Revisiting the crop coefficient–reference evapotranspiration procedure for improving irrigation management

• Published in: Theoretical and applied climatology 2019-11, Vol.138 (3-4), p.1785-1793
• Main Authors: Marin, Fábio R., Angelocci, Luiz R., Nassif, Daniel S. P., Vianna, Murilo S., Pilau, Felipe G., da Silva, Evandro H. F. M., Sobenko, Luiz R., Gonçalves, Alexandre O., Pereira, Rodolfo A. A., Carvalho, Kassio S.
• Format: Article
• Language: English
• Subjects: Adaptation; Aquatic Pollution; Atmospheric Protection/Air Quality Control/Air Pollution; Atmospheric Sciences; Cereal crops; Citrus; Citrus fruits; Climate science; Climatology; Consumptive use; Crop development; Cropping systems; Crops; Developmental stages; Earth and Environmental Science; Earth Sciences; Evapotranspiration; Glycine max; Irrigation; Original Paper; Potatoes; Soybean; Soybeans; Waste Water Technology; Water Management; Water Pollution Control; Water use; Wheat
• ISSN: 0177-798X; 1434-4483
• DOI: 10.1007/s00704-019-02940-7

The consumptive use of water by irrigated crops is typically quantified using the crop coefficient–reference evapotranspiration ( K c – ET o ) procedure; yet, recent results showed that K c might change with ET o , in response to high atmospheric demand. It is not known if the reduced K c at high ET o applies to other crops with different aerodynamic features of the canopies. This paper seeks to provide the K c values for soybean, wheat and potato, and propose an adaptation to the K c – ET o procedure, hypothesising that the inverse relation between K c and ET o would be general for all types of crops. Our results showed average K c values of 0.90, 1.18 and 1.28, respectively, for soybean, wheat and potato cropping systems in the Brazilian cropping systems. However, K c decreased as ET o increased, for all crops considered in this study, because of the increase of internal plant resistances to vapour diffusion from the leaves to the atmosphere. When ET o was above > 4 mm d −1 , the water use by such crops was lower than that prescribed by Allen et al. (JAMA, 1998). The time-based K c curves in Allen et al. (JAMA, 1998) are inappropriate for the studied crops under high demanding conditions and, besides the considerations suggested by Allen et al. (JAMA, 1998) (i.e., crop development stage, presence or absence of weeds), K c recommendations for practical irrigation management should be based on the average ET o values of the previous days of the irrigation procedure.