Soil organic carbon and phosphorus availability regulate abundance of culturable phosphate-solubilizing bacteria in paddy fields

Low availability of phosphorus(P) is a major constraint for optimal crop production, as P is mostly present in its insoluble form in soil. Therefore,phosphate-solubilizing bacteria(PSB) from paddy field soils of the Indo-Gangetic Plain, India were isolated, and their abundance was attempted to be correlated with the physicochemical characteristics of the soils. Ninety-four PSB were isolated on Pikovskaya's agar medium, and quantitative phosphate solubilization was evaluated using NBRIP medium. The isolates solubilized P up to a concentration of 1 006 μg mL~(-1) from tricalcium phosphate with the secretion of organic acids. These isolates were identified by 16 S rRNA gene sequence comparison, and they belonged to Gammaproteobacteria(56 isolates),Firmicutes(28 isolates), Actinobacteria(8 isolates), and Alphaproteobacteria(2 isolates). Phylogenetic analysis confirmed the identification by clustering the isolates in the clade of the respective reference organisms. The correlation analysis between PSB abundance and physicochemical characteristics revealed that the PSB population increased with increasing levels of soil organic carbon, insoluble P, K~+, and Mg~(2+). The promising PSB explored in this study can be further evaluated for their biofertilizer potential in the field and for their use as potent bio-inoculants.     

Computer-assisted tomography of macroporosity and its application to study the activity of the earthworm Aporrectodea nocturna

In a pre-alpine meadow in the Toggenburg (Switzerland), casts of the earthworm Aporrectodea nocturna, initially detected 20 years ago around a newly planted hedge, now extend 170 m from the hedge. The abundance of A. nocturma decreased between 140 and 170 m from the hedge from 237 (site: An+) to 0 (site: An?) individuals m^?2. The worm's activity and the macroporosity it has created have been studied using CAT scanning followed by automated image analysis of pores from 1·5 to 9 mm diameter. Brightness values in images from CAT scanning showed distinct local frequency maxima for stones, soil matrix and macropores. Measured diameters of pores were strongly linearly correlated with diameters of needles used to produce artificial pores. Pores from 1·5 to 3 mm were most abundant. The maximum number of pores from 1·5 to 9 mm (about 1600 m^?2) was larger than the maximum number of all earthworms (about 480 m^?2). Modelling the cast production of A. nocturna indicated that 23·8 kg m^?2 were deposited on the soil's surface within 3 months. The measured macroporosity (1·5–6 mm) was one-quarter to one-sixth of the pore volume corresponding to the removed casts. Thus, net production of pores by earthworms was a result both of the burrowing activity and of the refilling with eroded cast material. Depth distributions of bulk density, total porosity and pores from 1·5 to 9 mm were different at An+ from those at An?. However, diffusion of butane was equal at An+ and An?. Three-dimensional reconstruction suggested that the disposition (continuity, interconnectivity) of pores was more important for gas diffusion than the structure (size distribution, frequency) and bulk soil parameters.     

中国东南部红壤地区不同植被对土壤侵蚀和土壤养分的影响

The effect of different vegetation systems including bamboo plantation (BP), forest ecosystem (CF), citrus orchard (Ctr) and farmland (FL) on erosion and nutrients of red soil were investigated in hilly region of southeastern China to find effective control measures for soil erosion. The results showed that all the vegetation systems could significantly reduce soil erosion and nutrient losses compared to bare land (Br). The ability of different vegetation systems to conserve soil and water was in the order of Ctr > BP > CF > FL > Br. Vegetation could also improve soil fertility. The soil organic matter, total N and total P contents were much higher in all the vegetation systems than in bare land, especially for the top soils. Vegetation systems improved soil physical properties remarkably. Compared to the bare land, soil organic matter, TP, TK and available K, especially soil microbial biomass C, N and P, increased under all the vegetation covers. However, they were still much lower than expected, thus these biological measurements are still needed to be carried out continuously.     

Experiences with Rice Grown on Permanent Raised Beds: Effect of Crop Establishment Techniques on Water Use,Productivity, Profitability and Soil Physical Properties

