Changes in phosphorus fractions in three tropical soils amended with corn cob and rice husk biochars     

Joseph Osafo Eduah  Mark Kofi Abekoe  Mathias Neumann Andersen 《Communications in Soil Science and Plant Analysis》2020,51(10):1331-1340

ABSTRACT

The formation of phosphorus (P) compounds including iron-P, aluminum-P and calcium-P in highly weathered tropical soils can be altered upon biochar addition. We investigated the effect of corn cob biochar (CC) and rice husk biochar (RH) pyrolyzed at three temperatures (300°C, 450°C and 650°C) on phosphorus (P) fractions of three contrasting soils. A 90d incubation study was conducted by mixing biochar with soil at a rate of 1% w/w and at 70% field capacity. Sequential P fraction was performed on biochar, soil and soil-biochar mixtures. Increase in most labile P (resin-P_i, NaHCO₃-P_i) and organic P fraction (NaHCO₃-P_o + NaOH-P_o) in CC and RH biochars were inversely related to increasing temperature. HCl-P_i and residual P increased with increasing temperature. Interaction of CC and RH with soils resulted in an increase in most labile P as well as moderately labile P (NaOH-P_i) fractions in the soils. CC increased most labile P in the soils more than RH. The increase in most labile P fraction in soils was more significant at relatively lower temperatures (300°C and 450°C) than 650°C. However, the increase in HCl-P_i and residual P of the soils was more predominant at high temperature (650°C). The study suggested that biochar pyrolyzed at 300–450°C could be used to increase P bioavailability in tropical soils.  相似文献   

Transendoscopic biopsy of the horse's airway mucosa     

Virginia Buechner-Maxwell  Mark Crisman  Michael Murray  William Ley  Geoffrey Saunders  Amelia Walton 《Journal of Equine Veterinary Science》1996,16(9):375-379

Transtracheal wash and bronchoalveolar lavage are diagnostic techniques that have been adopted from human medicine for monitoring inflammatory changes in the airway of the horse. Transendoscopic biopsy has also proven to be a valuable tool for obtaining samples of the airway mucosa in human patients. A transendoscopic technique was developed in this study for obtaining a respiratory mucosal biopsy from standing, sedated horses. Six normal adult horses were sampled at eight-week intervals for a total of three sample periods. Horses were monitored for adverse effects of the technique and none were noted. Sample sites were completely healed after eight weeks with no gross or histologic abnormalities. Biopsy samples were 3 to 4 millimeters in diameter, and 17 of 18 samples provided interpretable histological sections. Methods for handling, staining and evaluating tissue were also developed. The results of this study demonstrated that airway mucosal biopsy is a safe, repeatable technique that can be performed in the sedated, standing horse.  相似文献   

Volatile chemical cues guide host location and host selection by parasitic plants     

Runyon JB  Mescher MC  De Moraes CM 《Science (New York, N.Y.)》2006,313(5795):1964-1967

The importance of plant volatiles in mediating interactions between plant species is much debated. Here, we demonstrate that the parasitic plant Cuscuta pentagona (dodder) uses volatile cues for host location. Cuscuta pentagona seedlings exhibit directed growth toward nearby tomato plants (Lycopersicon esculentum) and toward extracted tomato-plant volatiles presented in the absence of other cues. Impatiens (Impatiens wallerana) and wheat plants (Triticum aestivum) also elicit directed growth. Moreover, seedlings can distinguish tomato and wheat volatiles and preferentially grow toward the former. Several individual compounds from tomato and wheat elicit directed growth by C. pentagona, whereas one compound from wheat is repellent. These findings provide compelling evidence that volatiles mediate important ecological interactions among plant species.  相似文献   

Planktonic foraminifera of the California Current reflect 20th-century warming     

Field DB  Baumgartner TR  Charles CD  Ferreira-Bartrina V  Ohman MD 《Science (New York, N.Y.)》2006,311(5757):63-66

