Leaf wetness duration (LWD) records how long free water remains on a canopy during and after rain, irrigation, or dew. Interpret it with the wet-state method, sensing location, and logger output. LWD varies across a crop area and within one plant, so one sensing surface is not a whole-greenhouse condition. UF/IFAS, “Leaf Wetness Sensor Installation and Maintenance”
Measurement, proxy, or estimate?
An electronic sensor responds to wetness on its sensing surface. It is therefore a proxy for a leaf, not a direct measurement of every leaf.
Relative humidity can estimate wetness for a defined application, but it is a different method. Purpose, useful range, and RH accuracy affect the estimate. Label direct surface sensing and RH-based estimation separately before comparing values. UF/IFAS, “Your Farm Weather Station”
Read processed minutes and raw output separately
For a reported wet-duration column, identify the wet/dry classification rule, the interval covered by each value and how gaps are represented. Confirm whether the value is an interval duration, a cumulative total or another output before adding records.
A raw sensor reading and a duration are different quantities. Keep their units and column definitions with the export. Only combine duration intervals when their time windows and definitions are compatible; overlapping or missing intervals need separate treatment.
Build a comparable record
Before comparing two durations, preserve these fields:
| Field | Question to answer |
| Location and crop context | Where was the sensing surface, and which crop zone did it represent? |
| Sensor and method | Which model or method, wet/dry rule, or processed column produced the classification? |
| Observation window | What interval does the reported value cover, and are intervals aligned? |
| Output meaning | Is this processed wet minutes, a raw end reading, or an RH-based estimate? |
| Coverage and gaps | Which periods were observed, and which are missing or unknown? |
These fields make records easier to interpret; they do not make unlike methods equivalent. A missing interval is unknown, not proof of dryness. Keep valid coverage and missing periods visible when handing the record to the monitoring or crop lead. For generic logging and time context, see smart greenhouse climate control.
Use the record with its limits
For broader humidity context, see humidity control in greenhouses. For agricultural context, see Yakeclimate agriculture applications. This page does not set disease hours, installation rules, or equipment decisions.
Sources
- UF/IFAS, “How to Avoid Common Problems with Leaf Wetness Sensor Installation and Maintenance”
- UF/IFAS, “Your Farm Weather Station: Installation and Maintenance Guidelines”
Related technical reading
Disease interpretation depends on the crop and pathogen, not wet duration alone. Read Botrytis infection routes, powdery mildew without visibly wet leaves and crop-specific downy mildew conditions separately. The cloudy-weather Botrytis guide explains the limits of using weather as a warning.
