A soil test may sometimes reveal that you have too much of a certain nutrient or mineral in the soil. Sometimes you’ll even find instructions to extract them, whether it’s using water and gypsum to leach sodium or sawdust to pull out nitrogen. But how is this done, and are there alternatives to using the chemical fertilizers recommended when it comes to balancing those nutrients?
Thankfully, the answers are yes and yes. If you’re a beginning farmer in need of soil balance, here are some techniques for replenishing the nutrient load.
1. Leaching
Leaching is the removal or loss of soluble nutrients through the application of water, either naturally from rain or intentionally through irrigation. It’s most commonly associated with the depletion of nitrogen in commercial farming situations; however, if you live in an arid environment, you could have a surplus of sodium in your soil that a soil test may suggest you leach out.
When leaching salt, it’s often recommended that you mix sulfur or gypsum into the soil first, then several weeks later run three or more inches of water over the same soil. This process will indeed leach the sodium, but it might not be the best use of water—something arid environments are lacking—unless you have access to a pond. Alternatively, consider mixing in the gypsum or sulfur before the rainy season, and let the rain leach the sodium for you. Or you can skip the leaching altogether and move to suggestion No. 2.
2. Cover Crops
Cover crops are nifty things. You can use them to retain valuable soluble nutrients or to remove ones in excess. For example, if choosing not to leach excess sodium, you can grow mustards or barley, both of which can handle the high sodium and will also suck it up. Once the crop has grown and while it’s still lush, you can remove the plant matter from the field to a separate compost pile (as to not later add the nutrient back to the ground) or to a sodium-deficient plot.
Of course, utilizing cover crops in this way should not be limited to just sodium. Pick a cover crop that enjoys your excess nutrient, plant it, remove the growth and, with it, the excess nutrients. Alternatively, consider growing something edible with those excess nutrients.
3. Crop Selection
Let’s say your soil test comes back high in nitrogen. In this case, you have several options for removal: You can let it leach out over the winter or cover crop the plot, but nitrogen is a valuable nutrient and should be preserved however possible. That’s why perhaps the best option is to simply grow a crop that could take advantage of the excess nutrient, such as corn for high nitrogen, peppers or melons for high phosphorous, or peanuts or alfalfa for high potassium. The crop will effectively suck up the excess nutrients and turn it into food. For best yields, add mature compost to the planting area first.
If you are hoping to retain nutrients in the soil over winter, you could sow daikon radishes, aka oil-seed radishes, which will not only break up compaction but hold those nutrients over until the next growing season. Even if you have excess nutrients, this might not be a bad idea because you can always add the deficient nutrients to rebalance the soil in the new year. When planting daikons, add some organic matter to balance the soil, then add compost before planting the next successive crop.
4. Rotational Grazing
Ruminants—goats, sheep, cattle, et cetera—are special kinds of lawnmowers that efficiently convert grass into manure. With a little manipulation, they can deposit that manure wherever you need it. If a soil test shows an excess nutrient, some farmers quickly graze that grass before moving them onto a deficient part of the pasture. This activity is called rotational grazing. If the livestock isn’t moved off the ground with the excess nutrients, they’ll simply deposit the nutrients right back onto the ground and into the soil.
5. Mulch
In order for most mulches—especially those made from sawdust or soft wood—to break down, they need nitrogen. So the mulch takes that nitrogen from the soil before it starts its decomposition. If you leave the mulch there, it would eventually break down and become a part of the soil. If you remove the mulch after a couple months, however, it will contain much of the excess nitrogen your soil contained, and it can be added to a compost pile or a nitrogen-deficient plot.
6. 15-15-15
The most common soil tests, usually from state universities, will not give you organic alternatives to balance your soil. Often they will provide the soil pH and nutrient deficiencies, but recommend applying a chemical fertilizer with the desirable NPK ratio. The NPK numbers represent percentages of chemically derived nitrogen (N), phosphorous (P) and potassium (K), in that order. However, however, you can find viable natural alternatives. Feather or bone meal, for example, are both excellent sources of nitrogen; rock phosphate could be used to add phosphorus; and for potassium, try wood ash or greensand. You can even measure out the equivalent percentages of each ingredient to create a fertilizer of your own to meet the required ratio.
7. Balance with Compost
No matter how you choose to amend your soil, utilizing rich compost before planting helps guarantee the best crop possible. In fact, if you could only add one thing to your soil, it should be compost. Compost rebalances soil and reduces plant disease. It makes certain nutrients bioavailable to plants. It enriches the soil and adds valuable micronutrients and microorganisms while improving crop quality. Compost might not have a high NPK ratio, but it’s ability to build soil structure and balance pH helps plants access the nutrients that are there and protect those nutrients from leaching.
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