Improving your soil and plant growth with comfrey feed.

 Improving your soil and plant growth with comfrey feed.

Plant fertilisers such as Tomorite or Chicken pellets are getting increasingly costly to buy and sourcing suitable manure and transporting it to the farm is hard work. Increasingly at HCF we have become aware of the potential of growing our own fertiliser- Comfrey. When Andy Waterman first proposed growing it around the Old Fruit cage several years ago there was opposition from some team leaders, so we grew it in large pots for a few years before planting a small comfrey patch near the strawberry polytunnel. Demand for liquid fertiliser is increasing as are the potential uses and so the places where we are beginning to grow it are increasing.

Bocking 14 Comfrey 

Why is Comfrey so useful?

Leafy vegetables need lots of Nitrogen , Root vegetables need lots of Phosphorus (P), flowers and fruits need lots of Potassium (K). Or as Gareth Evans, my old Botany lecturer would say

“N for shoots, P for Roots, K for fruits.”

Comfrey is as good as Tomorite for plants such as tomatoes, peppers, and beans as well as greedy feeders like potatoes plus fruits such as strawberries, gooseberries and raspberries as the table shows.

In addition, it compares well with manure and compost:

One square metre will produce around 7 kg of comfrey a year which can be cut three or four times during the season and so a large biomass of plant material can be produced from a small space. The wonderful benefit of Comfrey is that it has extremely long roots which can mine nutrients from several metres below the surface and which would otherwise be totally unavailable to vegetable crops. The disadvantage is that once comfrey is growing the roots are difficult to kill off and the plant lasts for over 20 years. So don’t ever plant comfrey in a place if you might sometime later want to move it somewhere else.

How to grow comfrey.

We use a variety called Bocking 14 (developed in Bocking, Essex) which is a sterile hybrid clone of two Russian forms. Bocking 14 doesn’t set viable seed, but does spread slowly if not checked back. To make more plants a plant is cut up, the leaf removed and the stem and upper area of the root cut into small sections a few centimeters long.These are allowed to grow roots and leaves in a pot containing a light compost. The young plants are planted out into a cleared area of ground where they are expected to grow. Planting distances are approximately 60 cm between plants.

Comfrey growing along a fence line made of old pallets

How to use comfrey

There are several ways to use Comfrey.

Rotting comfrey at the bottom of a bucket

Toby Turl has recently introduced a new method of makes a concentrated liquid feed. He cuts the leaves and puts them in a bin with a hole at the bottom. As the comfrey breaks down liquid drains through the hole into a small container below which collects the concentrated liquid. He makes a litre every couple of weeks and this is diluted about 10 times over before being watered on plants.

Adding comfrey to a compost bin to speed up composting

I cut comfrey leaves, mixing them with pernicious weeds (nettles, couch grass, docks, dandelions and thistles) and toss them into a sack in an old rubbish bin which has been filled with water. After a few weeks when I need some liquid feed I push my watering can into the bin, draw up half a can full of liquid, dilute it further with water and pour onto my fruit bushes. After a couple of months all the comfrey and weeds have broken down in the sack, so I draw out the liquid for use on the plants then tip the completely dead slime into the compost bin or onto a plot. This is a much speedier method than cold composting and there are no viable seeds or pieces of root which will find their way back onto the soil.

Another use for comfrey is as a surface mulch on blackcurrants and raspberries. I use the “chop and drop” method. First chop your leaves, then lay a 5 cm mulch of the leaves on the soil around the plants. Within a couple of weeks the leaves will have gone black and within a month they will have disappeared completely. This mulch slows down evaporation of moisture from the soil and suppresses weeds. As the comfrey leaves wilt they attract slugs and snails, possibly from feeding on surrounding valuable plants and so reduce damage. Hopefully then, the slug will be devoured by a hungry ground beetle or blackbird.

So there are several ways in which we can use this most helpful of plants on our community farm.

 

Improving the soil with leaf-mould

 

Anyone who lives in this part of Great Britain knows the problems created by leaves at this time of the year. Yet they can be of great value if used wisely at the farm or in your garden or allotment.

