Vegetative production of kenaf and canola under irrigation in central California

Kenaf (Hibiscus cannabinus L.) and canola (Brassica napus L.) are potential alternative crops for forage production and phytoremediation adaptable to irrigated agriculture in central California. However, little information is available on the water requirements for growing these crops under irrigated conditions, particularly with regard to increasing their vegetative growth. A 3-year field study was undertaken to evaluate kenaf (cultivars: 7-N, Everglades-41, Tainung-2 and breeding lines: C-531, C-533) and one variety of canola (Westar) for potential cultivation. Kenaf was grown as a spring crop and canola was grown as a fall crop. Plants were irrigated at five different levels, ranging from 368 to 1413 mm for kenaf and from 62 to 359 mm for canola per growing season. For kenaf, shoot and root dry matter (DM) production increased as irrigation was increased incrementally from 25 to 125% crop evapotranspiration (Etc); water application at 150% Etc had no increased benefit. Bark:core ratio of the various kenaf cultivars, however, was unaffected by the level of irrigation. For canola, shoot DM and leaf:stem ratio increased with irrigation up to 125% Et, whereas root DM did not differ significantly among irrigation treatments. Kenaf produced at least twice as much biomass as canola and both crops produced maximum vegetative yields at 100-125% Et-c in central California. (C) 2002 Elsevier Science B.V. All rights reserved.