Increasing Soil Organic Matter and Rebuilding the Farm.
A decade ago, when I started work on an estate in the very south of England, I also started a journey in soil improvement, I joked the soil was merely sand over gravel. Meaning no soil and very dry. The summer rainfall was low most years while the total was a respectable 800mm. In my mind it was a case of improving the soil or dirt as people were calling low nutrient matter at the time. I set up a full soil testing regime to investigate ways of improving it. This was a Albrecht analysis which I used primarily to check on Soil Organic Matter and get some base figures. I planned to test every three years as an annual test will only show up discrepancies and the cost is prohibitive for more. Also, the detail is enough to keep you occupied, if not for 3 years, for a while anyway.
The paddocks had been down to grass for 8 years and grazed by Holsteins, in fact they went out had a look around and a few hours later waited by the gate! Hence there was little rotational grazing happening and most of the dung was deposited in the gateways. Surprisingly or perhaps not, the soil organic matter was only an aggregated average 2.5% and microbial activity 167. This was interesting as I would have thought it would be higher given the length of time the leys were down to grass; however, the fields were part of an arable rotation with plough and power harrow were the methods of seeding. Also, although slurry was applied, it was injected in very heavy doses and there appeared to be little benefit. Another measurement is the CEC or Cation Exchange capacity and indicates how the soil captures nutrients via chemical reactions close to the soil crumb. The sandy soils tend to turn nutrients over quickly where clays are more settled and churn inputs over slowly. The measurements of 14 were respectable for sandy soils.
I made sure I did the right things, correctly, based on those results, we rotationally grazed with keen Jersey cross- bred dairy cows using back fences, made sure the whole paddock was grazed and dung distributed evenly. I used “organic” type fertiliser such as kieserite and sylvanite this contained sulphur, magnesium, potassium, and sodium which were indicated from the soil tests. This improved soil and grass health, and this enabled me to reduce Nitrogen fertiliser from around 400kg/ha to 200 kg/ ha then to 100 kg/ha eventually. Around this time, we had a particularly dry summer and I stretched out the rotation from 30 days to around 50 days, unfortunately this resulted in little extra growth from the recently direct drilled perennial ryegrass. This meant a fresh approach was required and herbal leys were just coming on the scene, with their deep-rooted herbs, grasses and nitrogen fixing legumes, seemed to fit the bill.
On that initiative I direct drilled, with a simple Einbock machine, 16 ha of broad-spectrum drought proof herbals into an arable stubble adjoining the main milking platform, in 2013. In that difficult year we had 3 grazings complete with copious amounts of fat hen, which we trampled into the depleted soil.
This inspired a further 45 hectare of herbals to be planted in the autumn, again, direct drilled into rounduped old pasture with a dose of lime (one tonne per hectare). A pass with a Shakearator to break up previous pans then a 6m Vaderstad drill was used, creating enough top tilth for all the fine seeds to get a hold. A large amount of the milking platform now had a good drought insurance. The most important thing with herbals, in my opinion at the time and still is, that the roots fully develop. Therefore, we didn’t graze these areas with the dairy cows that year but gave them a light graze with yearlings in the late Autumn. They came back up perfectly in the Spring, with a good count of chicory, plantain, red and white clovers, burnet, sheep’s parsley with grasses cocksfoot and timothy joining the perennial ryegrass. The small amounts of sainfoin and lucerne sown didn’t show much as the soil pH was a bit low.
We were still calving in February and there wasn’t a lot happening on the herbal leys fortunately we still had plenty of perennial ryegrass to graze until March when there was a grazeable amount of forage. The leys looked a picture with a nice balance of herbs, legumes, and grasses, however there was the odd ragwort plant that was a blot on the scene. A few turned into many and forced us to top after grazings. Not ideal, but our hands are tied regarding spraying due to potential damage to the herbs and the GS4 agreement quite rightly prohibits spraying for weed control. However, as the soil health improved so the ragwort disappeared, proving that the weed is a coloniser and ordinary soils can be dysfunctional enough to let it in.
After all this excitement it was time, after 3 years for the next soil test. When I take a soil sample, I dig holes with a spade, investigate the soil structure, root development and count earthworms from a few sites within a paddock, then combine the samples in a bucket to get an aggregated average. I found the soil structure had definitely improved with better colour and crumb like aggregates and there were roots aplenty, very deep too. The previous ryegrass hadn’t developed any roots to speak of despite being challenged by drought conditions. Earthworm numbers were increased, so I knew things were improving and hopefully water holding capacity that comes from increased soil organic matter. The results were not quite as good as I had hoped. Soil Organic matter had only increased to 3.2% from 2.5% but the soil microbial activity had increased to 1007 from 167. It was this last figure that gave me hope as the soil isn't going to do anything without bacteria, so fingers crossed.
We carried on still rotational grazing, slowly at times and the paddocks grew huge amounts of herbage, the chicory especially bolted to over 6 feet tall were the cows simply pulled off the best of the leaves and trampled the remainder to be “worm Feed”, feeding the enlarging population of underground invertebrates. I concocted a method of fortifying the dirty water from the dairy which was applied via a combined slitter and spreader. An IBC tank was primed with imported inoculants containing aerobic bacteria and molasses, to this I added powdered mycorrhizal fungi. This I inoculated the lagoon periodically and observed the bubbling on the surface, which seemed to increase by the week. The annual muck out of the sheds resulted in a massive amount of manure that ended up on the yard at the back of my house. Naturally there were concerns of the smell, we ended up covering the heap, after it was delivered by a back spreader muck trailer. The resulting (Bokashi as it happens) compost was the best I had made and found its way onto the grazing paddocks too.
Yes, I was getting a little obsessed with soil improvement, but my other objective was to increase the profitability of the dairy herd, and this was on track.
Finally, after 6 years the final test was due, and I got the result I was after. An increase in Soil organic Matter of 135% over 6 years to 5.4%. This was on the herbal field, which with the ability to elongate rotations put more roots into the soil and improves the biology. Even the ryegrass paddocks increased by 60% to 4.2 %. Therefore, this extra organic matter meant that the paddocks would hold more water over the summer. Figures such as an extra 1% of increase of SOM equates to 160,000 litres of water available and that 1% can contain an extra 60 tonne of carbon. Over the 200 ha farm equals 12,000 tonnes. Both of which brings value to farm. The herbals brought grazeable forage mid-summer that increased the profitability of the farm by more than £100k before environmental payments.
Carbon credits and carbon offsetting are now on the horizon for future payments proving where there’s (composted) muck there’s money.
But what this also clarifies is that the regenerative farming theories are correct, and we can build soil. And yes, it was from a low base, but we can build more soil and draw down carbon from the atmosphere using depleted arable fields and livestock in a clear demonstrable way.