Potting

At this time of year I’m putting a lot of plants into pots. This will include sowing seeds, pricking off seedlings, potting up young plants from the propagator, potting on plants into bigger pots and potting up plants that have been dug from the ground.

As an ex nurseryman, I know that professional growers do not generally use the type of composts available in garden centres. When I left the industry around four years ago, most nursery stock was still being grown in moss peat, coming from Ireland, Finland or the Baltic states. To this would be added a controlled release fertilizer and ground magnesian limestone. Fine peats and green waste don’t have the right physical properties in terms of water retention and air filled porosity at field capacity.

The nursery where I worked had been using peat alternatives for its own production for over 20 years. The main supplier in this area is Melcourt, whose composted wood waste product has been developed over many years and is capable of producing results comparable to peat. We bought directly from them and from a compost producer who used their raw materials in their product.

For the last few years they have been retailing their basic compost, Sylvagrow, as a retail product but it is exactly the same as the bulk professional material we were using on the nursery. We added to it a 12-14 month controlled release fertilizer which fed the plant for a growing season and into the spring of the following year, by which time the plant would hopefully have been sold.

My local retail nursery grows the bulk of what it sells and it does so in Sylvagrow. They sell the 50 litre bags of Sylvagrow at £18 for three. That is cheaper than my nearest horticultural sundries wholesale supplier. They charge a little more for the ericaceous version, at around £9 a bag.

Sylvagrow

Controlled release fertilizer is never an ingredient of retail composts for the simple reason that it has to be mixed in immediately before being used. Once it is mixed, it starts to release fertilizer and if it is not removed, either being taken up by a growing plant or washed out by heavy watering, it can quite quickly build up to phytotoxic levels.

There are other ways of feeding plants but CRF’s ensure that the plant has the right amount of nutrients available to it for the whole season, all from the granules mixed in before potting.

Last year I had plans for this year that have not come to fruition. It seemed like a sensible thing to do to buy a 25kg bag of 8-9month Osmocote. It wasn’t. I could have bought 3kg on eBay for £22.45. Presumably someone is breaking down 25kg bags and reselling it in smaller quantities. You can get various formulations. It has to be kept dry and it has to kept airtight or it can absorb moisture from the air.

Osmocote

So I have my Sylvagrow and I have my Osmocote. I measure 20 litres of compost into a medium sized sack and add Osmocote at between 2.5 and 4 grams per litre, give it a good shake around to mix it thoroughly and use it within a day or two. I have a small electronic balance that weighs to a tenth of a gram. Bought online for a few quid. I can mix one litre of compost if that’s all I need.

Balance

I use Sylvagrow compost as is for seed sowing and for growing things in cells, direct sown or pricked off, which covers most of my veg production. If it needs supplementary feeding I use Maxicrop Triple. For just about everything else, from 9cm pots upwards, I use it with CRF added. It works for me.

Potting

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Allotment update – 28/3/2018

I’m into my fifth year of recording seed sowing dates for both veg and flowers. It gets a bit more patchy at the pricking off stage and worse still for planting out. I thought it would tell me how far behind I am this year, but it actually tells me very little.

It feels like a late season, I suspect they all do.

I have broad beans, sown in 9cm pots in early Feb, ready to go out. I want to get early potatoes in. I will soon want to get onions, started from sets in cells, out, with seed raised plants not so very far behind. I have lettuce, beetroot and spinach beet in cells, perhaps a fortnight from planting size.

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Broad Bean ‘Masterpiece Green’, sown into 9cm pots, 2 seeds per pot, 3/2/2018. Being moved out of greenhouse daily to harden off.

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Onion ‘Rumba’, planted in cells to get started, will soon need to go out.

Most of my seed I get from Kings. Why? well for no better reason than that I piggy backed someone else’s discounted allotment society order five years ago, got acceptable results and if it ain’t broke, I don’t fix it. I feel unadventurous, especially when I read other people’s blogs and they’re getting all sorts of stuff from all over the place.

