Effect of residue placement and chemical fertilizer on soil microbial biomass under tropical dryland cultivation

Four treatments (control, chemical fertilizer, wheat straw, and wheat straw+fertilizer) were established on the dryland experimental farm of the Institute of Agricultural Sciences, Banaras Hindu University. Organic in C in the different treatments ranged from 0.69 to 0.93%, total N from 0.08 to 0.11%, and total P from 0.018 to 0.021. The application of straw significantly increased the soil water-holding capacity. The maximum effect on the microbial biomass was realized with the straw+fertilizer treatment, followed by straw and then by the fertilizer treatment. During the study microbial biomass C ranged from 144 to 491 g g^-1 dry soil, biomass N from 14.6 to 50.1 g g^-1, and biomass P from 7.2 to 17.6 g g^-1 soil. Microbial biomass C, N and P represented 3.2–4.6% of total C, 2.6–3.8% of total N, and 5.8–8.2% of total P in the soil, respectively, in all cases the highest proportion occurred in the straw+fertilizer treatment and the lowest in the control. Microbial biomass C, N, and P were positively correlated with each other. Microbial biomass C and N increased by 77% in straw+fertilizer-treated plots relative to the control. The increase in microbial biomass P in the straw+fertilizer treatment over the control was 81%. The increase in the microbial biomass is expected to enhance nutrient availability in the soil, as the microbial biomass acts both as a sink and a source of plant nutrients.     

Leaf-Litter Decomposition in an Oak-Conifer Forest in Himalaya: The Effects of Climate and Chemical Composition

The decomposition rates of certain dominant litter species inan undisturbed oak-conifer forest in the Kumaun Himalaya wereinvestigated by enclosing pre-weighed, newly senesced leavesin litter bags, placing these bags on the forest floor and determiningthe weight loss by recovering the bags at monthly intervals.Among the species examined, Daphne cannabina decomposed fastestand Cupressus torulosa decomposed most slowly. The former took6 months for complete decomposition, while Cupressus torulosadecomposed to about 72 per cent in 18 months. A linear combinationof rainfall and temperature explained 80 per cent of the variabilityin monthly weight loss. The rate of decomposition was also relatedto the initial chemical composition of the litter. Initially,several constituents showed a significant relation with decomposition;these are nitrogen, calcium, water soluble compounds, totalnonstructural carbohydrates, lignin, acid detergent cell wallcomponents and fibre. Of these, lignin and fibre contents showeda negative relation with weight loss while the others were positivelyrelated. As decomposition progressed, only nitrogen, lignin,ADCW and fibre content remained important. With further lapseof time only two constituents, nitrogen and lignin, remainedimportant. Among these the effect of nitrogen declined withtime while that of lignin increased. A linear combination ofnitrogen and lignin explained 59 per cent variability in theannual weight loss.     

Effect of Irrigation, Mulch and Nitrogen on Yield and Composition of Japanese Mint (Mentha arvensis L. subsp. haplocalyx var. piperascens) Oil

Effects of irrigation, mulch and nitrogen on yield and composition of Japanese mini ( Mentha arvensis L. subsp. haplocalyx Briq. var piperascens) oil were studied using a replicated experiment. Two harvests were obtained 120 davs atter planting and 75 davs after the first harvest. Significantly higher drv matter and essential oil yields were obtained with frequent irrigations (50 mm Cumulative Pan Evaporation), application of mulch and Nitrogen. The economic optimum rate of N was 215 Kg ha^-1. The essential oil from the first harvest was richer in menthol (78.8%) than the oil obtained from second harvest (75.2%). Soil moisture extraction was maximum between 15 and 30 cm soil depths. Consumptive use, water use efficiency and moisture use rate-were maximum under higher irrigation levels and mulch application which reflect that more availability of moisture in soil profile with frequent irrigations and application of mulch.     

Ultrastructure of the host-pathogen interface of Peronospora viciae in cultivars of pea which show different susceptibilities

The ultrastructure of interactions of pea downy mildew ( Peronospora viciae ) on the leaves and petioles of two cultivars of pea, Superb and Maro, was examined. Tissue fixed at the time of sporulation (10 days after inoculation) revealed that many of the intercellular hyphae in Maro were showing evidence of partial or complete autolysis. The penetration matrices were enclosed in a thicker layer of callose-like material than in Superb, and many of the haustoria had collapsed, distorted profiles. Analysis of organelles lying close to the extra haustorial membrane revealed fewer associations with endoplasmic reticulum in Superb.     

