Assam ASSEB Higher Secondary Skill Subject Agri Engineering Technology cheat sheet

Drawbar power (kW) = draft (kN) × speed (m/s); draft of tillage implements rises with soil resistance, width, and depth.

Tractor PTO power is measured at 540 rpm (or 1000 rpm); belt power is measured at the belt pulley; drawbar power accounts for traction losses.

Wheel slip (%) = [(no-load travel − load travel) / no-load travel] × 100; optimum slip for agricultural tractors is about 10–15%.

Tractor stability: the centre of gravity must stay within the wheelbase; adding front ballast improves stability during rear-mounted implement transport.

Three-point hitch categories: Category I (20–35 hp), Category II (40–90 hp), Category III (80–150 hp); draft and lift capacity increase with category.

Combine harvester losses include header loss, threshing loss, separation loss, and cleaning loss; total loss should remain below 2–3% of grain yield.

Seed drill calibration: seed rate (kg/ha) = [seed collected (kg) × 10,000] / [effective width (m) × distance travelled (m)].

Gear selection affects draft: higher gear increases speed but reduces available drawbar pull; lower gear increases pull and reduces speed.

Moisture content: wet basis = (water mass / total mass) × 100; dry basis = (water mass / dry matter mass) × 100; convert between them using MCdb = MCwb / (100 − MCwb) × 100.

Safe storage moisture: paddy about 13–14% (wb), wheat about 12–13% (wb), maize about 12–13% (wb); above these, mould and insect risk rises sharply.

Drying rate falls in the falling-rate period; the constant-rate period is limited by surface evaporation, the falling-rate period by internal moisture diffusion.

Equilibrium moisture content (EMC) depends on relative humidity and temperature; grain is safe when its moisture equals the EMC at the storage air condition.

Milling: paddy hulling removes husk; pearling removes bran; head rice yield is maximised when paddy is milled at about 14% moisture.

Cold storage for fruits and vegetables: temperature and relative humidity must match the commodity; chilling injury occurs below the safe temperature for tropical produce.

Pasteurisation destroys vegetative pathogens; sterilisation (canning) destroys Clostridium botulinum spores; both depend on time–temperature combinations.

Material handling: bucket elevators for vertical grain movement; belt conveyors for horizontal movement; screw conveyors for short-distance transport of granular material.

Soil loss by water erosion is estimated with the Universal Soil Loss Equation: A = R × K × LS × C × P, where A is soil loss in t/ha/yr.

Contour bunds and graded bunds intercept runoff; the vertical interval between bunds is set by slope and soil erodibility.

Irrigation water requirement = crop evapotranspiration (ETc) − effective rainfall; ETc = ET0 × Kc, where Kc is the crop coefficient.

Duty (ha/cumec) = 8.64 × B / Δ, where B is the base period in days and Δ is the depth of water required in metres; delta is total depth of irrigation water.

Furrow irrigation is suited to row crops; basin irrigation to orchards and paddy; sprinkler and drip systems reduce conveyance and evaporation losses.

Drip irrigation efficiency is about 90–95%, sprinkler about 70–80%, surface irrigation about 40–60%.

Hydraulic conductivity and infiltration rate determine the application rate; applying water faster than the infiltration rate causes runoff.

Water harvesting structures include farm ponds, check dams, percolation tanks, and contour trenches; they store surplus runoff for supplemental irrigation.

Farm building orientation: the long axis should run east–west in hot climates to reduce direct solar gain on the side walls.

Roof pitch and overhang: wider overhangs reduce summer solar gain and protect walls from rain; roof slope must shed rainfall without ponding.

Ventilation rate in livestock houses is controlled by ridge openings, side curtains, and fans; minimum ventilation prevents moisture and ammonia build-up.

Psychrometrics: dry-bulb temperature, wet-bulb temperature, relative humidity, and dew point define the storage or livestock environment.

Grain storage structures: bag storage, bulk storage in silos, and hermetic storage; hermetic storage limits oxygen and controls insects without chemicals.