I have tried a bit. I did a small order to Real Seeds last year and a small order to Sow Seeds this year. It’s unfair to just pick at the margins of their ranges while getting the bulk from a big firm. I got mixed results, one out of three chilli varieties from Sow Seeds has not come up at all, against 100% on the other two. The Liria onions from Real Seeds did very well but didn’t keep nearly as well as Rumba from Kings. The sorrel is a perennial so I still have it, not that I use it much. Giant Goosefoot was not popular and the runners were nothing special.

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Chillies on the window ledge, pricked off a week ago. Two varieties germinated 100%, the third not at all; same conditions.

What I want is to get a decent return for the money and effort I invest in the plot. I don’t think my growing conditions are optimal so reliability is important and a high proportion of failures would eventually make me give up. All my experimentation goes into my growing methods rather than different crops. I’d rather succeed with something common than fail with something exotic.

 

 

 

Last year I bought a bag of Melcourt’s sowing and cutting compost. This year I have used their regular potting compost. This is the same peat free compost as is used by an increasing number of commercial nursery stock producers. I have seen no difference between the seed and potting composts, in appearance or in results.

I don’t sow much directly into the ground as I find most things fail, usually being eaten by slugs when very small. Planting out from cells is also easier when the ground still has the remains of a winter mulch on it, which most of my no dig plot does. The ground also gets another month to dry out and warm up before I try to grow anything in it.

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Remains of my autumn mulch are still protecting the soil surface of the plot. Weeds are only a problem if allowed to seed, which won’t happen. My Rhubarb is well away.

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Lettuce ‘Oakleaf Navara’, looking good but will soon need to go out.

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Carrots ‘Early Nantes’ will go out as soon as there is enough root to hold the compost together. They will then get planted just as they are. I may thin them slightly, to about 15 per pot.

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Cabbages were pricked off into cells from 9cm pots; beetroot and spinach beet sown in cells and will get planted as small bunches. Onions will get pricked off into cells very soon, one per cell, as will Celeriac and more lettuce.

Allotment update 11/2/2018

I made a quick visit to my allotment earlier. The wind was slicing across the very open site and, seeing very little that needed doing urgently, I didn’t stay long.

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Spinach, leeks, rhubarb and weeds, lots of weeds.

My leeks were a dismal failure; almost all of them produced flower stems. Sown too early seems to be the verdict. Spinach beet is OK, though it is very battered. There are parsnips in the ground, though they are pathetically small. Mesh over the top stopped root fly but cramped leaf development.

All the bare ground was mulched in autumn with compost, mostly from my compost heap, some fresh shredded material. It has done its job of protecting the soil surface over the winter but because my composting isn’t on a scale that generates much heat, there is a lot of weed to pull out.

 

In the first winter that I had the plot I sowed Italian ryegrass as a green manure. It was very effective but needed digging in. Since I adopted a no dig regime it has not seemed viable. I am going to try it again in autumn 2018, sowing it on the beds that will not be needed until relatively late in the spring. It should mean I can spread my compost a little thicker on a reduced area. The rye I will cover with mypex a couple of months before I need the ground. Hopefully that will be long enough to give me a good kill.

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More weeds, plus parsley, kale and garlic.

As well as not having as much compost as I would like, the stuff I do have doesn’t have the nutrients in it that my crops need either. This is a fairly high rainfall area and the ground is free draining, the more so because I am maintaining good soil structure. I suspect I am losing nutrients to leaching. I also shred a lot of woody material and put it into the compost. It resists decomposition and is effective all winter at protecting the soil surface, but at best it is poor in nutrients, if it isn’t actually drawing nutrients out for its own breakdown. I will feed more this season than I have in the past.

 

The one thing I did do when I was up there today was to open 2018’s account with my mole population. There are too many for my liking. I’m not bothered by their excavations so much as their impact on my worm population. I’m convinced it’s because I have far more worms than my neighbours that they seem to be mostly focussed on my plot. I set two traps though my success with them in the past has been dire. I have also scattered seed of caper spurge around the margins; supposedly it deters them. I sowed a couple of cell trays with spurge too.  I’ll let you know how it goes.