The Development of a Regional Multimetric Fish Model Based on Biological Integrity in Lotic Ecosystems and Some Factors Influencing the Stream Health

The objective of this study was to develop an index of biological integrity (IBI) for national-level monitoring of watersheds as an ecosystem health assessment methodology for the South Korean government. A 10-metric IBI model (IBI_KW) was developed for watershed management and then applied to 76 streams in four major watersheds in Korea. The model assessments showed that 32.9% of all streams were judged to be in ??excellent?Cgood?? condition, whereas 67.1% were in ??fair?Cpoor?? condition, indicating severely impaired ecological health. Nutrient analyses of stream water revealed a two- to fivefold increase in nutrient and biological oxygen demand (BOD) levels in urban- and cropland-dominant streams compared to forest-dominant streams. The guild structure within the watersheds indicated that tolerant species were predominant in severely degraded regions (BOD?>?6 mg L^?1), and sensitive species were distributed in regions with BOD?<?2 mg L^?1. Factors affecting ecosystem health (IBI_KW scores) included chemical water quality parameters, physical habitat parameters and land use around the stream. In particular, land use was one of the major factors influencing ecosystem health, as indicated by the strong relationships between the percentages of urban and forest streams and the IBI_KW scores. The integrated ecosystem health assessment technique developed here can be applied for both regular bioassessments and post-restoration assessments.     

Metagenetics of fairy rings reveals complex and variable soil fungal communities

Although fairy rings are widely observed, little is known about the community processes associated with them. Here, we studied fairy rings in a natural grassland in northern Mongolia by sampling soils outside (future stage), directly under (present stage), and within (past stage) the rings, to represent different time stages during the expansion of fairy rings. Soil DNA was extracted for amplicon sequencing of the fungal ITS1 region. The present stage had reduced fungal diversity and different fungal communities toward the other stages. Most strikingly, there was an increase in the pathogenic fungus Gibberella baccata in the present stage of most rings and the saprotrophic fairy ring fungus Lepista luscina in several. However, no mushrooms of Lepista had been recorded from any of these rings during several years of observation. Known fairy ring fungi were not found in the present stage of every ring, even in some known rings to have previously displayed mushrooms of such species. It is possible that these fungi occurred or were more abundant at the unsampled leading edge of the ring. The increase in G. baccata is intriguing, but its importance, if any, is unclear. It is also unclear whether consortia of fungi or other microbes might be present in these rings. The absence or low abundance of the previously reported fairy ring fungal species suggests that their presence is transient, with rapid replacement by other fungi. No differences in soil parameters were found between the fairy ring stages, except for aluminum. There is a need for broader sampling, including analysis of non-fungal biota, to understand the functional diversity of fairy ring fungi and the consequences for plant communities.     

Utilization of lignocellulosic plant residues for compost formation and its role in improving soil fertility

Globally, urbanization and a steady increase in population generate a huge amount of wastes, which leads to a series of economic, social, and environmental changes, mainly in developing countries. There is an utmost need for efficient management strategies for the beneficial utilization of these wastes into useful products. Among these strategies, composting is gaining attention due to its benefits of solid waste management, such as proper sterilization, and economical and effective bioconversio...     

Arbuscular mycorrhizal fungi for salinity stress: Anti-stress role and mechanisms

Salinity stress is considered one of the most harmful environmental plant stresses, as it reduces irrigated land crop production by over 20%worldwide.Hence, it is imperative to develop salt-tolerant crops in addition to understanding various mechanisms enabling plant growth under saline stress conditions.Recently, a novel biological approach that aims to address salinity stress has gained momentum, which involves the use of arbuscular mycorrhizal (AM) fungi in plant-microbe interactions. It has ...     

Reproductive biology of a hillstream catfish, Glyptothorax madraspatanum (Day), from the Garhwal, Central Himalaya, India

Abstract. This paper studies maturity and spawning tendency of a hillstream catfish, Glyptothorax madraspatanum (Day), in the Western Nayar River, Garhwal, Central Himalaya, India. The fish is a protracted spawner as it spawns only once during the limited period from July to August. Fecundity ranges from 1640 to 6830 eggs and is more closely related to ovary weight and fish weight than ovary and fish length. There was a non-significant sex ratio of 1:1·24 between males and females.