Concrete for farm structures: mix ratio 1:2:4 (cement:sand:aggregate) for general work; curing for at least 7 days for normal cement concrete.

Floor slope in dairy barns should be about 1 in 40 to 1 in 60 toward the drain to remove wash water and urine.

Cold storage insulation: polyurethane foam and expanded polystyrene are common; insulation thickness is chosen to limit heat gain through walls and roof.

Biogas: anaerobic digestion of cattle dung produces methane-rich gas (about 55–65% CH4); a family-size plant needs about 25 kg dung per day per cubic metre of gas.

Solar photovoltaic panels: output power = irradiance (W/m²) × area (m²) × efficiency; panel output falls with rising cell temperature.

Solar water pumping: the pump flow rate depends on head and panel power; a solar pump is sized for the peak-sun period and total daily water requirement.

Solar drying: cabinet and tunnel dryers use glazed collectors; drying temperature must stay below the crop's heat-damage threshold.

Biomass gasification produces producer gas (CO, H2, CH4) from rice husk, wood chips, and crop residues; gas is used for engines or thermal applications.

Wind energy: power in the wind is proportional to the cube of wind speed and to rotor swept area; wind pumps are used for low-lift water pumping.

Briquettes and pellets from crop residue increase bulk density and improve combustion; moisture content must be low for efficient burning.

Solar greenhouse dryers combine a collector and a drying chamber; forced convection improves uniformity and reduces drying time.

GPS guidance: RTK correction gives centimetre-level accuracy; SBAS or autonomous GPS gives metre-level accuracy.

Variable-rate application (VRA) uses prescription maps based on soil tests, yield maps, or sensor data to vary seed, fertiliser, or pesticide rates.

Yield monitors combine GPS position with flow and moisture sensors; yield maps reveal within-field variability.

Remote sensing: NDVI = (NIR − Red) / (NIR + Red); higher NDVI indicates healthier, denser vegetation.

Soil electrical conductivity (EC) mapping indicates soil texture and salinity variability; it guides zone sampling.

Drones and UAVs with multispectral cameras are used for crop scouting, spraying, and mapping; flight altitude and overlap determine image resolution.

ICT in agriculture includes mobile advisory services, e-market platforms, weather-based advisories, and farm management software.

Precision irrigation uses soil moisture sensors and evapotranspiration data to schedule irrigation only when needed.

Tractor rollover protection structure (ROPS) with a seat belt prevents death in overturns; a tractor without ROPS must not be used on slopes.

PTO safety: the PTO shaft must be guarded; loose clothing must not be worn near rotating shafts; the master shield must be in place.

Noise exposure: prolonged exposure above 85 dB(A) requires hearing protection; tractor cabs should be maintained to reduce noise.

Dust and mould in grain handling can cause respiratory disease; masks and ventilation are required in threshing and milling areas.

Pesticide safety: wear gloves, mask, and protective clothing; observe pre-harvest interval; never eat or smoke during spraying.

Ergonomics: work height should suit the operator; repetitive lifting should be reduced; hand tools should have grip diameter suited to the hand.

Machine guards: all belts, pulleys, chains, and gears must be guarded; guards must not be removed while the machine is running.

First aid for pesticide poisoning: remove the person from exposure, wash contaminated skin, and seek medical help immediately; carry the pesticide label.

Cost of production per unit = total fixed cost + total variable cost divided by total output; break-even output = fixed cost / (price − variable cost per unit).

Gross margin = gross return − variable cost; it is used to compare enterprises without allocating fixed costs.

Working capital is the funds needed for day-to-day operations; it includes seed, fertiliser, labour, and fuel costs.

Marketing channels: direct sale to consumer gives the highest share to the producer; long channels reduce the producer's share.

Value addition: grading, packaging, processing, and branding raise the sale price of farm produce.

Skill practicum: plan the job, select tools, follow safety, complete the task, and record the result; measurement and record-keeping are part of the skill.

Record keeping: keep a farm diary of inputs, operations, and outputs; records support loan applications and enterprise analysis.

Entrepreneurship: identify a market need, prepare a project report with cost, return, and payback period, then arrange finance and implement.