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Moles. Their hills are all along the edges of the plot but their tunnels are everywhere.

Allotment update.

During the summer I was up to my plot at least every other day, now it’s more like every other week. Such crops as I have still standing seem to include several that have not covered themselves in glory this year, rusty leeks, piddling little parsnips, moth eaten spinach. Cauli’s were not bad, but you only want so much.

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Skanky spinach, gone to seed leeks, piddling parsnips.

 

A good part of the ground is empty and has been mulched with compost to protect it over the winter. Mulch does prevent damage to soil structure from winter rain but not loss of nutrients from leaching. Green manure would do that but then needs digging in, which conflicts with my no-dig ambitions, or smothering, which takes time I don’t have in spring, or spraying, which I am not going to do.

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Weeds. I can weed from the path where the pot is, I never step on the cultivated bit.

 

My compost is weedy. It is made from material from various sources, some of which are full of weed seeds. The quantities I have mean it doesn’t get hot enough to kill the weeds effectively, so where I mulched a few weeks back I now have weeds. I don’t want them going to seed and I don’t want them to get so big I have to dig them out; other than that they are holding onto nutrients and providing further protection for the soil. On closer inspection, there are a few that, even in November, are threatening to flower and seed as very small plants. Annual meadow grass, bittercress, pearlwort, groundsel, chickweed  and petty spurge are all included. Then there were grasses, dandelions and buttercups that needed out while still small and manageable.

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Clockwise, pearlwort, annual meadow grass, hairy bittercress, petty spurge.

 

I weeded that bed. There is another that needs doing too. I spread more compost too. Everything gets shredded so it breaks down quickly, I will try to get more spread in the next couple of weeks, it will do far more good on the ground than in the heap. Because a significant part of its volume comes from shredded leaves and twigs, its nutrient content is not great, so I will apply fertiliser at a moderate rate in the new year. Some of the shortcomings I’m seeing in what I’ve grown this year are for lack of nutrition.

I find myself deviating from the no-dig template in its classic form but consider myself to be responding to my local conditions in as constructive a way as I can.

Composting.

When something in gardening is agreed by absolutely everyone to be a good thing it seems perverse to ask the question “why?”. I tend to the view that that is when it most needs to be asked.

Composting and the multiple benefits of compost are among of the great untouchable sacred cows of gardening, especially among the organic fraternity. However, ask a bunch of gardeners to explain why and I bet you’d get a very mixed bag of responses. Ken Thompson, author of a book on compost, called “Compost”, says “Few things are better for your plants and for the environment than home made compost”.  He then goes on to explain how decaying plant material ends up as humus. He points out though that only a small proportion of the original material ends up as humus, the rest being broken down to carbon dioxide and water.

The breakdown process is effected  by microbes which secrete mucilages that bind soil particles together into crumbs, creating what is known as “soil structure”. However, a protein called glomalin, produced by mycorrhizal fungi, has been found to be present in soils in far greater amounts than humus, and it is largely glomalin that aggregates soil into crumbs, not humus. Since the mycorrhizal fungus is getting its nutrition from its symbiotic partner, the growing plant, not from organic matter added to the soil, the humus derived from compost is somewhat sidelined in the narrative. It is growing plants (including weeds) and their associated mycorrhiza, that are doing the heavy lifting when it comes to soil improvement.

Wikipedia has a bullet point list of the benefits of soil organic matter and humus, the first of which is that organic matter feeds microorganisms, maintaining high and healthy levels of soil life. There is an implication in much of what you read that there is a direct correlation between lots of life in a soil and how well plants will grow in it. To which I would ask why, in commercial horticulture, do nurserymen almost all grow nursery stock in the all but sterile medium of peat and tomato growers in equally sterile variations of hydroponics.

Plants have evolved to grow in an extraordinary range of environments. The ferns growing on my neighbour’s roof, or the sedum around my other neighbour’s chimney, do not have their roots in a lovely friable living soil. Yet they survive perfectly well. Plants that need constant moisture or higher levels of nutrients would struggle or even die, but could all be grown in a peat nursery compost or by hydroponics.

