As many gardeners have experienced, one of the most common problems of starting a new garden with brand new, well-mixed garden soil is too much soil nutrition. Take, for example, my mom’s experience from two years ago, when she planted tomatoes in a new garden bed that had new, nitrogen-rich soil:
Good Soil Fertility = Tomato Jungle
We affectionately called it a “Tomato Jungle”. The picture above was taken after a full afternoon of cutting back the vines which, in some cases, were in excess of 8-10′ in length.
When farmers and gardeners discuss soil fertility, they are most often referring to the amount of Nitrogen, Phosphorus, and Potassium that is in the soil. When you buy a fertilizing product, these three macro-nutrients are represented by three numbers on the package, which indicate the concentrations of the nutrients in the fertilizer. They are displayed as N-P-K – the atomic symbols for Nitrogen, Phosphorus, and Potassium. There are many other important nutrients and micro-organisms that are necessary for healthy soil, but that subject is best addressed in relation to Organic Gardening principles – I’ll talk about those in a later post.
In new, well-mixed garden soil, there is often an abundance of nitrogen. When establishing a new garden, it is common to also add manure and compost, which increase the nitrogen concentration even more. Nitrogen is the macro-nutrient that allows the plant to grow larger, so a high level of nitrogen causes rampant, very dark green, seemingly out-of-control growth. Hence my mom’s Tomato Jungle pictured above. This may sound like a really great thing, but plants that grow quickly are also weaker and therefore more likely to fall victim to pests and disease; Mom’s tomatoes had to be pruned because they had been decimated by blight and wilt. They also produce fewer and smaller fruit – in fact, large, very dark green growth together with low fruit production is one of the best ways to tell if you’ve added too much fertilizer to the soil.
When the Garrison Creek Park Community Garden was built this spring, I expected we would have exactly the problem I described above – huge, dark green, overwhelming plants with low yield. Unfortunately, we ended up having the opposite problem – to put it really bluntly, our soil kinda sucked**.
The early signs of this were classic symptoms of nutrient deficiencies:
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Within days of being planted, seedling leaves would turn various shades of yellow, purple and red.
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As the plants matured, they didn’t grow any larger. Tomatoes, especially, are well-known to explode in size in the first few weeks after transplanting. In July I had some tomato seedlings that were the same size as when I planted them 4-5 weeks earlier.
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Seeds planted directly into the soil took much longer than usual to sprout and the seedlings grew excrutiatingly slowly once they did pop out of the ground.
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The plants were very slow to flower, then to set fruit, then to ripen. Once they did start to fruit, many plants produced much lower yields than we expected.
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For those of us who applied organic fertilizers to the soil, we noticed immediate improvement in all of the above symptoms – green returned to the leaves, new growth emerged, and growth of carrots and other directly-sown plants, as well as the number of blossoms on the fruiting plants increased dramatically.
So if you are dealing with tomato plants that are still only 1 foot tall, have purple stems, and have yet to produce a tomato, don’t worry – it’s not your fault! It seems that our soil may not have been as great as we were told and the result has been a very difficult and frustrating summer. It has been made worse by the record-breaking rainfall – heavy rains can strip nutrients from the soil, especially in raised beds that drain as well as ours do!
Now we come to the most important part – what do we do about the problem? As I mentioned above, some of us have been using organic fertilizers to add nutrition to our plots since we first noticed the dificiencies – “organic” because our garden rules forbid the use of chemical fertilizers! It is late in the season to be applying fertilizers, since the majority of the growth for the season has finished, but addition of some ammenders before the fall arrives would help for next spring. If you’d like to try that, I’d recommend using well-rotted compost or manure (Fiesta Farms may still have some in stock) dug into the top 4-6″ of the soil. You could also add blood meal, fish meal, kelp meal, or vermicompost (if you don’t know what those are, just use manure or compost – I’ll talk about other fertilizers in a later post). Don’t bother with any liquid fertilizers – once the plants have stopped growing for the season, the liquid fertilizers are likely to just wash through the soil in the rain and be wasted.
The leaf compost from the city is great for adding organic matter to the soil, but isn’t very high in nutrients so it probably isn’t appropriate for solving our nutrition deficiencies.
As Kat mentioned in her last post, we’re also considering getting a cover crop to grow through the fall. If you’re interested in trying that out, send us an email at garrison.creek.park@gmail.com and we’ll pass along more information. (For more than you ever wanted to know about cover crops, go here.)
Come spring, we hope to be able to arrange a group-order of compost/manure for all interested members. Stay tuned for more information.
If you have any questions, please email me at garrison.creek.park@gmail.com.
Melanie
** Please note: our soil is safe for growing food crops – it’s just a little low in essential nutrients.
