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.
The PHYTOS31 manual cautions that response may differ from leaves with different hairiness or waxiness. Keep the model and method with the record; do not relabel a surface response as plant-wide wetness. PHYTOS31 Manual, §3.3
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
The PHYTOS31 manual gives a METER example. In this format, the logger reads each minute, evaluates wetness during a wake interval, and reports minutes classified wet in that interval. Add intervals for cumulative duration.
The export also contains a final raw reading: the last sensor output, not accumulated wet minutes. Read the column definition before comparing, and add intervals only under the same duration definition. These meanings apply to this PHYTOS31 METER format, not every export. PHYTOS31 Manual, §2.3.1
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.
