LCA Agriculture/Horticulture cheat sheet

Slope gradient (%) = (rise ÷ run) × 100; run is horizontal distance, not slope length.

Slope length correction: true slope length = horizontal run ÷ cos(arctan(rise/run)).

Aspect: north-facing slopes stay cooler and wetter; south-facing slopes dry faster and warm earlier in spring.

USDA textural class is determined by percent sand, silt, and clay plotted on the soil texture triangle.

Percolation test rate for drainfields is typically expressed as minutes per inch of water-level drop in a test hole.

Depth to seasonal high water table is read from mottling (redoximorphic features) and monitoring wells, not from surface ponding alone.

Solar exposure: full sun ≥6 h direct summer sun, part sun 3–6 h, shade <3 h.

Utility locate before any excavation; hand-dig within the tolerance zone around marked lines.

Soil pH below 6.0 reduces phosphorus availability; above 7.5 reduces iron, manganese, zinc, and boron availability.

Cation exchange capacity (CEC) rises with clay content and organic matter; sandy soils often have CEC under 5 cmol(+)/kg.

Bulk density above roughly 1.6 g/cm³ in loam restricts root growth; compaction layers are found with a penetrometer or spade probe.

Infiltration rate classes: sand >25 mm/h, loam 5–15 mm/h, clay <1 mm/h (order-of-magnitude guidance).

Organic matter amendment: incorporate 5–10 cm compost into the top 15–20 cm; do not exceed ~1/3 compost by volume in planting mixes.

Field capacity vs. wilting point: plant-available water = field capacity − permanent wilting point.

Runoff coefficient rises with slope, compaction, and impervious cover; use it in the rational method Q = CiA.

Test soil before amending; a standard lab test reports pH, buffer pH, P, K, Ca, Mg, and CEC.

Match plants to USDA hardiness zone, AHS heat zone, and site microclimate; zone ratings describe average annual minimum temperature.

Right plant, right place: check mature height and spread, root space, light, soil moisture, and salt/drought tolerance before specifying.

Nursery stock grades (caliper, height, spread, root ball diameter) come from American Standard for Nursery Stock (ANSI Z60.1).

Planting hole: 2–3× the root ball width, no deeper than the root flare; root flare must sit at or slightly above grade.

Water newly planted trees at installation and regularly for the first 1–2 growing seasons; establishment takes roughly one year per 2.5 cm of trunk caliper.

Mulch 5–10 cm deep, pulled back from the trunk; do not mound against bark.

Pruning timing rule: prune spring-flowering shrubs right after bloom; prune summer-flowering shrubs in late winter/early spring.

Structural pruning removes codominant stems and included bark early, when cuts are small and compartmentalization is fast.

Application rate (mm/h) = emitter flow (L/h) ÷ emitter spacing (m) ÷ lateral spacing (m).

Distribution uniformity (DU) = average of the lowest quarter of catch-can readings ÷ overall average; low-quarter DU below ~70% signals maintenance need.

Scheduling: replace evapotranspiration (ET) minus effective rainfall, adjusted by plant factor and irrigation efficiency.

Pressure-compensating emitters maintain rated flow across a wide pressure range (commonly 1–4 bar); line-source drip needs filtration to prevent clogging.

Backflow prevention is required on any irrigation connection to a potable supply; the assembly type depends on hazard level.

Sprinkler head spacing at 50–55% of diameter for head-to-head coverage; matched precipitation rate across a zone prevents wet/dry stripes.

French drain: perforated pipe in washed gravel, filter fabric separating gravel from soil, minimum slope ~1% (10 mm/m).

Dry wells and retention basins must be sized for the design storm and soil infiltration rate; overflow route must be defined.

IPM hierarchy: prevention and cultural controls first, then mechanical/physical, biological, and chemical controls last.

Economic threshold = pest density at which control cost equals crop loss prevented; action threshold triggers treatment.

Scouting: sample representative areas on a fixed schedule; record pest stage, density, and natural enemies.

Weed control: identify lifecycle (annual, biennial, perennial) and growth habit (grass vs. broadleaf) before choosing method; control before seed set.

Pre-emergent herbicides must be applied before weed germination and are ineffective on emerged weeds.

Resistance management: rotate herbicide modes of action (WSSA groups) and integrate non-chemical tactics.

