Influence of irrigated agriculture on soil carbon and microbial community structure

Increasing the amount of carbon (C) in soils is one method to reduce the concentration of carbon dioxide (CO2) in the atmosphere. We measured organic C stored in southern Idaho soils having long-term cropping histories that supported native sagebrush vegetation (NSB), irrigated moldboard plowed crops (IMP), irrigated conservation-chisel-tilled crops (ICT), and irrigated pasture systems (IP). The CO 2 emitted as a result of fertilizer production, farm operations, and CO2 lost via dissolved carbonate in irrigation water, over a 30-year period, was estimated and used to calculate net C fixation. Organic C in ecosystems decreased in the order IP>ICT>IMP> NSB. In February 2001, active fungal, bacterial, and microbial biomass was greater in IP soils than all other soils. Active fungal, bacterial, and microbial biomass was least in ICT soils at the 15-30-cm depth than all other soils. In August 2001, active bacterial biomass was greater in IMP soils than IP, ICT, and NSB soils. Active fungal biomass was greater in IP soils than all other soils. Whole-soil fatty acid profiles differed among management regimes and sampling dates and, to a lesser extent, with soil depth. FAME profiles from the NSB soils were distinct from the agricultural treatments and contained greater amounts of total fatty acids than the other treatments. The IMP and ICT soils yielded fatty acid profiles that were similar to each other, although those at the 15-30-cm depth were distinct from all other treatment-depth combinations. The IP FAME profiles suggest that arbuscular mycorrhizal fungi are more common in these soils than soils from the other treatments. Differences in carbon substrate utilization patterns (BIOLOG) among treatments were more variable and less pronounced that FAME results. In general, irrigated arid soils can both increase C storage while increasing microbial biomass and changing microbial diversity

The influence of vegetation in riparian filterstrips on coliform bacteria: II. Survival in soils

Survival of total and fecal coliform bacteria was measured in the 0 to 5, 5 to 15, and 15 to 30 cm soil depths at 1, 3, 7, 14, and 90 to 120 d after swine (Sus scrofa) wastewater application to riparian filterstrips in southern Georgia during each season of the year. Vegetative treatments evaluated were: (i) 20 m grass-10 m forest, (ii) 10 m grass-20 m forest, and (iii) 10 m grass-20 m maidencane (Panicum hemitomon Schult.). During winter, spring, and summer vegetation type in riparian filterstrips did not affect survival of total and fecal coliform bacteria. Total and fecal coliform bacterial numbers were usually higher in the top 0 to 5 cm of soil than in the 5 to 15 and 15 to 30 cm soil depths in all treatments. Total and fecal coliform numbers in the 0 to 5, 5 to 15, and 15 to 30 cm depths declined approximately 10-fold every 7 to 14 d after waste application in all seasons of the year. At 90 to 120 d after waste application, total and fecal coliform numbers in the three soil depths did not differ from riparian filterstrips that did not have animal waste applied. Total coliform bacteria in the O to 5, 5 to 15, and 15 to 30 cm soil depths correlated with temperature and moisture in a curvilinear relationship (r2 = 0.80 , 0.77, and 0.64, respectively). Fecal coliform bacteria in 0 to 5, 6 to 15, and 16 to 30 cm of soil also correlated with temperature and moisture in a curvilinear relationship (r 2 = 0.56 , 0.53, and 0.53, respectively)

The influence of vegetation in riparian filterstrips on coliform bacteria: I. Movement and survival in water

Swine (Sus scrofa) wastewater was applied to three separate 4 m wide x 30 m long riparian filterstrips consisting of 20 m grass and 10 m forest, 10 m grass and 20 m forest, and 10 m grass and 20 m maidencane (Panicum hemitomon Schult.) in Southern Georgia during each season. Total and fecal coliform numbers in the applied wastewater pulse did not decline as water moved downslope regardless of vegetation type or season. The pulse of applied wastewater did not move beyond 15 m in any treatment in autumn or summer (dry seasons) and only moved beyond 7.5 m in the 20 m grass-10 m forest treatment in the summer. Total and fecal coliform numbers in soil water and shallow ground water declined by approximately 10-fold every 7 d for the first 14 d regardless of vegetative treatment or season. Soil temperature and soil moisture correlated with total coliform bacteria in both 13 m wells (r2 = 0.89) and 2.0 m wells (r2 = 0.89), and with fecal coliform bacteria in 1.5 (r2 = 0.82) and 2.0 m (r2 = 0.76) wells. Animal production operations may need to locate in warm–dry climates so animal waste can be applied to lands to help ensure enteric bacteria input to surface and ground water will not occur

Influence of C02 enrichment and nitrogen fertilization on tissue chemistry and carbon allocation in longleaf pine seedlings

