Week 7 - Nutrient Deficiencies & Fertilization

For episode/article 7 for This Week in the Garden, we’ll cover nutrient deficiencies and fertilization. Micro- and macronutrients are the building blocks for vegetables and deficiencies can ruin a good start to the season. In this article/vlog, we’ll go over how to identify deficiencies, different types of fertilizer, and how to fertilize throughout the season.

Nutrient deficiencies often show up as discoloration of the leaves. This discoloration is usually yellow or light green but can turn brown or tan over time. When identifying which nutrient the vegetable needs, it is essential to determine where on the leaf the color change started. Some deficiencies, like iron or manganese, show up near the veins, while others like copper show up on leaf tips. This guide from Montana State University has a good chart and pictures to help you determine what nutrients your vegetables might be missing. If you’re familiar with reading keys, this key from the Pacific Northwest Pest Management Handbook is a quick way to identify issues.

Once you’ve identified your plant’s deficiency, you’ll want to act fast, but be patient. What I mean by this is that you’ll want to apply a fast-acting fertilizer. Liquid fertilizers are the best option if available. Make sure to apply these to the roots, where the vegetables uptake the most nutrients. You’ll then need to be patient. It can take plants 2-4 weeks to show signs of improvement. This will likely show up on new growth, or if it was most prevalent on old leaves, it will seem like it has stopped spreading.

Aside from liquid fertilizers, granular fertilizers are the recommended products for normal fertilizer applications. They release nutrients more slowly over time, resulting in longer effectiveness. The best time to apply granular fertilizers is before planting. I recommend taking a soil sample to know exactly how much to put down. If this is done properly, most people won’t have issues with nutrient deficiencies in vegetables. The only exception would be if weather conditions like excess rain or cold temperatures prevent the plants from uptaking the nutrients.

With that in mind, applying additional fertilizer throughout the season can boost production from your plants. This process, called side-dressing, most commonly takes place by adding nitrogen to plants like sweet corn, melons, and squash. Granular fertilizers work best in this method because they slowly release the nutrients. Side-dressing vegetables usually takes place near flowering to give the plants nutrients for fruit set. For a more specific guide, check out Colorado State University’s fact sheet.

The last thing to consider is how to apply fertilizers. They should be focused near the roots of the plant, as that is where the nutrients will be taken up. You’ll want to water in granular fertilizers. If you have a large area to fertilize, you can do so before a light rain. Make sure it’s not before heavy rain, or the excess water can wash the nutrients into the waterways. It will take a week or more before you notice nutrient uptake, so plan accordingly.

That’s all for this article from This Week in the Garden. If you’ve missed any articles, check out our website where we keep them archived and fill out our form if you have any comments or questions. Of course, stay tuned until next time for This Week in the Garden.

-Adam