Soil organic C,nutrients, microbial biomass,and grain yield of rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.) after 18 years of fertilizer application to an infertile paddy soil

We have studied the influence of long-term fertilization on organic C, nutrients, microbial biomass of soil, and grain yield of rice (Oryza sativa L.) after 18 years of inorganic and organic fertilizer application to an infertile paddy field under subtropical conditions. After 18 years of fertilization, soil organic C and total N contents were 9.56~12.17 and 1.01~1.25 g kg⁻¹, which were 190~269% and 135~191% higher than those of the initial soil, respectively. Organic manure application increased soil organic C, total N, available N, and available P contents by 19.2%, 14.4%, 13.2%, and 78.3% on average compared with organic manure-omitted treatments. Phosphorus fertilizer application increased soil available P content more significantly than organic manure application, and it was an average 385% higher than P-omitted treatments. Soil microbial biomass C, N, and rice yield were 48.9%, 33.2%, and 133% higher in organic manure application treatments and 36.8%, 38.8%, and 239% higher in P fertilizer application treatments than organic manure-omitted or P-omitted treatments, respectively. Incorporation of organic manure-enhanced and P fertilizer-enhanced rice yields by 382% compared with the unfertilized treatment and yield increment index was 123% compared with that observed during 1991–1994, implying that organic manure application combined with P fertilizer was needed to ensure high and sustainable productivity. Rice yield was significantly correlated with all soil chemical properties except available K content, and stepwise regression analysis showed that soil available P content was the limiting factor to rice yield.     

A Bayesian Model for Presence-Only Semicontinuous Data,With Application to Prediction of Abundance of <Emphasis Type="Italic">Taxus Baccata</Emphasis> in Two Italian Regions

In studies about the potential distribution of ecological niches, only the presence of the species of interest is usually recorded. Pseudo-absences are sampled from the study area in order to avoid biased estimates and predictions. For cases in which, instead of the mere presence, a continuous abundance index is recorded, we derive a two-part model for semicontinuous (i.e., positive with excess zeros) data which explicitly takes into account uncertainty about the sampled zeros. Our model is a direct extension of the one of Ward et al. (Biometrics 65, 554–563, 2009). It is fit in a Bayesian framework, which has many advantages over the maximum likelihood approach of Ward et al. (2009), the most important of which is that the prevalence of the species does not need to be known in advance. We illustrate our approach with real data arising from an original study aiming at the prediction of the potential distribution of the Taxus baccata in two central Italian regions. Supplemental materials giving detailed proofs of propositions, tables and code are available online.     

Mercury Flux to Sediments of Lake Tahoe, California–Nevada

We report estimates of mercury (Hg) flux to the sediments of Lake Tahoe, California–Nevada: 2 and 15–20 µg/m²/year in preindustrial and modern sediments, respectively. These values result in a modern to preindustrial flux ratio of 7.5–10, which is similar to flux ratios recently reported for other alpine lakes in California, and greater than the value of 3 typically seen worldwide. We offer plausible hypotheses to explain the high flux ratios, including (1) proportionally less photoreduction and evasion of Hg with the onset of cultural eutrophication and (2) a combination of enhanced regional oxidation of gaseous elemental Hg and transport of the resulting reactive gaseous Hg to the surface with nightly downslope flows of air. If either of these mechanisms is correct, it could lead to local/regional solutions to lessen the impact of globally increasing anthropogenic emissions of Hg on Lake Tahoe and other alpine ecosystems.     

No‐tillage corn response to placement of fertilizer nitrogen,phosphorus, and potassium

Abstract

Fertilizer placement for corn (Zea mays L.) has been a major concern for no‐tillage production systems. This 3‐yr study (1994 to 1996) evaluated fertilizer phosphorus (P) or potassium (K) rates and placement for no‐tillage corn on farmers’ fields. There were two sites for each experiment involving fertilizer P or K. Treatments consisted ofthe following fertilizer rates: 0,19,and 39 kg P ha^‐1 or 0, 51, and 102 kg K ha^‐I. The fertilizer was broadcast or added as a subsurface band 5 cm beside and 5 cm below the seed at planting. Early plant growth, nutrient concentrations, and grain yields were measured. At the initiation of the study, soil test levels for P and K at the 0–1 5 cm depths ranged from optimum (medium) to very high across sites. Effects of added fertilizer and placement on early plant growth and nutrient concentrations were inconsistent. Added fertilizer had a significant effect on grain yields in two of twelve site‐years. Therefore, on no‐tillage soils with high fertility, nutrient addition, and placement affected early plant growth and nutrient utilization, but had limited effect on grain yield. Consequently, crop responses to the additions of single element P or K fertilizers under no‐tillage practices and high testing soils may not result in grain yield advantages for corn producers in the Northern cornbelt regardless of placement method.     