Why is leaf-mould useful?

 It’s not that leaves have great nutritional value. The tree tends to suck the nutrients out of the leaves before they drop them. Well-rotted leaf-mould greatest benefit is as a soil conditioner, improving the structure of a soil, rather like peat, but without the damaging environmental costs of extracting peat. Leaves tend to have a high Carbon:Nitrogen ratio, averaging around 50:1 and low levels of essential nutrients: Nitrogen 0.66-1.62%, Phosphorus 0.02-0.29%, Potassium 0.09-0.88%.

Leaves also contain useful amounts of Calcium and Magnesium.

How do you make leaf-mould?

First brush up your leaves or rake them off a lawn. We actually collect several wheel-barrow loads from our road. Then there are several options for making use of it;

1.     Store leaves in bin liners. Moisten the leaves if they are dry and prick holes in the bag. Tie loosely, pile up the bags and leave in a quiet spot for up to two years.

2.     Build a chicken wire frame in a hidden corner of the garden about 1m³ and pile up with leaves. Turn the pile occasionally. (See the frames at HCF).

3.     Store in an open topped barrel or compost bin with drainage holes at the bottom for up to 2 years.

4.     Put layers of leaves as your brown material in a compost bin and alternate with green material such as grass clippings, weeds or food waste.

5.     Cover frost sensitive plants which die back in the autumn to protect the plants from winter rain and frosts. You can make a wire frame around a plant such as a banana after the trunk has been cut off, then pack and insulating layer leaves around the stump and cover the stump with a plastic bag.

Which leaves are best to use?

Leaves that will quickly break down include: ash, beech, birch, cherry, elm, hazel, lime, hornbeam, and willow.

Laves that slowly break down include: hawthorn, maple, magnolia, oak, sycamore and horse chestnut.

The best leaves to use are oak, beech and hornbeam.

Evergreen leaves should be shredded first as they take a very long time to break down. They include: holly, bay, rhododendron, photinia and skimmia.

Conifer needles take a very long time to break down even if moistened and turned every few weeks, so they are best used as a mulch over acid loving plants such as blueberries and azaleas.

How do you use leaf-mould?

Some plants such as vegetables, annuals and grasses prefer soils dominated by bacteria so it is best to use compost or well-rotted manure as soil conditioners for these groups. The bacteria quickly break down the organic material which generally has a higher level of nutrients and a lower C:N ratio. Leaf mould contains lower nutrient levels plus lots more carbon locked up in complex substances like starch, lignin and cellulose which fungi tend to slowly break down. So leaf-mould is better used on trees, fruit bushes, shrubs and perennials which prefer soils dominated by fungi. Well rotted leaf-mould should be added to the soil surface of these groups as a mulch in the autumn or spring to help build the soil mycorrhizal fungi. The mycorrhiza will bring more water and nutrients to the plant roots and so help to create stronger, healthier plants.

An alternative use of leaf-mould is to dig it into the soil when it has been partially broken down to raise the humus content of the soil. This is especially useful for heavy clay soils or light sandy soils. As well as improving soil structure by providing more food for soil living organisms it will help the soil to hold more water to enable the plants to tolerate drought better and hold more nutrients bound onto the humus.

Finally leaf-mould can be mixed with sharp sand, garden compost and soil and used as a potting compost.

Using green cover crops

Having been so stimulated by our visit to Charles Dowding's no dig garden, a visit to the student gardens at Kew botanical gardens and a discussion with an organic farmer at the Alresford show, all within the space of a week, we have decided to try a little experiment  with four green cover crops or manures this autumn at Highbridge Community Farm.

These beds are 6ft (180 cm) wide with a 1 ft (30 cm) path of wood chip between the beds. Each bed has been sown with a different  cover crop 

Ideally a green cover crop for winter use must germinate in the late summer or early autumn after a crop has been removed, grow as much as possible during the autumn, covering the ground to suppress other weeds from growing, and then provide biomass for later composting. The leaves reduce soil erosion from run off and wind. The roots of the green manure plants bind the soil together, feed the mycorrhiza, and draw up nutrients which otherwise might be leached deeper into the soil by the rains. Ideally too, a green manure should be cheap to buy and, for economy, it should set seed that's easy to save. Then the plants should be killed off by the frosts of winter.

