Most of the time garden soil will need to be amended in order to grow a successful crop. The term "amendment" implies improvement.
If your soil doesn't need a given amendment, then, for that soil, it isn't an amendment. For instance, some folks believe that, if a little fertilizer is good for the garden, more will be better, but such is not the case. If your soil doesn't need any nitrogen, adding more nitrogen can be harmful to your plants. You can overdose a plant as easily as you can overdose yourself.
A soil test is helpful in determining what nutrients your soil needs to grow good crops. Unfortunately, soil tests do not measure so many important things. They do a good job of telling you the pH level and the state of the three macronutrients: nitrogen (N), phosphorus (P) and potassium (K), but there is so much more involved in building a rich, organic soil structure. Nevertheless, knowing the pH of the soil and having the correct amounts of the big three nutrients is important.
The source of these nutrients is also important. You can run down to the store and buy commercial fertilizer and grow your garden that way, or you can use natural sources that feed the microorganisms in the soil and thus feed your plants. It's up to you. The problem with commercial fertilizers is they are highly concentrated synthetics that tend to kill microorganisms in the soil as well as the earthworms that are so important to the soil's health and ecology. Think in terms of feeding the soil instead of the plant. A healthy soil will equal healthy plants.
I hope it goes without saying that compost is one of the best amendments you can add to your soil. Well-rotted animal manures, earthworm castings, and various plant residues make great soil amendments; and all of these will encourage microbial and earthworm life in the soil. Compost will also add many trace minerals to the soil which a soil test does not take into account. Trace minerals are important to the health of the soil and, as an extension of the soil, the plants we grow.
On the other hand, synthetic, commercial fertilizers do not improve soil structure and are detrimental to soil life. They are too hot for earthworms and eventually, if used over time, they will cause a loss of organic material in the soil. This leads to compaction of the soil and loss of beneficial microbes.
Here are some natural nutrients and their sources (the application rates on the package should be adjusted to any soil test recommendations you might have for your garden).
Nitrogen Sources: Alfalfa meal, blood meal, fish meal, hoof and horn meal and cottonseed meal are some of the best sources. If you are completely organic, then you might want to stay away from the cottonseed meal. There is a chance it could have some pesticide residues.
It is usually quite a bit cheaper to buy these products at a farm supply store rather than at a gardening center. You might actually get a 50 pound bag at Nelson's Feed Store for about what you would pay for 5 or 10 pounds at Lowe's or Walmart. Just saying.
If you are into making your own compost and do not have a good source of nitrogen to help your compost pile heat up, you can use blood meal for this purpose. Just mix it with whatever carbonaceous material you have and let it work its magic.
Phosphorus sources: Bone meal is a good source of phosphorus. Use as much as 5 pounds per 100 square feet. Phosphorus can last a good while, up to a year or longer. Phosphorus from bone meal is considered fast release. Another very good source of phosphorus is rock phosphate. This is a very slow release phosphorus. You can use up to 10 pounds per 100 square feet. Rock phosphate will last about 10 years so does not need to be added every year. You can mix the fast release and slow release for better results. Soft rock phosphate, also called colloidal phosphate, is a medium-release phosphate which contains many trace minerals that are beneficial to your soil ecology. It will last 2 or 3 years with similar application rates as rock phosphate. Nitron Industries, (479-358-6248), 5703 S. Hewitt St., Fayetteville, is a good source for any of these products if your local farm store can't get them.
Potassium sources: Greensand is a good source of potassium. In fact, greensand is one of the best amendments you can add to your soil. Greensand is a mined sea deposit. It's green color is an indication of the potassium it contains, so the greener the better. And it also contains silica, which is good for your soil. Granite dust or meal is another good source for potassium; but it is very slow-release, so you need to take that into account by adding it to your soil early. Greensand and granite dust both last up to 10 years. Greensand contains many trace minerals that are good for soil fertility. Kelp meal and liquid seaweed supply potassium as well as a number of trace minerals. Wood ashes contain potassium in variable rates (hardwood is best) and will also raise the soil's pH.
Another great all-around amendment to the soil is a product called Sul-P0-Mag (22 percent potash, 18 percent magnesium and 22 percent sulfur). This product will give your plants a real burst of energy when they are young.
About pH: pH is a measure of potential of hydrogen the soil contains. The percentage of hydrogen determines a soil's alkalinity (sweetness) or acidity (sourness). Lime is considered the best choice for improving a soil's pH if it is too acidic. But there are different types of lime and different needs in the soil. Dolomitic lime (high magnesium) is used when the soil needs magnesium as well as calcium. Calcitic lime or calcite is used when the soil doesn't need magnesium. You can also use oyster shell lime in its place. Gypsum or plaster, also called calcium sulfate is used where magnesium levels are already too high. Do not under any circumstances use dry wall as a source of gypsum in your garden. It contains other chemicals and contaminants that would be unhealthy.
While most of these natural products are slower-release than synthetic fertilizers, they do not leach out of the soil as quickly, they do not damage or kill the microflora and earthworms and they are very gentle on the land. They will also aid garden plants in resisting attack from insect pests.
As mentioned above, Nitron Industries in Fayetteville is a good source for all of these products, as well as for compost and other natural soil amendments. They usually have a horticulturalist on staff to answer any questions you may have. Happy gardening!
Sam Byrnes is a Gentry area resident who has been gardening from his youth. He may be contacted by email at [email protected]. Opinions expressed are those of the author.
Editorial on 06/24/2015