Agriculture Reference
In-Depth Information
Mineral Fertilizers
Naturally mined mineral products such as calcitic lime and glacial rock dust can be in-
credibly beneficial for the garden. There are a couple of important points to note. We gen-
erally should only use natural products, not those that have been altered or mixed with
chemicals, so be sure to check the label and ask first.
Even for most of the mineral products we do use, an annual application (for good meas-
ure) is mostly unnecessary and potentially harmful. We should use them only when we
know we need them, and as the landscape moves into balance, we'll need them less and
less, especially if we're focusing on organic matter. Organic matter should still be the main
focus, but it's usually not enough on its own for optimal health.
Fortunately, there are products that can greatly help us bring our ecosystems into balance
more quickly. Many of the products out there, even organic fertilizers, bring in large
amounts of minerals that are often expensive, unnecessary, and are potentially harmful if
they aren't needed. Other than rock dust, most mineral products are composed primarily of
just one or two minerals, such as calcium and phosphorus. Generally, they should not be
applied in much quantity without both a soil test and often visual verification of certain
conditions in the garden.
Let me give an example of why we need to look at both the soil test and the garden. Oc-
casionally, a soil test may indicate you have plenty of phosphorus, but your lawn might be
riddled with broadleaf weeds, a sure sign of a phosphate to potash ratio that is too narrow.
In that case, regardless of what the soil test says, I would probably bring in a source of
phosphorus and more importantly, use several techniques to stimulate the biology in the
soil. Soil tests are great, but we need to remember to look at our gardens, too. Conversely,
sometimes a soil test will show you things you cannot see in the garden.
When it comes time to fertilize, it used to be that some of the earlier rock fertilizer pro-
ponents recommended applying only one at a time to avoid having them interact, but now
many people advocate applying them at the same time. For example, it's now common
practice for soil labs to recommend calcitic lime, soft rock phosphate and gypsum together.
Any of these are best applied in spring or fall. Try to find products that are suitable for or-
ganic use, which means they may be labeled organic, but more likely you have to find out
what's in them. If possible, it's best to avoid inappropriate additives such as binding agents.
Some gardening topics go into great detail on the role of each of the nutrients in plant
growth. I'm not going to do too much of that. Not that it isn't interesting, but most nutrients
have many different purposes in plant growth and to list them all becomes overwhelming. I
will list a few points that are most interesting.
Likewise, I won't spend much time on diagnosing plant nutrient deficiencies through
visual inspection because I feel this is much more complicated than it's often made out to
