Today, Ethan Walter discusses nutrient deficiencies: what they are, how to identify them, and how to treat them.
A nutrient deficiency occurs when a plant is not getting enough of a nutrient for the normal plant functions. Common deficiencies are N, P, K, (three of the macronutrients), and Ca, Mg, and Fe.
In previous videos like this one (https://youtu.be/jaZ_x-sgLO4), you learned that nutrients are measured in water with a number called EC. EC is a very useful number, but it doesn’t tell you what *ratio* of one nutrient to another is. If you have the wrong ratio of one nutrient to another, you could be reading the EC as sufficient, when a certain nutrient is actually too low.
Deficiencies are identified by their symptoms. Some common deficiencies are chlorosis, necrosis, and stunted growth. The pattern that those symptoms occur in are important. Pay attention to where symptoms occur, whether it’s on new or old growth, and what combinations symptoms occur in.
Plant nutrients are categorized as either mobile or immobile in the plant. Mobile nutrient deficiencies occur first in older growth, and immobile nutrients occur in younger growth.
A plant deficiency key is a useful tool for farmers to identify deficiencies. If you’re still having trouble, consult with your local extension agents. Google is not a great way to ID deficiencies unless it’s from a peer reviewed source
Treat deficiencies by supplementing the nutrient that is lacking. You can supplement through your nutrient reservoir or foliar feeding (but be careful; high concentrations can burn the foliage and ruin a crop). Consider making regular supplements or switching suppliers if the deficiency occurs commonly.
Here are some common deficiencies and diagnosis tips:
Nitrogen is the “green up” nutrient. Nitrogen is mobile, so it will affect older growth first, and will cause total chlorosis starting at the tip of the leaf. You will also see stunted growth.
Phosphorus deficiency rarely displays outward symptoms noticeably or quickly. You may see stunted growth and the leaves will begin to get darker and purplish/bronze. Like nitrogen, these symptoms will begin on the old growth.
Potassium deficiencies is slow to show symptoms similar to phosphorus. Over time, you’ll see chlorosis around the edge of the leaf (the margin). Chlorosis will move from the tip to the back, but will leave the center of the leaf untouched. Like nitrogen, these symptoms will begin on the old growth.
Magnesium is a very common deficiency in hydroponics. It’s mobile, so it starts on old growth first. It looks similar to nitrogen deficiency, but will have inter veinal chlorosis instead of complete chlorosis. It also turns almost completely white (in comparison to the light green of a nitrogen deficiency). When you correct it, the old foliage will stay chlorotic, but new leaves will look healthy.
Calcium is an immobile nutrient, so it affects the the top of the plant (new growth) first. Calcium deficiencies show up as necrosis on the margin on the leaf. It will usually start at the tip of the leaf – which gets confused with tip burn – but be splotchy along the margin unlike tip burn.
*Calcium deficiency happens a lot in indoor systems with poor HVAC systems. The more airflow, the more respiration the plant does, allowing the immobile calcium to be sent to the leaf tip. Another cause is high humidity. Try to keep humidity between 40-60%.
Iron is an immobile nutrient, so it affects the the top of the plant (new growth) first. The example used here is basil, and it’s worth mentioning that basil deal with this a lot. The symptom is inter veinal chlorosis in new growth, similar to calcium.
*Iron deficiencies are especially common in symptoms that use UV filtration. The UV light creates a chemical reaction in the plant-ready iron (chelated iron) and makes it precipitate out of the solution. It sinks to the bottom, and the plants can’t use it. When we add iron, we unplug the UV filter for 24 hours. Iron can also be added through foliar applications.
00:17 What are Nutrient Deficiencies?
00:49 Common Deficiencies
02:19 Identifying Deficiencies
04:23 Treating Deficiencies
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Music by: Scott Gratton