Abstract:

Intercropping of sweet potato with beans is common in highly
populated medium and high-altitude areas of Uganda. Both sweet potato
and bean are crops on which abundant research information is available.
However, knowledge is still lacking on how the two crops interact yvwhen grown in the proximity of each other. This problem was addressed by
conducting two sets of sweetpotato/bean intercropping experiments
between 1993 and 1995 at Namulonge Agricultural and Animal
Production Research Institute (NAARI), Kampala. The first experiment aimed at evaluating the compatibility of different sweet potato morphotypes with bean of different growth types. It consisted of eight
sweetpotato genotypes (Wagabolige, Entry 20, Entry 21, Bitambi, Tororo
3, New Kawogo and Tanzania) and four bean genotypes (White Haricot,
MMS 224, A 197, and GLP 585) in the 1993/94 season with the objective to study the compatibility of the mixtures. In the 1 994/95 season, six sweet potato genotypes (Wagabolige, Bitambi,
Tororo 3, New Kawogo and Tanzania) and two bean genotypes (White
Haricot and GLP 585) were used. In both seasons double rows of bean
were planted with double rows of sweet potato at densities of about
440,000 and 33,333 plants/ha for bean and sweet potato, respectively in a split plot design in four replications. The second experiment aimed
at determining the effects of spatial arrangements and plant population
density of sweetpotato on the productivity of the components. It consisted of one bean genotype (White Haricot); three sweetpotato
genotypes (Wagabolige, Bwanjule and
Tororo
3);
two
spatial
arrangements (single and double rows) and four sweetpotato plant
densities (1 6,666; 22,222; 33,333 and 66,666 plants/ha). Double rows
of bean were planted with either single or double rows of sweetpotato
in
a split-split plot design in. three replications.
Growth and yield
measurements were done at 4 WAP and continued at two weeks interval. Beans and sweet potato were harvested at three and six MAP, respectively. Light interception efficiency increased by an average of 8.1% of the sole crop. Sweet potato vine growth rate was reduced by
intercropping in all plant types except the spreading type. Bean plant
height and leaf area indices of both species were also reduced by
intercropping. Sweet potato LAI increased with an increase in sweet potato population while bean LAI increased with an increase in plant height and number of primary branches.
Storage root yield was increased by intercropping in the first
experiment by an average of 23.1%,of the sole crop yield, but was
reduced by an average of 22% in the second experiment. Bean yield
was reduced by an average of 40.7% and 54% in the first and second
experiments, respectively. The most compatible sweetpotato and bean
morphotypes for intercropping relative to their respective sole crop yield
was the erect and the determinate types, respectively