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Seed flavonoid concentration in cowpea genotypes and the effect of plant density on growth, N₂ fixation and rhizosphere phosphatases and grain yield of cowpea intercropped with sorghum
Author(s)
Makoi, Joachim HJR
Date Issued
2009
Type
Thesis
Publisher
Cape Peninsula University of Technology
Abstract
A 3-factorial experiment involving two cowpea densities (83,000 and 167,000 plants.ha-1), two cropping
systems (i.e. monoculture and mixed culture) and five cowpea genotypes (i.e. three farmer-selected
cultivars, Bensogla, Sanzie and Omondaw and two improved varieties, ITH98-46 and TVu1509) was
conducted in the field for two consecutive years in 2005 and 2006. The aim was to assess the effect of
plant density, cropping system and cowpea genotypes on: (i) chlorophyll and gas-exchange, (ii)
rhizosphere mineral concentration and tissue uptake of nutrients, (iii) acid and alkaline phosphatase
activities in the rhizosphere, (iv) plant growth and symbiotic performance, and (v) concentration of
flavonoids and anthocyanins in seed extracts and plant organs and their effect on pest infestation and
diseases.
The results showed that high plant density (167,000 plants.ha-1) and mixed culture significantly decreased
gas-exchange parameters, leaf chlorophyll content, 13C and %C in both cowpea and sorghum plants
compared with low plant density (83,000 plants.ha-1) and monoculture. The data also showed significantly
higher 13C and lower %C in ITH98-46 and TVu1509 compared with Bensogla, Omondaw and Sanzie
genotypes with a significant correlation between 13C and water-use efficiency. At harvest, grain yield of
cowpea and sorghum was significantly decreased by high plant density and mixed culture compared with
low plant density and monoculture. Sanzie genotype was generally superior in grain yield (2,550 kg.ha-1)
followed by cvs. Omondaw and Bensogla (2,250 and 2,150 kg.ha-1, respectively) compared with the
improved cultivars. Sorghum plants in mixture with cv. TVu1509 or cv. ITH98-46 performed better
(1,570 and 1,550 kg.ha-1, respectively) compared with those in mixture with other cultivars. The results
also showed greater land equivalent ratio (LER = 1.42 to 1.52), suggesting that mixed culture produced
greater total yields per unit land area compared with monoculture.
systems (i.e. monoculture and mixed culture) and five cowpea genotypes (i.e. three farmer-selected
cultivars, Bensogla, Sanzie and Omondaw and two improved varieties, ITH98-46 and TVu1509) was
conducted in the field for two consecutive years in 2005 and 2006. The aim was to assess the effect of
plant density, cropping system and cowpea genotypes on: (i) chlorophyll and gas-exchange, (ii)
rhizosphere mineral concentration and tissue uptake of nutrients, (iii) acid and alkaline phosphatase
activities in the rhizosphere, (iv) plant growth and symbiotic performance, and (v) concentration of
flavonoids and anthocyanins in seed extracts and plant organs and their effect on pest infestation and
diseases.
The results showed that high plant density (167,000 plants.ha-1) and mixed culture significantly decreased
gas-exchange parameters, leaf chlorophyll content, 13C and %C in both cowpea and sorghum plants
compared with low plant density (83,000 plants.ha-1) and monoculture. The data also showed significantly
higher 13C and lower %C in ITH98-46 and TVu1509 compared with Bensogla, Omondaw and Sanzie
genotypes with a significant correlation between 13C and water-use efficiency. At harvest, grain yield of
cowpea and sorghum was significantly decreased by high plant density and mixed culture compared with
low plant density and monoculture. Sanzie genotype was generally superior in grain yield (2,550 kg.ha-1)
followed by cvs. Omondaw and Bensogla (2,250 and 2,150 kg.ha-1, respectively) compared with the
improved cultivars. Sorghum plants in mixture with cv. TVu1509 or cv. ITH98-46 performed better
(1,570 and 1,550 kg.ha-1, respectively) compared with those in mixture with other cultivars. The results
also showed greater land equivalent ratio (LER = 1.42 to 1.52), suggesting that mixed culture produced
greater total yields per unit land area compared with monoculture.
Additional information
Thesis (DTech (Faculty of Applied Sciences)--Cape Peninsula University of Technology, 2009
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