that an increasing number of people want to stay away from for a variety of reasons.
I would rather use seed meal if I could get it conveniently, but the rolled oats
seems like a decent replacement to try this season, despite reservations
that I have about burying food in the soil. But this is an interesting possible benefit of
using ingredients like seed meal and rolled oats, as they contain a lot more than just nitrogen.
And with the quantities that I will be adding to the soil, this will be a significant amount of
very rich organic matter and other nutrients for the soil organisms, and I would not be
surprised if this results in a significant increase in the number of worms in the soil.
So in a way, using these rolled oats as part of the Complete Organic Fertiliser mix,
will be feeding the soil, as well as feeding the plants.