This article comes out of a complete sense of disbelief. As an Astrologer with a passion for Biodynamics my interests in agriculture have been more concerned with how the planets effect plant growth than soil science. Over my twenty years of growing things on various scales from home garden to commercial farming I have accepted the basic premise that if I treat the soil right it would look after me. So I have composted green manured, and mulched with whatever has been available. Some years ago I did a permaculture course which brought me a sharper understanding of landscape and microclimates. It is only over the last three years I have finally come to study soil science. Luckily I have had two very good soil consultants to teach me the basics of their art. As indeed it is an art. There are up to 100 elements currently understood to influence plant growth. Being a person who thinks and understands systematic patterns I have found both soil science and chemistry relatively esoteric due in part to their piece meal approach of describing each element in isolation to every other element. This element does this and that one does that. There seems very little attempt to find groupings and patterns. The periodic table, cations, anions etc are the obvious attempt in doing this, Naturally a whole new language has to be learnt. To my amazement I have found that although farmers livelihoods depend on the soil and its science many have been `beaten' by its complexity or the complexity presented to them by science and have tended to give up and use soil consultants. This could be a good thing if there was some agreement as to what is good soil science. Alas there is not and there are as many theories of soil science as there are clouds in the sky.
There are however a few real basics which most people can recognise. The most stunning aspects of this and the cause for my disbelief are that the elementary basis of soil science seems to be completely disregarded by our modern agricultural business. One basic concept one comes across in most fields of natural study is the concept of finding a balance between acidity and alkalinity. Growers often talk about the pH of the soil. This pH reading is an indicator of the level of hydrogen ions in the soil. Hydrogen reacts with other elements to create acids. The more hydrogen ions in the soil the more acidic that soil will be. Once a soil is acidic it has the ability to liberate elements such as iron and aluminium which in turn either lock up elements such as phosphorus or go on to create toxic overloads in grass and animals. So most farmers agree pH is important. The rest of the story of soil balance is based on what the hydrogen is in proportion too. This is where we come across the concept of a soils base saturation. Base Saturation is the saturation in the soil of what we call the Bases. These are the positively charged elements Calcium, Magnesium, Potassium and Sodium. If you look at an ARL soil tests you will find this reading tucked away down the bottom and for most people totally forgotten about. According to the understanding of base saturation and soil balance, a soil is considered to be balanced when the pH is between 6.2 and 7. This means that only around 9% of the positively charged cations on the soil colloid is hydrogen. The rest of the soil saturation is meant to be made up of calcium, magnesium, potassium, sodium and other bases. As you can imagine the exact percentage of each of these elements is one of continual debate between all concerned. Naturally, different crops will like to have different balances. Fruit crops would like more Potassium than Dairy pasture and so on. So this is a discussible ,science. However there are some basics than can be agreed on. To achieve a 6.2 pH you need to achieve approximately:
Calcium of 60-70%, Magnesium of 9-18%, Potassium of 2-4%
Sodium of 1-2%, and other bases of around 7%
with hydrogen of around 9%.
At this kind of balance and a soil pH of 6.2, the most beneficial range of elements will be available in your soil. The other 80 or so elements need also be consider however the above elements are the building blocks upon which our soil' house ` can be successfully built.
Like most things, soil is not simple. Different soils have different soil colloid nature. e.g. sandy soils have a smaller ability to hold cations, while clay soils can hold heaps. So when on comes to work out how much of any element to apply to achieve this balance one must take the `size' of the soil or the exchange capacity of the soil into account. This can be another story some other time. In my studies it seems perfectly natural to accept Base Saturation as a sensible and natural starting point to build soil fertility on. My sense of disbelief has come from working with the average dairy farm and being confronted with the soil programs they are using.
Base saturation is almost unheard of and the application of Lime or Magnesium is almost considered unnecessary . The fertiliser companies have got them believing that because superphosphate has 23% Calcium in it there will be enough to sustain a farm. Super has a pH of 4.5. There is only enough calcium in 'Super' to neutralise the sulphuric acid to allow a pH of 4.5. How is a substance with a pH of 4.5 going to raise the pH of a soil? Lime and Dolomite have become things of the past while Nitrogen, Potassium and Phosphate have become the gods of the day. Hence many of the dairy farms in New Zealand today are returning soil tests of pH of 4.5 with hydrogen levels of 30% upwards of base saturation. The calcium and magnesium show corresponding reductions. This in turn, leads to no end of problems which then becomes a problem for the vet to solve. Amazingly, little connection has been made between the need for dairy cows to be drenched with calcium and magnesium in the spring to over come milk fever and sleepy sickness and the lack of these elements in the soil. Economically this is madness. Farmers are paying a $1 per shot to supply calcium to there cows as drench instead of 10c worth of calcium to their soils which has all sorts of other positive side effects along the way, such as enhancing clover growth which leads to free nitrogen, more protein in the grass and more milk. Yet Dolomite is not considered by many to be a useful fertiliser.
Another aspect of the chemical companies madness comes through the apparent contradiction of their own philosophy. The chemical boys will tell you what ever goes out the farm gate needs to be brought back in a bag. Milk is marketed as a calcium product. So heaps of calcium is leaving the farm every day. Yet very little is ever being replaced to the soil. Odd!
There are farmers who do use Dolomite ( Calcium 22% Magnesium 12% ) and they are very quiet about what they are doing. It is old fashioned in the eyes of the bright young Ag consultants from university. However the farmers using dolomite have conception and calving rates, general animal health and production amongst the best of their district.
Craziness number 27. Urea. Dairy cows do really well on clover. It is well known that applying nitrogen to a soil will inhibit the clover growth and the nitrogen fixation ability of the clover. So farmers are applying massive amounts of nitrogen to grow rye grass. Instead of applying dolomite to grow clover. Why are they doing this? The smallest economic Dairy unit will cost close to 1 million dollars to purchase. So a 300 cow unit which could be considered average will be in the value of a 2 million dollar business. Being a person who lives in much smaller figures than this I stand in awe of these amounts of money and believe people who control such large assets would at least be able to understand such a basic building block as good soil pH and base saturation levels. So I am being proved wrong everyday. These `successful' farmers are prepared to destroy their soils, pay huge fertiliser bills, large animal health budgets and work unnecessarily long hours in the production of their `good' product.
This can only happen in a society based on Darwinian capitalism. The one with the most money and the loudest voice wins; What is right is not a consideration. Luckily the winds of change are blowing. This NPK farming is being swallowed up by its own expenses. The positive side of capitalism is the system that produces the most dollars wins in the long run. The system doing that most effectively and most easily is one which concentrates on the old time basics od soil management, using slow release fertilisers and a balanced approach to soil fertility. There are examples of this all over New Zealand and they will become more obvious over the next few years as the growing disaster of the 'grass growers' becomes evident.