Disease triangle: susceptible host + virulent pathogen + favorable environment; remove any leg to reduce disease.

Read and follow the pesticide label - it is the legal use document; PPE, re-entry interval (REI), and preharvest interval (PHI) are label-specified.

N-P-K on a fertilizer label is percent nitrogen (as N), available phosphate (as P2O5), and soluble potash (as K2O) by weight.

Convert P2O5 to elemental P: P = P2O5 × 0.44; K2O to elemental K: K = K2O × 0.83.

Fertilizer rate: kg nutrient needed ÷ (% nutrient in product ÷ 100) = kg of product.

Apply no more than about 0.5 kg actual N per 100 m² per application on turf to limit leaching and burn risk.

Slow-release and controlled-release N reduce leaching and burn compared with highly soluble sources.

Soil test results drive rates; do not apply phosphorus unless the soil test shows it is needed.

Fertilizer placement: band or incorporate for trees and shrubs; surface broadcast is appropriate for turf and established beds.

Avoid fertilizing near waterways and impervious surfaces; buffer setbacks reduce nutrient runoff.

Base compaction for pavers is typically achieved in lifts of 50–75 mm with a plate compactor; test density against project spec.

Paver base depth depends on traffic: pedestrian ~100 mm compacted aggregate base, vehicular much deeper per engineer.

Slope hardscape away from structures at ~1–2% minimum for drainage; check with a level and straightedge.

Retaining walls above roughly 1 m (or with surcharge/steep backslope) typically require engineered design, geogrid, and drainage.

Wall drainage: granular backfill, filter fabric, and weep holes or perforated pipe prevent hydrostatic pressure buildup.

Edging restraints hold segmental pavers against lateral creep; joints are filled with graded sand, not topsoil.

Concrete: cure time and joint spacing control cracking; control joints at regular intervals and at all corners.

Set grades and elevations from a benchmark; string lines and laser levels verify consistent plane and positive drainage.

Chain saw kickback occurs at the upper tip of the guide bar; chain brake, low-kickback chain, and proper stance reduce risk.

PPE for cutting and spraying: eye/face protection, hearing protection, gloves, and leg protection for saw work.

Two-stroke engines require fuel mixed with oil at the manufacturer's ratio; four-stroke engines use straight gasoline.

Never operate a mower with discharge chute removed or pointed toward people; shut off before clearing jams.

Lockout/tagout and pre-use inspection apply to all powered equipment; remove damaged tools from service.

Ladder rule: 4:1 ratio (1 unit out per 4 units up); maintain three points of contact.

Pesticide mixing: triple-rinse containers, never mix incompatible products, and keep an eyewash and spill kit on site.

Hearing damage risk rises above 85 dBA; typical equipment noise exceeds that, so hearing protection is required.

Estimate = quantity takeoff × unit cost + labor + overhead + profit + contingency.

Labor cost = crew hours × hourly rate × burden factor (payroll taxes, insurance, benefits).

Contingency is typically 5–15% of direct costs, higher for renovation or unknown site conditions.

Change orders must be written and signed before work proceeds; they amend scope, price, and schedule.

Critical path method (CPM) identifies the longest sequence of dependent tasks that sets the project duration.

Contract essentials: parties, scope, price and payment schedule, schedule, change procedure, warranty, and termination terms.

Markup on cost vs. margin on price differ: margin = markup ÷ (1 + markup) when expressed as a fraction.

Retainage commonly holds 5–10% of progress payments until substantial completion and punch-list closeout.

Stormwater permits commonly require erosion and sediment controls, stabilized construction entrances, and inspection records.

Silt fence is installed on the contour with the bottom trenched in; it ponds water and must be maintained.

The Clean Water Act regulates discharges to waters of the United States; state and local rules add requirements.

Pesticide applicator certification is required for restricted-use products; recordkeeping includes product, rate, date, location, and applicator.

Endangered Species Act and local tree ordinances can restrict removal, pruning, and work windows.

Buffer setbacks along waterways and wetlands reduce nutrient, sediment, and pesticide movement.

Spill prevention: store fuels and chemicals on secondary containment; report releases per regulatory thresholds.

Invasive species prevention: clean equipment between sites and avoid moving soil or plant debris that spreads pests.