Does Clover Add Nitrogen to Soil? I Tested It.

So a couple years back, I had tested my garden soil and discovered that it was pretty low in nitrogen (N). See my initial soil testing article here. I wasn’t surprised at those results, because I had noticed that my peppers are always struggling and yellowish, but would improve if I scattered a bunch of used coffee grounds around them (which are supposed to be high in nitrogen). I have always read that clover fixes nitrogen in the soil, so I decided to plant some as a cover crop in part of my garden to see – does clover add nitrogen to soil by a significant amount?

For this experiment, I used White Dutch Clover seed that I got from Outsidepride.com. In the spring of 2022, I just scattered some of this seed around the same vegetable bed where I had taken the previous soil sample from in 2021. I made it a point not to add any compost or fertilizer in this bed all year. I wanted to see what clover could do alone in adding nitrogen.

I let the clover do its work and grow all around the large tomato plant I had in that spot. Then this spring (2023), we tilled that bed, digging the clover under, since I had read that that’s the best way to incorporate the most N into the soil. Ideally, I should have waited a few weeks for the clover to decompose in the soil before I tested it again, but we were a bit late in getting everything tilled and I needed to start planting, so I took a sample of the soil probably a week or so after the tilling.

Clover Cover Crop Nitrogen Testing Results

For comparison, here is a photo of the soil test I did in 2021:

And here’s a photo of the soil test I did this spring:

The results are a little confusing. My nitrogen levels do look a little better. They’re probably around a “low” level instead of “very low” like they were before. So some improvement. My potash level also seems much improved. But somehow my phosphorus levels are now almost non-existent. Although if I shook the container again, the liquid turned much more blue, the color had all settled to the bottom. But the instructions said to put the powder in the water, shake well and then wait 10 minutes. So I assumed they were supposed to be left to settle. So I’m not really sure what the true reading for phosphorus is.

Conclusion:

Clover does seem to add nitrogen to soil, however, it’s a long process and would probably work best if you have areas of garden that you can leave fallow for an entire year. My yard is so small that I really don’t have that luxury, so I will probably stick with composting and adding some good organic fertilizer. I have been trying out a vegetable fertilizer this summer and so far loving the results. See my article “Does Dr. Earth Fertilizer Grow Bigger Veggies? I Tested It.”

Related posts:

Does Dr. Earth Fertilizer Grow Bigger Veggies? I Tested It. Home Soil Tests vs Lab Soil Tests Growing Indoor Plants in Garden Soil – A Test Making Potting Soil from Garden Soil