I have bought a useful app called Sectormentor for Soils, thanks to which keeping a record of DIY soil assessments is more entertaining than it used to be.
Encouraged by the app’s user-friendly features, I have recently carried out slake tests, nodulation and earthworm counts. Water filtration rate, CO2 respiration and a menu of several other home-kit tests are still to do. It will be interesting to see how the information I record correlates with the precision farming data collected with high-tech satellite imaging and laboratory testing.
Now, in October, soil conditions are damp, making it a good time to dig for test samples. I prefer a small pitchfork to a spade as it is lighter to carry around while enjoying a walk on the farm and it does not smear the sides of the dug-out sample. About 10–15 earthworms per 20cm2 (the width of the fork, to keep it simple) is considered an indicator of good soil health. There are estimated to be more than 3,000 species globally, but I will be happy if I can learn to tell the difference between the epigeic, endogeic and anecic, the three most common types in UK arable and grassland soils.
One of the many interesting findings of the Allerton Project is that worm populations are boosted by cover crops, which form an integral part of farming at Hemsworth. While a group of us were recently marvelling at the rate cover crops grow and flower, someone suggested I count the number of different species in the fields at the moment.
Our cover crops are a mix of nine plants, including fodder radish, phacelia, clovers and mustard. Our herbal leys consist of 17 different plants, ranging from tetraploid rye-grass, burnet and chicory to sanfoin, birdsfoot trefoil and sheep’s parsley. Added to these is an abundance of cereal volunteers and a wide array of other ’unintended’ plants. The diversity is not only satisfying to witness but should also add about 22 tonnes/ha of dry matter, as well as control erosion, feed soil microbes, stimulate biological processes, hold nutrients and fix nitrogen.
I remember a soil scientist asking me in 2011 if I grew cover crops. I looked completely blank and had little idea of the possible benefits. Now, seven years on, I would be reluctant to leave a field bare over the winter. It is difficult to quantify the financial return from cover crops because the benefits are cumulative and not necessarily immediately evident in a yield increase – a good example of why higher yields are not always the best barometer of progress. From mere observation, however, cover crops convincingly improve soil structure and thereby increase fuel efficiency, while also helping to mitigate the adverse effects of ploughing. Over time, if I keep up with my new app, trends will emerge on which to base decisions.
At present, our soil temperatures continue to be above 8degC, so the legumes are still fixing nitrogen. The pinkish hue of the root nodules indicates the presence of nitrogen. During investigations with my new app, I have noticed that longer-established clovers, under-sown into cereal crops last April/May, have pinker nodules than the cover crops put in after harvest.
It is no surprise that the longer-established legumes have a better opportunity to fix nitrogen before colder conditions set in. This is already a useful observation, gleaned from using Sectormentor and it will press me to under-sow more frequently. The downside is that, to avoid competition with the cereal and consequent difficulties harvesting, I will stick to low-growing plants like white clover and trefoil, which will mean a reduction in much-prized diversity. I am also thinking it would be a good idea to add a rhizobia inoculant when next establishing legumes. My observations tell me that rhizobia root associations should be more plentiful.