• Single application of the total fertilizer amount, and
• Base dressing followed by top dressing (side dressing)

• How quickly and what quantities of the applied nutrient dissolve in the soil water (example: phosphate).
• Whether transformation processes are required before the plant can take up the nutrient (example: urea).
• Whether these nutrient quantities are sorbed to soil particles or not (keyword: cations/anions), become spatially accessible to the root (keywords: diffusion, mass flow), or can be leached within the soil profile (keyword: rooting depth).

• The application technology available on the farm or accessible elsewhere. (e.g., if only a centrifugal spreader is available, applying blended single-nutrient fertilizers may not be advisable due to risk of segregation).
• The farm's strategy regarding fertilization across the crop rotation (practicable only for large farms with large, uniformly managed fields). For example:

Farm #1 might apply P and K only once every x years to the most sensitive crop, but apply N to every crop.

Farm #2 might have decided to replace the P and K removed by the previous crop with each fertilization event and apply N to the current crop.

• The necessity to use fast-soluble compounds to secure yields. This can lead to the use of triple superphosphate in one case, and partially acidulated rock phosphate in another.

• The entire (often high) nutrient quantity can be applied in a single application.
• Saves labor time due to one-time application.
• Avoids high nutrient concentrations in the soil/substrate for sensitive and/or young plants, thereby reducing the risk of nutrient leaching.

• The fertilizer must release nutrients in a "demand-oriented" manner.
• Nutrients in the fertilizer must be bound in a way that allows them to gradually enter the soil solution.
• The formulation of the fertilizer must not pose ecological risks.

• Physical Principle: Coating of soluble salts.

The coating, made of polymer or natural compounds (waxes, etc.), slows the dissolution of the salts in the fertilizer granule and their diffusion into the surrounding soil. By choosing the thickness and chemical composition of the coating, the duration of effectiveness can be influenced, offering fertilizers of the "3-month, 6-month... type," although the release duration still depends significantly on temperature. The most widely used fertilizer of this type (worldwide) is sulfur-coated urea (SCU). Its effectiveness largely depends on the quality of the sulfur coat, which often cracks or breaks, losing its function.

• Chemical Principle: Polymerization of urea-containing compounds.

Examples include urea-formaldehyde (Ureaform-N), crotonylidene diurea (Crotodur), and isobutylidene diurea (Isodur). The release rate depends on moisture, temperature, and particle size (for Isodur, also on soil pH).

• Physico-Chemical Principle: Ion Exchange.

Synthetic resin beads with ion exchange sites are loaded with nutrients and used (primarily) in hydroponic systems. Nutrients are released from the resin in exchange for ions in the irrigation water—thus, it only works with water containing salts, not with distilled water.

• Labor-management considerations
• Cost-benefit considerations (input vs. effect)
• The sensitivity of the crop
• The temporal pattern of the plant's nutrient demand in relation to the fertilizer's release rate.

• Increase Nutrient Use Efficiency (NUE): Places nutrients where roots can access them immediately, minimizing fixation, immobilization, or leaching.
• ​Reduce Fertilizer Inputs: Lower total amounts can be used compared to broadcasting.
• ​Overcome Soil Constraints: Effective in soils with high phosphorus-fixing capacity, low pH, or poor nutrient mobility.
• ​Stimulate Early Root Growth: Encourages root proliferation in the fertilized zone, leading to better crop establishment.
• ​Avoid Seed Damage: Prevents salt injury or ammonia toxicity near germinating seeds by keeping fertilizer at a safe distance.

Banding:

Pop-Up/Seed-Placed: A small amount of fertilizer is placed in direct contact with the seed. Used only with safe, low-salt-index fertilizers (e.g., some MAP/DAP in small doses). High risk of germination damage if not managed correctly.

Side-Dressing (2x2 Placement): A band of fertilizer is placed 2 inches to the side and 2 inches below the seed at planting. This is the gold standard for starter fertilizer application for row crops (corn, cotton, sugar beet). It provides readily available nutrients without seed burn.

Deep Banding: Placing fertilizer (especially P, K, S) 6-12 inches deep, often in fall or before planting, to place it in a moist soil layer for root access later in the season. Common in conservation tillage systems.