Issues related to classification of garden soils from the urban area of Toruń, Poland

ABSTRACT

Nowadays, the city area of Toruń is dominated by anthropogenic and technogenic soils – developed by humans or significantly altered, mainly disturbed in terms of morphology and chemical and physical properties. This study is a continuation of research on the soil cover of the city. The aim of the presented study is to assess extent of garden soils in the city and characterize its properties on the base of five soil profiles in four exemplary gardens in Toruń and evaluate if they meet the classification criteria for Hortic Anthrosols according to World Reference Base (WRB) for Soil Resources. Within the administrative boundaries of the city, 66 allotment gardens are located which totally cover an area of more than 300 ha. They occupy 3% of the city area. None of the studied mineral surface horizons meets the criteria for hortic horizon according to WRB 2015, due to too low phosphorus content. Other hortic criteria were fulfilled. The research on classification issues of garden soils should be continued on larger scale to evaluate if WRB criteria are not too strict taking into account the features of most typical, few decade-old garden soils.     

Live and death of streptomyces in soil—what happens to the biomass?

The formation of soil organic matter (SOM) has been proposed to depend on fragmentation of biomass after cell death. However, this is hard to mimic in laboratory experiments showing the process directly. We used heavy metal contamination in order to provide an environment in which one Streptomyces strain, the heavy metal resistant S. mirabilis P16B‐1, could survive while the sensitive strain S. lividans TK24 was expected to die and disintegrate; the necromass fragments would then contribute to SOM formation. Both strains were grown for 30 d in sterile mesocosms containing either highly metal‐contaminated soil from a former uranium‐mining site in Ronneburg, Germany, or control soil from a municipal park, Jena, Germany. The fate and morphology of living and dead bacterial biomass (necromass) was observed using scanning electron microscopy. Attachment of soil particles to the intact mycelium as well as decay of dead biomass was observed. Dead bacterial biomass was identified in form of patchy fragments while the superordinate filamentous structure of the hyphae was still visible and obviously stabilized in soil. The fate of cytosolic compounds was followed using the example of a nickel‐containing superoxide dismutase (NiSOD) which was found to be released after death of cells grown in liquid soil‐extract medium. Activity of the enzyme was proven for concentrated media supernatant by a gel‐based qualitative activity assay. This indicates that NiSOD remains active in soil after cell death. Hence, bacterial cell death results in the release of cytosolic compounds, e.g., intact proteins, as well as the formation of residual cell‐envelope fragments contributing to SOM formation.     

Regulation of macro,micro, and toxic element uptake by <Emphasis Type="Italic">Salix</Emphasis> × <Emphasis Type="Italic">smithiana</Emphasis> using liming of heavily contaminated soils

Purpose

Willow cultivation in soils heavily contaminated by risk elements is a challenging issue due to phytotoxic effects that restrict plant growth. Liming reduces the mobility of some risk elements in contaminated soils and therefore can be a suitable measure for contaminated soils but can also affect availability of nutrients for planted willows. We investigate how liming affects concentrations of macro, micro, and toxic elements in the organs of willows planted in contaminated soils.

Materials and methods

We established a 3-year pot experiment with Salix × smithiana planted in weakly acid and alkaline soils anthropogenically seriously contaminated by As, Cd, Pb, and Zn. Soils were both untreated and treated with two doses of lime and dolomite in the first year before planting. We determined biomass production, mortality, and the concentration of macro- and micronutrients and toxic elements in the willows’ aboveground organs.

