About

Precise irrigation planning determines the success of agricultural yield and landscape sustainability. Over-watering leads to nutrient leaching, root rot, and resource waste, while under-watering causes plant stress and reduced growth. Professional growers and landscape managers rely on volumetric calculations derived from evapotranspiration rates to apply the exact amount of water a specific vegetation type requires.

This tool calculates the total water volume required per week by correlating the plot area with the specific water depth requirement (mm/week) of the selected crop or plant. The calculation assumes standard meteorological conditions and provides a baseline for irrigation scheduling. Adjustments for soil type (clay vs. sand), local precipitation, and system efficiency (drip vs. sprinkler) are necessary for final calibration. This data supports efficient water management strategies in both residential gardening and small-scale agriculture.

Formulas

The calculation of irrigation volume relies on the dimensional analysis of area and depth. One millimeter of water depth distributed over one square meter equates to exactly one liter of volume.

V_total = A × d_req × k_unit

Where:

V_total is the total weekly water volume (Liters or Gallons).
A is the surface area of the irrigated zone (m² or ft²).
d_req is the water requirement depth (mm).
k_unit is the conversion factor for input units (if Area is ft², k ≈ 0.0929 to convert to m²).

For gallon output, the conversion is applied:

V_gal = V_liters × 0.264172

Reference Data

Vegetation Category	Specific Plant	Weekly Requirement (mm)	Weekly Requirement (in)	Daily Avg (L/m²)
Turfgrass	Cool Season Grass (Fescue/Rye)	25.0	1.0	3.6
Turfgrass	Warm Season Grass (Bermuda/Zoysia)	20.0	0.8	2.9
Vegetables	Leafy Greens (Lettuce, Spinach)	30.0	1.2	4.3
Vegetables	Fruiting (Tomatoes, Peppers)	45.0	1.8	6.4
Vegetables	Root Crops (Carrots, Beets)	25.0	1.0	3.6
Fruit Trees	Citrus (Orange, Lemon)	35.0	1.4	5.0
Fruit Trees	Stone Fruit (Peach, Plum)	40.0	1.6	5.7
Ornamentals	Roses & Flowering Shrubs	30.0	1.2	4.3
Ornamentals	Native/Drought Tolerant	10.0	0.4	1.4
Ornamentals	Tropical Foliage	40.0	1.6	5.7
Trees	Mature Shade Trees	20.0	0.8	2.9
Succulents	Cacti & Aloe	5.0	0.2	0.7

Frequently Asked Questions

No. The output represents the total water requirement of the plant. If rainfall occurs, subtract the precipitation amount (in mm) from the tool's recommended depth before calculating the supplementary irrigation needed.

The total volume remains constant, but the application frequency changes. Sandy soils drain quickly and require frequent, smaller applications. Clay soils hold water longer but absorb it slowly, requiring infrequent, deep watering cycles to prevent runoff.

Established trees have extensive root systems capable of extracting moisture from a larger soil volume and deeper horizons. Vegetables typically have shallow roots and rapid growth rates, demanding constant moisture availability in the topsoil.

Irrigation systems are not 100% efficient due to evaporation and wind drift. To find the actual amount to pump, divide the calculated volume by the system efficiency (e.g., 0.90 for drip, 0.75 for rotors, 0.60 for spray heads).