At Kew botanical gardens they sow Phacelia (Phacelia tanacetifolia) in beds during spring where tender plants like courgettes and squashes will be planted in June. The purple flowers attract beneficial insects, such as hoverflies whose larvae eat aphids. However Phacelia can be sown up to September, so we are going to try some this autumn. As Kew use a no dig system they either hoe or pull out the plants when they are ready for the next planting. All the biomass goes into the compost. If we have a strong frost they may die, but failing that we will pull them out just before we sow the next crop and compost the biomass. They should keep the weeds down during the winter.

We spoke to an Organic farmer at the Alresford show who has been planting green manures for 20 years. He recommends Daikon Radish to plant from June -September as it matures in 60-70 days. It dies off in frost. It produces a large leafy rosette and a long white taproot up to 20 cm long but has longer fine root hairs which pull nutrients up from maybe a metre below the surface. You can eat the leaves and the roots. The roots make long deep holes ideal for drainage. If the roots are left in the ground after the leaves have died they will rot over the winter and the nutrients from deeper down will be released in the surface layers

Bob Flowerdew (from Gardeners question time) recommends Claytonia (Montia perfoliata). It is sometimes called Miner’s Lettuce or Purslane. It is a low growing ground covering salad plant  It thrives in cool and damp conditions where it may grow  so densely that it excludes all else, yet it seldom becomes a problem for it dislikes hot dry conditions. Soon there should be a lush green carpet which could survive mild winter frosts but would disappear by early summer. It is remarkably easy to weed out with a wolf hoe.  You can either incorporate it in situ by hoeing it under or very easily strip it off to compost the plants as extra biomass. Either way Claytonia improves the soil leaving a fibrous matt of tiny rootlets which soon decay.

The Poached egg plant, (Limnanthes douglassii), has long been recommended as a good attractant for beneficial insects. It dies down naturally in summer leaving the soil bare, after a raking. However on vegetable beds you can strip it away and compost it incredibly easily leaving the soil bound with a mass of fine roots which do not regrow. Or you can cover it with an opaque plastic sheet and it rots down incredibly quickly in situ. You can even tear out patches to plant through.

Additional beds have been covered with mulches of organic matter- this one covered with pond weed Elodea from the pond the other side of the track past the cars.

More lessons learned from our visit to Charles Dowding's NO-DIG garden

We learned a lot from observing and reflecting on the practices of Charles Dowding in Somerset. As well as being useful on our plots these tips might be helpful for those stakeholders who have gardens at home.

New ground coming into cultivation - the NO-DIG method.

If you have a weedy patch (like a new allotment or neglected area) that you wish to bring into cultivation, rather than put in lots of effort into digging and weeding why not follow Dowding method? First spread a thin layer of spent hops to encourage the worms. [If you can't get spent hops, why not try a mixture of grass cuttings and pondweed?]. Then cover with large sheets of cardboard (from bike shops or supermarkets).  Put a 3 in layer of spent hops on top of the cardboard. Monitor for 6 months and hoe off any weeds that make it through the cardboard

If you began this process in the autumn by late May/June you can plant pre sown plants through the hops and cardboard - plants such as courgettes, squash, pumpkins - to get an autumn harvest.

Following on from this you can monitor for weeds through the next winter. Then the following Spring rake away what is left of the hops and cardboard and put on the compost heap. Pull out any persistent weeds. Cover with a 1in layer of compost and its ready for a normal season of sowing. Again you don't have to dig, just plant in modules grown in the polytunnel.

Weeding in a standard plot - the NO-DIG method

 You need to keep on top of weeds. Ideally take them out when they have just germinated and are small. Dowding does 2-3 "weed strikes" in March and April using a swivel/oscillating hoe in the surface compost, to kill small seedlings.  If you miss them in April pull them up whenever you spot them on your plot. Don't ignore the weeds on your plot even if you are concentrating on a different crop in a different area. You really shouldn't have weeds that are flowering on your plot. If you let them set seed you are building up problems for your team in subsequent years.

