Fertilizing a raised bed veg garden
I recently did a soil test on my raised bed garden which was performing quite badly. EG: Beets... flowery tops with roots the size of marbles. Carrots and radishes small too. Tomatoes and peppers undersized and few. Plot size about 120 ft sq Results: PH about 7 Nitrogen: depleted Phosphorous: adequate Potassium: depleted No compost added yet but will include in winter crop planting. I hear that compost doesn't contain many nutrients but does aid in the uptake of nutrients. Which means I need to put nutrients into the soil so the compost can facilitate its use, correct? So I need to amend the soil with compost as well as NPK fertilizer. Im planning on using an organic mixed release 8-8-8 fertilizer. What do you think about that? Lower or higher numbers? I've heard Gypsum is good for tomatoes. What are your thoughts on use of epsom salt (for magnesium?) Bob Sankey San Marcos ca, zone 23-24 858 229 8753 [email protected]
Certified GKH Gardening Expert
Oh man, do we have a lot to discuss! Ok So let me start by mentioning this: Compost that is properly maintained, is HIGHLY packed with nutrients. So much so, that some things, when planted straight into compost, will burn straight up from too much nutrients. Now worm castings on the other hand, are a very good soil amendment.
Now, let's backstep a little bit. Your soil results aren't THAT bad. I have seen much worse. There are a few things I would do to amend your soil, however.
You mention epsom salt... Unless you are doing it for the sulfur, there are better ways to get usable magnesium into your soil.
I recommend dolomitic lime. It does take a bit longer to break down in the soil, but it is a less toxic alternative to hydrated lime. this will do THREE things for your soil.
1. This will supplement more than enough calcium.
2. This will supplement an equal amount of magnesium.
3. This will keep that soil pH at that BEAUTIFUL level of 7.
This is a must have in the garden and in containers.
Now let's revisit the nutrients... If you are mixing in quite a bit of compost, I would recommend NOT feeding it extra fertilizer, or it will cause the exact opposite problem you are having now. There are only a few plants that will tolerate these levels of fertilizers, and we don't help with that on this site!
If after all of this, you are still seeing odd levels in your soil sample, then you might look at fertilization, however, after following these steps... Your garden should be in tip top shape.
One last thing... When the season is over, it is often a good idea to solarize the bed. This means to put black plastic over the bed all winter, to heat up the soil, and promote better breakdown of all of those good nutrients. This will also kill any unwanted weeds leftover in the soil.
good luck with your bed, and please feel free to contact us again.