Phosphorus: very high. Both beds. The results landed in my inbox on Wednesday night while I was sorting a stack of second-grade self-portraits, and I read that line twice before it sank in that I'd spent five years feeding our raised beds something they already had plenty of.
Five seasons without a test
Nate built our two cedar beds in the spring of 2021, 4 by 8 feet and 11 inches tall. We filled them with bagged soil and compost, and every spring since then I've topped them off with more compost and scratched in a bag of tomato fertilizer at planting time. The plants grew, so I never asked questions. A winter of reading extension fact sheets at the kitchen table finally made me admit that "the plants grew" is not the same thing as knowing what's in the soil.
On March 2 I mailed two samples, one per bed, through our county's Cornell Cooperative Extension office, at $18 each. That $36 sits in this year's garden budget. Sampling was easier than I expected. I pushed a trowel about six inches down in ten spots in each bed, dropped the slices into a clean bucket, mixed them, and spread the soil on newspaper on top of the basement dryer for two days. About a cup from each bed went into the bags, labeled EAST and WEST in my best bulletin-board lettering.
What came back
I'm sharing our numbers only because I was curious what other people's looked like before I sent mine. They describe two particular boxes of soil in our backyard and nothing else. The extension office is the place to ask what yours mean.
- pH: 6.8 in the east bed and 6.6 in the west bed. That's the range vegetables like, and no lime was recommended.
- Organic matter: high in both, around 10 percent, which I gather is what five years of compost will do.
- Phosphorus: very high in both, well past the top of the optimum range.
- Potassium: high in the east bed and optimum in the west.
- Calcium and magnesium: fine in both.
The recommendation section was short. No phosphorus, no potassium, no lime. Modest nitrogen for heavy feeders like tomatoes and onions, and much of that the compost and leaf mulch already supply.
The phosphorus was the surprise, though it shouldn't have been. Every bag of compost carries some, and so did the tomato fertilizer I scratched in every single May. The plants take out less than I was putting in, so the extra just stayed and built up. From what I've read, too much phosphorus doesn't do the tomatoes any favors, and whatever washes out of the soil ends up in the streams. Everything in this part of the county drains toward the reservoirs sooner or later. I'd been paying about $15 a year to add something that was already piling up.
What I changed this spring
No tomato fertilizer in the beds. Last spring's bag cost $14.99, and this year I left it on the store shelf. The one bag of all-purpose Garden-tone I did buy ($13.49) is for the porch containers, where potting mix starts out with very little in it and loses more every time I water.
Less compost on the beds. I used to spread an inch or more every spring. This year each bed gets a single bag, a thin layer forked into the top few inches. The other three bags are going where they're actually needed: the new cut-flower strip along the chain-link fence and the porch pots.
Leaves as mulch, same as always. Last fall's shredded leaves are free and they break down slowly. The report didn't argue with that.
Watching the plants instead of the calendar. If the tomatoes or onions look pale and stalled in June, I'll feed them a little. If they look fine, I'll leave them alone. It's a strange feeling, planning to do less on purpose.
I also wrote "TEST AGAIN: SPRING 2029" across the top of this year's bed map in red pencil, so I don't let another five seasons slide by.
The first crop after the results
This morning I sowed snap peas along the chain-link fence, the way I do every late March. The soil thermometer read 43 degrees, one degree warmer than last year's planting day. Peas team up with bacteria on their roots to pull in some of their own nitrogen, which makes them about the least demanding thing I grow, and they went into the ground with nothing but water from the galvanized can. Mateo pushed half of them in with his thumb, one knuckle deep, then went back to drawing a comic on the back steps. It felt like the right first crop for a year of adding less.