One-year old, nursery-grown longleaf pine (Pinus palustris Mill.) seedlings were grown in 45-L pots containing a coarse sandy medium and were exposed to two concentrations of atmospheric CO2 (365 or 720 µmol?1) and two levels of nitrogen (N) fertility (40 or 400 kg N ha?1 yr?1) within open top chambers for 20 months. At harvest, needles, stems, coarse roots, and fine roots were separated and weighed. Subsamples of each tissue were frozen in liquid N, lyophilized at ?50 ?C, and ground to pass a 0.2 mm sieve. Tissue samples were analyzed for carbon (C), N, nonpolar extractives (fats, waxes, and oils = FWO), nonstructural carbohydrates (total sugars and starch), and structural carbohydrates (cellulose, lignin, and tannins). Increased dry weights of each tissue were observed under elevated CO2 and with high N; however, main effects of CO2 were significant only on belowground tissues. The high N fertility tended to result in increased partitioning of biomass aboveground, resulting in significantly lower root to shoot ratios. Elevated CO2 did not affect biomass allocation among tissues. Both atmospheric CO2 and N fertility tended to affect concentration of C compounds in belowground, more than aboveground, tissues. Elevated CO2 resulted in lower concentrations of starch, cellulose, and lignin, but increased concentrations of FWO in root tissues. High N fertility increased the concentration of starch, cellulose, and tannins, but resulted in lower concentrations of lignin and FWO in roots. Differences between CO2 concentrations tended to occur only with high N fertility. Atmospheric CO2 did not affect allocation patterns for any compound; however the high N treatment tended to result in a lower percentage of sugars, cellulose, and lignin belowgroun

Polyacrylamide (PAM) - A one million acre progress report

Water soluble polyacrylamide (PAM) was recognized in the early 1990s as an environmentally safe and highly effective erosion-preventing and infiltration-enhancing chemical, when applied in very dilute concentrations in furrow irrigation water (Lentz et al., 1992; Lentz and Sojka, 1994; McCutchan et al., 1994; Trout et al., 1995; Sojka and Lentz, 1997; Sojka et al., 1998a,b). The mode of action involves surface soil structure stabilization and maintenance of pore continuity. A recommended conservation practice standard was published by NRCS in 1995 (Anonymous, 1995) and is being revised in 1999. It delineates considerations and specifies methodology for. PAM-use. Commercial sales of erosion-preventing PAMs began in 1995. Approximately one million acres were treated in the United States in 1999. Extent of adoption of the practice outside the US is less certain, but interest is growing in several countries and continents. Key aspects of this PAM technology development are presented below

An ecoinformatics tool for microbial community studies: Supervised classification of amplicon length heterogeneity (ALH) profiles of 16S rRNA

Support vector machines (SVM) and K-nearest neighbors (KNN) are two computational machine learning tools that perform supervised classification. This paper presents a novel application of such supervised analytical tools for microbial community profiling and to distinguish patterning among ecosystems. Amplicon length heterogeneity (ALH) profiles from several hypervariable regions of 16S rRNA gene of eubacterial communities from Idaho agricultural soil samples and from Chesapeake Bay marsh sediments were separately analyzed. The profiles from all available hypervariable regions were concatenated to obtain a combined profile, which was then provided to the SVM and KNN classifiers. Each profile was labeled with information about the location or time of its sampling. We hypothesized that after a learning phase using feature vectors from labeled ALH profiles, both these classifiers would have the capacity to predict the labels of previously unseen samples. The resulting classifiers were able to predict the labels of the Idaho soil samples with high accuracy. The classifiers were less accurate for the classification of the Chesapeake Bay sediments suggesting greater similarity within the Bay's microbial community patterns in the sampled sites. The profiles obtained from the VI +V2 region were more informative than that obtained from any other single region. However, combining them with profiles from the V1 region (with or without the profiles from the V3 region) resulted in the most accurate classification of the samples. The addition of profiles from the V9 region appeared to confound the classifiers. Our results show that SVM and KNN classifiers can be effectively applied to distinguish between eubacterial community patterns from different ecosystems based only on their ALH profiles

Experimental system to displace radioisotopes from upper to deeper soil layers: chemical research