The role played by the living and once living fraction of soil then is to provide the simple things that plants require, water, air and simple inorganic nutrients. A soil in good condition is open enough to allow the free passage of excess water whilst retaining good quantities in the porous organic matter. It holds nutrients sufficiently tightly for them not to be leached by rain, but loosely enough to be readily available to plants.

Humus, organic matter derived from but no longer recognisable as decomposing plant material, is beneficial to the soil in many ways. It adds to a soil’s cation exchange capacity and its water holding capacity. It acts as a buffer against excessively acidic or alkaline conditions and can absorb toxic materials such as heavy metals and excess nutrients.

Another claim about composting that is not true is that all the nutrients in the plant material added to the heap are retained within the heap. One study found that nearly a quarter of the nitrogen in mixed organic refuse was lost in the first twenty weeks of composting, probably mainly as gaseous ammonia. Adding soil to the mix stopped the loss, presumably because the ammonia was absorbed by the clay fraction of the soil. Additionally, any liquid draining from the heap will be taking dissolved potassium with it.

Composting can generate high temperatures, but only if there is sufficient volume of material for heat loss to be reduced enough. The small volume of a typical domestic compost heap has far too high a surface area to volume ratio to heat sufficiently to destroy weed seeds and plant pathogens.

It turns out that simply mixing plant wastes into the soil, or spreading it on the surface and letting worms do the mixing, adds more humus and more nutrients to the soil than if it is composted first and  has also been shown to produce higher yields. The relatively coarse nature of uncomposted material means that adding it to light sandy soils might make them even more open to the detriment of the crop, whereas compost holds much more moisture and will reduce the openness of the soil. On heavy soils there will be a benefit from the opening up of the soil.

What I have been unable to find any reference to is the benefits arising from the early stages of breakdown of organic matter if that takes place in the soil rather than on the compost heap. It seems to me that the level of activity in the early stages is far greater than in the later stages. The very rapid build up of heat, the product of respiration by bacteria, within hours of a pile of suitable material being stacked up, followed by a peak in worm activity in the weeks following, is then followed by a tailing off of activity and a finished product which is not generating any heat or supporting hardly any fauna visible to the naked eye.

It is worth pointing out that nature does not build compost heaps. Plants die down in autumn, or leaves fall from trees, and breakdown happens at ambient temperature. A significant amount of vegetation may be eaten by herbivores and the breakdown process is then well under way when it is deposited on the soil surface.

So it seems to be the case that we put stuff onto a compost heap for convenience. During the growing season there may be no bare ground on which to spread organic material. It is sometimes suggested that fresh material encourages slugs, but if they eat it, rather than the crop, they become part of the solution and less of a problem.

Almost all of what goes on my allotment compost heaps goes through my shredder first, so it breaks down to a material I can use for mulching in my no-dig regime quite quickly. Most of what I accumulate over the growing season is used for mulching bare ground ahead of the winter. There isn’t too much opportunity for nutrients to be lost to the heap in that time, rainfall would likely never be sufficient to run through the heap removing soluble nutrients. Soft material such as peas and beans gets mixed with woodier material like hedge trimmings.

mulch

Pea haulms, shredded and spread directly on the soil.

I believe it is very beneficial to have any bare ground covered in the winter to protect its structure and I have used compost for that purpose. What I am now planning to do is to spread shredded material directly onto the plot where bare ground appears that I am not planning to crop again until spring. I would anticipate the softer material disappearing quickly, the tougher stuff remaining to provide protection to the soil. If a suitable area presents itself, I shall do half with composted material, the other half with uncomposted material. Then if I grow the same crop in both areas I can look for any visible differences.

References.
Roger Brook – The no dig gardener – http://www.nodiggardener.co.uk/search/label/Glomalin
USDA AgResearch Magazine – https://agresearchmag.ars.usda.gov/2002/sep/soil
E. W. Russell – Soil Conditions and Plant Growth 10th edition. Composting – pp 271-3