It is currently unclear whether observed pelagic ecosystem responses to ocean warming, such as a mid-1970s change in the eastern North Pacific, depart from typical ocean variability. We report variations in planktonic foraminifera from varved sediments off southern California spanning the past 1400 years. Increasing abundances of tropical/subtropical species throughout the 20th century reflect a warming trend superimposed on decadal-scale fluctuations. Decreasing abundances of temperate/subpolar species in the late 20th century indicate a deep, penetrative warming not observed in previous centuries. These results imply that 20th-century warming, apparently anthropogenic, has already affected lower trophic levels of the California Current.  相似文献   

Transformation of the nitrogen cycle: recent trends, questions, and potential solutions   总被引：12，自引：0，他引：12  

Galloway JN  Townsend AR  Erisman JW  Bekunda M  Cai Z  Freney JR  Martinelli LA  Seitzinger SP  Sutton MA 《Science (New York, N.Y.)》2008,320(5878):889-892

Humans continue to transform the global nitrogen cycle at a record pace, reflecting an increased combustion of fossil fuels, growing demand for nitrogen in agriculture and industry, and pervasive inefficiencies in its use. Much anthropogenic nitrogen is lost to air, water, and land to cause a cascade of environmental and human health problems. Simultaneously, food production in some parts of the world is nitrogen-deficient, highlighting inequities in the distribution of nitrogen-containing fertilizers. Optimizing the need for a key human resource while minimizing its negative consequences requires an integrated interdisciplinary approach and the development of strategies to decrease nitrogen-containing waste.  相似文献   

Fear of predation slows plant-litter decomposition     

Hawlena D  Strickland MS  Bradford MA  Schmitz OJ 《Science (New York, N.Y.)》2012,336(6087):1434-1438

Aboveground consumers are believed to affect ecosystem functioning by regulating the quantity and quality of plant litter entering the soil. We uncovered a pathway whereby terrestrial predators regulate ecosystem processes via indirect control over soil community function. Grasshopper herbivores stressed by spider predators have a higher body carbon-to-nitrogen ratio than do grasshoppers raised without spiders. This change in elemental content does not slow grasshopper decomposition but perturbs belowground community function, decelerating the subsequent decomposition of plant litter. This legacy effect of predation on soil community function appears to be regulated by the amount of herbivore protein entering the soil.  相似文献   

Compatibility of Beauveria bassiana with Neoseiulus barkeri for Control of Frankliniella occidentalis     

WU Sheng-yong  GAO Yu-lin  XU Xue-nong  Mark S Goettel  LEI Zhong-ren 《中国农业科学(英文版)》2015,(1):98-105

The entomopathogenic fungus Beauveria bassiana(Balsamo) Vuillemin and predatory mite Neoseiulus barkeri Hughes are effective biological control agents of F rankliniella occidentalis Pergande(Thysanoptera: Thripidae), one of the most important pests of ornamentals and vegetables world-wide. Combined application of both may enhance control efficiency. T he functional response for N. barkeri on the first instar larvae of western flower thrips which were infected by B. bassiana for 1 2 and 24 h in the laboratory((25±1)°C,(70±5)% RH, L:D=16 h:8 h) was determined. The virulence of B. bassiana against the secon d instar and pupae of the thrips attacked by N. barkeri were also tested. The re sults showed that N. barkeri exhibited a Hollin g type II fu n ctional response on treated thrips. After having been treated with the fungus for 12 h and then offered to the predator, thrips were more vulnerable to be killed by N. barkeri. The second instar larvae and pupae of the thrips which had been attacked by predatory mites were m arkedly more susceptible to B. bassiana infection than normal thrips; the cu mulative corrected mortality of B. bassiana of the second instar and pupae which were attacked by N. barkeri were 57 and 94%, respectively, compared to 35 and 80% in controls on the day 8. These findings highlight the potential use of B. bas siana in combination with N. barkeri to control F. occidentalis.  相似文献   

