Tropical and Subtropical Agroecosystems 26 (2023): #075 Njuguna et al., 2023 1 WATER USE EFFICIENCY OF TARO ( Colocasia esculenta) UNDER VARYING WATERING REGIMES AND PLANTING DENSITIES IN EMBU, KENYA † [EFICIENCIA EN EL USO DEL AGUA DEL TARO ( Colocasia esculenta) BAJO VARIOS REGÍMENES DE RIEGO Y DENSIDADES DE PLANTACIÓN EN EMBU, KENIA] Joyce Wambui Njuguna 1* , Anne N. Karuma 1 , and Patrick Gicheru 2 1 Department of Land Resource Management and Agricultural Technology, University of Nairobi. P.O BOX 29053 - 00625, Nairobi, Kenya. 2 Kenya Agricultural and Livestock Research Organization, P.O BOX 27 - 60100, Embu, Kenya. Email*: joycenjuguna20@gmail.com *Corresponding author SUMMARY Background. Taro (Colocasia esculenta) can be grown in a variety of environmental and edaphic conditions, but it is most typically grown in wetlands. The optimal conditions for its growth are two water regimes i.e., waterlogged or flooded conditions to dryland or unflooded conditions. An important criterion in crop yield is water use efficiency (WUE), and it has been suggested that crop production per unit of water used can be increased. Objectives. To determine the WUE of taro in Kenya’s sub-humid environment under different watering regimes and planting densities. Methodology. A study was conducted at the Kenya Agricultural and Livestock Research Organization (KALRO) – Embu Research Centre, during the long rains (LR) 2021, short rains (SR) 2021/2022, and long rains (LR) 2022. A factorial experiment with a split-plot layout arranged in a completely randomized block design was used. The main factor was the irrigation levels while the sub-factor was the planting density, with three replications. The three irrigation levels were at 100 %, 60 %, and 30 % based on the field capacity (FC). The planting densities used were 0.5m × 0.5m (40,000 plants ha -1 ), 1m × 0.5m (20,000 plants ha -1 ), and 1m × 1m (10,000 plants ha -1 ), representative of high, medium, and low planting densities respectively. Results. The WUE was influenced by season and watering regime (P < 0.05). The 30% FC had the highest WUE with the 100 % FC having the lowest. The high WUE under 30 % FC (19.40 kg ha - 1 mm -1 ) was associated with the high biomass (1.97 kg) and low water use (2269.41 mm) recorded under limited water conditions. The medium (1m × 0.5m) planting density attained the highest WUE (12.16 kg ha -1 mm -1 ) with the high planting density (0.5m × 0.5m) having the lowest (10.65 kg ha -1 mm -1 ), though no significant differences were recorded. Implications. The varying watering regimes and planting densities in this study have different capacities to utilize the supplied water. The total taro biomass increased with decrease in water supplied and in turn maximized the water use efficiency. Conclusion. To achieve the highest yield per unit of water consumed, a watering regime of 30 % FC and a planting density of 1 m × 0.5 m (20,000 plants ha -1 ) is recommended. Key words: water use efficiency; irrigation; planting density; yields. RESUMEN Antecedentes. La malanga (Colocasia esculenta) se puede cultivar en una variedad de condiciones ambientales y edáficas, pero generalmente se cultiva en humedales. Las condiciones óptimas para su crecimiento son dos regímenes de agua, es decir, condiciones anegadas o inundadas o condiciones de tierras secas o no inundadas. Un criterio importante en el rendimiento de los cultivos es la eficiencia en el uso del agua (WUE), y se ha sugerido que se puede aumentar la producción de cultivos por unidad de agua utilizada. Objetivos. Determinar la WUE del taro en el ambiente subhúmedo de Kenia bajo diferentes regímenes de riego y densidades de plantación. Metodología. Se realizó un estudio en la Organización de Investigación Agrícola y Ganadera de Kenia (KALRO) - Centro de Investigación Embu, durante las lluvias largas (LR) 2021, lluvias cortas (SR) 2021/2022 y lluvias largas (LR) 2022. Se realizó un experimento factorial con arreglo de parcelas divididas en un diseño de bloques completamente al azar. El factor principal fueron los niveles de riego mientras que el subfactor fue la densidad de siembra, con tres repeticiones. Los tres niveles de riego fueron al 100 %, 60 % y 30 % de la capacidad de campo (FC). Las densidades de siembra utilizadas fueron 0.5m × 0.5m (40,000 plantas ha -1 ), 1m × 0.5m (20,000 plantas ha -1 ), y 1m × 1m (10,000 plantas ha -1 ), † Submitted March 22, 2023 – Accepted May 16, 2023. http://doi.org/10.56369/tsaes.4847 Copyright © the authors. Work licensed under a CC-BY 4.0 License. https://creativecommons.org/licenses/by/4.0/ ISSN: 1870-0462. Authors ORCID = Joyce Wambui Njuguna: http://orcid.org/0000-0002-6583-6058; Anne N. Karuma: http://orcid.org/0000-0002-4497-2173