Last reviewed 1 Oct 2026 · 9 min read
Fertiliser application
Methods
| Method | Description | Remarks |
|---|---|---|
| Broadcasting | Spreading fertiliser uniformly over the field, before sowing or as a top-dressing | Fast; less efficient (fertiliser also feeds weeds; losses) |
| Band (row) placement | Placing the fertiliser in a band beside and below the seed (about 5 cm to the side, 5 cm below) | Best use of P and K; avoids seed burn |
| Drilling with the seed (combined drill) | Fertiliser box on a seed drill | One pass; good for P |
| Side dressing / top dressing | Fertiliser placed beside growing plants (N for maize, sugarcane, cotton) | Uses inter-row fertiliser applicators |
| Deep placement | Putting N (urea briquettes) in the reduced soil layer in rice | Reduces N loss |
| Foliar application | Spraying a nutrient solution on leaves | Micronutrients, quick correction |
| Fertigation | Dissolved fertiliser through irrigation (drip or sprinkler) | Precise, water efficient |
| Liquid / anhydrous ammonia injection | Injector tines place liquid fertiliser into the soil | Large farms |
Fertiliser distributors (spreaders)
| Machine | Principle | Notes |
|---|---|---|
| Centrifugal (spinner) spreader | A rotating disc with vanes throws the granules; gravity feed from the hopper | Wide swath (6–24 m); non-uniform pattern — overlap needed; affected by granule size, wind |
| Gravity (drop) spreader | Fertiliser falls through slots at the bottom of a hopper over the width | Accurate placement, narrow width |
| Pendulum spreader | An oscillating tube | Even spread |
| Pneumatic spreaders | Air carries fertiliser to booms | Large scale |
| Row-crop fertiliser applicator (side-dresser) | Metering units feed placement tubes alongside crop rows; disc or tyne openers | N, P, K for row crops |
| Fertiliser drill (combined) | Runs with a seed drill | |
| Liquid applicators | Pump, tank, nozzles or injection tines; pressure-controlled flow | Urea ammonium nitrate (UAN), liquid fertilisers |
| Slurry tankers and manure spreaders | Spread farmyard manure or slurry | Organic nutrients |
Metering mechanisms
Star wheel, fluted rollers, belt, rotary vane, auger, and agitator in the fertiliser box; the rate is adjusted by gate opening and speed (sprocket ratio). Corrosion resistance is essential (fertiliser salts) — plastic, stainless steel or coated metal; wash after use.
A row-crop applicator with 4 rows spaced 0.75 m ( m) has a ground wheel of 0.6 m diameter. In 10 revolutions (18.85 m) the metering units deliver 1.10 kg of fertiliser.
Area covered ; rate . To obtain 150 kg/ha the feed gate is closed slightly (rate × 150/194.5) and the test repeated.
Plant protection equipment
Objectives
To apply pesticides (insecticides, fungicides, herbicides, acaricides) efficiently — target coverage, minimum drift and waste, operator safety.
Types of formulations
Liquids (emulsifiable concentrates, wettable powders, soluble liquids) are diluted in water; dusts and granules are applied dry; fumigants are gases.
Sprayers
A sprayer breaks the liquid into droplets and projects them on the target.
