Plants absorb nutrients from the soil that are essential for growth, development, and survival. These nutrients can be divided into primary (or macro), secondary, and micronutrients. Plants take in these nutrients through their roots. Some nutrients may move freely throughout the plant, while others cannot. If a nutrient can be moved, the plant will be able to provide newer parts with nutrients taken from older tissue. When the plant is unable to move nutrients and cannot take up anymore from the soil, a lack or deficiency may develop. When a plant lacks certain nutrients, it may show symptoms such as stunted growth, yellowing, or smaller fruits. However, most of these symptoms are similar to those caused by plant diseases, insects, changes in air circulation or soil, and so on. It is important to check the plants for other causes and to test the soil, before adding more nutrients.
Nitrogen (N) is the most important nutrient for plants. It is found in the soil and helps plants grow (photosynthesis), produce fruit, tissue growth, and helps form proteins and chlorophyll. This nutrient is also an ingredient for plant protoplasm or the living part of the cells. The plant can move the nitrogen around, providing newer growth with more nitrogen by taking it from older growth. A lack of nitrogen appears as a general yellowing of the plant, less and smaller fruits, leaves may start growing up, and a reduction in growth. Too much nitrogen is unhealthy for the plant as well. When a plant contains too much nitrogen, root growth is stunted, fruits take longer to ripen and they will have a shorter storage life.
Potassium (K) is another primary plant nutrient since it is very important for plant growth and development. Plants require potassium in large amounts for growth and reproduction. Potassium regulates the CO2 uptake by stomata, triggers the activation of enzymes, influences protein, and starch synthesis, affects water uptake and respiration, and is essential for the production of Adenosine Triphosphate (ATP). A potassium deficiency is hard to notice. Signs are found on (older) leaves, such as brown spots or brown veins.
Phosphorus (P) facilitates growth and development. Phosphorus is especially beneficial to plant roots, needed for storage and transfer of energy, division of cells, respiration, and to help the plant convert other nutrients into units for growth. Because phosphorus helps plants develop and grow better, they are more protected from diseases. Plants require phosphorus from seedling to maturity. Phosphorus is an important requirement of genes and plays a role in the transfer of genes from one generation to the next. This plant nutrient is also essential for the production of Adenosine Triphosphate (ATP). When a plant lacks phosphorus, it may take longer to mature and will not grow to its normal size. Shorter plants and darker leaves are symptoms of phosphorus deficiency, as well as bronze coloration under the leaves.
Calcium (Ca) is important for activating enzymes, holding together the cell walls of plants and other cellular activities. Ca makes sure the plant is strong and can stand up straight. Calcium can not move freely through the plant, therefore, when a plant runs out of calcium it can not take from older tissue and move it to newer tissue. Water carries calcium through the plant; when plants get too little water, the plant may not get enough calcium. Symptoms of a calcium deficiency include distorted growth of new tissue, leaf curling, death of root tips, and death of leaf tips. In rare cases, an excess of calcium can lead to the plant not being able to take up any of the other plant nutrients important for its growth.
Magnesium (Mg) is important for photosynthesis since it enables chlorophyll to absorb light energy needed for this process. This nutrient also facilitates cell division, stabilization of cell membranes, the formation of proteins, respiration, carrying phosphorus in plants, and (phosphate) metabolism. Magnesium can move freely through the plant, moving from older parts to newer tissue. Older and low leaves turning yellow, red, purple, or brown is the first sign of magnesium deficiency.
Sulfur (S) is important for plant proteins, enzymes, hormones, vitamins, the formation of certain oils, making it a key factor in determining the nutritional value of the plant and its fruit and vegetables. S is also important for nitrogen metabolism, photosynthesis, and helps improve winter hardiness. Sulfur cannot move within a plant, making symptoms of Sulfur deficiency usually show up in younger leaves first. These symptoms include pale green or yellow leaves, stunted growth, and a smaller plant in general.
Iron (Fe) helps a plant carry important elements through its system, is vital in the production of chlorophyll (and consequently carrying oxygen through the plant and giving the plant its green color), and enzyme functions. Iron deficiency shows up as leaves turning a sickly yellow color. Symptoms of iron deficiency include yellowing of newer leaves, less fruits, dark green veins, brown leaf edges, and death of leaves.
Boron (B) controls the transfer of energy (or sugars) into the growing parts of the plants, helps in seed development, pollination, the formation of cell walls, and the maintenance of membranes. B is especially important for the health and growth of crops. Boron deficiency results in stunted growth, poor pollen vitality, empty pollen grains, reduced number of flowers, and yellowing of lower leaves.
Zinc (Zn) helps in the formation of chlorophyll, it’s a building block for many enzymes and proteins. It also plays a role in many processes, such as the production of growth hormone and stem elongation. Zn also helps plants withstand cold temperatures. A zinc deficiency is one of the most common nutrient deficiencies and can reduce yield greatly before any visual symptoms appear. Zinc deficiency symptoms include stunted growth, short and narrow veins, brown spots on the leaves, and death of the affected parts.
Manganese (Me) is important for chlorophyll synthesis, regulates the splitting of water molecules during photosynthesis, regulates carbohydrate metabolism, immobilizes free oxygen radicals, and influences the uptake of other nutrients. Manganese deficiency can appear in the form of a pale green color between leaf veins, brown spots on leaves, or withering leaves. Manganese deficiency affects younger leaves first.
Copper (Cu) plays a key part in the formation of chlorophyll, several enzyme processes, photosynthesis, respiration, and the metabolism of carbohydrates and proteins. A plant cannot move the copper through its system, so when a deficit develops, it will affect newer leaves first. Copper deficiency symptoms include discoloration, the formation of smaller new leaves, spots on the leaves, leaf wilting, pale pink color between veins, and shorter stem lengths. A copper excess can burn root tips and prevent other nutrients from being absorbed by the plant.
Molybdenum (Mo) is a mineral from which plants need the smallest amount. Mo assists a plant in turning nitrogen into essential compounds, such as amino acids and chlorophyll. Molybdenum is mobile within the plant, so it can move freely from older parts to new tissue. Molybdenum deficiency affects older and middle leaves first. Symptoms of Molybdenum deficiency include leaves turning pale, death of leaves, misshapen leaves, and flowers failing to form.