Fertilizer for crops and farming: nutrient types, commercial fertilizers and farm selection
Choose commercial fertilizers using the crop’s nutrient recommendation and the supplied product’s analysis. Start with soil testing. When soil supplies enough of a nutrient, no additional fertilizer may be needed.
Understand fertilizer grade
Fertilizer grade gives the weight percentages of nitrogen, phosphate and potash, in that order. A ratio describes their proportions; a grade describes their concentration. Two products can have the same ratio and different quantities of nutrients in an equal weight of material.
Grade is on a weight basis; use the liquid's density to convert volume to product weight.
Compare dry blends and granules
Granulated materials distribute nutrients within each granule. Physical blends contain separate particles. Particle-size compatibility matters because dissimilar particles can segregate during handling and spreading.
Put application placement in the purchase decision
Free ammonia from some fertilizers can injure germinating seed when placed too close.
Read the units before comparing the quotation
A fertilizer recommendation and a supplier analysis can use different chemical expressions. Distinguish elemental phosphorus from phosphate, and elemental potassium from potash.
Match the physical form to the equipment
Fertilizers can be solids, fluids or gases. Fluid products include clear solutions and suspensions. Suspensions contain fine undissolved particles stabilized by added clay. Keep them under constant agitation, including during storage.
Choose a local recommendation rather than a national average
For Minnesota corn, nitrogen recommendations depend on soil productivity, fertilizer price relative to crop value, and previous crop. Irrigated sandy soils require a different assessment. Use the local recommendation for your production system.
Microbial fertilizers
Microbial inoculants aim to improve access to nutrients already in soil, but their effectiveness is poorly documented.
Farmers use fertilizer: when the crop needs it
Farmers use fertilizer to supply the nutrients the crop needs; the amount comes from the crop's nutrient recommendation and the product's analysis, after a soil test. When the soil supplies enough of a nutrient, no additional fertilizer may be needed.
Synthetic nitrogen fertilizer and liquid fertilizer for tank sprayers
Ammonium nitrate and ammonium sulfate, below, are synthetic nitrogen fertilizers. Liquid fertilizer for tank sprayers is a different task from a dry fertilizer; read the section on spray AMS and the page on mixing fertilizer with pesticides before putting fertilizer in a sprayer.
Ammonium nitrate in agriculture: nitrogen fertilizer, nutrient use and farm checks
Ammonium nitrate is a nitrogen fertilizer. The typical solid analysis is approximately 33.5–34 percent nitrogen, with no phosphate or potash.
Keep ammonium nitrate and other products distinct
Solid ammonium nitrate differs from liquid urea-ammonium nitrate, commonly abbreviated UAN.
Ammonium sulfate (ammonium sulphate) in agriculture: fertilizer uses and planning
Ammonium sulfate can serve as a nitrogen-and-sulfur fertilizer or a pesticide spray additive. Decide which job you need it for before choosing a product. Ammonium sulfate supplies sulfur as well as nitrogen and has greater acidifying potential than other common nitrogen sources.
Ammonium sulfate analysis for crop nutrition
Solid ammonium sulfate typically contains 21 percent nitrogen.
Keep your spray records in one place. Free to start.
Put timing and site in the decision
Sulfate can leach, especially in sandy soils.
Spray AMS is a different task
Ammonium sulfate can reduce hard-water antagonism of glyphosate. Dissolved positively charged metals bind glyphosate and interfere with movement into plants.
Read the newer evidence about sulfur carryover
Outside sandy soils, sulfate generally leaches more slowly than nitrate. Minnesota research reported in February 2026 found carryover into later crops after sulfate applications.
Distinguish ammonium sulfate from ammonium thiosulfate
AMS and ATS both provide nitrogen and sulfur but differ in composition and sulfur availability. Sulfur in ammonium sulfate is already sulfate. Ammonium thiosulfate must undergo transformations in soil before its sulfur reaches that form; elemental sulfur has a further delay.
Pale plants: sulfur or nitrogen deficiency
Sulfur deficiency can resemble nitrogen shortage. Sulfur symptoms are clearest on younger leaves; nitrogen symptoms are most prominent on older leaves.
Account for sources beyond the new fertilizer order
Soil properties and organic matter influence sulfur supply. Account for contributions from irrigation water, manure, compost and crop residues.
Calculate nutrient mass from the supplied analysis
Calculate product quantity from its nutrient weight percentages. Preserve the unit throughout: pounds of material, pounds of nitrogen and pounds of sulfur are different entries.
Potassium nitrate agricultural fertilizer: nutrient use and crop checks
Potassium nitrate fertilizer supplies nitrogen and potassium. A typical solid grade is 13-0-44, expressed as nitrogen, phosphate and potash by weight. Compare the supplied product’s analysis with the nutrient recommendation.
Confirm which nutrients the crop needs
Use soil testing to predict potash need. Plant analysis can help confirm a suspected deficiency or monitor a nutrient program. Use the appropriate interpretation for the actual test rather than selecting a source from leaf appearance alone.
Compare source choice and cost
Potassium nitrate is a readily available potassium source used primarily for high-value crops because of cost. Compare it with potassium chloride, potassium sulfate and potassium-magnesium sulfate.
Soil potassium forms and plant uptake
Soil potassium occurs in unavailable, slowly available and readily available forms. Moisture, aeration, temperature and tillage influence plant uptake.
Choose a grade appropriate to the delivery system
For fertigation, choose a dry soluble or suitable liquid product and confirm that it dissolves for the intended irrigation use.
Match a fertigation instruction to the planted area
Calculate delivery from crop requirements and planted acreage using the local nutrient recommendation.
Review stock-solution compatibility before mixing
Some fertilizers are incompatible in concentrated solutions.
Test the source water and read the report
Test irrigation water for water-quality problems and nutrient content relevant to fertigation. For a diagnostic water submission, preserve analyte names such as nitrate-nitrogen, ammonium-nitrogen, potassium, calcium, magnesium, chloride and bicarbonate exactly as the laboratory reports them. Electrical conductivity, alkalinity and hardness are reported separately from individual nutrient concentrations.
Next step
See fertigation requirements for injected products.