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How do I adjust my vegetable garden soil after testing #885448

Asked September 16, 2024, 2:42 PM EDT

Below are the test results from Deleware of my vegetable gardens: - [ ] PH 6.7 - [ ] Phosphorus 202 - [ ] Potassium 218 - [ ] Magnesium 473 - [ ] Calcium 362 How do I get these levels down? All I have ever added to the soil is Leafgrow. What am I doing wrong?

Anne Arundel County Maryland

Expert Response

I just sent the information to you about my recent soil test:
- [ ] PH 6.7
- [ ] Phosphorus 202
- [ ] Potassium 218
- [ ] Magnesium 473
- [ ] Calcium 362- 

and wanted to know how to get these levels down.  The Lab said to -  Apply 1 lb. N per 1000 square feet and rake it in just before planting. I always stayed away from chemical fertilizers in my organic garden.  What do you recomment?
The Question Asker Replied September 16, 2024, 2:53 PM EDT
It's hard to assess the numbers from the soil test without the entire report being visible (since they chart-out numerical values as "high," "low," etc.)...without them, we have less context. We can say, though, that the pH is fine as-is, and any level of mineral measured as "excessive" is not a problem. The use of "excessive" may imply that it's too high for plant health and needs to be lowered, but all it really means is that the nutrient is so plentiful in the soil that adding more (via fertilizer or other supplementation) is not needed and won't benefit the plants, because they already have more than they need. You don't have to try to remediate the soil to remove nutrient excesses like for Calcium and Magnesium, nor would it be easy to do so. Our page Understanding Your Soil Test Report has more information that might be useful.

The reason the lab recommends nitrogen application is because soil testing labs don't measure nitrogen (it fluctuates too much naturally, so a single measurement won't mean much over the course of the growing season) and because plants use nitrogen in the greatest quantity of all the nutrients used in growth and development. Some will be supplied by the compost you apply, which releases nutrients more slowly because microbes in the soil usually need to convert them into forms plants can use first, and microbe activity depends on environmental conditions like ambient temperature and moisture.

Nitrogen supplementation is available in organic forms, not just synthetic fertilizer forms. Examples or organic fertilizers, including those that supply mainly (or only) nitrogen, are given in our Garden Fertilizer Basics page. Applications aren't needed when nothing is growing, but if you've started a cool-weather crop, it can be added to boost the growth of the young plants before they slow and pause growth during winter. More tips can be found on our Fertilizing Vegetables page, including whether certain crops prefer certain types of fertilizer (say, more nitrogen than average, or less fertilizer overall than average).

Although we tend to think of fertilizer as plant "food" and talk about it as such in shorthand, it's really more like a multivitamin, supplementing what roots have access to in the soil, as sunlight is more accurately considered the main "food" of a plant. Therefore, only healthy plants getting the other resources they need (enough sun, enough water) can make good use of supplemental nutrients, and stressed plants should not be fertilized unless a nutrient deficiency in the soil is the only issue causing their decline. Since vegetables are producing a harvest compared to ornamental garden plants that we just grow for aesthetics or wildlife value, they do get fertilized more often than other garden plants (which usually are fine with little to no routine fertilizer), which is why soil testing helps us to determine which nutrients (if any) are deficient in the soil.

Miri

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