Last week we covered the primary nutrients (nitrogen, phosphorus and potassium). This week it is time to cover secondary nutrients and micronutrients.
Secondary and micronutrients are required in lower amounts than the primary nutrients. However, they are just as important to plants.
Calcium is a secondary nutrient that is definitely not needed in the Antelope Valley. The limestone or caliche that is abundant in the Antelope Valley is primarily calcium.
Besides being a nutrient, calcium can be a soil amendment that raises the pH of the soil. The only time I need to raise the pH is when I use a lot of peat moss in a container. Our soil does not need to have the pH raised.
Calcium is used by the plant as the building blocks of the cells — primarily cell walls. The only time I fertilize for calcium is when I grow tomatoes in containers that are filled with bagged potting soil.
Magnesium is commonly deficient in the Antelope Valley. Magnesium is the center of the chlorophyll molecule. Without it, the plant cannot make chlorophyll, and it is chlorophyll that makes the plant green. Without chlorophyll, plants cannot convert sunlight into sugar.
It also works as an activator for many plant enzymes. If your plants are deficient in magnesium, the leaves will show interveinal chlorosis on older leaves. That means the veins in the leaves will stay green, while the rest of the leaf will turn yellow — in other words, yellow between the veins.
The third secondary plant nutrient is sulphur. Sulfur is normally deficient in the Antelope Valley. Its deficiency symptom can be confused with a nitrogen deficiency.
Nitrogen and sulfur deficiencies show pale green to yellow leaves. The yellow leaves in nitrogen deficiency start with older leaves, whereas sulfur starts with new leaves. Sulfur is also a soil amendment and helps lower the soil pH. It is used by the plant to make three primary amino acids. Sulfur also gives the smell to garlic and onions.
Micronutrients are used by the plant in very small amounts. They are just as important for plant growth. The first micronutrient is zinc, one of the most deficient nutrients in the Antelope Valley. It is used by the plant to make indoleacetic acid, which is a plant growth regulator. Without zinc, the plant will not grow properly and will become dwarfed. Zinc deficiency is commonly seen as interveinal chlorosis of younger leaves.
Iron is also one of the most deficient nutrients in the Antelope Valley. Iron is required to produce chlorophyll in the plant, and it is an activator for respiration, photosynthesis and the absorption of nitrogen. Iron deficiency is also seen as interveinal chlorosis of younger leaves.
Manganese is used to assist iron in chlorophyll formation and can be deficient in the Antelope Valley. Manganese deficiency is also seen as interveinal chlorosis of younger leaves.
Copper is an activator of several plant enzymes. It may play a role in Vitamin A production. It is not usually deficient, but in some areas of Leona Valley, it has been known to be deficient. Have your soil tested before applying copper, because it can lead to toxicities.
Boron functions in the plant’s cell division. Cells will continue to divide without boron, but they will not change into different types of cells. This means they will not become specialized cells that carry food- or water-carrying cells. Boron does not need to be added to the soils in the Antelope Valley.
Molybdenum is essential to help nitrogen form into amino acids. Molybdenum is more likely to be at toxic levels instead of deficient levels in the Antelope Valley.
Chlorine is required by plants, but enough is carried by the winds from the ocean or from the chlorine used to disinfect your tap water. Tap water can carry toxic amounts of chlorine and fluorides for some houseplants.
The biggest nutrient problems for most plants in the Antelope Valley are the metals. These include magnesium, zinc, iron, manganese and possibly copper.
These nutrients are found at deficient levels in the soil and are unavailable to the plants due to the soil pH. Our alkaline soil prevents the plant from absorbing metals from the soil. Typically, the metals are best applied as a chelated fertilizer, which allows metals to be absorbed by any tissue of the plant. A common fertilizer with chelated properties is Miracle-Gro.
Secondary and micronutrients are very important for your plants in drought. Continue to fertilize using these nutrients as needed to help your plants survive the stress.