Nitrogen deficiency


I bought a load of new soil and used it in deck planters that receive 7 hours of sun daily, in Toronto. The tomatoes, squash and beans have yellowing leaves. How can I give them the nitrogen they probably need need without burning the plants? The soil mix has a high proportion of wood chips in it. It is from Homeland Market, which has a good reputation.

Would fertilizer remedy the situation?: What kind, how much, how often? I watered with fish emulsion 2 days ago, and see no change.

Would top-dressing with manure work, and how can I avoid burning the plants?

For the tomatoes, should I dig out a hole and replant them in a soil pocket of good soil?

Thank you, Nellie Sue


Thank you for contacting Toronto Master Gardeners.

Microorganisms use up nitrogen as they break down organic matter such as wood chips. So, soil filled with lots of wood chips is not suitable for growing annuals and many vegetables. Once the chips have decomposed, the nitrogen is released back into the soil as these bacteria die off. When this happens depends on many variables – wood chip size and type, temperature, soil microorganisms in place etc.

While low nitrogen is likely the problem, to accurately determine what is wrong with your soil, you would need to have the soil analysed. Based on the results, you would then add fertilizer of the type and amount needed to correct for any identified soil deficiency.

If nitrogen deficiency is the problem, adding fish emulsion and top dressing with manure will provide additional nitrogen to your plants, but this is not an immediate fix.

I had the same problem with wood-laden triple mix I purchased this year for a raised vegetable bed. My plants were not thriving, even the beans and peas which are able to release nitrogen into the soil, were not healthy. I tried adding soluble fertilizer, with only a little improvement. I ended up removing the triple mix and replacing it with a quality garden soil. Plants are now growing well.

Since all your vegetables are suffering, to rescue this year’s growing season, I would replace the soil in your deck planters with quality potting soil identified as suitable for vegetable growing.

Good luck with your veggies.