Optimal planting densities have not been established for vegetable cowpeas [Vigna unguiculata (L.) Walp.] with different bush-type growth habits. The dynamics of pod production and snap-pod yields of contrasting bush-type vegetable-cowpea cultivars were investigated under different plant densities during the summers of 1985 and 1986 at the University of California, Riverside. A split-split plot experimental design was used, with cultivars as mainplots and plant densities as subplots. In 1985 three cultivars, UCR193, UCR206, and Snapea were used, while in 1986 only UCR193 and UCR206 were used. In both years the cultivars were planted at densities of 100, 133, 200 and 400 thousand plants ha-1 (tph), achieved by varying row width from 100 to 25 cm, with a constant spacing between plants in the rows of 10 cm. Total yields of fresh pods by UCR193 progressively increased with increasing plant density up to 400 tph, whereas pod yield of UCR206 was not influenced by plant density. Pod yields were significantly greater for UCR193 than UCR206 at the highest density of 400 tph, but were similar at the lowest density of 100 tph. UCR193 is more compact, and has a more open canopy and began flowering earlier than UCR206. Average pod yield of the current U.S. cultivar, Snapea, which had a more viney canopy, was 84 and 71% less than UCR193 or UCR206, respectively. Picking pods at the 'snap' stage delayed plant senescence and stimulated pod production in UCR193, but suppressed pod production in UCR206. This was attributed to picking-induced damage of raceme growth and pod-set processes in UCR206, but not in UCR193. High levels of pod production by vegetable cowpeas were achieved by using extremely high plant densities and a bush-type variety that is adapted to high densities. Also, this cultivar had the physiological capacity to tolerate the physical injury and disturbance of sink/source balance associated with frequent harvesting of snap pods. © 1990.