BACKGROUND: Radioisotopes are introduced into the environment following nuclear power plant accidents or nuclear weapons tests. The immobility of these radioactive elements in uppermost soil layers represents a problem for human health, since they can easily be incorporated in the food chain. Preventing their assimilation by plants may be a first step towards the total recovery of contaminated areas. METHODS: The possibility of displacing radionuclides from the most superficial soil layers and their subsequent stabilisation at lower levels were investigated in laboratory trials. An experimental system reproducing the environmental conditions of contaminated areas was designed in plastic columns. A radiopolluted soil sample was treated with solutions containing ions normally used in fertilisation (NO(3)(-), NH(4)(+), PO(4)(--- )and K(+)). RESULTS: Contaminated soils treated with an acid solution of ions NO(3)(-), PO(4)(--- )and K(+), undergo a reduction of radioactivity up to 35%, after a series of washes which simulate one year's rainfall. The capacity of the deepest soil layers to immobilize the radionuclides percolated from the superficial layers was also confirmed. CONCLUSION: The migration of radionuclides towards deeper soil layers, following chemical treatments, and their subsequent stabilization reduces bioavailability in the uppermost soil horizon, preventing at the same time their transfer into the water-bearing stratum

Litterfall, litter decomposition and associated nutrient fluxes in Pinus halepensis: influence of tree removal intensity in a Mediterranean forest

The online version of this article (doi:10.1007/s10342-015-0893-z) contains supplementary material, which is available to authorized users[EN] Our knowledge about the influence of silvicultural treatments on nutrient cycling processes in Mediterranean forests is still limited. Four levels of tree removal were compared in an Aleppo pine forest in eastern Spain to determine the effects on litterfall, litter decomposition and the associated nutrient fluxes after 12 years. Removal treatments included clearfelling, two shelterwood intensities (60 and 75 % of basal area removed) and untreated controls. Twelve years later, the basal area removed still explained 60 % of litterfall mass variance and 60 % of C, 52 % of N, 45 % of P, 17 % of K, 47 % of Ca and 60 % of Mg return variances. Litter decomposed somewhat more slowly in clearfellings compared to controls (p = 0.049), accumulated more Ca and released less K compared to the other three treatments. This was explained by contamination with mineral particles due to the poorly developed O horizon in clearfellings. We conclude that the management practices reduced the nutrient return via litterfall, but the nutrient release through decomposition seems poorly sensitive to canopy disturbance. In order to accurately quantify the harvesting impacts on nutrient cycling in this Mediterranean forest system, it is necessary to measure the litterfall of the understory layer.This work has been supported by a fellowship from the Generalitat Valenciana, Conselleria de Educacion, Formacion y Empleo awarded to L. Lado-Monserrat (BFPI/2008/041). Silvicultural treatments were carried out by the Mediterranean Centre for Environmental Studies (CEAM) through programme "I + D en relacion con la restauracion de la cubierta vegetal y otros aspectos de investigacion forestal". Dataloggers and probes were provided by the Generalitat Valenciana through Project "Efecto de diferentes sistemas de aclareo de masa forestal sobre la disponibilidad de agua, nutrientes y la regeneracion de la masa arborea y arbustiva en parcelas de pinar" (GV06/126). We acknowledge Joana Oliver, Ruth M. Tavera and Daniel Fortanet for their help in the laboratory and in the field. The authors wish to thank Francisco Galiana for his assistance, including help in fieldwork and providing information about the experimental design of the silvicultural treatments. Thanks also go to Rafael Herrera from the Centro de Ecologia, Instituto Venezolano de Investigaciones Cientificas, Caracas, Venezuela and two anonymous reviewers for critically reviewing the manuscript.Lado Monserrat, L.; Lidón, A.; Bautista, I. (2015). Litterfall, litter decomposition and associated nutrient fluxes in Pinus halepensis: influence of tree removal intensity in a Mediterranean forest. 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Effect of Biocontrol Agent Pseudomonas fluorescens 2P24 on Soil Fungal Community in Cucumber Rhizosphere Using T-RFLP and DGGE

Fungi and fungal community play important roles in the soil ecosystem, and the diversity of fungal community could act as natural antagonists of various plant pathogens. Biological control is a promising method to protect plants as chemical pesticides may cause environment pollution. Pseudomonas fluorescens 2P24 had strong inhibitory on Rastonia solanacearum, Fusarium oxysporum and Rhizoctonia solani, etc., and was isolated from the wheat rhizosphere take-all decline soils in Shandong province, China. However, its potential effect on soil fungal community was still unknown. In this study, the gfp-labeled P. fluorescens 2P24 was inoculated into cucumber rhizosphere, and the survival of 2P24 was monitored weekly. The amount decreased from 108 to 105 CFU/g dry soils. The effect of 2P24 on soil fungal community in cucumber rhizosphere was investigated using T-RFLP and DGGE. In T-RFLP analysis, principle component analysis showed that the soil fungal community was greatly influenced at first, digested with restriction enzyme Hinf I and Taq I. However, there was little difference as digested by different enzymes. DGGE results demonstrated that the soil fungal community was greatly shocked at the beginning, but it recovered slowly with the decline of P. fluorescens 2P24. Four weeks later, there was little difference between the treatment and control. Generally speaking, the effect of P. fluorescens 2P24 on soil fungal community in cucumber rhizosphere was just transient