Chemical fertilisers have been used for only 150 years. But within that period they have helped mine the one thing that earth had an abundance of – carbon. Carbon is a crucial component to all living organisms. Everything relies on it, from the largest animal, to the tiniest of microbes. We couldn’t survive without it.
It is universally recognised the supply of carbon to agricultural soils is limiting soil fertility and productivity most of the time. The order of the four essential nutrient elements in soil fertility is carbon (50%), nitrogen (5%), phosphorous (0.5%) and sulphur (0.5%). There is a large focus for farmers to add or replace the last three nutrients, but because carbon is almost impossible to apply to the farm through conventional fertilisers, it is mostly ignored or assumed that nature will take care of it (even though there is ten to a hundred times more carbon required). In a natural system the plant has a relationship with soil organisms, including microbes, fungi, bacteria and algae. When the plant interacts with this soil life, it releases carbohydrates that help feed energy to them. It is a symbiotic relationship – the plant receives nutrients, the soil life gets energy in return, and carbon is added to the soil. However, when acidic water-soluble fertilisers are used, this can disrupt the process.
Firstly, the acidic fertilisers can kill off the beneficial microbes by osmotic shock. They, and other beneficial soil life, will not survive in an acid environment; a diversity of soil life only thrives in one that has a neutral pH (pH 6.5-7.5 in top 10mm of soil). Secondly, because the fertiliser is water soluble, the plant becomes lazy and stops relying for its existence on root systems and soil organisms for its food. It doesn’t have to sacrifice its own carbohydrates. Instead it can now save the energy for itself and put it all into growing above ground.
However, this is not ideal for New Zealand pastoral land. Encouraging this system completely ignores the dung, urine, dead pasture, excess nutrients, drenches, herbicides etc that all eventually need to be quickly dealt with and purified by the soil life. Acidic water-soluble fertilisers can force-feed the plant excessive nitrogen, phosphorous and sulphur. The plant can then have trouble obtaining enough carbon to maintain the balance, and the stated ratios above become distorted. The stock eat it in this high crude protein, unbalanced state, and the farmer is left feeling their pasture has “no guts”.
Thirdly, the microbes needed to recycle the waste on the soil surface (if they haven’t already been killed), lie in a dormant state waiting for the storm to pass. Even though they can get energy from the recycling process, this is insufficient compared to the 40% the plant is capable of pushing down |
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into the soil. The efficiency of the recycling process declines, and important soil and plant nutrients, and run-off are not absorbed. This produces an unhealthy litter layer which can then foster such problems as facial eczema.
The answer is a simple one. Lime (calcium carbonate) and dicalcic are one of the very few simple products that can be applied to farmland to help supply a source of carbon. When left to react with the soil acid, carbon dioxide is released. There are certain beneficial soil microbes that can use this carbon themselves, but it also supplies the plant with additional carbon dioxide above the ground to help complement the natural resource already in the atmosphere; increasing the carbon dioxide content of the atmosphere automatically increases photosynthesis and therefore plant growth. In fact, the more intensive farming gets with higher rates of NPKS being applied, the bigger the requirement is to restore balance in the pasture by supplying extra carbon. Organic material is mineralised to carbon dioxide, and in an agricultural soil, where carbon is most limited (as apposed to a forest soil), a rapid organic cycle is the key to productivity.
Hatuma clients’ pastures maintain that important symbiotic relationship with the soil life. The plant has ready access to phosphorous, nitrogen and other important nutrients, a neutral pH is maintained, and the lime, dicalcic and the rapid organic cycle strengthen the carbon supply. The plant can then more easily feed the soil life, have the correct nutrients fed to it in return, and still have enough energy for itself. The soil life are able to do their job too – absorbing and recycling the waste and potential run-off from the litter layer.
Back on the surface this looks like the pasture on a dicalcic and lime farm is not necessarily growing as quickly as if it were fed water-soluble fertilisers, but the pasture now has plenty of energy, or carbohydrates. Hatuma clients talk about “quality over quantity” because they know the stock will do very well off pasture grown this way. It has “guts”. |