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Factors affecting Soil Health
Factors affecting Soil Health
Soil health can be defined as a soil's ability to function and sustain plants, animals and humans as part of the ecosystem. The factors that impact the health of the soil can be classed
Physical - structure and water
Chemical - N:C balance and SO
Biology - plants, fungi, bacteria & animals working together
Impacts of land use management, including cover crops, on erosion. Measured across the EU
A healthy soil will have a good combination of all these factors. Any structural problems - compaction, plough pans, or water-logging have a cascade effect until all the other factors are impacted. A healthy soil will provide a buffer to extremes in temperature and rainfall - reducing the impact of extreme weather events and has plenty of air spaces within it, maintaining aerobic conditions and providing spaces for the small animals to exchange materials.
Anaerobic conditions lead to waterlogging and stagnation of roots and the proliferation of anaerobic microbes and denitrification (the loss of nitrogen from the system). A healthy soil will filter water slowly, retaining the nutrients and pesticides applied to the crop. If surface runoff increases, it takes soil, nutrients and pesticides with it, increasing the risk of flooding.
Soil organic matter (SOM) is a central soil property that is heavily affected by management practices, which in turn influences soil physical, biological, and chemical functions.
All these functions interchange in the soil realm.
What other factors would you add to this schematic drawing?
The central soil property that influences soil functions is organic matter. The organic matter component of the soil system is only a small fraction of the topsoil horizon (ranging from 1-5% or greater by dry weight depending on the soil type and other formation factors), but essential for the soil physical, biological, and chemical functions and general soil ecosystem services.
It has been estimated (given soil conditions vary wildly) that an extra 1%C can lead to an extra 3000 gallons being held in an acre otherwise holding 7,000
Functions are sequentially influenced by each other starting with organic matter as the building block for the well linked functions.
But we have to look at organic matter, as not all organic matter is the same.
- Physical - structure and water
Ploughings cuts through soil, turning it over, exposing parts that were previously protected. Many surface creatures must die, and this is witnessed by the birds behind a plough eating the creatures. Much else will be going on.
Pasture to arable There are half the number of small soil creatures under arable soi, as under pasture. Save our arable soils
Compaction - as with ever heavier machines - compresses the pores, smashing up life, and preventing aerobic processes. Compaction leads to increased runoff with loss of soil, erosion and silting rivers.
- Chemical - C:N balance and SOM
SOM is the basis for most soil evaluation, yet it should be classified into two - the checking C account and the savings C account. The checking account turns over carbon quite quickly and is not held tight, whereas the savings carbon is tied firmly into minerals and goes much deeper. Curiously fields with no-till may conserve soil near the surface, but ploughed soil maintains carbon lower down.
Fertilisers drown the soil systems in nitrogen, reducing biological versions.
Herbicides kill weeds, which each would have provided small carbon capture & Storage unit
C:N ratio explained Whereas most chemical analyses of soil involve, the famous N P K - the elements that encourage such rich growth in crops, here we may want to look more at the C:N - the 'Carbon/Nitrogen ratio. Just like when you make compost, you want to have a mixture of brown and green, so too does the soil need that. The brown carbon represents structure & sugars, while the green nitrogen more nutrients. The soil needs a balance and curiously that balance is much the same the world over @ 10:1 But C:N ratios are hard to measure.
- Biology - plants, fungi, bacteria & animals working together
Inside those soil cities below, are a mixture of creatures and characters - who are all represented above ground. They have members of every phylum.
There is as many interrelations below ground as above ground, but we can't see them. So we try to make up the connections. Monocultures will reduce lots of interconnections, concentrating on a few.
Rotations, especially those with animals and legumes, increase the mix of creatures and microorganisms
Slurry (anaerobic) versus muck spreading (aerobic). Dung Beetles
The relations between roots and fungi and bacteria are know, and the role of the worm as the earth excavator go back to Darwin. However, how do springtails pass between roots and fungi, and do how mites relate with worms is yet to be explored. Any indicator of soil health has somehow to represent thi.s
Do you measure one parameter or try and measure a mixture?
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