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An experiment was carried out at the Goat and Rabbit Research
Center, Sontay, Hatay, Vietnam, from February 2003 to November 2004
to measure effects on biomass yield, soil fertility and soil
erosion in response to increasing ratio of number of cassava rows
to Flemingia macrophylla rows in an inter-cropping system. Two rows
of Flemingia were associated with 1, 2, 3, 4 and 5 rows of cassava.
Flemingia was planted first and cassava 14 days later. Fertilizer
was applied in the form of organic manure (from mixed cattle and
buffalo excreta) before planting at the rate of 2 kg/m2
fresh weight in the first year and the same amount again in March
the second year. No other fertilizers were applied during the
experimental period. The first harvest was made when the cassava
reached 100 cm in height and subsequent harvests of the re-growth
from 56 to 75 days. All the foliages were removed at 30 cm above
ground level.
Biomass yield of cassava and Flemingia in an inter-cropping
system was improved by increasing the number of cassava rows
relative to cassava in the first year, but decreased slightly in
the second year. The maximum biomass yield was obtained in the
system with 2 rows of cassava and two rows of Flemingia. The crude
protein contentof the cassava foliage deceased as the area of
cassava rlative to Flemingia increased. Soil fertility over a 24
month period increased in the plots with the highest ratio of
Flemingia and decreased as the ratio of cassava to Flemingia was
increased. Protein content in the cassava foliage decreased
linearly with decreased in soil fertility. Soil erosion was high
in all plots in the first year and was directly related to the
relatve area planted with Flemingia. In the second year soil eroson
was much less and was inversely related to the proporton of
Flemingia n the inter-cropping system.
It is concluded that the optmum ratio of Cassava to Flemingia,
in terms of biomass yield and maintenance of soil fertility, is
two rows of each planted alternately.