Under our present system of soil fertility, we are being encouraged to under-fertilise. This state has existed for many years, but the degree of under-fertilising is getting worse. Applying so-called maintenance levels of nutrients is not even ensuring soil fertility is static - it is declining.
Base saturation is simply the percentage of exchangeable cations. Cations are the positively charged soil fertility elements. Base saturation is used to identify and measure the percentage of each cation to determine the soil's available relative mineral makeup.
Total exchange capacity is the sum of the total exchangeable cations. For example, a volcanic soil has a smaller sum than heavy, alluvial silt loam.
The balance of cations determines soil structure, nutrient holding capacity and fertiliser requirement for optimum production. Economic decisions can then easily be made to on fertiliser applications.
Some cations are: calcium, magnesium, potassium, sodium, manganese, cobalt, copper, iron, zinc, hydrogen and ammonium.
What we try to achieve, as indicated by a Perry Agricultural lab test, is calcium to be about 68 per cent, magnesium 10 to 12 per cent, potassium 2 to 5 per cent, sodium 0.5 to 3 per cent, hydrogen 10 to 15per cent, and other bases about 5 per cent. Don't try to fit these numbers around another test; it won't work.
If the cation balance is close to this ideal we will get good soil structure, moisture movement and retention, drainage, and maximum crop and pasture production and quality. All elements work together without antagonism, with the pH being ideally constructed. Pasture and crop palatability and consequently, animal performance will all excel.
Calcium: When this is present in the correct amount with other cations, the soil is at its most productive.
If calcium is deficient the other cations will dominate the herbage to the detriment of animal health. If calcium is excessive the soil will dry out faster. Phosphorus, trace elements and magnesium availability will be low. Crops and pastures may show symptoms of magnesium, iron, manganese and zinc deficiency. An application of ferrous sulphate will help.
Magnesium: An excess is not common. Too little in the soil results in too little in plants. Nitrogen efficiency is also affected. Soils stick to machinery when wet and set hard when dry.
It is far more common to find a deficiency, particularly as a result of over-liming. Dolomite is the best material to build up magnesium.
Potassium: If potassium dominates, pasture palatability will be poor. Stock will require salt to compensate or metabolic problems will develop. Leaf carbohydrate can also break down, leading to lower yields. High potassium suppresses manganese, cobalt and magnesium. Potassium causes the most angst among farmers whose dilemma is having high potassium in herbage but a low level in the soil. Most farmers are used to potassium chloride, not potassium sulphate. Potassium sulphate should be used instead. Keep calcium, magnesium and potassium soil levels up, and high plant potassium will not be an issue. Sodium: This must always be lower than potassium. We find in a surprising number of cases that it is the other way around. That situation leads to excess sodium uptake. Plant cell walls can then burst on hot days, leading to dehydration.
Perhaps that situation arises if farmers neglect the potassium, but apply sodium to raise pasture palatability. That is attacking the problem from the wrong end.
Always try to solve a problem by removing the cause, not by removing symptoms. If potassium and sodium together exceed 10 per cent, or if sodium is higher than potassium, then manganese uptake will be blocked.
pH: The above four cations influence pH. The closer they are to balance the closer the pH will be to the optimum.
Say that is 6.4; however, a 6.4 pH may be obtained by cations out of balance. For this reason, never use fertiliser to change pH. Only add it to change the proportion of the cations. pH should be the result of your fertiliser programme, not the cause of it.
Why use base saturation percentages?
They give a logical explanation of your soil.
They give a total blueprint of your soil.
They allow you to solve problems.
Farmers can relate data results to both good and problem areas.
No previous knowledge of nutrient levels in the soil is required.
The principles apply to all soils, plants and animals.
They give outstanding yields and quality of both plants and animals.
Practical considerations:
In the short term, balancing the BS can be an expensive exercise. The alternative is to put on fertiliser to get your crop or pasture through the season.
Remember that chemical agriculture is a self-serving, input-driven system.
You are advised to apply an unbalanced fertiliser to an unbalanced soil to sustain a state of imbalance, which will then require constant chemical intervention. After 20 years of doing that, you may be no better off in year 20 than you were in year one. Many farmers say they are worse off.
Balancing will require extra fertiliser. For some, the way to approach that is do part of your farm at a time.
Hill farmers need to look at their flats, flat farmers at their silage paddocks or parts of the property not doing so well.
Over time farm performance will increase, while eventually, your fertiliser applications will decrease.
The point at which the fertiliser spend decreases depends on how long it takes to reach a balanced plateau.
Once there it is plain sailing .
The system we use at Kiwi Fertiliser has been proved throughout the world, including: a world record yield of wheat in Germany; best quantity and quality wheat in New Zealand; 37-42t+/ha maize silage in the United States; 20t+/ha of lucerne throughout the world, and outstanding prices for high-yielding grapes in California.