Bioenergetic and energy constraints in increasing cereal productivity

The grain yield potential of cereal crops such as wheat, rice, barley, oats and sorghum has increased by genetic improvement in the harvest index (grain yield/biological yield). Such alterations in the harvest index were analysed from the point of view of intrinsic energy and nitrogen, phosphorus and potassium requirements. A higher harvest index, without any reduction in biological yield, increases the harvest of: (a) energy (MJ) in the above ground parts of the crop and (b) nitrogen and phosphorus in the grain. In addition, it enhances the fertiliser requirement of the crop. From bioenergetic considerations, higher grain yields, obtained by improving the harvest index, represent a path which demands least increments in photosynthate and nutrient inputs. The other alternatives available for increasing cereal productivity, once the upper limits of the harvest index are reached by breeding, have higher costs in terms of photosynthate and fertiliser requirements (energy inputs). There seems to be no other immediate plant breeding alternative to increase productivity without additional energy (fertiliser) inputs.     

Fracture propagation to the base of the Greenland Ice Sheet during supraglacial lake drainage

Surface meltwater that reaches the base of an ice sheet creates a mechanism for the rapid response of ice flow to climate change. The process whereby such a pathway is created through thick, cold ice has not, however, been previously observed. We describe the rapid (<2 hours) drainage of a large supraglacial lake down 980 meters through to the bed of the Greenland Ice Sheet initiated by water-driven fracture propagation evolving into moulin flow. Drainage coincided with increased seismicity, transient acceleration, ice-sheet uplift, and horizontal displacement. Subsidence and deceleration occurred over the subsequent 24 hours. The short-lived dynamic response suggests that an efficient drainage system dispersed the meltwater subglacially. The integrated effect of multiple lake drainages could explain the observed net regional summer ice speedup.     

Impact of Biofertilizers on grain yield in spring wheat under varying fertility conditions and wheat-cotton rotation

High nitrogen fixing and phytohormone producing diazotrophs such as Azotobacter were isolated, identified and used as bioinoculants on wheat and cotton with varying doses of nitrogen under field conditions. The impact of bio-inoculants was determined on the basis of their effect on yield, dry weight and survival rate of bacteria at different days of plant growth under field conditions in two consecutive seasons (2000–01 and 2001–02). Pronounced effects were seen by the use of bio-inoculants in wheat crop. The effects were more visible in the second year as the level of bio-inoculants was maintained in the soil. A net saving of 25–30?kg nitrogen was observed using chosen bio-inoculants for wheat crop.     

A maximin–minimax approach for classifying soybean genotypes for drought tolerance based on yield potential and loss

Screening for drought in soybean is often a bottleneck in plant breeding programmes. Sixteen genotypes were evaluated for drought tolerance during 2012, 2013 and 2014. The experiment was conducted in a split‐plot design, and the main plots consisted of irrigated and water stress treatments, and subplots consisted of 16 genotypes. The average seed yield was highest in 2012 (1708 kg/ha), followed by 2014 (1364 kg/ha) while very low yields (958 kg/ha) were observed during 2013. The per cent reduction in average soybean yield under water stress conditions was maximum (43%) during 2014 followed by 2012 (40%) and 2013 (31%), respectively. The average yields of soybean genotypes also differed significantly, which ranged from 892 (NRC 12) to 2008 kg/ha (JS 97‐52). The maximin–minimax approach was used to classify these genotypes, and only, one genotype was identified as drought resistant and high yielding (EC 538828), three as tolerant and high yielding (JS 97‐52, EC 456548 and EC 602288) and none as low yielding and resistant, while the remaining 12 genotypes were found to be low yielding and susceptible to drought.     

Biomass production and changes in soil productivity during longterm cultivation of Prosopis juliflora (Swartz) DC inoculated with VA mycorrhiza and Rhizobium spp. in a semi-arid wasteland

The growth of Prosopis juliflora and its contribution to soil enrichment following inoculation with three vesicular-arbuscular isolates, Glomus caledonius, Gigaspora calospora, and an indigenous strain, and two Rhizobium isolates, P-5 and Tal-600, were assessed. The trees were 6 years old and grew on a semi-arid wasteland. There was a significant increase in the biomass of closely spaced P. juliflora inoculated with G. caledonius alone. P. juliflora, growing on a relatively nutrient-deficient wasteland, significantly restored the soil productivity by ameliorating and enriching the soil. A significant reduction in the soil reaction (pH) and a considerable improvement in soil organic carbon build-up and phosphorus, at both depths, were observed in all the treatments by the end of the experiment. Moreover, although the total nitrogen content increased in comparison to controls, this increase was not statistically significant when comparisons were made between respective treatments at the beginning of the experiment and after 6 years‘ growth. Received: 5 February 1997     

Comparative evaluation of IHA and CIEP in the diagnosis of Toxocara vitulorum in pregnant cows and buffaloes

Tropical Animal Health and Production -     

Gamma radiation susceptibility of strains of Tribolium castaneum (Herbst) resistant and susceptible to fenvalerate

Gamma radiation susceptibility of adults of the fenvalerateresistant strain of Tribolium castaneum (Herbst) (Coleoptera : Tenebrionidae) was studied under laboratory conditions. Selection for resistance to fenvalerate in adult beetles was carried out up to the sixth generation. In each generation of selection, adults of the fenvalerateresistant strain were evaluated for susceptibility to gamma radiation and compared with their fenvalerate-susceptible counterparts. Susceptibility to 60Co gamma radiation was evaluated on the basis of dosage-mortality (LD) and time-mortality (LT) responses. We found the LD values 50 50 50 for the fenvalerate-resistant and-susceptible strains to be 89.16 and 97.46 Gy respectively, showing no significant difference in susceptibility to gamma radiation. LT values were 7.58 and 17.20 days for the 50 fenvalerate-resistant and-susceptible strains respectively, showing that mortality in the resistant strain occurred markedly earlier than in the susceptible strain.