Notice the organic matter in the mulch that has been added
and the weed free nature of the soil

Edges - the NO-DIG method

Keeping on top of edges is more work for Dowding than weeding. He has a good sized valley at the edge of the footpath to prevent the bindweed and couch grass creeping in from the path. He trims the edges every 3-4 weeks with long handled shears and removes the clippings. Adjacent to his polytunnels he has an edge about 50 cm away from the polytunnel and keeps it clear of weed by growing quick growing lettuce or radish there to ensure that he is weeding these areas and preventing couch and bindweed getting into the polytunnel.

Notice how Dowding clears the weeds and grass from the edges of his polytunnel and keep the weeds down by growing quick maturing vegetables

Pests -- the NO-DIG method

According to Dowding slugs like rotting brassica leaves because they contain a form of alcohol. (That is why beer traps work!). Minimise slug habitat by keeping path edges short and neat and removing lower leaves of brassicas before they yellow. Dowding claims that alcohol is a by-product of anaerobic fermentation which develops when organic matter breaks down in the fairly anaerobic conditions of dug soils. He claims that no dig helps reduce the amount of alcohol in the soil (which is what the slugs like) because all the organic matter breaks down on the surface where there is more oxygen and none is dug into the soil.

By removing the older leaves from the Cavolo Nero there is nothing breaking down which would provide alcohol for slugs and so they are almost absent from no-dig beds

Please let all of us know if you are going to try any of these NO-DIG methods on your plot.

A visit to Charles Dowding's No-DIg garden and Kew Gardens

Introduction

Recently we have been learning more and more about the benefits of No dig gardening.

We have visited Charles Dowding’s garden in Somerset, the vegetable plots at Kew Gardens and had conversation with an organic farmer at the Alresford Show. We would like to share our findings with you. Firstly thoughts on Dig v No dig using trial results of Charles Dowding.

Dig v No dig

Two beds 5x16ft were started in 2013 and the harvested yields over the following six years are compared in the table below.

There were the same sowing and plantings into both beds. First sowing and plantings 12th March, then covered with fleece for 6 weeks. Growth was sometimes similar, sometimes very different.

	Dig	No dig
	Dug each December. 2in compost put under a spit of soil. 3-4 hrs extra needed for digging and then weeding the extra weeds in dug soil.	2in compost spread on top in December. No forking or disturbance except when harvesting potatoes (pulled out) and Parsnips (levered out with spade).
	Sow into surface soil	Sow into compost
Year	Kg saleable veg	Kg saleable veg
2013-14	186.68	188.25
2015	96.63	101.40
2016	99.37	109.43
2017	104.72	120.62
2018	79.70	104.10
Total	567.10	623.80

It looks as if there is not much difference in yields for the first two years but then the no dig bed outperforms the dug bed. Why is this? It may be because mycorrhiza develop in the No dig bed. It may be because when the soil is dug oxygen is added and the bacteria break down the organic carbon in the compost to carbon dioxide and the water holding capacity of the soil is lower.   

Comparing Dig and No dig and no rotation

Charles Dowding set up another trial comparing Dig and no dig, using different composts with no rotation year on year with surprising results

In this trial each strip of 2m x 9m was divided into 6 small beds where a wide variety of the same vegetables were planted each year.

Year		Minimal Dig Bought compost	No Dig Bought compost	No Dig Cow manure compost
		Soil loosened by forking each winter (no inversion) Then 2in bought compost (mix of green waste/ mushroom compost) on the surface each winter	2in bought compost (mix of green waste/mushroom compost) on the surface each winter.	2in composted cow manure on the surface each winter.
		Kg saleable veg	Kg saleable veg	Kg saleable veg
2014		67.92	78.55	74.51
2015		90.23	101.71	102.42
2016		120.33	142.14	111.97
2017		144.69	148.08	157.18
2018		105.27	115.37	112.03
[AR1] Totals		528.44	585.85	558.11

The vegetables grown were winter salads, beans, broad beans, Uchiki Kuri squash, spinach, land cress, cabbage, potatoes, leeks, lettuce, chicory and kale. Some beds were interplanted. Major weights came from Lettuce 16-20kg,  spinach 11-14 kg, broad beans  15-17 kg and potatoes 16 kg each year.

