It’s bound to happen.. you’re growing a plant, things are moving right along, and then you start to notice something not going to plan. Perhaps the leaves are turning yellow, or the fruit blossoms are falling before any fruit sets. Before you start looking into what disease your plant now has, perhaps you should first take into consideration any plant nutrients that might be missing.
Over time, plants deplete the soil of various nutrients and minerals that they need. It’s helpful to be aware of the tell-tale signs when your plant is lacking specific nutrients. Luckily, there are ways to tell what nutrients are missing so that you can amend your soil for your plants to grow healthy and happy.
There are many different plant nutrients. Terms you’ll commonly hear referencing nutrients are macronutrients and micronutrients. Macronutrients represent nutrients that plants need in larger quantities compared to micronutrients, which plants need less of. Regardless, both types of nutrients are important for a plant to thrive.
The most basic nutrients needed are carbon, hydrogen, and oxygen. Next, come the macronutrients which are divided into two classes – primary and secondary. The three primary nutrients are nitrogen, phosphorous, and potassium. These are typically referred to as NPK and are commonly found listed for fertilizers. The secondary macronutrients are calcium, magnesium, and sulfur. Finally, the micronutrients that plants need include iron, manganese, zinc, copper, boron, molybdenum, and chlorine. We’ll discuss each nutrient, what it’s responsible for, how to detect deficiencies, and how to amend your soil appropriately using organic methods.
Basic Plant Nutrients
The first three macronutrients – carbon, hydrogen, and oxygen – are known as basic nutrients, or structural elements, that are present in the growing environment for your plants with the air, water, and soil. These are all vital for your plants to survive.
All living things are carbon-based. Plants use carbon dioxide during photosynthesis, where the plant converts the energy from the sun into a carbohydrate molecule. Plants then use this to grow. Adding organic matter such as manure or compost can add carbon to the soil. Plants can get carbon dioxide from the air, or they can get carbon from the soil.
Plants need the hydrogen they obtain from water for photosynthesis. By simply watering your plants they will receive the hydrogen that they need. The hydrogen they receive in the form of H2O combined with carbon dioxide helps to form a simple sugar called glucose, along with excess oxygen that is then released into the air.
Plants absorb oxygen through carbon dioxide in the air as well as from water. As previously mentioned, oxygen is used for photosynthesis to create energy from glucose. In addition, oxygen helps the roots of plants to absorb nutrients. Oxygen is required to move nutrients across the cell wall and into the roots. Keeping your soil aerated can help with this.
The primary macronutrients are probably the most popular and well-known of all the plant nutrients. If you have ever seen a bag of fertilizer, you’ve likely noticed three numbers listed, such as 10-5-5. This symbolizes the balance of nutrients in the bag for nitrogen (N), phosphorous (P), and potassium (K), respectively. The 10-5-5 example would mean that the fertilizer contains 10% nitrogen, 5% phosphorous, and 5% potassium.
Nitrogen helps your plants become more green and lush. It’s the nutrient that is responsible for vegetative growth and utilizes chlorophyll produced during photosynthesis. Plants need a large amount of nitrogen because it plays a part in photosynthesis. Plants that don’t have enough nitrogen can have yellow, or faded, wilted leaves because they’re unable to produce enough chlorophyll. Chlorophyll converts sunlight into sugars and energy. Plants constantly use this, which means plants constantly need nitrogen. Organic and natural sources of nitrogen include blood meal, fish emulsion, and alfalfa meal.
Phosphorous is needed for root growth, flower growth, and photosynthesis. Phosphorus is especially important when plants are developing roots, so it’s good to add some when plants are just starting out or when you’re transplanting them into your garden. When plants are deficient in phosphorus they can produce stunted growth, spindly stems, underdeveloped flowers, or no flowers at all. Leaves can also have dark veins while the rest of the leaf turns dark. Organic and natural sources of phosphorous include bone meal, rock phosphate, and manure.
Potassium improves the overall health of the plant. It helps the plants grow faster, make carbohydrates, fight off disease and pests, and make better use of water. Potassium also regulates and activates plant enzymes. A deficiency of potassium can cause weak or deformed plants and stems and early loss of fruit. Older leaves may wilt or look scorched. You can amend your soil for this deficiency in potassium with potash, wood ash, or composted banana peels.
Secondary macronutrients are just as important as primary macronutrients, but they’re needed in smaller quantities. This is similar to how micronutrients are needed in smaller quantities compared to secondary macronutrients. The secondary macronutrients are calcium, magnesium, and sulfur.
Calcium aids in the development of cell walls, which helps to strengthen stems and new shoots. Well-developed cell walls can help resist disease. It also helps with root ends and prevents blossom-end rot (where fruit becomes dark and eventually rots). Without calcium, garden plants can experience yellowing and curling of the leaves, blackened shoots, and stunted growth. When plants are deficient it will show in the leaves and fruit of the plant. For leaves, it will show in the younger leaves first. The leaves will look deformed, with tips dying, and eventually, leaf production will stop altogether. Roots will also be stunted. You can amend your soil for deficiency in calcium with bone meal, limestone, or crushed eggshells.
Magnesium assists plants in the production of chlorophyll. Plants are unable to process sunlight without it. Magnesium essentially gives leaves their green color. Magnesium is also used by plants for the metabolism of carbohydrates. Older leaves turn yellow at the edge leaving a green triangle shape in the center of the leaf. You can amend your soil deficiency in magnesium with dolomite, Azomite, or Epsom salts.
Sulfur helps form amino acids, proteins, enzymes, and vitamins. It also helps plants resist disease and plays a role in giving flavor to mustard, onions, and garlic. Younger leaves will turn yellow first and sometimes followed by older leaves turning yellow as well. You can amend your soil for this deficiency with gypsum or manure.
Micronutrients are needed in small amounts for your garden to thrive. There are multiple ways that you can go about adding these micronutrients, but most can be added by using a single amendment. Compost, kelp meal, glacial rock dust, Azomite, and liquid kelp can help to add these plant nutrients back into your soil.
Iron: is required for the production of chlorophyll in plants. A deficiency in iron can cause yellowing between the veins of young leaves.
Manganese: assists iron in chlorophyll formation. It also serves as an activator for enzymes in the growth process and breaking down carbohydrates. A deficiency in manganese can cause slow growth and yellowing between the veins of young leaves, along with curled leaves.
Zinc: helps change carbohydrates into sugars. A deficiency in zinc can cause yellowing between the veins of the new leaves.
Copper: helps plants reproduce and boosts metabolism in roots. A deficiency in copper can cause leaves to be limp and dark green and plants to be stunted.
Boron: regulates the metabolism of carbohydrates in plants. It’s critical for new growth, seeds, and fruit. A deficiency in boron can cause poor root growth and discoloration of leaf buds and the dropping of buds.
Molybdenum: is needed by plants for the utilization of nitrogen. Without molybdenum, plants can’t transform nitrogen into amino acids. A deficiency in molybdenum can cause the yellowing of older leaves, and the rest of the plant might be pale.
Chlorine: aids in plant growth and health. Chlorine helps the chemical reaction that allows for the opening and closing of tiny pores, called stomata, that allows gas water to be exchanged. Without this, photosynthesis can’t occur. A deficiency in chlorine can cause wilting and leaf molting.
Once you are able to identify your plant nutrient deficiencies you will be well on your way to amending your soil and getting your plants back on track to a healthy state.