Water
Water stress in cotton, wheat and maize
Water stress happens when a crop cannot get enough water from the soil: leaves wilt, growth slows and yield is lost. It is the most widespread risk of irrigated farming in Central Asia. Losses range from 10% to complete crop failure – cotton sheds squares and bolls, wheat fills shrivelled grain.
Crops: Cotton, Wheat, Maize, Rice, Vegetables, Potato, Melons
When it is dangerous
It matters all season, with the peak at flowering and grain fill. The most sensitive stage is budding and flowering: lost bolls and grains cannot be recovered, and during grain fill stress cuts grain weight and fibre quality. On irrigated land the risk rises when water delivery fails, downstream supply runs short or the irrigation season ends.
Causes
- A long dry spell with rainfall below the seasonal norm
- A missed irrigation because a pump or equipment failed
- Irrigation running behind schedule
- Not enough water in the canal, or downstream withdrawal limits
- Heat and dry air sharply raising evaporation
Signs on the field
- Leaves wilt and droop during the day
- Leaf blades curl
- The crop looks dull and yellows early
- Growth slows down
- Cotton sheds squares and bolls
How ClusterOS notices it
ClusterOS reads optical Sentinel-2 images: the NDMI index tracks water in the leaves and NDVI tracks how green the field is. Both are compared with the same field's past seasons since 2019, while weather data shows how long it has been dry and how hot it is. The earliest stage – leaves heating up – is only visible in the thermal range, so stress is usually caught once leaf water has already dropped, and in spring clouds allow a clear image only every 10–20 days. Salinity, nitrogen shortage and hot dry wind look similar; we separate them using weather, soil moisture and your irrigation records.
What to do
- Check irrigation and soil moisture on the ground
- If confirmed, adjust the irrigation schedule
- Log irrigations and water supply interruptions – this makes the assessment more accurate
- If plants wilt while the soil is wet, test the soil for salts to rule out salinity
Questions
How can I tell that cotton is short of water?
The first visible signs are leaves that droop and curl during the day, a dull-looking crop and slower growth. Later the plants shed squares and bolls. If plants wilt while the soil is wet, salinity may be the cause rather than lack of water.
Why doesn't the satellite see water stress right away?
First the plant closes its stomata and the leaves warm up, which only thermal imagery can see. Optical images show the next step, when leaf water has already dropped, and the loss of green comes later still. That is why irrigation records and field checks still matter.
Learn about this risk on your fields before it becomes a loss
We will show ClusterOS on your own fields: history since 2019, crop stage and all 24 risks.
Other risks in «Water»
Scientific basis
- Berger K. et al. 2022, Remote Sensing of Environment 280:113198, DOI: 10.1016/j.rse.2022.113198
- Gao B.-C. 1996, Remote Sensing of Environment 58:257–266, DOI: 10.1016/S0034-4257(96)00067-3
- Idso S.B. et al. 1981, Agricultural Meteorology 24:45–55, DOI: 10.1016/0002-1571(81)90032-7
- Sommer R. et al. 2013, Agriculture, Ecosystems & Environment 178:78–99, DOI: 10.1016/j.agee.2013.06.011