He commented that he had excellent beans and broad beans. But that the squash were not so good this year(2019). I observed from his more detailed results that there was no difference in the potato yields between the three strips this year. Maybe the lack of rotation is finally causing some nutrient deficiencies for some crops.  In other areas of his garden, Charles Dowding does not always follow a strict 4 year rotation as it is then easier to interplant and succession plant.

An overall conclusion from these two trials is that simple mulching with compost does improve yields of vegetables over digging or loosening soil by forking. Let the earthworms do the work!

---

 [AR1]

Improving our soils at HCF; some more thoughts and ideas.

Over the last 150 years many of the world's best agricultural soils have lost between 30-75% of their carbon, and this has contributed billions of tons of CO₂ to the atmosphere.  1/10 of all CO₂ emissions since 1850 have been from farm soils! This has had a major impact on climate change! Many of us will remember learning at school about the creation of the American dust bowls from the prairies in the 1930's. Most of the agricultural soils in southern England, especially those situated on the South Downs have less than 2% soil organic matter and could easily become dust bowls! Around 30% of the world's farm soils have been abandoned in the last 4 decades because of poor soil.

A recent study from the US has clearly shown that organic agricultural practices build healthy soils by storing away appreciably larger amounts of carbon and for longer periods than typical agricultural soils.  Probably the most compelling findings was that on average, organic farms have 44% higher levels of humic acid, (a component of humus) that sequesters carbon over the long term, than soils not managed organically. (Misiewicz, 2017)

So we ask the question; what practices are most important for building soil organic matter while at the same time ensuring good harvests of organic vegetables at HCF? Here are three more suggestions.

1. Minimise soil disturbance

There is an increasing body of evidence that suggests that digging, rotivating or tilling on the larger scale is utterly devastating to the soil if practiced five or six times a year. First it "slices and dices" many of the beneficial soil organisms like worms and destroys their habitat. As we saw in our worm survey on 29th March 2019 there are a group of earthworms, the epigeic worms that live in the surface litter and help to break it down. These actually form quite a large portion of thrushes' diets, and soil ploughing may be partially responsible for their massive population decline of more than 50% between 1970 and 1995.(Lusher, 2019). The anecic worms that are the drainage worms that make deep vertical burrows which help water infiltration and deep plant rooting are also disturbed or destroyed by frequent digging and their numbers decline leading to poorer drained soil. (Chambers, 2019)  

Soils which are tilled mechanically or repeatedly dug and raked to raise a mechanical tilth are often great for planting seeds in. The problem is that it destroys soil structure. It breaks up the soil crumbs or aggregates (particles held together by glomalin) breaking them to a powder. This tilth may only last a few days or weeks before settling back into a packed, consolidated and homogeneous structure with little pore spaces and structure. If heavy rain falls the surface can become a hard pan and be compacted afterwards and resistant to further water infiltration. 

A second problem associated with digging is that it turns the soil, introducing air containing oxygen to pockets in the soil which enables bacteria to thrive. Bacteria increase in numbers if the conditions are right: good levels of oxygen, moisture, nitrogen and carbon. If the soil is rich in nitrogen (has been manured or fertilised), the bacteria will take in as much nitrogen as they can, but they need about 20 times as much carbon as nitrogen. So the bacteria pull as much carbon from soil organic matter as they can, excreting the bulk of it into the atmosphere as carbon dioxide. Once all the easily digestible soil organic matter (SOM) has been used they will then turn to any humus available in the soil and more slowly break that down! This has been giving a yield boost to the farmers on the South Downs, which is what they want, but it is causing the humus levels in the fields on the Downs to fall dangerously low. So as we can see after just a few seasons of tilling the soil becomes carbon depleted.

