Short-term Effects of N-fixing Legumes on Some Properties of Calcareous Salt-affected Soils

Abstract

Cultivation of legumes in calcareous salt-affected soils may
decrease soil sodicity. A field experiment was conducted in Soba
Research Station, 15 km south of Khartoum, to determine the potential of
three N fixing legumes: guar (Cyamopsis tetragonolobus), hyacinth bean
(Dolichos lablab L.) and cowpea (Vigna unguiculata L) in amelioration of
sodic soils. The treatments consist of control (without plant and gypsum),
gypsum, cowpea; guar and hyacinth bean relying on either inorganic
nitrogen or N fixation. Treatments were arranged in a Randomized
Complete Block Design with four replications. Soil samples (0-25 and 25-

50 cm depths) were taken before and after harvest and analyzed for pH,
electrical conductivity (ECe), soluble cations (Ca2+, Mg2+, Na+
, K+
),
soluble HCO3
-
and sodium adsorption ratio (SAR). Results of the first
season indicated that pH and ECe were not significantly different among
treatments whereas; Ca2+, Na+
and SAR were significantly (P ≤ 0.001)
different among treatments. Total dry matter of hyacinth bean relying on
N- fixation was higher than the hyacinth bean relying on inorganic N by
49.4%. In the second season, total dry matter of guar relying on Nfixation was 36% higher than that relying on inorganic N whereas
hyacinth bean relying on N-fixation has increased soil soluble HCO3
-1
and
decreased SAR. It may be concluded that cultivation of N-fixing plants in
calcareous salt-affected soils could be a promising alternative to chemical
amendments which may be expensive for small farmers