Master Gardener: Explaining the numbers on fertilizers | Home & Garden

I assume my soil desires some form of fertilizer, but how do I know which fertilizer to select and how much to use? — F.M.

Fertilizer can be an scary matter. For the reason that of this, numerous men and women tend to go with a “balanced” fertilizer — something with equivalent amounts of the huge 3 vitamins of nitrogen, phosphorus and potassium. The issue with this tactic is that not being aware of the nutrient material of your soil leaves you with two possible outcomes: You will utilize possibly far too a great deal or too small. Equally of these alternatives fail to give your landscape what it needs.

To far better have an understanding of soil nutrition, let us search to an illustration involving a fuel-powered garden mower. To run adequately, it wants gasoline and oil. When the mower is running properly, gas is consumed to power the mower while the oil retains the mower lubricated and working thoroughly. No gas, no go. Also much gas — fire hazard. Way too significantly or as well tiny oil — motor does not do the job proper. Equally gasoline and oil should be present in the appropriate amounts for the engine to run the way it should really. Fortunately, we can open the fuel cap and look at to see if a lot more gasoline is desired and use a dipstick to verify oil levels.

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In this illustration, gasoline is analogous to nitrogen and oil is analogous to phosphorus and potassium. For plants, nitrogen is the fuel they will need to expand. Phosphorus and potassium are like the oil. These vitamins and minerals need to be existing at the appropriate degree to empower the chemistry to do the job like it should really.

To keep track of soil nutrient amounts, the soil examination is our dipstick. It lets us to find out no matter if we need to incorporate vitamins and minerals. Devoid of a soil exam, we are just guessing. Consider how properly your lawnmower would operate if you just guessed at gas and oil concentrations.

When we guess at the nutrient concentrations, we very likely guess incorrect. We have facts on our web page in the Warm Topics portion about how to go about receiving your soil tested.

When purchasing for fertilizer, the to start with issue you will discover is that there are a lot of alternatives and a lot of numbers. The figures explain to you the nutrient written content of the fertilizer. For illustration, if the fertilizer is labeled 10-20-10, the very first selection is the proportion of nitrogen, the second is the proportion of phosphorus and the final amount is the proportion of potassium. So, this fertilizer would incorporate 10{d4d1dfc03659490934346f23c59135b993ced5bc8cc26281e129c43fe68630c9} nitrogen, 20{d4d1dfc03659490934346f23c59135b993ced5bc8cc26281e129c43fe68630c9} phosphorus, and 10{d4d1dfc03659490934346f23c59135b993ced5bc8cc26281e129c43fe68630c9} potassium. The rest of the elements would be inert or neutral binding agents.

Now, let’s believe you collected your soil sample, took it to the OSU Extension, and you now have your test outcomes. Frequently, soil exams will show that your soil is minimal on nitrogen while phosphorus and potassium stages had been ideal or perhaps high. In this circumstance, you would only require to increase nitrogen to your soil. Furthermore, this indicates that if you have been purchasing fertilizer that contained phosphorus and potassium, you would not only be having to pay for a thing you did not need to have, but by continuing to raise your phosphorus and potassium degrees, you could essentially be worsening growing ailments in your soil.

Often, the suggestion from a soil check is to increase 1 pound of nitrogen for every 1,000 sq. toes. A fertilizer these kinds of as urea, which incorporates 49{d4d1dfc03659490934346f23c59135b993ced5bc8cc26281e129c43fe68630c9} nitrogen, would be an correct choice in this scenario. Now you will need to do a small math.

Urea is marked 49– which implies it is 49{d4d1dfc03659490934346f23c59135b993ced5bc8cc26281e129c43fe68630c9} nitrogen and {d4d1dfc03659490934346f23c59135b993ced5bc8cc26281e129c43fe68630c9} phosphorus or potassium. With a nitrogen degree of 49{d4d1dfc03659490934346f23c59135b993ced5bc8cc26281e129c43fe68630c9}, this signifies just one pound of this fertilizer would be almost 50 percent nitrogen. To get 1 pound of nitrogen, you would want 2 lbs of urea.

The following issue we generally get is where to established the drop level on the fertilizer to fall 2 lbs . of urea per 1,000 sq. ft. The ideal way to determine this out is to do a tiny experiment.

Get started by stepping off a 1,000-square-foot location in your garden. This would be somewhere around a 33-foot by 33-foot sq.. If your garden is 100 ft large, just use a 10-by-100-foot part or some variation of that.

Now, set enough fertilizer in your spreader so that you have 1 pound of nitrogen. For the 49– in our instance, this would be 2 lbs. If you have been employing 10-20-10, that would be 10 pounds of fertilizer. Up coming, just take a guess at exactly where to established your spreader to deliver this amount in excess of your check location. Commence on the minimal aspect as you begin spreading the fertilizer on the test place. You may possibly require to regulate as you go or even do a second take a look at to affirm you are dropping fertilizer at the supposed rate. The fantastic news is that if you use the similar fertilizer upcoming time, you won’t have to repeat this process, just copy your options on the spreader.

If this still appears a minimal perplexing, we have numerous tutorial videos on our web site ( Just go to the Lawn and Yard Support Section and simply click on Soil. I have just about every self confidence you can determine it out. See you in the backyard!

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You can get solutions to all your gardening concerns by contacting the Tulsa Master Gardeners Support Line at 918-746-3701, dropping by our Diagnostic Middle at 4116 E. 15th St. or by emailing us at [email protected].