Result

The crop coefficients built in here are general reference values for a well-watered crop under standard conditions, and real coefficients shift with variety, planting density, climate, soil evaporation and management, so a locally derived value should always take priority. Reference evapotranspiration is the dominant term in the whole calculation, which is why a measured figure from a nearby weather station matters far more than any refinement elsewhere. Effective rainfall is genuinely hard to pin down because it depends on rainfall intensity, soil infiltration rate, slope and how dry the profile already was, so the fraction here is an approximation rather than a measurement. Application efficiency similarly varies with system design, maintenance, wind and operator practice, and a poorly maintained drip system can easily underperform a well-run sprinkler. Stage durations in the season table are typical values and shift with sowing date and climate. Salinity leaching requirements, deep percolation for salt management and any regulatory allocation limits are outside the scope of this calculation and can add materially to the water actually needed.