Hilling or Hill Placement:

Common in vegetable production (e.g., potatoes, tomatoes). Fertilizer is placed in the hill or mound where the plant is set.

Pocket or Spot Placement:

Used in perennial crops (orchards, vineyards), forestry, or with widely spaced plants. Fertilizer is placed in holes or pits near individual plants.

Fertigation with Solid Dissolvable Fertilizers (Granular/Urea):

Technically not a solid application at the end point, but specialized solid fertilizers are dissolved in water and applied via irrigation systems (drip/sprinkler) for localized liquid delivery.

• High Analysis Granular Fertilizers: MAP (Monoammonium Phosphate), DAP (Diammonium Phosphate), TSP (Triple Superphosphate), Urea, MOP (Muriate of Potash
• Controlled-Release or Slow-Release Fertilizers (CRFs/SRFs): Polymer-coated urea (PCU), sulfur-coated urea (SCU). Ideal for localized placement as they provide a long-term nutrient source in the root zone.
• Micronutrient Granules: Specific formulations of Zn, B, Mn, etc., can be band-applied to correct deficiencies.

• Planter-Mounted Fertilizer Attachments: Modern row-crop planters have dedicated units for precise 2x2 placement.
• Deep Banding Rigs: Toolbars with knifes or shanks that place fertilizer at depth.
• Side-Dress Applicators: Machines that apply fertilizer to the side of established crop rows.
• Manual Tools: Hoes, jab planters, or specialized tools for small-scale or horticultural use.

• Higher Efficiency: Especially for immobile nutrients like Phosphorus (P), Zinc (Zn), and Iron (Fe).
• Reduced Losses: Less exposure to runoff, erosion, and volatilization.
• Lower Fixation: In high-P-fixing soils, banding reduces the soil surface area the fertilizer contacts, minimizing fixation.
• Faster Early Growth: Provides a "starter effect" for seedlings.
• Complements Conservation Tillage: Efficient nutrient placement in no-till/minimum-till systems where mixing is limited.

• Higher Equipment Cost: Requires specialized, often more expensive, application machinery.
• Increased Skill Requirement: Precise calibration and operation are crucial to avoid root damage or inefficient placement.
• Risk of Root Burn: If bands are too concentrated or too close to seeds/roots.
• Potential for Nutrient Stratification: Nutrients remain only in the banded zones, which may not be optimal if root systems do not fully explore them.
• Not Suitable for All Nutrients: Mobile nutrients like Nitrate-N (NO₃⁻) are better managed with split applications or fertigation, as they move with water.

• Know Your Soil: Understand pH, fixation capacity, and nutrient mobility.
• Follow the 4R's:

Right Source: Use fertilizers suitable for banding (e.g., low salt index for seed placement).

Right Rate: Adjust rates based on soil test and placement method (band rates are often 50- 70% of broadcast recommendations for P).

Right Time: Usually at planting for the starter effect.

Right Place: Precise 2x2 placement is generally safer and more effective than seed-placed.

• Calibrate Equipment: Ensure accurate application rates and placement depth/spacing.
• Monitor Salinity: Avoid placing high rates of salts (e.g., KCl, Urea) in direct seed contact.

• Affecting microbial activity. Example: Reduced nitrification of ammonium when applying large tablets of ammonium salts (CULTAN method, see paragraph Mscellaneous Information) or ammonium solutions.
• Stimulating root growth (observed for N and P) or even reducing it (at very high concentrations).
• Reducing the buffering capacity for nutrients with low mobility to such an extent that the solution concentration, and thus the availability of the ions, increases significantly.

• How long the positive effect of localization on physico-chemical and biological processes lasts.
• Whether and for how long the roots in contact with the fertilized soil volume can sustain the supply for the entire plant (keyword: lifespan of a root segment).

• The smaller this volume is, the lower the proportion of roots likely in contact with the nutrient, and the sooner the positive effect should diminish (if found at all, it is typically observed in plants during early development, consistent with the above reasoning).
• If fertilizer cost is not a predominant concern, enriching as large and densely rooted a soil volume as possible is preferable.