What I learned over a year of growing with Soil Biology

It’s been just over a year that I completed Elaine Ingham’s Life in the Soil classes. It seems a good time to take stock, as we go into the colder part of the year when practical fieldwork winds down. So what have I learned?

The polytunnel with the tomatoes
The polytunnel with the tomatoes

There is certainly promise in the end results – very visibly in the case of the beans, and noticeably in the improved taste and productivity of the tomatoes. We only have one polytunnel for the tomatoes in 2016, but we got almost as much yield this year from this one than from two polytunnels of tomatoes [ref]We have three polytunnels, all of the same size and colocated[/ref] in 2015.

I know of no way of quantitatively analysing taste, but several of our CSA members observed the much better flavour of our tomatoes compared with shop bought ones. However, one other thing we changed across the years was have a dedicated CSA member Ann look after the tomatoes, pinching out all the offshoots and training the stems along the frames. Because we could not afford a control plot with the tomatoes, the almost doubling of yield could be the result of her extra care and attention to detail, or a combination of the her work assisted by the compost extract.

The compost extract was used in the polytunnel with the tomatoes in July 2015 and some of what was left over was also used in polytunnel 1 which was where the beans were planted, with the ribbon tied to the frame to show the extent of the coverage, the left behind compost after extraction also went into the tomatoes in polytunnel 2.

The beans at the back show very noticeably more vigorous growth and had a much higher yield, and this coincided exactly with a ribbon showing the limit of the compost extract.
The beans at the back show very noticeably more vigorous growth and had a much higher yield, and this coincided exactly with a ribbon showing the limit of the compost extract.

Not every attempt showed success – last year we tried some outdoor tests on defined plots in the sweetcorn crop. This crop was lost to the initially wet and dull start to 2015 and not enough manpower for weeding. I felt there was some difference in one of the plots, but not enough to make a clear picture and not enough to redeem the crop.

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Compost from start to thermal equilibrium

a compost heap tracked all the way from start to thermal equilibrium. The sensr for the green trace was reallocated to ambient about 1/4 way through
a compost heap tracked all the way from start to thermal equilibrium. The sensr for the green trace was reallocated to ambient about 1/4 way through

I recently tracked a compost heap from start to reaching thermal equilibrium. Partway through we started another one, and one of the sensors was allocated to tracking ambient. While a single data point isn’t conclusive, it was interesting to see the week 37 (12-18 Sept 2016) second breath of this heap after the second turn coincided with a week of particularly warm weather. This points to a potential ambient sensitivity and it being worth tracking ambient in future and perhaps insulating the heap more in the later stages.

I will keep the technology of remote temperature sensing here, because I’d imagine horticulturalists aren’t that into electronics 😉

Compost reaching thermal equilibrium – temperature chart

Both of our current compost heaps, 160901 and 160910 have now reached stable equilibrium. The two graphs below show the complete “heap lifetime” temperature against time. The tail of each chart is now reasonably steady, suggesting they are now “mature”. It’s between five and six weeks since we first built these heaps.

The complete “lifetime” temperature profile of compost heap 160901 started on the 1st September 2016. The second probe was first at a different level within the heap, and then reallocated to monitoring outside temp at the start of week 37
Temperature profile of the heap using chicken manure slurry, heap number 160910, showing the much faster burn initially

In both of these there seems to be a reasonable evenness through the pile when both temperature probes are active, the temperature recording tips of the probes were set in the centre of the pile horizontally, and at about 1/3 and 2/3 from the top of the compost heap material.

We had a quick look at 160901 compost under the microscope a little while back and it was very exciting!

Fungal hypha in heap 160901
Bacteria and protozoa, magnification 400x in heap number 160901
Another fungal hypha
Another fungal hypha

Laverstoke Park Tea Brewer

Laverstoke Park Farm is a UK site with specialised knowledge of Elaine Ingham’s methods. Sadly their farm shop has closed, we dropped by on route back from holiday last week in the hope of buying a bag of their compost (to inoculate our soil and compost heaps), but no joy, so we’ll email them in the hope of being able to buy a bag or two, or maybe even visit (it looks fantastic!)

We had invested recently in a small compost tea brewer which Laverstoke Park developed, to learn more about how it is done, before we try this on a bigger scale. We have used compost extract rather than compost tea to date as it is easier and safer.

The kit is basically a 3W aquarium pump, an air stone and bucket

Air stone in bucket
Air stone in bucket
Air stone running
Air stone running

The kits came with some microbes in a tube, but the tube seemed to be out of date. Sadly our first attempt with this mix failed as the pump fell from its perch (no harm done, fortunately) and this, admittedly early aborted, brew didn’t appear to contain much exciting under the microscope.

We are now going to wait until we have some promising Oak Tree compost (from heap 160901 , or heap 160910 if either look good under the microscope) or have some Laverstoke Park compost before we try using the brewer again. We’ll keep you posted!

Outer wrapping restored about 13:00 to maintain temp

The heap is now dropping below the 66 deg C temperature mark so the outer wrapping was replaced around 1pm. Today is a hot day, the highest September recorded for many years, so the heap has ambient temp on its side.

Temperature against time and date of this compost heap.

Good points and bad points of this heap:

This heap heated up far more successfully than any of our previous heaps! and we look forward to putting some of the matured compost (when it has dropped ambient temperature) under the microscope. We put this sucess down to the pelleted chicken manure pellets mixed into a slurry with water which raised the temperature dramatically!

Outstanding issues:

  • It is possible the fast high burn rate of the early stages has exhausted the material, or that some was pasteurised at 74C?
  • The temperature profile isn’t 100% perfect, but it is certainly very promising.

Second compost turn at 70C

After the drama of needing to turn this heap very early on a Sunday morning (we had obviously overdone the chicken manure slurry) it  heated up over the day so we turned again at about 19:30 Sunday evening.

Before the turn.
Heap uncovered
Heap uncovered
close up
close up

This time we left off the insulation around the outside of the container, though retained the insulation in the top made of bundled up mypex woven black weed control fabric.

First compost heap turn at 74C

This graph shows the temperature against time/date of a new heap that included a slurry of pelleted chicken manure, as explained in this earlier post. There is a gap in the data near the top of the graph – Richard had an upper limit of 70C on the data logger which he swiftly raised as a result!! You may notice that the rapid rise of temperature to danger point happened at approximately 5.30 am on a Sunday morning. Yes, this meant that Joanne woke Richard at this time to tell him, “the heap is going anerobic!!!” (very worrying and could cause a fire!) so we rushed up to the farm to turn it…!

overheating compost heap, turned in the morning at about 6am
overheating compost heap, turned in the morning at about 6am
heap contents
heap contents
Heap had gone down about a third (it wasn’t loaded to the top before, down to about the first set of holes probably)
Close up of outside
Close up of outside
Showing inner core. It really was hot!
Showing inner core. It really was hot!
detail of photo above.
detail of photo above.
Turning the heap
Turning the heap