Biochar Experiment (2)

The biochar samples arrived from Oxford Biochar (Biochar Experiment). What we are required to do is to grow a crop of our own choice in two adjacent square metres of soil, identical except that one of the two mini-plots has biochar added. Today I have prepared two beds on part of one of my new raised beds and added the biochar to one of them. Although I won't be planting for a few weeks yet, by preparing them now I am giving the biochar a chance to be 'primed' by the soil organisms and the compost that I added (to both plots to maintain equality). Oxford Biochar didn't indicate if their material has gone through any priming process. When I submit my results I'll make sure that I record the length of time the biochar has been in the soil prior to planting. I know from reading about other biochar experiments that sometimes results which show no positive, or even negative results, from biochar application are explained by the fact that 'fresh' biochar has been used.

The application rate recommended by Oxford Biochar is 1.5Kg (the bag you see in the picture) per sq. metre. That is the equivalent of about 6 tonnes to the acre (15 tonnes/hectare)and is at the mid to lower end of recommended agricultural application rates, certainly not excessive.

With reasonable care taken to ensure that the soil and growing conditions of the two plots are comparable, it is reasonable to assume that any significant differences in crops yields will be because of the biochar. However, assuming there is a difference, there remains the problem of identifying which characteristics of biochar are responsible for the variation. In itself it has no nutrient value but one or more of its physical characteristics may increase my yields:

• There could be a rise in PH. This could be marginally helpful for some crops but my PH is generally OK for most things I am likely to grow.
• Biochar can help with drainage on sticky soils but my raised beds are fine in that respect.
• On the other hand they can also help retain moisture. In a dry summer that could be helpful.

You can begin to see how biochar's effect are most pronounced on degraded soil or those which suffer from a particular negative characteristic. On these criteria I can't imagine a dramatic effect but biochar's trump cards are:

• an ability to store nutrients in its maze of microscopic channels
• encouragement of microbial and fungal activity leading to
• increased availabity of Ca, Mg, P, and K

If I do see growth differences in this experiment I expect that it will be these latter characteristics which will be at work. I'll have to wait and see but there is one observable characteristic of biochar which is immediately obvious - the albedo effect. I hope you see in this picture (click to enlarge) how the biochar, although mixed into the soil, has left enough on the surface to darken it. My soil is a dark loam anyway but the additional darkening affect should retain that little bit more heat, valuable at this time of year as the soils struggles to heat up.

Of course there is one more important variable - what to grow! I might try to squeeze as much as possible from the experiment and plant to different veg, perhaps a root crop and something leafy. Carrots and lettuce?

Saturday, Seaweed and a Flurry of Snow

These past few days here in the North-East of Scotland we've had a bit of weather reversal with our English neighbours. Usually we are colder but while England has been coping with freezing rain and records lows we've had some balmy days. Is 11ºC (52ºF) balmy? From where you're sitting maybe not, but for us in February it's almost enough to tempt you to indulge in a frenzy of planting. Bad mistake, which I resisted because I am surrounded by old hands who have seen more snow falls in April than snowdrops in January and who are guided by dates not ephemeral warm spells. If global warming is kicking in these guys will need 20 years solid data before they'll plant their early tatties before the end of March.

So instead of premature outdoor planting I took advantage of a calm day, a warm sun and a tide which had left an offering on the strandline to collect some seaweed. The shore is a five minute stroll with the wheelbarrow.

You can see the line of seaweed deposited by the tide. Note the prolific growth nearer the low tide mark but this is growing, anchored seaweed which I wouldn't take. In fact I think it might be illegal. Few moral dilemmas though when I could have filled my barrow many more time from the strandline but I am reminded by Gardenzine that '. . . seaweed that is left behind when the tide retreats will be returned to the sea at high tide. In the meantime, it is providing shelter for hundreds of creatures and protecting them from dehydration until the sea picks them up again. Pick seaweed that has been pushed beyond the reach of the tide or has been washed up by storms and wash the seaweed in the sea if you can to allow any sea-dwelling creatures sheltering there to escape.'

The view is looking back upstream to the harbour but it's also the outfall for the River Dee and so although this is tidal there's a huge volume of fresh water passing this point too. That makes me think that the seaweed I am gathering may be lower in salt. Advice seems to vary about whether seaweed needs to be 'washed' before using. I'll take a chance with my composted, 'lo-salt' harvest which I'm using here to top off a compost bin.

I don't have to be convinced of the value of seaweed but I was intrigued to read, again in Gardenzine, that some bloggers complain that the flavour of Ayshire's famous potatoes has declined since a lack of available labour to cart seaweed on to the potato fields has meant that this traditional fertiliser is no longer used. More pejoratively, it was seaweed that underpinned so-called 'lazy-bed' agriculture in Ireland and the West coast of Scotland where the low fertility of peat-based soils were supplemented by the nutrients supplied by spread seaweed. The term lazy-bed seems unfair both to the crofters and the seaweed as it was probably the most productive solution to a poor soil and an easily available resource. And I know that even with my relative proximity to the source, carting seaweed from the shore to the land is not for the lazy.

With the harvest put to bed in the compost heap and given its covering blanket the sun disappeared in a darkening sky and a few snow flakes flurried in a bitter wind. The seasonal temperatures had returned. The tools went back in the shed and I was pleased to have kept the seeds in their packets for the time being.

Gaining An Edge - Small Increment No. 1

OK, it's not a brilliant drawing, I concede. Let me explain.

I doubt if any of us have a garden or allotment which is perfect in every respect. We all have to work round limitations of one kind or another - soil, aspect, shading, wind, temperature, builders' rubble. Your gardening limitation is the biological equivalent of the slowest ship in a convoy. What is slowing you down? For me, I know it's not the soil - deep, free-draining in the raised beds, reasonable PH. But give me a longer a season and another 5° on average temperature and I'm sure I could double the yield I'm expecting.

Some things we have to accept; others we can squeeze a little.

Things I Have To Accept No. 1 Daylight hours on 22 December (shortest day) amount to 6 hours 40 minutes

Things I Have To Accept No. 2 My plot is on a north-facing slope.

Things I Have To Accept No. 3 Average annual temperature 7.9 °C (46 °F).

What this means is that the long winters, amplified for me by the hill to the south shielding an already low sun, causes the soil to warm very, very slowly in spring, late frosts can wipe out early plantings and even when summer does come higher temperatures are elusive. What I have to do is find ways to extend the season by using all the tricks that I can to squeeze a little here, a little here...

Small Increment No. 1: level the soil So back to my 'graphical representation'. What is happening here is that by making the soil in the raised beds level, rather than following the natural slope, I've increased the angle that the sun hits the soil from 20° to 30°. Joy Larkcom, in her inspiring Grow Your Own Vegetables quotes research that suggests that a 5° gain in slope is equivalent to moving 30 miles to the south. On that basis, my raised beds at least, if not my rhubarb languishing on my un-levelled border, have moved to Dundee with their 10° gain. (Perhaps by creating 10° south-facing slopes in the raised beds they could be in Edinburgh.)

More Small Increments to follow. Dundee is only the first stop!