International soil expert Kinsey believes that feeding the soil by providing it with all the necessary nutrients in the right amounts to achieve optimum fertility should be the main focus of every farming operation. He told delegates at a recent SA Biofarm course on soil fertility in Johannesburg that plant and foliar feeds should be applied to ensure plants have sufficient nutrition. However, the problem with most feeders is that they don’t build soil fertility and this can become an extremely expensive type of production. Soil feeders, on the other hand, if applied at the correct dosages, can help to improve soil fertility and provide nutrients to the plants. Correcting soil nutrient levels is much better than simply feeding the plant.
The Albrecht method
T he Albrecht method was developed by Dr William Albrecht, a US scientist who found that the decline in soil fertility was caused by a lack of organic material, major elements and trace minerals in soils, which then yielded poor crops. He said major elements must be present in the soil in certain ratios and as soil can only contain a certain amount of nutrients, an excess of one nutrient would result in the deficiency of another.
Nitrogen, phosphates, potassium and soil pH used to be the only factors in soil fertilisation programmes, but Dr Albrecht included all the other essential elements. He also explained that the composition of ideal soil is similar to that of humus. Where humus consists of 50% minerals and 25% air and water respectively, the ideal soil contains 45% minerals and 5% humus with the same percentages of air and water. Hence Dr Albrecht concluded that “the basic make-up of the plant and animal kingdom as it decomposes and becomes humus, matches the nutrient make-up of the most productive soils.”
Accepting your soil type and improving it
However, it’s impossible to change your soil into humus, just as it’s impossible to change a specific soil type like clay into sandy soil. So, says Kinsey, it’s better to accept your soil type and work to improve its structure by getting the relationship between the minerals, humus, air and water right. This will create the optimal conditions for plant growth.
There are various ways in which a farmer can try to affect the soil structure. One way could be through stimulating soil biology by using manure, compost, mulches and biological stimulants. But this would probably not make a significant difference to the soil structure if there isn’t sufficient air and water available to foster soil microbial life. Another way would be through physical means, such as deep tillage. “This could have a temporary effect by breaking up hardpans, but it should not be considered a long-term solution without first correcting key nutrient levels,” Kinsey says. The ideal method to address soil structure is to correct the chemistry of the soil, as this affects the porosity and the availability of nutrients.
Albrecht said calcium should represent 60% to 70% of the exchange capacity of the soil, and magnesium between 10% and 20% (see the article Biological Farming: putting more fuel in your soil’s tank in Farmer’s Weekly, 18 April 2008). These levels will vary according to the type of soil. A clay soil, for example, should have lower magnesium and higher calcium percentages than a sandy soil, because magnesium tends to tighten the soil, while calcium tends to loosen the soil. Higher calcium levels help to improve soil aeration. In sandy soil, a high magnesium level closer to 20% would improve the soil’s water-holding capacity.
It’s all about balance
Another factor is that calcium and magnesium should ideally total 80%. The soil will become hard and increasingly unmanageable if these elements exceed 80% of the mineral content. Kinsey says correcting these levels results in a huge change in production, but if finances are limited, he advises farmers to correct the calcium levels first. “By correcting the calcium and magnesium levels, you not only affect the soil structure, but also the availability of other nutrients, as these get into the plant over the back of calcium,” Kinsey explains.
“Once the soil structure is improved, soil biology and water efficiency also improve.” And when farmers have balanced the calcium/magnesium levels, they can continue to balance and correct the levels of other nutrients. Kinsey cautions, however, that soil can’t create something that isn’t there. “Balancing calcium and magnesium might help to make elements available that used to be tied up, but that’s only if there were enough of these elements present already. “Soil can’t produce elements. If you removed them via production, you need to reintroduce them.” In terms of balancing the other major cations, potassium should be around 3% to 5%, hydrogen between 10% and 15% and the other bases between 2% to 4%.
Then phosphorous, sulphur, and all the micronutrients need to be built up to their minimum levels. Kinsey recalls that one of his clients took 10 years to balance his soil due to his limited fertiliser budget. The crop yield however, improved significantly during this time. He goes on to say that even though crops have different nutritional needs, all will thrive in a well-balanced soil. “Plants will do much better in a soil with the right nutritional balance than in a soil that has the right pH but doesn’t have sufficient nutrients,” Kinsey concludes. “Once soil balance has been established, farmers can continue to fine-tune the amount of fertiliser. Contact SA Biofarm on (012) 333 4222 or www.sabiofarm.co.za. |fw