In recent years, conventional rice production technologies have been leading to deterioration of soil health and declining farm profitability due to high inputs of water and labor. Conservation agriculture(CA) based resource-conserving technologies i.e. zero-tillage(ZT), raised-bed planting and direct-seeded rice(DSR) have shown promise as alternatives to conventional production technologies to overcome these problems. Present study was undertaken during 2009–2012 to establish an understanding of how permanent raised bed cropping system could be practiced to save water at the field application level to improve water productivity and also have the capability to enhance productivity, profitability and soil physical quality. The results showed that among different crop establishment techniques, conventional-tilled puddle transplanted rice(CT-TPR) required 14%-25% more water than other techniques. Compared with the CT-TPR system, zero till direct-seeded rice(ZT-DSR) consumed 6%–10% less water with almost equal system productivity and demonstrated higher water productivity. Wide raised beds saved about 15%–24% water and grain yield decrease of about 8%. Direct-seeded rice after ZT or reduced tillage or on unpuddled soil provided more net income than CT-TPR. The CTTPR system had higher bulk density and penetration resistance due to compaction caused by the repeated wet tillage in rice. The steady-state infiltration rate and soil aggregation( 0.25 mm) were higher under permanent beds and ZT and lower in the CT-TPR system. Under CT-TPR, soil aggregation was static across seasons, whereas it improved under no-till and permanent beds. Similarly, mean weight diameter of aggregates was higher under ZT and permanent beds and increased over time. The study reveals that to sustain the rice productivity, CA-based planting techniques can be more viable options. However, the long-term effects of these alternative technologies need to be studied under varying agro-ecologies in western Uttar Pradesh, India.     

Early pathogenesis of equine Streptococcus equi infection (strangles)

Reasons for performing study: Little is known about entry and subsequent multiplication of Streptococcus equi following exposure of a susceptible horse. This information would have value in design of intranasal vaccines and understanding of shedding and protective immune responses. Objectives: To determine entry points and sites of subsequent replication and dispersion of S. equi at different times after intranasal infection or commingling exposure. Methods: Previously unexposed horses and ponies were subjected to euthanasia 1, 3, 20 or 48 h following intranasal inoculation with biotin labelled or unlabelled S. equi CF32. Some ponies were inoculated with suspensions of equal numbers of CF32 and its mutants lacking capsule, S. equi M‐like protein or streptolysin S. Others were infected by commingling exposure and subjected to euthanasia after onset of fever. Tonsils and lymph nodes were cultured for S. equi and tissues sectioned for histopathological examination and fluorescent microscopy. Results: Tonsillar tissues of both the oro‐ and nasopharynx served as portals of entry. Entry was unexpectedly rapid but involved few bacteria. Small numbers of organisms were detected in tonsillar crypts, in adjacent subepithelial follicular tissue and draining lymph nodes 3 h after inoculation. By 48 h, clumps of S. equi were visible in the lamina propria. At onset of fever, tonsillar tissues and one or more mandibular and retropharyngeal lymph nodes were heavily infiltrated by neutrophils and long chains of extracellular S. equi. Mutant S. equi lacking virulence factors were not seen in draining lymph nodes. Conclusions: Although very small numbers of S. equi entered the lingual and nasopharyngeal tonsils, carriage to regional lymph nodes occurred within hours of inoculation. This observation, together with visual evidence of intracellular and extracellular multiplication of S. equi in tonsillar lymphoid tissue and lymph nodes over the following days, indicates involvement of potent antiphagocytic activity and failure of innate immune defences. Relevance: Future research should logically address the tonsillar immune mechanisms involved including identification of effector cell(s) and antigens.     

Germination of Seeds of Cirsium arvense (L.) Scop.

Cirsium arvense (L.) Scop. is a persistent and troublesome weed which reproduces vegetatively. Establishment from seeds (achenes) is considered negligible under natural conditions in the United Kingdom (Bates, 1946), although germination under normal farm conditions was found to be good in America (Hansen, 1918). Korsmo (1930) in Norway and Hayden (1934) in Iowa found that the seeds had no dormancy period, but Niethammer (1934) and Zilke (1967) recorded seed dormancy in Germany and South Dakota respectively. An examination was therefore made of some of the factors which may regulate the germination of seeds of C. arvense in this country.     

Carbon and water footprints of major crop production in India

Scarcity of water and emission of greenhouse gases (GHGs) are the two key environmental issues affecting crop production in India.Reducing the carbon footprint (CF) and water footprint (WF) of crop production can help to mitigate the environmental hazards that stem from GHG emissions and water scarcity.The CFs and WFs of three major cereal crops,rice,wheat,and maize,were estimated for the year 2014 under the environmental conditions in India,based on national statistics and other data sources.To...     

Silicon and plant nutrition—dynamics,mechanisms of transport and role of silicon solubilizer microbiomes in sustainable agriculture: A review

Silicon (Si) is the second most abundant element in the Earth’s crust and has numerous roles in both soils and plants, although it is inaccessible to plants in its native state (insoluble silicate minerals). This inaccessibility can lead to insufficiency, which induces anomalies in plant growth and development.Specifically, Si alleviates various biotic and abiotic stresses in plants by enhancing tolerance mechanisms at different stages of uptake/deposition as a monosilicic acid. Exclusive utiliz...     

Outbreak of MAV-type barley yellow dwarf virus on wheat in the Garhwal Hills in India

A serious outbreak of barley yellow dwarf luteovirus (BYDV, MAV-type) on wheat in the Garhwal Hills, Central Himalayas, India is reported. This is the first conclusive evidence based on serology for the presence of MAV-BYDV in India.