Soil is a living breathing organism, and as with any other oxygen dependent organism potential performance increases with improved ability to suck air in and breathe out gases. Conversely when unable to breathe soil dies and what remains is no longer soil.
In an ideally structured soil, by volume 25% is air and 25% moisture. Air and moisture are inversely related meaning that after rain moisture levels will increase as firstly large pore spaces are filled displacing air.
As soils dry out in summer the amount of moisture in the soil will decrease relative to air. Where soils are dominated by very small pore spaces they tend to be poorly aerated, with moisture tightly held and slow to move. These soils after rain are also slow to become sufficiently moist for strong pasture growth.
Maybe a useful analogy is a vehicle fuel tank. When designed with a very small breather they are frustrating slow to fill, however this is not necessarily related to the rate at which fuel is consumed.
Likewise soils with a higher proportion of space as macro pore space are not necessarily the quickest to loose moisture in dry weather. Macro pore space relates to the space in the soil large enough for excess moisture to percolate freely through.
The ability of the soil to hold onto moisture during periods of hot dry weather is largely related to the amount of humus in the soil. Humus is sometimes referred to as the ‘glue’ in the soil. It acts as a sponge and has approximately five times the moisture holding capacity of a clay soil containing very little humus.
Humus and organic matter are often confused. Humus is the result of fully decomposed organic matter and is very stable. Organic matter is supplied to soil by dead roots, dead leaf matter, dung and urine. To become humus organic matter needs to be worked on by soil organisms and these organisms require air.
Hence the situations where humus is formed most rapidly is where air is able to enter most quickly and gases to leave freely. These soils are therefore able to store more moisture and produce the most pasture growth over summer.
With more pasture grown there is more dung deposited along with increased root matter and uneaten pasture to further build humus and stimulate even more growth, and it requires only a little assistance from us. Grazed soil is regularly subjected to considerable pressure from animals’ feet. When the effect of this pressure is not relieved compaction occurs and macro pore space is reduced and consequently growth slows.
This can often be fully relieved by an annual application of Golden Bay Dolomite containing 11.5% magnesium and 24% calcium.
Dolomite is unique as it contains calcium and magnesium both in the carbonate form. Calcium has the ability to force soil particles apart and stimulate beneficial biological activity. Magnesium adds a little stickiness giving dolomite the ability to increase macro pore space by clumping together very small soil particles. This process is known as flocculation.
For more information call 0800 4 DOLOMITE, 0800 436 566 or send us an email.