Effect of farm management on topsoil organic carbon and aggregate stability in water: A case study from Southwest England,UK

There are few reliable data sets to inspire confidence in policymakers that soil organic carbon (SOC) can be measured on farms. We worked with farmers in the Tamar Valley region of southwest England to select sampling sites under similar conditions (soil type, aspect and slope) and management types. Topsoils (2–15 cm) were sampled in autumn 2015, and percentage soil organic matter (%SOM) was determined by loss on ignition and used to calculate %SOC. We also used the stability of macroaggregates in cold water (WSA) (‘soil slaking’) as a measure of ‘soil health’ and investigated its relationship with SOC in the clay‐rich soils. %SOM was significantly different between management types in the order woodland (11.1%) = permanent pasture (9.5%) > ley‐arable rotation (7.7%) = arable (7.3%). This related directly to SOC stocks that were larger in fields under permanent pasture and woodland compared with those under arable or ley‐arable rotation whether corrected for clay content (F = 8.500, p < .0001) or not (F = 8.516, p < .0001). WSA scores were strongly correlated with SOC content whether corrected for clay content (SOC_adj R² = .571, p < .0001) or not (SOC_unadj R² = 0.490, p = .002). Time since tillage controlled SOC stocks and WSA scores, accounting for 75.5% and 51.3% of the total variation, respectively. We conclude that (1) SOC can be reliably measured in farmed soils using accepted protocols and related to land management and (2) WSA scores can be rapidly measured in clay soils and related to SOC stocks and soil management.     

Direct and indirect efficacy of truck-mounted applications of s-methoprene against Aedes albopictus (Diptera: Culicidae)

Aedes albopictus (Skuse) is a globally significant vector that complexifies management programs already contending with Aedes aegypti (L.). The Ae. albopictus mosquito is a daytime biting, container breeding, anthropophilic mosquito that is generally considered unresponsive to operational larviciding that does not also incorporate source reduction. S-methoprene is a readily available juvenile hormone mimic common to pest management. This 14-week study examines direct and indirect treatment efficacy using s-methoprene as an ultra-low volume (ULV) truck spray in area-wide operations against Ae. albopictus in the southeastern United States. An overall 63.3% reduction of Ae. albopictus adults and 47.8% reduction of deposited eggs in treatment areas were observed compared with control. Indirect plots saw reduction in Ae. albopictus adults by 32.7% and eggs by 32.3%. Using insect growth regulator bioassays, truck-mounted ULV application of s-methoprene was effective to an inhibition of emergence (IE) of ≥92% within directly treated (sprayed) areas and >65% IE among containers placed up to 90 m away. S-methoprene could still benefit urban vector management programs when applied at an operational scale.     

Competitive and noncompetitive adsorption of silicate and phosphate by two acid Si-deficient soils and their effects on P and Si extractability

The effects of pH on the adsorption of silicate and phosphate, either singly or in competition, by two acid soils were investigated. Both soils adsorbed two to three times more P than Si and adsorption isotherms at pH 5.0, 5.5, 6.0 and 6.5 showed that increasing pH greatly increased Si adsorption but decreased that of P. Silicate adsorption was very low below pH 5.0, increased rapidly up to pH 9–10 before decreasing again. Adsorption of P was at a maximum at pH 2.0, decreased slowly up to pH 7.0 and then more rapidly above pH 7.0. When Si and P were added at equimolar concentrations, the presence of P decreased Si adsorption between pH 6.0 and 8.0 while the presence of Si decreased P adsorption in the pH region 6.0 and 11. Addition of calcium silicate at rates equivalent to 300, 600 and 1200 kg Si ha^?1 resulted in a progressive increase in soil pH. Separate samples of soil were treated with Ca(OH)₂ to give the same pH values so that the effect of Si could be identified. The highest rate of Si (1200 kg ha^?1 which gave a pH of 6.5) caused a significant decrease in P adsorption (as determined by adsorption isotherms) and an increase in resin-extractable P but the lower rates had little effect. Addition of P to the soil as calcium phosphate at rates equivalent to 30, 60 and 100 kg P ha^?1 all caused a decrease in Si adsorption capacity and an increase in CaCl₂-extractable Si. It was concluded that the strategy of adding Si to lower P requirements in acid soils is not likely to be effective while addition of fertilizer P may well lower Si adsorption and promote Si desorption and its increased mobility.     

