Effect of Plant and Row Spacing on the Yield and Oil Contents of Castor (Ricinus communis L.) in the Central Rift Valley, Ethiopia

Castor (Ricinus communis L.) is an industrial non edible oilseed adapted to drier areas. An experiment was conducted in the Central Rift Valley of Ethiopia to determine optimum plant population of castor variety Hiruy. Four plant (50, 60, 70 and 80 cm) and four row spacing (60,80,100 and 120 cm) were arranged in factorial combination and RCBD design in three replications. The experiment was carried out for two years at Melkassa and Arsi Negelle in the Central Rift Valley of Ethiopia. The result showed that plant population has no effect on the oil content of Castor. Plant spacing of 60 cm and row spacing of 80 cm resulted in longer main raceme, heavier seed weight and higher seed yield. Therefore, a plant population of about 20 833 plants per hectare or plant and row spacing of 60 x 80 cm can be used for castor production in the Central Rift Valley of Ethiopia for an upper branching variety such as Hiruy. Length of main raceme, capsules per plant and seed weight are the main yield components in castor.

蓖麻（Ricinus communis L.）是一种适生于干旱地区的工业用非食用油料作物。本研究在埃塞俄比亚中部裂谷带开展田间试验，旨在明确蓖麻品种Hiruy的最优种植密度。试验设置4个株距水平（50、60、70、80 cm）与4个行距水平（60、80、100、120 cm）的完全因子组合，并采用随机完全区组设计（Randomized Complete Block Design, RCBD）设置3次重复。试验于埃塞俄比亚中部裂谷带的Melkassa与Arsi Negelle两个试验点开展，为期两年。试验结果表明，种植密度对蓖麻含油率无显著影响。株距60 cm配合行距80 cm的处理组合，可使蓖麻获得更长的主花序、更高的种子粒重以及更优的籽实产量。因此，对于Hiruy这类上部分枝型蓖麻品种，在埃塞俄比亚中部裂谷带开展蓖麻生产时，可采用约20833株/公顷的种植密度，或60 cm×80 cm的株行距配置。主花序长度、单株蒴果数及种子粒重是蓖麻主要的产量构成因子。