The first weeds of spring are here and they are quite visible. When we drive to town we see them on lawns, in hay fields and lots of them are growing close to the road where residual road salt residue blows in.
We see some people mowing, we see some people pulling them out of their lawn and other, more ambitious home owners digging them out with a little shovel.
Many yard owners bought weed and feed to kill off the dandelions and fertilize the lawn. Many an old farmer used to say, “The dandelions have choked out my alfalfa!”
Dandelions are just Mother Nature’s way of telling you that your field or lawn is getting low in calcium. The more abundant the dandelions are, the lower the soil is in calcium. The old farmer that noticed that his field was getting to be thicker in dandelions and thinner with alfalfa was observant but his diagnosis was wrong.
Alfalfa needs high calcium content in the soil to be healthy while dandelions grow better in ground that tests low in calcium. If the calcium content in the field had been high the dandelions would not have grown at all. The weed and feed that the home owner used to spread worked for one year but the weed killer in the weed and feed only killed the dandelions for that one application.
When dandelions grow with their very deep roots they can get calcium from the subsoil as deep as six feet down. When the dandelions die the calcium that they pumped up from the subsoil is now on the surface in the dead dandelions. This is Mother Nature’s way of getting the calcium up to the surface.
Some farmers and even so called soil experts confuse soil PH with calcium content in the soil. The better soil labs will use base saturation that tells the percentages of potassium, magnesium and calcium rather than a rating of very low, low, medium, high and very high when informing land owners of what nutrients are available in the soil.
These soil labs guide the land owners to aim for a base saturation of seven per cent K, 15 per cent Mg and 75 per cent Ca. If the magnesium and potassium get too high and the calcium gets too low; dandelions thrive! (Check the book,“Weeds and Why They Grow” by Jay L. McCaman)
Don’t expect instant results by putting calcium (calcitic lime) on. It will take lots of rains or lawn watering to get the calcium down into the soil. Farmers commonly apply three tons of calcitic lime per acre. If in a year or two the calcium saturation is still low; (dandelions are still growing) then more calcitic lime is applied.
An acre is 43,280 sq. feet, so three tons per acre would be 43,280 sq feet/6,000 lbs of lime = one pound of calcitic lime spread over seven and a quarter square feet of ground.
Calcitic lime is usually gray in colour while dolomitic lime (which also contains magnesium) is white. Applying white lime will increase the PH and magnesium content in the soil but if your soil is already too high in magnesium content the dandelions will just grow better. Weed killer and more fertilizer will kill the dandelions and make the lawn green quick but it’s like putting a band aid on a broken arm. There is a better way that will give lasting success. Often applying calcium to the soil will make other soil nutrients like phosphorus more available to grow crops, vegetables, hay, and grass.
Chris Judd is a farmer in Clarendon on land that has been in his family
for generations.gladcrest@gmail.com
