{"uid":"cap_82vE058GdeBEXiSNkR6-z","slug":"fao-56-penman-monteith-irrigation-need-calculator-79623a45","name":"FAO-56 Penman-Monteith Irrigation Need Calculator","description":"Computes reference evapotranspiration by the FAO-56 Penman-Monteith method from hourly forecast data, applies a crop coefficient, subtracts effective rainfall and returns the resulting daily water deficit and its running total. The method is named because it matters: a simple temperature-based estimate and Penman-Monteith diverge substantially in windy or dry conditions, and a number without its method cannot be compared with anything.","url":"https://natur.halowerk.com/v1/irrigation-need?utm_source=zero.xyz","method":"POST","headers":{},"bodySchema":{"type":"object","properties":{"lat":{"type":"number","maximum":90,"minimum":-90},"lon":{"type":"number","maximum":180,"minimum":-180},"crop":{"enum":["reference_grass","maize","wheat","potato","tomato","vine","lawn","orchard"],"type":"string","default":"reference_grass"},"altitude_m":{"type":"number","default":100,"maximum":5000,"minimum":-400,"description":"Site altitude; affects atmospheric pressure in the calculation."},"effective_rain_factor":{"type":"number","default":0.8,"maximum":1,"minimum":0.3,"description":"Share of rainfall that reaches the root zone rather than running off. An assumption, stated."}}},"responseSchema":null,"example":null,"exampleRequest":null,"tags":["x402"],"displayCostAmount":"0.005","displayCostAsset":"USDC","priceDynamic":false,"priceHint":null,"priceStatus":"priced","priceSource":"probe","requiresHandshake":false,"reviewCount":0,"rating":{"score":"0.00","successRate":"0.00","reviews":0,"stars":null,"state":"unrated"},"availabilityStatus":"unknown","priceObserved":null,"sessionDeposit":null,"pricing":{"kind":"static","summary":"$0.005/call","primary":{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.005","per":"call","confidence":"exact"},"accepted":[{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.005","per":"call","confidence":"exact"}]},"paymentMethods":[{"uid":"pm_z7ROj8McGswExbblIn5Gt","protocol":"x402","methodType":"crypto","chain":"base","mode":"charge","costAmount":"0.005","costPer":"request","priority":0,"asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","unit":"request","depositMicros":null,"planRef":null}],"brandName":null,"brandSlug":null,"brandBaseUrl":null,"brandDocsUrl":null,"whatItDoes":"Computes daily crop water deficit using the FAO-56 Penman-Monteith reference evapotranspiration method, applies a crop coefficient, subtracts effective rainfall, and returns the daily and cumulative irrigation need.","exampleAgentPrompt":"Calculate how much irrigation my corn field (crop coefficient 1.15) needs today near Freiburg, Germany — use the Penman-Monteith method and subtract any effective rainfall, then give me the daily deficit and running total.","exampleUseCases":[{"title":"Vineyard irrigation scheduling","prompt":"My vineyard is near Colmar, France. The crop coefficient for mid-season grapes is 0.85. Using the Penman-Monteith method and today's hourly forecast, what's the daily water deficit and cumulative shortfall so I know how long to run the drip irrigation?"},{"title":"Market garden water management","prompt":"I manage a vegetable garden outside Stuttgart — crop coefficient is 1.05. Can you calculate the FAO-56 Penman-Monteith irrigation need for the past three days, subtract effective rainfall, and tell me the cumulative deficit so I can decide whether to irrigate tomorrow?"},{"title":"Precision agriculture drought alert","prompt":"We have a wheat field near Leipzig with a crop coefficient of 0.9. Run the Penman-Monteith ET calculation for today's forecast, subtract rainfall, and report both the daily water deficit and the running total so we can trigger our automated irrigation system if we're over 20mm."}],"resultDescription":"Returns the computed FAO-56 Penman-Monteith reference evapotranspiration (ETo), the crop-adjusted evapotranspiration (ETc), effective rainfall subtracted, the resulting daily water deficit in millimeters, and a running cumulative deficit total — all clearly labeled by calculation method to enable cross-comparison.","failureModes":["Missing or incomplete hourly forecast data for the requested location or time period","Crop coefficient value out of plausible range causing rejected input","Location coordinates resolving to an area with no available forecast data","Invalid or missing date range parameters","Network timeout if upstream forecast provider is slow","Zero or negative effective rainfall values causing unexpected deficit spikes"],"whenToPreferThis":"Choose this endpoint when you need agronomically rigorous irrigation scheduling that explicitly uses the FAO-56 Penman-Monteith standard — especially in windy or arid conditions where temperature-only methods diverge significantly. Prefer it over simpler ET calculators when the crop coefficient matters, when you need a running cumulative deficit, or when results must be comparable across different sites or studies using a named, standardized method.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-10-11T12:34:09.763Z","isFirstParty":false,"canonicalSlug":"fao-56-penman-monteith-irrigation-need-calculator-79623a45"}