Of all the chemical elements available in nature, plants only need 17. Three of those 17 are obtained from air and water, being the main elements in the synthesis of organic matter as a result of the photosynthetic magic. These three elements are carbon, hydrogen and oxygen.
What about the rest 14?
They are known as minerals because all of them come from the parent rock (except for the nitrogen). Such elements are divided into macronutrients (nitrogen, potassium, calcium, phosphorus, magnesium and sulfur) and micronutrients (chlorine, iron, boron, manganese, zinc, copper, molybdenum, nickel) according to the concentration inside the plant.
All these elements are essential to the plant’s lifecycle, even the less concentrated. Growth, floration, blooming and fruit development depend on them.
When these elements are missing, it’s possible to identify certain visual symptoms such as chlorosis (leaves turn yellow), necrosis (leaves turn brownish or blackish) and morphological changes and deformities. However, these symptoms appear when the nutrient deficiency is substantial and the growth has already been affected. It might be a good idea then to prevent it or follow a fertilizing calendar.
Bear in mind too that sometimes the nutrients are actually in the soil, but they are unavailable for the roots to absorb them as a result of the pH, for example. Besides, sometimes these symptoms may not be nutrient deficiencies but illnesses or pests, but usually these sort of things produce additional symptoms (bugs, leave loss, oddly shaped stains…). Lastly, be careful with that feeding, as an excess of nutrients can be toxic!
How to identify a nutrient deficiency?
It’s a bit difficult, especially if you don’t have a healthy plant to compare, but impossible is nothing to the trained eye. These are the most common deficiencies and the symptoms they produce in plants.
Nitrogen is a macronutrient, and it’s essential for the plant’s growth as it’s a basic component of amino acids, which in turn make up the structural proteins in the plant. The lack of nitrogen slows down the growth. With similar age and conditions, nitrogen deficient plants are about 50% the size of the healthy ones. Leaves usually turn a bit yellowish as well (chlorosis). Pinkish spots sometimes appear.
Iron is a micronutrient, but it’s fundamental for the synthesis of chlorophyll, the pigment that makes plants green and allows the photosynthesis to occur. Hence, iron deficiency results in marked chlorosis (way more intense than in the case of nitrogen). In addition, this element doesn’t move inside the plant, so the newest leaves are the more affected, appearing bright yellow or even white. Iron is usually present in the soil, but sometimes the roots are unable to absorb it for various reasons.
Manganese takes part in several reactions, including photosynthesis, respiration and nitrogen assimilation. Like iron, manganese is usually in the soil but sometimes the plants can’t incorporate it (this is especially common for acid loving plants). When manganese is missing, yellow spots or even holes appear between the leaves’ nerves. The edges may turn brown as well. The light effects are very similar to those of the iron deficiency but less obvious.
This mineral participates in numerous biochemical reactions. Phosphorus deficiency thus affects all the plant, slowing the growth down and making the foliage to turn yellowish. The oldest leaves may appear darker than normal. In extreme cases, leaves start to fall.
Magnesium is fundamental for the movement of the photosynthesis products, for protein synthesis and chlorophyll and as a regulator in certain biochemical reactions. When this mineral is lacking, leaves (especially the older ones) start turning yellow from outside going in, while the veins remain green. This occurs because the plant starts mobilizing the magnesium to other parts of the plant where it’s more necessary. Long lasting deficiency may result in necrosis, with wrinkly leaves and brownish, red or slightly purple in color.
It’s essential for water intake and photosynthesis. Potassium deficiency makes the younger leaves (and sometimes the medium sized as well) turn yellow in the edges and tips. Sometimes they appear slightly purple and, in extreme circumstances, leaves turn brown. Potasium is also very relevant for abundant flowers and fruits.
Calcium keeps the cell walls attached to one another. It kind of keeps the plant’s shape. When calcium is scarce, young leaves are misshapen or stunted. The rest of the plant looks normal, as this element doesn’t move inside the plant. In extreme cases, the base of the fruit starts to rot (blossom end rot).
Now you know how to identify a nutrient deficiency. The rest is easy! Just choose the right fertilizer or soil treatment to amend it (future post incoming). Good luck! ; )