Every artist needs to understand her medium.
For example, to choose the right paint she needs to know if she is applying her skills on canvas or plaster. Will the sculptor be carving marble or moulding bronze? August Escoffier himself said to produce haute cuisine skill could not overcome poor ingredients.
The artful gardener needs to know her soil. Is it (like mine) sandy, or does it have a heavier clay content? Does that matter? Shouldn’t adding compost and fertilizer be enough to grow a good crop anyway? This is where the difference in medium comes in.
I have dealt with both kinds of soils and treated them the same way, but experience and research have taught me that crops don’t grow equally well on both types of soil. Dolomite is a common ingredient in fertilizers because it contains both calcium and magnesium so a gardener gets extra bang for the buck — if the soil is sandy, that is. Dolomite contains magnesium, which makes clay bind more tightly together; thus, the more dolomite is added the tighter the clay gets. Adding sand to clay soils turns it into concrete.
For heavily clayed soil, a better alternative is to use agricultural lime in the mix, avoiding magnesium altogether while still increasing the calcium. The clay will gradually flocculate, or flake apart naturally, instead of sticking together more tightly which it will do with excess magnesium. The difference in crop quality is measurable when this clay opens up to allow nutrients to become accessible.
To discover what kind of soil you have, perform a “soil fractional analysis:” dig a pint of soil (don’t include roots or plant parts), dry it out and break it up as finely as possible, and then put tape on the side of a quart jar vertically to check the height of the soil. Add water to the top, leaving an inch of air, then a few drops of dish soap; put the lid on and shake, shake, shake. Put the jar down and two minutes later mark the level where settling occurred. This shows where the sand has settled. Wait another two hours, and make a mark where any more has settled; this layer is silt. Any more particles in the water is clay, and it may take two weeks to settle out.
When the water has finally cleared, mark the level and this shows the amount of clay in the soil.
Clay is not always a bad thing. Some clay in the compost heap fosters the development of humus in the guts of the red worms that will proliferate there. Since my soil is very sandy I bring some in to create a better balance. Easy for me, but harder to achieve in the other direction; adding sand to clay soil is the gardener’s equivalent of the baker mixing glue into the flour. Fortunately the gardener with clay soil merely has to use his own soil in the compost, adding Steve Solomon’s mineralized fertilizer mix for clay soils when gardening:
4 litres of oilseed meal (I use alfalfa)
2 cups agricultural lime
2 cups gypsum
2 tsp. borax
1 litre of any of the following: soft rock phosphate, bone meal or high phosphate guano
1 ½ tsp. zinc sulphate
1 tsp. copper sulphate
2 cups kelp meal
Directions: mix altogether (I would use a wheelbarrow and wear a dust mask) and use at the rate of four litres per hundred square feet/one square metre to start, and half that as a side dress later.
Please contact mary_lowther@yahoo.ca with questions and suggestions since I need all the help I can get.
