Soil improvement methods that are quick and reliable

Soil improvement involves modifying the balance relationships between the constituents of each of the three functional components of the soil. The most important of these (because it gives us a common starting point for all soils) is know as the soil cation balance. Cations (pronounced "cat-irons") are simply elements in the soil that carry a positive electrical charge.

This is important because the clay and organic particles in the soil carry a negative charge and, of course, opposites attract. In addition, any of the elements held in the soil in this way can be 'exchanged' for other cations - giving us the means for soil improvement. And so, improving the cation balance relies on applications (in the right amounts) of materials such as lime, dolomite or gypsum.

Of course, working out the right amounts of such materials will first require a soil test, so the first two steps of the soil improvement process are:

1. Test the soil

For proper cation balancing the soil test should measure (not just estimate) the exchangeable Hydrogen. The test for exchangeable Hydrogen was developed in 1960, but many laboratories still prefer to simply estimate it from the soil pH. For many soils, however, this simply is not accurate enough to ensure reliable results.

2. Improve the cation balance

The objective here is to begin the process of soil improvement by adjusting the relative proportions of the five major soil cations (relative to the Cation exchange capacity of the soil, or CEC) so that calcium is 65-70%, Magnesium is 12-15%, Sodium is less than 5%, Potassium is 3-5% and Hydrogen is less than 10%.

Achieving these proportions will produce friable soil that is free draining and yet also retains moisture well. It will be biologically active and will deliver nutrients to your plants by preventing the 'lock-up' of fertilizer.

In short, this one step makes garden soil improvement so much easier.

An important point to remember though, it that lime, dolomite and gypsum need time to work, so allow six months (longer in low rainfall areas) before using any fertilizer. However, once you have made the appropriate applications and given them time to work, we can move on to step 3:

3. Balanced Plant Nutrition

There are 16 elements that are essential to healthy plant growth, but they are needed in different amounts by each different type of plant. Furthermore, some (such as zinc) are needed early in the growth cycle, while others like Potassium are needed later and nutrients like sulfur and nitrogen may need to be tapered in or out as the season progresses.

Sounds difficult, right? Well if you haven't done steps 1 and 2 yet, then its downright impossible! But with steps 1 and 2 well in hand, you can safely let the soil (and the millions of microbes living in it) do all this work for you. So all that is needed for this part of the soil improvement process is to adjust the levels of any nutrients that your soil test said were below their desirable levels. 99.9% of the time, this will be all that is needed. Occasionally, the soil will be in a bit of an 'uncooperative' mood and some deficiency symptoms may show up. Don't worry, I will come back to dealing with these situations later.

4. Stimulate soil biology

There are many different kinds of microbes in the soil, living in an inter-connected 'web of life'. Research has shown that given the proper cation balance and no heavy applications of fertilizer, they will settle quickly into a stable, balanced community. However, this community is very sensitive to any 'disturbance'.

We will talk more about the nature of this disturbance under Garden Ecology. For now, it is only necessary to recognize what sorts of things can impose a disturbance on the soil. Any application of a soil amendment or fertilizer (even organic fertilizer or compost) will cause some kind of disturbance. As will cultivation, heavy rain or drought. Not all disturbances are large and some are unavoidable. Not all are necessarily bad either, but the same treatment should follow each one.

It is now possible to get an extended soil test to assess the state of the biological community in the soil. This will tell you exactly what is needed to stimulate biological activity and help overcome the effects of disturbance. However, if you don't have one of these tests, there is one shortcut, that may help. A combination of kelp extract and fish emulsion will provide a broad-based stimulus for many microbial groups, provided you don't use to much. About 1 ml/litre of each in a watering can will do the job.

Bear in mind, however, this is no more than a bit of a 'tonic' for the soil. To do the job properly will require an appropriate soil test.

Now there is just one more thing to do:

5. Monitor and fine tune

Not even the best soil test will last forever. The soil is a dynamic living system and changes will occur over time. You should re-test the soil every 12 to 18 months - with the repeat tests always being done at the same time of year as the first.

The advantage of this 'whole system' approach is that as the soil improves, less is required to keep it in good condition. If any of the recommendations are seen to increase over two or more rounds of testing, something is wrong and you should identify the problem before going further.

Further reading and Useful links

Using Bioactive materials like Kelp and fish emulsions, etc.
There is now some good research to show what effects things like fish emulsion and kelp extracts have on soil biology.

Are Organic fertilizers better than Chemical ones?
This is a common question, but one that is too often answered by people with vested interests in one type or the other. The information on this page has been written from a truly objective point of view and so may be more useful.

Soil improvement fact sheets
Here are some free fact sheets you can print or download on a range of soil improvement topics.

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