Digital photography applied to irrigation management of Little Gem lettuce

• Calibrated image-based methodology for estimating Kc in lettuce crops.
• Digital photography applied to water balance in root zone of a lettuce crop.
• Optimum irrigation management applied to a lettuce crop.

The fundamental principle of adequate irrigation management is to satisfy crop water requirements while optimizing agronomic profits with the lowest possible consumption of water. Based on this idea, new techniques have been incorporated into different irrigation scheduling approaches. Among these techniques, computer processing of digital photographs of vegetation cover has given researchers an opportunity to obtain the crop development parameters that are used to estimate water requirements. The fraction of ground cover, which is obtained by applying classification techniques to digital photographs, is a useful parameter for determining crop water requirements based on the FAO-56 methodology because it is directly related to a crop coefficient. In this research, irrigation scheduling based on the water balance of a ‘Little Gem’ lettuce crop was carried out using digital photography to estimate water requirements using a crop coefficient. The results were compared with the actual irrigation management of a test plot, which was monitored using soil moisture probes to analyse management deficiencies and to quantify excess irrigation. In sum, a 6.93% increase in production and a 17.80% reduction in water consumption compared to the reference plot were achieved.