For farmers, nutrient management is key to maintaining or increasing crop yields. To meet these needs throughout the growing seasons, growers must understand what nutrients are in the soil. In total, 14 nutrients are supplied to crops from soil and fertilizer sources. We can break down these different nutrients into primary nutrients, secondary nutrients, and micronutrients. Each one plays an essential role in determining crop heath. The E4 Crop Intelligence team will discuss what these nutrients are, the tools farmers use to find nutrient deficiencies, and the methods used by farmers to add nutrients back into the soil.

Crop Nutrients 

As mentioned before, the nutrients essential for plant growth can be divided into three categories: primary nutrients (nitrogen, phosphorus, and potassium), secondary nutrients, and micronutrients. These nutrients can be supplied to the field by other products and processes such as organic manure, plant residues, and biological nitrogen fixation.

Nitrogen

Nitrogen (N) plays a big part in determining overall plant growth and is one of the most abundant elements in Earth’s surface and atmosphere. However, nitrogen deficiency is one of the most common crop nutrient problems that farmers face. The reason for its scarcity in farming is that most of the N in the atmosphere and in the Earth’s crust is not available for immediate uptake by plants. Most organic forms of nitrogen, such as the N found in plant residue, soil organic matter, or bacteria, are not readily available for plants.

Even though it’s not directly available for plant uptake, organic nitrogen is an important factor in soil health because it’s relatively stable within the system and can provide plants with a long-term slow release of nitrogen. Mineral N in the inorganic forms ammonium (NH4+) and nitrate (NO3-) are plant-available forms of nitrogen. However, NO3- is also quite susceptible to being lost from the system because it is water-soluble and does not interact with soil particles.

Phosphorus

Phosphorus (P) is an essential macronutrient for plant reproduction, which may significantly impact crop yields. P deficiency is a common problem and can lead to crop stunting or discoloration. The major contributing source of phosphorus for crops comes from soil organic matter. This soil organic matter will generally contain a range of organic phosphorus compounds, which must be converted into inorganic phosphate by soil microorganisms, which plants then take up. Soil organic matter can be an excellent source of stable organic P compounds that can be released over time. Although, the phosphorus available to plants is only found dissolved in the soil solution.

Potassium

Soil potassium (K) is an essential macronutrient (large chemical element) for crops and can generally be found in different forms in agriculture. The K that’s immediately usable by plants is found within the soil solution. This form is most significant for plant uptake. However, it’s only a tiny fraction of the total potassium in the soil. Exchangeable K and other mineral forms of K are far more prevalent within the ground. Mineral K is the most stable form and is generally tightly held within the soil itself. The availability of this form of the nutrient is relatively low for crop uptake. Exchangeable K, on the other hand, is an important pool of K available for crop growth. This form of potassium is a positively charged ion that is loosely attracted to the negatively charged surfaces of soil particles.

Secondary Nutrients

The nutrients calcium (Ca), magnesium (Mg), and sulfur (S) are considered secondary nutrients (a.k.a. secondary macronutrients) because they are needed in smaller amounts than what’s required for N, P, or K. Even though these elements are not available in large amounts they are equally important for plant growth and nutrition. Often, necessary amounts of these nutrients can be found in the soil and supplied to crops from chemical weathering or atmospheric deposition (a process whereby precipitation moves from the atmosphere to the earth’s surface).

Micronutrients

Micronutrients are essential nutrients for plant growth that are used in relatively small amounts by crops. Boron (B), zinc (Zn), manganese (Mn), iron (Fe), copper (Cu), molybdenum (Mo), nickel (Ni), and chlorine (Cl) will only make up a small proportion of a plant; however, a deficiency in any of these elements has the potential to cause a decrease in crop quality or yield. In contrast, excess availability may cause toxicity. The availability of each of these micronutrients will depend on environmental and soil conditions. While visual clues may point a grower in the right direction towards identifying deficiencies, the most common method for determining deficiencies is through soil testing or plant tissue analysis. The most common method for ensuring proper micronutrient content within the soil is increasing and enhancing the soil organic matter, which can be seen as a reservoir for holding stable nutrients. 

Determining Nutrient Needs

How do farmers determine what nutrients are needed in their field? There are a couple of different ways farmers can analyze their soil nutrients. Soil sampling is where a core sample of the field’s soil is taken and is sent to a lab for analysis. Results help identify nutrient deficiencies and inform on the amount and type of fertilizer needed for the field. Plant tissue testing allows growers to measure the nutrient levels in the plant itself during growth. This type of testing can signal to growers how effective their fertilization and other nutrient application practices have been. Crop consulting firms can provide soil sampling and plant tissue testing services. E4 Crop Intelligence provides both testing services to inform on decision-making that improves yields for growers.

Adding Nutrients Back Into The Soil

To add nutrients to their fields, farmers apply nutrients in the form of chemical fertilizers and organic material, which provide crops with the primary, secondary, and micronutrients necessary to grow their crops. Other methods of adding nutrients to soils include the application of gypsum and lime. E4’s fertilizer prescription services offer expert nutrient recommendations based on the unique conditions of a grower’s field. As an independent and unbiased agronomy firm, E4 helps optimize ROI for fertilizer placement. 

For more information about crop nutrients, soil sampling, plant tissue testing, and more on being successful in the field, visit E4 Expertise.