Genetic analysis of the maximum germination distance of Striga under Fusarium oxysporum f. sp. strigae biocontrol in sorghum     

Emmanuel Mrema  Hussein Shimelis  Mark Laing  Learnmore Mwadzingeni 《农业科学学报》2018,17(7):1585-1593

Maximum germination distance(MGD) is an important component of Striga resistance in sorghum. The objective of this study was to determine gene action influencing MGD of Striga hermonthica and Striga asiatica among selected sorghum lines treated with a biocontrol agent, Fusarium oxysporum f. sp. strigae(FOS) for effective breeding with Striga resistance, and FOS compatibility. Twelve sorghum genotypes were selected based on their Striga resistance, FOS compatibility, and superior agronomic performance. Selected genotypes were crossed using a bi-parental mating design to generate six families for genetic analysis. Agar-gel assays were used to determine low haustorium initiation factor(LHF) using the 12 parental lines, their F_1 progenies, backcross derivatives, and F_2 segregants in two sets. One set had S. hermonthica seed and the other one had S. asiatica seed. Both were treated with and without FOS. Genotypes were evaluated using a split-plot design with three replications and MGD data were recorded followed by generation mean analysis. FOS reduced MGD by 1cm under both S. hermonthica and S. asiatica infestations. Additive, dominance, and epistatic gene actions were involved in the control of MGD of the two Striga species in the evaluated populations. On average, the relative contribution of additive, additive×additive and dominance×dominance genetic effects on the MGD of S. hermonthica and S. asiatica, with FOS, were 20, 33, and 36%; and 21, 32, and 35%, respectively. Breeding methods exploiting these genetic effects may provide enhanced response to selection for Striga resistance and FOS compatibility in integrated Striga management(ISM) programmes.  相似文献   

Environment not ‘nativeness’ dictates reproductive trait shifts in Ponto‐Caspian gobies          下载免费PDF全文

Markéta Konečná  Michal Janáč  Kevin Roche  Pavel Jurajda 《Ecology of Freshwater Fish》2016,25(1):167-170

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Effects of cover crop quality and quantity on nematode-based soil food webs and nutrient cycling     

S. Tianna DuPont  Howard Ferris  Mark Van Horn 《Applied soil ecology》2009,41(2):157-167

Soil food webs cycle nutrients and regulate parasites and pathogens, services essential for both agricultural productivity and ecosystem health. Nematodes provide useful indicators of soil food web dynamics. This study was conducted to determine if nematode soil food web indicators and crop yield can be enhanced by combinations of cover crops in a conservation tillage system. The effects of three cover crop treatments (vetch/pea, oat/wheat and oat/wheat/pea/vetch) with low, medium and high C:N and a bare fallow control were investigated in Davis, CA. Nematode fauna, soil properties and plant productivity were measured. Soil food web indices, including the Enrichment Index (EI), Structure Index (SI), Basal Index (BI), and Channel Index (CI), based on the composition of nematode assemblages, were calculated to infer soil food web condition. Cover cropped tomato/corn rotations had twice the number of enrichment opportunist bacterial feeding nematodes, active participants in nitrogen mineralization, than fallowed tomato/corn rotations (opportunist bacterial feeders = 163 versus 98). In winter fallowed plots food webs were basal, common in disturbed, nutrient-poor conditions (BI = 37). Total number of enrichment opportunist nematodes, soil NH₄-N levels, and inferred nitrogen mineralization, were higher in cover crop treatments with low to mid C:N ratios. Omnivore and predator nematodes were scarce, averaging less than 6 nematodes 100 g^?1 in all treatments. In year one, plant productivity was highest after fallow. In contrast, in year two productivity was highest after cover crops with high nitrogen content and productivity significantly correlated with the structure of the soil fauna. Monitoring the abundance of enrichment opportunists may provide managers with a new tool to evaluate soil food web nitrogen mineralization and plant productivity.  相似文献