Lalita Batra

Dehydrogenase activity and microbial biomass carbon in salt‐affected soils of semiarid and arid regions

Excessive amounts of salts present in the soil have an adverse impact on soil microbial population and their activities. Since microbial biomass represents an important reservoir of nutrients and is of crucial importance for long‐term fertility of soils, the dehydrogenase activity (DHA) and microbial biomass carbon (MBC) were determined in typical saline, alkali, and saline‐alkali sandy soils of northwestern India by collecting soil samples from the surface 030 m. In the 0–0.15 m soil layer, DHA declined by 71% at electrical conductance (ECe) 28.0 and by 87% at ECe 40.8 dS m‐1 compared with ECe 18.0 dS m‐1 for the soils saturation paste extract. The decrease in MBC was evident at ECe > 32.0 and 19 dS m‐1 in the 0–0.15 and 0.15–030 m soil layers, respectively. A reduction in pH of an alkali soil from 10.6 to 85 with gypsum application increased DHA from 25 to 10.4 μg TPF g‐¹’ soil. In the saline‐alkali sandy soil of an arid region (0–0.15 m), DHA was 53 μg TPF g‐1 at ECe 33.4 dS m‐1, which increased to 16...

Ammonia volatilization from applied nitrogen in alkali soils

Incubation studies in a highly alkali soil showed ammonia volatilization losses from applied nitrogen to be largely governed by pH/alkalinity of the system. Submergence of the soil decreased the pH value resulting in lower losses. The anion of ammonium did not influence the losses. Ammonia volatilization obeyed first order kinetics. The losses were considerably reduced by deep placement of urea but were unchanged with variation in temperature from 20° to 40°C. Urea or ammonium sulphate lost similar amounts of nitrogen. Losses from green manure were very low. The results are discussed for their implication in nitrogen fertilizer efficiency and management in alkali soils.

Microbiological and chemical amelioration of alkaline soil by growing Karnal grass and gypsum application

In a field experiment, microbiological and chemical amelioration of a highly deteriorated alkaline soil (pH 10.6, exchangeable sodium percentage 95) was undertaken during 1989–92 using two reclamation technologies: namely, growing Karnal grass ( Leptochloa fusca ) as a first crop in the absence of any amendment (biological reclamation) or applying gypsum as a chemical amendment for different cropping sequences. After ten months average dehydrogenase activity, used as a measure of catabolic activity of micro-organisms under anaerobic conditions, was 49.5 μg triphenylformazan (TPF) per g soil in treatments where the soil was reclaimed by growing Karnal grass, compared with 26.8 μg TPF by applying 50% of the estimated requirement of gypsum. After three years of reclamation, average dehydrogenase activity was 118.7 μg TPF per g soil with Karnal grass and 96.1 μg TPF with gypsum. After three years average microbial biomass carbon was 28% greater in the gypsum treatments (206.5 mg per kg soil) compared with Karnal grass treatments (161.7 mg). However, at this stage the ratio between average dehydrogenase activity and microbial biomass carbon was greater with Karnal grass (0.77) than in gypsum treatments (0.47). The microbiological properties 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 with the original soil. Higher microbial biomass carbon in gypsum treatments corresponded with lower exchangeable sodium percentage, higher availability of nitrogen and potassium and greater total yield of sensitive winter clovers.

YIELD RESPONSES OF WINTER (RABI) FORAGE CROPS TO IRRIGATION WITH SALINE DRAINAGE WATER

A field experiment in an alluvial sandy loam saline soil was conducted during the winter ( rabi ) season from 1997–98 to 1999–2000 at the Central Institute for Research on Buffaloes, Hisar, to study the effect of saline drainage water (EC=3.6 –7.4) on five ( rabi ) forage crops: oat ( Avena sativa ), rye grass ( Lolium rigidum ), senji ( Indian clover ) ( Melilotus indica ) berseem (Egyptian clover) ( Trifolium alexandrinum ) and shaftal (Persian clover) ( Trifolium resupinatum ). All the crops were established using canal water as pre-sowing irrigation and the various irrigation strategies were imposed subsequently. Irrigation with canal water resulted in a 115% increase in forage yield compared with the saline drainage water. The results suggested that alternate irrigation with saline drainage water increased the yields of all the forage crops compared with using saline drainage water only. Further, alternate irrigation, starting with canal water, was superior to alternate irrigation starting with saline drainage water because less salt was added in total. Oat produced the largest green-forage yield (32.3 t ha -1 ) in the first year while rye grass gave its maximum in the second (34.6 t ha -1 ) and third years (37.0 t ha -1 ). Persian clover performed better than did Egyptian clover in all the three years. Interaction between species and irrigation treatments was significant. In comparison with canal irrigation water, there was a 36 %, 42 %, 54 %, 68 %, and 85 % yield reduction in rye grass, oat, Persian clover, Egyptian clover and senji, respectively when only saline drainage water was used for irrigation reflecting their relative tolerances of salinity. Yields declined linearly for all crops with increases in the quantity of salt applied.

Forage Yield of Sorghum and Winter Clovers as Affected by Biological and Chemical Reclamation of a Highly Alkaline Soil

A field experiment was conducted on a highly alkaline soil (pH 10.6, exchangeable sodium 95%) to compare biological reclamation using Leptochloa fusca with chemical reclamation using gypsum. Rice gave satisfactory yields in the first year of gypsum application but sorghum and Sesbania gave extremely poor yields. The yield of Leptochloa was not affected by gypsum application. Trifolium resupinatum yielded more than T. alexandrinum when sown in the winter season. The green forage yield of sorghum was greatest when the sorghum followed Leptochloa grown for two years, with the harvested grass allowed to decompose on the site. The results show that biological reclamation with Leptochloa is a good substitute for chemical reclamation with gypsum.

Effect of exchangeable sodium on growth and concentration of important macronutrients in needles and stems of four Casuarina spp.

A greenhouse experiment was conducted to evaluate the effect of increasing exchangeable sodium percentage (ESP)viz. 11, 17, 35, 58 and 70 on the growth and the concentration of important macronutrients in needles and stems of Casuarina obesa Miq., C. glauca Sieb. ex. spreng., C. cunninghamiana Miq. and C. equisetifolia Forster and G. Forster. A significant increase in the dry matter was found with increasing soil sodicity. At ESP 70, the percentage increase in dry matter over ESP 11 for the first three species was 44%, 35% and 124% in the needles, and 78%, 37% and 86% in stems, respectively. On the other hand the yields of C. equisetifolia decreased with increase in soil sodicity. Among the 4 species, C. obesa and C. glauca produced comparatively more DM under sodicity than did C. cunninghamiana and C. equisetifolia. The effect of sodicity was more pronounced on needles than on stems. Sodium concentration in plant parts increased with increasing sodicity, whereas concentration of potassium, calcium, magnesium, nitrogen and phosphorus showed a decrease.