Soil fertility is more than just minerals

I used to think soil fertility was little more than making sure the correct chemical elements or nutrients ( N, P, K, S, Ca etc) as measured by soil nutrient test are available in the soil in the right amounts.

I realise now that this view of soil fertility is a very narrow one and certainly not sufficient if one wishes to grow quality food that is resistant to pest and disease, handles and keeps well, is tasty and nutritious. For this we need to consider two other equally important aspects of soil fertility; physical aspects and biological aspects.

To illustrate physical aspects, consider for a moment a soil that has all the desired nutrient elements and levels but physically is continually water-logged. It is self evident that this soil can not be considered as fertile. Other physical considerations that might impact on a soil's fertility is how hard or compacted it is, or if it has the presence of a hard pan within its profile.

Biological aspects of a soil are equally significant to a soil's  fertility. The great majority of the nutrient uptake processes by plants actually involve a soil micro-organism at least somewhere in the process. Even the uptake of nitrogen from an application of urea fertiliser requires the services of an intermediary microbe, in order to convert urea- nitrogen into a form that a plant can uptake. There are all manner of symbiotic associations with micro-organisms in a plant roots zone, where plant root exudate’s energy rich from plant photosynthethis feed microbes within the root hair rhizosphere in return for nutrients the microbes harvest from the soil. These mutually beneficial relatiohships that should be occuring in all healthy soils are not only generally poorly understood; it seems that modern conventional farming practices activily discourage their activity since many of the common tillage practices and  chemical fertilisers, herbicides and insecticide applied to soils actually harm these organisms very existence.

While soil biological is surprisingly resilient to much of the abuse, over time a toll will be taken and plant and eventually entire soil micro biological ecosystems will suffer and break down. This can be witnessed in many ways, from the lack of earthworm activity to the loss of soil structure and organic matter content. Not only do these represent a loss to soil fertility, they also lead to an ever increasing reliance of chemical fertiliser inputs for continued plant production often with corresponding costs associated with pollution  to the environment environmental from the chemical fertilisers and pesticides used. It appears almost all pesticides are harsh on soil microbes to at least some extent as are a good deal of the chemical fertilisers, but certainly not all.

Many argue that this cost to the biological fertility and the environment is something that modern life must accept since it is impossible to produce food otherwise. This is simply not the case as many are consistantly, productively and profitably demonstrating. The good news is that there are ways to build fertility in soils that can easily, reliably and economically grow quality nutritious food that is weed and pest free without having to suffer the adverse effects of modern chemical farming methods as a matter of course. And it is not as if modern chemical fertiliser and pesticides have no role to play. Not all chemical inputs are harmful and even those that do have potential to harm, where used carefully and strategically can achieve outcomes that have little or no long term adverse effects.  With fertiliser inputs, there is often a non chemical alternatives  that can be used to deliver nutrient requirements. Some of these may not be as concentrated in their chemcial analysis resulting in greater cartage costs, or not as quick acting compared to highly soluble chemical alternatives. However with time and the aid of a healthy and active soil biology, they are soon become as effective if not better. Many of the pest and disease problems requiring chemical  herbicides and pesticides can be minimised through the use of alternative husbandary and cultural methods but also through simply attaining a high degree of health in the soil, plant and animal, which in a great majority of instances, results in a natural resistance to pest and disease. A key aspect of attaining high health is to address all three aspects of soil fertility, ie the physical, chemical and biological aspects together and it will simply happen!

Can it really be this easy?  Well the short answer is yes. The reality is that if the physical, chemical and biological aspects are optimal, and there is now plenty of information as to what the optimal levels for each apsect shoud be. Food that is produced this way will naturally be of good handling and keeping quality, will naturally be highly nutritious, and amazingly, will naturally be highly resistant to problems associated with pest and disease, as will the animals that consume the food.

To some, this might all sound wishful and fanciful, and lacking science. Yet this is not so. What you are effectively doing is thinking holistically, that is, considering all the aspects of soil fertility in a dynamic, integrated and interelated way.

This is also how nature works and  this why you will get good results, because you will be thinking with nature in mind.

Nature is not linear, it is a dynamic integrated and interrelated entity where many things happen at the same time - just as is soil fertility is where the physical, chemical and biological aspects all affect each other and work in an interrelated and dynamic fashion. Conventional agricultural science has let the side down badly here, in failing to recognise this plainly self evident truth and as a result, all but ignores the biological aspects of soil fertility.

Thinking about soil fertility in a more holistic fashion where physical, chemical and biological aspects are considered collectively, will allow you to harness wisdom and energy of nature, and in doing so, making her a powerful ally in your quest for optimal soil fertility. Nature has had aeons of time throughout her evolution to figure out what works, and what doesn't in soil fertility. She knows what to do and how to go about it, with seemingly a dozen alternative ways as well. To harness this power, all we need to do is continually ask ourselves when carrying out our farming activities is, is this activity going to help or hinder nature? So long as our actions are not hindering nature, nature will invariably help in return, and the more we work with her, the easier it seems to get. It is like catching the main current in a stream and get taken to good places with little effort.

This is not an fluffy and esoteric concept. This is what happens. We are after all part of nature, as farming and growing food is little more than working with nature while trying to exercise some control over it. We really need to recognise that as farmers, we are somewhat akin to a mahout on an elephant. By this I mean while a mahout may think he's in control of his elephant, in reality, the elephant only does what the mahout wants if it finds it agreeable to do so. Mans relationship with nature is somewhat similar.

Our challenge is to use science and knowledge to understand better how nature works and then apply this knowledge to ensure nature is getting the best assistance we can provide.

Since so much of our very existence starts with the soil, it is perhaps not surprising that this holistic view of soil fertility is so effective.

Roger Martyn

March 2015






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