Tropentag, October 9 - 11, 2007 in Witzenhausen "Utilisation of diversity in land use systems: Sustainable and organic approaches to meet human needs"

Leaf Gas Exchange and Growth Response of Juvenile 'Valencia' Orange to Dry Season Irrigation in Southwestern Nigeria

¹University of Agriculture, Research and Development Centre, Nigeria
²University of Agriculture, Department of Horticulture, Nigeria

Abstract

In August 2006 at Abeokuta southwestern Nigeria, 18-month old budded seedlings of ‘Valencia' sweet orange (Citrus sinensis L. Osbeck) on Cleopatra mandarin (Citrus reticulata) rootstock were transplanted 3.5m apart. Between January and April 2007 which corresponded to the dry season, the seedlings were irrigated with 7.5, 30 and 60 l water/plant/week. The aim was to determine if juvenile sweet orange plants responded to dry season irrigation, the critical volume of water for growth and by which mechanism irrigation exerted its influence on vegetative growth. Local farmers do not irrigate their juvenile citrus plants during the dry season. Effects of dry season irrigation on photosynthesis and transpiration were determined using the CIRAS^-1 leaf gas exchange metre in the morning (9-10am), afternoon (1-2pm) and evening (5-6pm). Growth was determined using measurements of plant height, number of leaves and leaf area of citrus plants taken at 2-week intervals. Application of 30 l water/ week enhanced photosynthesis of citrus in the morning, afternoon and evening, while 7.5 and 60 l water /week decreased it. Conversely, application of 7.5 l water/plant/week significantly decreased morning afternoon and evening transpiration while application of 30 or 60Lwater /plant/week enhanced it. Compared with application of 7.5 l water/plant/week, application of 30 l water/plant/week significantly increased plant height and leaf area but 60 l water/plant/week decreased it. Effect of irrigation on number of leaves was not significant. Irrigation influenced the growth of citrus by influencing photosynthesis. Irrigation cycles of 7.5 l water/plant/week induced water stress while 60 l water/week/plant induced water logging conditions. Water stress and water logging impaired photosynthesis and growth of citrus. Irrigation with 30 l water /week/plant is considered critical for optimum photosynthesis and vegetative growth of juvenile sweet orange seedlings during the dry season. The application of 30 l water/week/plant is recommended to citrus growers in southwestern Nigeria

Keywords: Citrus, irrigation, water stress

Contact Address: Isaac Aiyelaagbe, University of Agriculture, Research and Development Centre, Alabata Road, 110001 Abeokuta, Nigeria, e-mail: ola_olu57yahoo.com