Components
| Component | Function |
|---|---|
| Tank (reservoir) | Holds the spray liquid; corrosion resistant; with strainer at filling |
| Pump | Develops pressure — piston, plunger, diaphragm, centrifugal, gear or roller types |
| Pressure chamber (air chamber) | Smooths pressure fluctuations |
| Pressure regulator / relief valve | Keeps the set pressure and bypasses excess flow |
| Agitator (mechanical or hydraulic) | Keeps suspensions (wettable powders) mixed |
| Hose, lance, boom | Carry liquid to the nozzles |
| Nozzle | Atomises the liquid into droplets, controls flow rate, droplet size and spray pattern |
| Filters / strainers | Protect the nozzles from blocking |
| Shut-off and control valves | Control flow |
Types of sprayers
| Type | Description | Capacity and use |
|---|---|---|
| Hand-operated compression sprayer | The tank is pressurised by a hand pump (up to 3–4 bar) before spraying | Small areas, 0.5–1 L/min; domestic and gardens |
| Knapsack (lever-operated) sprayer | Back-carried, tank of 10–20 L; a lever-driven plunger or diaphragm pump gives pressure up to 3–7 bar while spraying | Field crops, vegetables; 0.5–1.5 ha/day; the most common in India |
| Foot sprayer / rocker sprayer | Operated by foot; for taller crops, orchards (up to 15–20 bar pressure with a rocker pump) | |
| Power knapsack sprayer | Small petrol engine drives the pump; up to 30 bar; some with air-assisted/mist blower (mist blowers produce fine droplets with a high-speed air stream) | Orchards, plantation crops; 1–2 ha/h |
| Tractor-mounted (boom) sprayer | Pump driven by the PTO, tank 200–1000 L, boom 6–15 m with nozzles every 50 cm | Field crops, herbicides; 4–8 ha/h; pressure 2–5 bar |
| Orchard (air-blast) sprayer | A PTO-driven axial fan blows air with the spray through an outlet; fine droplets reach tall trees | Orchards, vineyards; high capacity |
| Self-propelled (high-clearance) sprayers | Large-scale | |
| Aerial (aircraft) sprayers and drones | Ultra-low volume (ULV); drones carry 5–20 L and cover about 1 ha in 10–20 minutes | Large or difficult terrain; strict regulation and a trained pilot |
| Electrostatic sprayers | Droplets are given an electric charge and are attracted to the plant surface (better deposition, less drift) | Special |
| Controlled-droplet applicators (CDA), ULV | Spinning-disc atomiser gives uniform droplets; 1–5 L/ha of undiluted formulation | Cotton, pasture; low water use |
Nozzles
| Nozzle | Pattern | Use |
|---|---|---|
| Hollow cone | A ring-shaped cone of fine droplets | Insecticides and fungicides on foliage (good coverage) |
| Full cone | Full solid cone | Herbicides, soil applications |
| Flat fan | A flat fan-shaped sheet | Boom sprayers for herbicides and broad coverage |
| Even flat fan | Uniform across the width | Band spraying |
| Flood nozzle | Wide, coarse | Liquid fertiliser |
| Air-induction (low-drift) | Large air-filled droplets | Reduced drift |
| Twin-fluid, pneumatic (air atomisation) | Air breaks the liquid | Fine mists |
- Nozzle discharge — it is proportional to the square root of the pressure: doubling the flow rate needs four times the pressure. A worn nozzle gives a higher flow and bad pattern.
- Droplet size — decreases with higher pressure, a smaller orifice, and greater cone angle; classified (by VMD, volume median diameter): very fine (< 100 µm), fine (100–175), medium (175–250), coarse (> 250). Fine droplets give good coverage but drift; coarse droplets reduce drift but cover less.
Application rates
| Volume class | L/ha | Typical use |
|---|---|---|
| High volume (HV) | > 600 | Fruit trees, field crops with the lever knapsack (up to 500–1000 L/ha) |
| Low volume (LV) | 50–200 | Boom sprayers, field crops |
| Very low / ultra-low volume (ULV) | < 5 | Cotton, aerial, CDA |
Calibration of a boom or knapsack sprayer
The application rate (volume rate) is:
where is the discharge per nozzle (L/min), the forward speed (km/h) and the nozzle spacing (m) (for a boom). The constant 600 is a unit conversion ().
A tractor boom has nozzles at 0.5 m spacing, each delivering 0.80 L/min at 3 bar. The tractor travels at 5 km/h.
. To halve the rate one would change the speed (doubling it to 10 km/h) or choose smaller nozzles (flow ∝ √pressure means a pressure of one quarter would halve the flow, not recommended because it changes the droplet size).
For a pesticide dose of 1.5 kg active ingredient per hectare with a formulation of 50 % a.i., the product needed is kg/ha; mixed in 192 L of water, the tank concentration is .
Knapsack sprayer calibration
Spray a measured area (for example 100 m²) with the water at the normal walking speed and pressure, measure the volume used, and compute L/ha; then calculate the pesticide per tank: