If you’ve completed a soil test this spring, you may have gotten a recommendation that says to apply a 30-20-10 fertilizer to support your soil nutrition. But fertilizer nutrient concentrations don’t run that high without chemical help. Thankfully, you can still meet your soil’s needs with organic fertilizer, you just have to do a little math.
Research suggests that 50-80% of the nitrogen in chemical fertilizers never reaches the plants that need it. Unlike organic nitrogen, chemical nitrogen sources are almost all water-soluble, so they are prone to leaching and evaporation. And since most soil test recommendations assume you’ll be using chemical fertilizers, when they recommend a 30% nitrogen fertilizer, they are only expecting 15% (at best) to stay in the soil.
That means you’d really need a 15-10-5 fertilizer, which is still pretty hard to accomplish with organic ingredients. So instead, try to find the same ratio of N to P to K, but at lower values (e.g. divide each by 2) and adjust how many times you apply. For our 15-10-5 example, look for a 6-4-2 fertilizer formula, and apply it twice as often. It can be tempting to just apply twice as much, but you run the risk of burning plants. Many small meals are better than one big meal, in the words of our Chief Formulator, Bill.
Of course, it is often difficult to find the exact ratio recommended – unless you use the Garden Maker Naturals customizer to create your own uniquely tailored formula! But if you are looking to use a pre-blended formula, it is important to match the nitrogen requirement most closely, even if the phosphorus and potassium levels are slightly above or below the recommendation. Plants tend to require more nitrogen than any other nutrient, and it is crucial to many plant functions.
No matter what your soil test recommends, though, a periodic application of compost can help address almost any soil deficiency. When you fix the microbial environment, the rest of the soil health fixes itself. And it is almost impossible to over-apply compost. Chock full of nutrients, humus and microbes, it’s like a multivitamin for your garden!