Effects of Plant Population on Castorbean Yield¹

Abstract

Plant population effects on yield and growth of irrigated and non‐irrigated castorbeans (Ricinus communis L.) was tested for 3 years. The optimum plant population of irrigated dwarf‐internode castorbeans was about 58,000 plants per ha. Row spacings from 0.5 m to 1.0 m did not significantly affect yields, if plant population was held constant. The optimum plant population for nonirrigated castorbeans was near or higher than the highest population in our tests. It was clearly higher than the current recommendation of 20,000 plants per ha. Linear regression of yield on plant population was significantly different among cultivars and among tests for the nonirrigated castorbeans. Cultivars with bushy growth and small racemes had greater yield depression from low populations than did more erect cultivars with large racemes. Plant population effect on yield was reduced as the yield level of the nonirrigated tests decreased. Low plant population in nonirrigated tests increased plant height, hypocotyl diameter, length of primary raceme, number of racemes per sequential set, and yield of all sets of racemes. Low population reduced height of the primary raceme from the soil. Population had no effect on nodes to the primary raceme. Oil content of the seed or test weight were not affected by plant population of nonirrigated castorbeans.

Productivity of Rainfed Castor as Influenced by Plant Geometry and Nitrogen Levels

“…The variability of micro climate condition of a crop alters the number of spikes plant -1 and variability in the yield. This is in agreement with the earlier findings of Kittock and Williams (1970) in castor. Reduced number of spikes under closer spacing might be due to higher competition for nutrients, space and air between the plants.…”

<b>Optimizing row spacing and plant population arrangement for a new short-height castor genotype in fall-winter

“…Because castor plants with thin stems are favorable for mechanical harvesting (LOPES et al, 2008), our results indicate that the implementation of a high plant population can promotes plants with thinner stems, thus facilitating mechanical harvesting techniques ( Figure 2B). Plant height was not significantly affected by the row spacing and plant population, and the average plant height was 1.15 m. Kittock and Williams (1970) and Bizinoto et al (2010) also found no effect of plant density on the height of castor plants. The effects of plant density on plant height is very complex and depends on both environmental factors and plant architecture.…”

“…Distinct plant arrangements may affect the quality and quantity of the sunlight intercepted by plants. Kittock and Williams (1970) the diameter of castor stems. Bizinoto et al (2010) found that the castor stem diameter decreased in response to an increased plant density.…”

“…Kittock and Williams (1970) observed that, for short-height castor in a 1.02 m row spacing, the best plant population was 58,000 plants ha -1 under irrigation and 30,000 plants ha -1 under rainfed conditions. For the IAC 2028 cultivar, plant populations greater than 25,000 plants ha -1 did not increase the seed yield, regardless of the row spacing used, in the fall-winter cropping season (SOUZA-SCHLICK et al, 2011).…”

Growth performance of castor bean hybrids under different plant densities

“…After 1945, the plant density recommendation has gradually increased based on field observations and technical articles (Kittock & Williams, 1970). Zimmerman (1958) suggested densities of about 30,000 ha -1 plants, while Brigham & Spears (1961) suggested densities between 40,000 and 50,000 ha -1 plants for dwarf cultivars.…”