L. Batra et al., MICROBIOLOGICAL AND CHEMICAL AMELIORATION OF ALKALINE SOIL BY GROWINGKARNAL GRASS AND GYPSUM APPLICATION, Experimental Agriculture, 33(4), 1997, pp. 389-397
In a field experiment, microbiological and chemical amelioration of a
highly deteriorated alkaline soil (pH 10.6, exchangeable sodium percen
tage 95) was undertaken during 1989-92 using two reclamation technolog
ies: namely, growing Karnal grass (Leptochloa fusca) as a first crop i
n the absence of any amendment (biological reclamation) or applying gy
psum as a chemical amendment for different cropping sequences. After t
en months average dehydrogenase activity, used as a measure of catabol
ic activity of micro-organisms under anaerobic conditions, was 49.5 mu
g triphenylformazan (TPF) per g soil in treatments where the soil was
reclaimed by growing Karnal grass, compared with 26.8 mu g TPF by app
lying 50% of the estimated requirement of gypsum. After three years of
reclamation, average dehydrogenase activity was 118.7 mu g TPF per g
soil with Karnal grass and 96.1 mu g TPF with gypsum. After three year
s average microbial biomass carbon was 28% greater in the gypsum treat
ments (206.5 mg per kg soil) compared with Karnal grass treatments (16
1.7 mg). However, at this stage the ratio between average dehydrogenas
e activity and microbial biomass carbon was greater with Karnal grass
(0.77) than in gypsum treatments (0.47). The microbiological propertie
s changed more than the chemical properties of alkali soil as the time
period advanced. After three years of reclamation, the average pH of
the alkali soil dropped from 10.6 to 9.45 and the average exchangeable
sodium percentage was reduced from 95 to 47.5. The increase in total
organic carbon was 64% and in available nitrogen about 38% compared wi
th the original soil. Higher microbial biomass carbon in gypsum treatm
ents corresponded with lower exchangeable sodium percentage, higher av
ailability of nitrogen and potassium and greater total yield of sensit
ive winter clovers.