Determination of Nitrogen fertilizer requirement in Bambara groundnut(Vigna Subterranea (L.)Verdc.)

This study was carried out during the 1993 /94 cropping season
at the University of Zambia (UNZA) Farm and Lusitu Sub-Research
Station which are situated in Agroecological Zones II and I
(medium and low rainfall), respectively. The objective was to
determine the nitrogen fertilizer requirement for Bambara
groundnut using accessions of different yielding potential. A
split plot design was used, with six accessions (ZAVs 3, ZAVs 7,
ZAVs 120, ZAVs 6, ZAVs 5 and ZAVs 8) and five nitrogen levels (0,
15, 30, 45 and 60 kg N/ha) as main and sub plots, respectively.
The accessions were chosen on the basis of yielding potential,
i.e., low (ZAVs 6 and ZAVs 8), medium (ZAVs 7 and ZAVs 120) and
high (ZAVs 3 and ZAVs 5) as judged by results of a study carried
out during the 1992/93 season. The yield parameters measured
were: days to 50 % flowering, days to maturity, number of leaves
per plant, number of stems per plant, number of branches per
plant, number of nodes per plant, number of pods per plant, plant
spread, plant height, 100 seed weight and grain yield. However,
due to severe moisture deficit, yield was measured at UNZA Farm
only. The total nitrogen content of leaves at pod formation and
in the soil after harvesting were also measured. The results
indicated that at both locations, nitrogen fertilizer did not
have any effect on yield and all yield attributes measured except
plant spread and number of pods per plant. However, accessions
responded differently to N fertilizer, but this was true for ZAVs
7 only. Highest yields were obtained with 15 kg N /ha (321
kg/ha)grain, while the lowest was obtained with 30 kg N/ha
(65.70 kg/ha) while other treatments had similar. Yield was
V
positively correlated with number of leaves per plant, plant
height and the number of pods per plant. The nitrogen fertilizer
levels did not have any significant effect on plant N content
as well as on N content of the soil after harvesting. Location
had an effect on some yield attributes, i.e. , plants at UNZA Farm
were taller and wider with a higher number of stems than those
at Lusitu. Plants at Lusitu had 3.66 % N content which was
higher than UNZA Farm's 3.13 % N. The experiment was seriously
affected by moisture and temperature stress. The average yield
at UNZA farm was 183 kg/ha. A concrete conclusion cannot be made
from this experiment. It is therefore recommended that the
experiment be repeated under a controlled environment in order
to get a more accurate and reliable conclusion