The soil, a thin layer covering the Earth’s surface, is composed of various essential constituents. While mineral matter serves as its chief component, organic matter, bacteria, soil, air, and water also play crucial roles. Within the soil, plants derive most of their essential elements from mineral matter. Although these elements constitute only a small percentage of the plant’s tissue composition, their significance varies. Phosphorus and potassium, for instance, are vital elements derived from mineral matter that are often deficient in average soils or exist in forms that are released too slowly to meet the demands of cultivated crops. Additionally, calcium, magnesium, sulfur, iron, manganese, boron, zinc, copper, molybdenum, chlorine, and possibly sodium are other essential elements derived from mineral matter.

Among the essential elements, nitrogen stands out as one of the most crucial, yet it is frequently limited. In nature, nitrogen is introduced to the soil through the decomposition of organic matter and via bacteria residing in nodules on the roots of certain plants, particularly legumes. A small but notable amount of nitrogen enters the soil through ammonia carried by rainfall.

Carbon, hydrogen, and oxygen, which form carbohydrates and water in varying combinations, constitute the bulk of plant composition. These elements are acquired from the air and soil moisture. While their universal presence eliminates them as concerns for gardeners, water deficiency and insufficient carbon dioxide levels may hinder optimal plant growth.

Nitrogen: Essential Nutrient for Plant Growth

Nitrogen, a fundamental component of proteins, plays a pivotal role in plant development. It constitutes a significant portion of protoplasm, the living matter, and is crucial for chlorophyll production, which enables photosynthesis and sugar synthesis. Nitrogen is also found in amino acids, alkaloids, and aromatic compounds within plants. Its presence stimulates vegetative growth, promotes lush foliage, and enhances flower coloration.

Given nitrogen’s importance in plant growth, it is essential to ensure an available supply. Since nature often cannot provide sufficient nitrogen quantities, alternative sources such as commercial fertilizers and manures are necessary. Materials like nitrate of soda, sulfate of ammonia, dried blood, cottonseed meal, and various manures are commonly utilized to supplement nitrogen when the soil’s natural provision is insufficient.

Phosphorus

Phosphorus, another vital nutrient, is a fundamental constituent of proteins. It is abundant in the nucleus and, to a lesser extent, in the cytoplasm of cells. Phosphorus plays a crucial role in cell division and is closely associated with reproductive processes, making it abundant in seeds. It also aids in root development and helps maintain nitrogen balance. However, excessive phosphorus levels can hinder the availability of iron and zinc, leading to chlorosis (foliage yellowing) and stunted growth.

Addressing phosphorus deficiency is a widespread concern, as most soils naturally contain low levels of this element. Moreover, the majority of phosphorus exists in the form of tricalcium phosphate, which is relatively unavailable to most garden crops. To enrich the soil with phosphorus, applying commercial fertilizers such as superphosphate (20% phosphorus) or treble phosphate (45% phosphorus) proves highly effective. Bone meal, although carrying about 23% phosphorus, provides it in a less accessible form.

Potassium

Potassium, despite not becoming part of cell walls or solid plant structures, is required in relatively large quantities by plants. It functions in conjunction with enzymes, organic “catalysts” that regulate digestion, nutrient transportation, and other metabolic processes. Potassium also plays a significant role in the activity of lateral meristems, contributing to the growth in diameter of plant structures such as beets, potatoes, and dahlia tubers. Additionally, potassium helps plants withstand low temperatures.

Potassium deficiency is prevalent in most soils, even when seemingly abundant, as it often exists in chemical combinations that plants cannot utilize. A heavy soil rich in organic matter generally provides sufficient available potassium, while a deficiency of organic matter in the soil often correlates with potassium deficiency. Potassium can be added to the soil through potassium chloride or potassium sulfate (muriate or sulfate of potash), as well as hardwood ashes and manures.

Calcium and magnesium

Calcium and magnesium, both commonly found in limestones and many fertilizers, are essential elements for plant growth. Calcium contributes to the development of cell walls in new tissues and aids in the utilization of nitrates in some plants. Magnesium is necessary for chlorophyll formation and the functioning of various plant enzymes.

Sulfur

Sulfur, while not present in all commercial fertilizers, is a constituent of certain amino acids, proteins, and plant hormones.

Minor or trace elements (iron, manganese, boron, zinc, copper, and molybdenum) have gained attention from agricultural researchers and fertilizer manufacturers due to their crucial roles in plant growth and development. Although required in minute quantities, they play vital functions. Historically, relatively unrefined fertilizers and organic matter contained significant amounts of these elements. However, modern inorganic fertilizers often lack them. Consequently, the need for adding minor elements to fertilizers is increasing, especially as tillage practices and the use of refined chemical fertilizers have become more prevalent. It is generally recommended to incorporate minor elements into fertilizers based on guidance from county agricultural extension services or fertilizer experts familiar with the specific soil conditions in the area.

Some fertilizers provide small but significant amounts of minor elements, although these quantities may not be sufficient to address established deficiencies within a short timeframe. However, continued use of such fertilizers over time can prevent deficiencies from occurring. Additionally, “frits” or soft glasses are being manufactured to supply minor elements in slowly soluble forms. A single application of these nutrient sources can sustain a crop for multiple seasons.

Understanding the functions and sources of these essential nutrient elements is crucial for maintaining healthy plant growth. By ensuring an adequate supply of nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, and minor elements, gardeners and farmers can support the development, vigor, and productivity of their plants.