Comparative Studies on the Role of Organic Biostimulant in Resistant and Susceptible Cultivars of Rice Grown under Saline Stress - Organic Biostimulant Alleviate Saline Stress in Tolerant and Susceptible Cultivars of Rice

Plants are sessile organisms that experience various abiotic stresses during their lifespan and try to adapt to these environmental stresses by manipulating their physiological, biochemical, cellular, and molecular mechanisms. Salinity is one of the important abiotic stress that affects the metabolism and physiology of plant cells that leads to serious damage to crops and productivity. We investigated the response of two contrasting (salt susceptible and tolerant) cultivars during saline stress by modulating its effect with the application of an important natural biostimulant panchagavya (PG). The results showed that the salinity stress greatly influenced and negatively affects the plant growth, biochemical attributes, and induces the expression of various genes in both cultivars. Furthermore, we assessed the effect of PG alone and by amending with NaCl to alleviate the saline stress which showed a significant enhancement of biochemical and physiological characteristics in both cultivars. Furthermore, we assessed the response of seven autophagy associated gene (ATG1, ATG3, ATG4, ATG6, ATG7, ATG8, and ATG9), BAX Inhibitor -1 (BI-1), Mitogen activated Protein Kinase–1 (MAPK-1), WRKY53, Catalase -1 (CAT-1), Superoxide Dismutase (SOD), and Glutathione Peroxidase (GPX) genes in rice that displayed the differential expression pattern during saline stress in both cultivars. We concluded that saline stress can be manipulated by the application of PG and positively regulate the physiological, biochemical, and gene expression response in salt-susceptible and -tolerant rice cultivars. Furthermore, the current study also suggested that salinity is a mutifactorial and multigenic response. Autophagy and programmed cell death regulated along with salinity and was helpful in adapting the tolerance against the stress condition.     

An evaluation of methods used to cull invasive cane toads in tropical Australia

To identify cost-effective ways to control invasive species, we need to evaluate alternative methods. The invasion of tropical Australia by cane toads (Rhinella marina) has killed many native predators, prompting efforts to cull adult toads. We analyzed a dataset on >?17,500 toads killed by government-employed teams from 2005 to 2008, using a range of methods (incidental captures, targeted searches, traps) as well as records of toads found as road kills. The culling occurred in the northwestern part of the Northern Territory, moving west as the toad front expanded into Western Australia. Both season and method affected rates of capture and demographic attributes (sex ratio, proportion of adults) of the culled anurans, with a strong interaction between these factors. Most methods were more effective during and after the seasonal monsoons (when moist conditions facilitated anuran activity), but that seasonal variation was greater for numbers of toads found on the roads than captured in other ways. Juvenile toads and adult female toads constituted higher proportions of total captures in the Early Dry than in other times of year, reflecting seasonal breeding. Traps caught a higher proportion of adult female toads than did other methods, but overall had low capture rates. Rates of range expansion by toads were similar before, during and after the culling effort, suggesting that removing adult toads did not affect the speed of the invasion. Nonetheless, culling adult cane toads may be effective in some situations (“island” populations, extralimital translocations), and results from this program may be valuable for future toad-control efforts.     

Methodological Approaches toward Chemico-Biological Diagnostics of the State of Soils in Technogenically Transformed Territories

The comprehensive diagnostics of the state of soils in the impact zone of thermal power station (TPS-5) in the city of Kirov was performed on the basis of the soil chemical analyses and the study of biota response to the loads at different organization levels. The chemical analyses attested to a satisfactory state of the soils. However, the use of soil cyanobacteria and bird’s-foot trefoil (Lótus corniculátus) as test objects showed the toxicity of studied soil samples. The toxicity of the samples was judged from the bioindication effects of cyanophytization and melanization of soil microbial complexes. The obtained results demonstrated that at relatively low concentrations of total and mobile heavy metal compounds in the soil samples, their amount released into the tested soil water (1: 4) extract exceeded the limit allowable for normal functioning of living organisms. For the first time, the express cyanobacterial tetrazole-topographic method of biotesting was applied in the geoecological study to estimate the toxicity of the soil samples. The results obtained with the help of traditional and express methods proved to be comparable. The express-method was sufficiently sensitive and efficient. It allowed the determination of the samples' toxicity in five hours, i.e., four to five times faster than the traditional technique. An inverse relationship between the number of viable cells of cyanobacteria (as judged from the inclusion of formazan crystals) and the concentration of lead ions in the tested soil extracts was found. This finding can be considered a prerequisite for further study and application of the express method in the practice of geoecological monitoring. Our study demonstrated the necessity of a comprehensive approach for the assessment of the real ecological state of soils in the investigated impact zone of the thermal power station.