There are other disadvantages to lots of digging or rotivating: dug or rotivated soils release far more nutrients than the soil plants can use and these leach through the soils or are washed out by heavy rains.  Finally digging stimulates weed seed germination. Weeds love disturbed, bacterially dominated soil because their goal is to grow quickly, set seed, die and get another generation of weed seeds into the soil.

Charles Dowding began practicing a "no-dig" method of soil cultivation in 1983 which seems to obtain good results on an allotment scale (Dowding, 2019).  By not digging a good biological tilth has developed over time. Biological tilth is the kind of crumb structure that good organic soils becomes as the fungal mycorrhiza produce glomalin which causes particles to aggregate together in little clumps roughly 1 cm across. This is often first found in a soil around the roots of healthy plants. It is resistant to weathering and degredation by digging, while at the same time allowing water to enter easily, but holding onto the water so it doesn't drain though too quickly and take the nutrients with it.

To understand better how Dowding's "no-dig" method works watch this 19 minute video Spring in the No- dig garden at https://mail.google.com/mail/u/0/#inbox/KtbxLxGgHQSXRTZNcHgjvZmXGbnJKXDlCL?projector=1 

Initially we may want to consider a "minimal dig" policy and reduce the use of rotivators on the soil.

2. Sheet Mulch in the autumn

We dealt last week with adding a few centimetres of an organic material to a crop as it is being planted out or adding a composted manure or mulch in the autumn before sheet plastic is used to cover the plot. What I am suggesting here is rather different.

As a teenage I remember buying dry tubifix worms to feed to my tanks of tropical fish. But then I discovered I could grow my own worms by placing bread on damp soil in a margarine tub in our shed and a few days later under the bread would be loads of worms! It saved me my pocket money! Sheet mulching is a bit like that on a bigger scale.

In Rwanda 35 years ago we made a deep bed full on any unwanted organic matter: old grass rugs, chicken droppings, sorghum and maize stalks, sheep and goat shed straw and poo, chopped down banana stems, old leather sandals and shoes, paper and wood shavings. Eventually it formed a bed about 20 cm high. We covered it with cardboard and then left it to the microbes to break it down and the worms to mix it for a few months. Then we grow all sorts of wonderful crops on it for several years. Might we not consider making a sheet mulch bed somewhere on the farm by collecting all sorts of unwanted organic matter over the summer: cotton tee shirts, paper, cardboard boxes, coffee grounds, garden weeds, leaf mould, sawdust, straw, urine and biochar? We could then make a deep bed in the autumn, to rot down over winter and grow in next year? By making one sheet mulch bed a year for several years we could slowly move to reduced digging this way!

 3. Focus on building soil resilience.

One of the features of climate change is that the seasons are becoming more unpredictable. Since we began at HCF we have had wet winters, dry winters, very cold late springs, warm early springs, droughts in summer, really damp summers, typical autumns and indian summer autumns! We have had to become flexible with planting dates and careful about hardening off crops grown in the polytunnels. We have lost whole sowings of crops to freak weather and we've lost plots full of potatoes to blight in damp summers. As we are becoming more resilient to climate change so we need our soil to be more resilient: able to cope with water stress, flooding, frost, snow, humidity, heat and sunshine.

Studies show that organic growing systems get around 30 percent higher yields in periods of drought than con­ventional systems due to the increase of SOM and its ability to capture and store water for crops. What causes this higher yield? We know that organic matter holds anything between 4 and 10 times its own weight of water. This is partly because organic matter acts like a sponge and partly because organic matter particles have a charged surface that attracts water so that it adheres to the particle surfaces. So if we can increase our SOM at HCF it is most likely that our soil will be able to hold more water and maybe the plants will be able to keep going without being watered for another 3 or 4 days. This could help a crop survive through a dry spell.  Similarly, after a very heavy period of rain the soil might be able to hold more water and so reduce runoff to flooding rivers and the loss of precious crop nutrients.

So if we are to build soil resilience at HFC we may need to be more proactive in putting organic material such as manure, compost, mulch, crop waste, progro, leaf mulch, wood chip, straw, bio-char and other sources of organic carbon onto our fields and try to avoid letting the majority of it turn to carbon dioxide within a few months by digging or rotivating.

What are your thoughts?