Results and discussion

Lime application increased biomass production in both soils; dose of lime played an important role for its increase only in alkaline soil. Lime in a higher dose was incompatible with the vitality of just-planted willows in both soils. Doses of dolomite significantly affected the biomass production and mortality of willows, where lower doses caused a permanent decrease of biomass production and mortality in weakly acid soil. The toxicity of Cd and Zn in leaves was recorded in both untreated soils; the latent deficiency of P and deficiency of Fe in leaves was only recorded in weakly acid untreated soil.

Conclusions

Lime application irrespective of dose with foliar Fe application seemed to be the most suitable measure for increasing biomass production and decreasing toxic elements, especially Cd and Zn, without decreasing the macro- and micronutrients in the aboveground organs of willows in weakly acid soil. In alkaline soil, only higher doses of lime had a positive effect on the studied parameters. Dolomite application is not a suitable measure for planting willows in both contaminated soils. Dolomite in a lower dose impairs the growth of willows in weakly acid soil.

     

Concentrations of total nitrogen in squash,cucumber and melon in relation to growth,and to a piper‐steenbjerg effect

Abstract

Squash (Cucurbita pepo), cucumber (Cucranis sativus), and sweet melon (Cucumis dudain) were grown in sand cultures with N supply concentrations as the variable. For several reasons, total‐N values were found to be less satisfactory than NO ‐N for the purpose of determining the critical nitrogen concentration for maximum growth. Concentrations of total‐N in mature petioles were higher in plants severely deficient in N than in less deficient plants, characteristic of a Piper‐Steenbjerg effect.     

Can field populations of the enchytraeid,Cognettia sphagnetorum,adapt to increased drought stress?

The ability to evolve increased drought tolerance in response to climate change was investigated in the enchytraeid, Cognettia sphagnetorum. Populations exposed to reduced precipitation or increased night time temperature for more than six years were collected in mixed Calluna/grass heathland at the Mols Laboratory, Denmark. The level of prolonged drought and increased temperature corresponded to a predicted climate change scenario and has been applied since 1999. In autumn 2005, enchytraeids were sampled in 3 cm intervals down to 9 cm depth and total number, biomass, diversity and soil organic matter were determined. The drought treatment resulted in a significant reduction of the density and biomass of enchytraeids, as well as changes in the species composition. In total, five different genera were found at the site in all three treatments (control, temperature and drought). C. sphagnetorum was the dominant species, especially in the upper 0–3 cm, and was clearly affected by the drought treatment. C. sphagnetorum from all plots were cultured in the laboratory to rear second or third generation adults. Results showed that populations of drought treated plots had not developed an increased drought resistance compared to populations of control or warming plots even after several years of a putative severe selection. Lack of adaptive potential in C. sphagnetorum suggests that more frequent periods with drought in the future will have a very strong negative influence on enchytraeid density, biomass and diversity.     

Wild rocket – effect of water deficit on growth,flowering, and attractiveness to pollinators

Wild rocket, Diplotaxis tenuifolia (L.) DC. (Brassicaceae), is one of the three cultivated rocket species, the demand and production of which have recently increased in Mediterranean countries where irrigation water is scarce. Besides its use as a crop, D. tenuifolia has been observed to flower for a long period and to be attractive to pollinators. In this study we assessed the effect of drought stress and moderate- and severe-deficit irrigation on growth, flower development, and attractiveness to pollinators in D. tenuifolia. The results showed that in greenhouse conditions, potted D. tenuifolia could be without irrigation for 4 days without affecting its growth, flowering, and attractiveness to pollinators. However, lack of irrigation for 8 days or longer significantly reduced the vegetative growth, number of open flowers, total floral area, flower diameter, corolla tube diameter, and corolla tube length of D. tenuifolia. This study shows that regulated-deficit irrigation can improve water use efficiency, and depending on the purpose of growing D. tenuifolia, as a crop or as a beneficial plant to attract pollinators, it can reduce water consumption from 40% to 70% without affecting its vegetative and floral development and without reducing its attractiveness to pollinators.     

Do arsenate reductase activities and oxalate exudation contribute to variations of arsenic accumulation in populations of <Emphasis Type="Italic">Pteris vittata</Emphasis>?

Purpose

Although arsenic (As) hyperaccumulation is a constitutive property for Pteris vittata, there is intraspecific variation in As accumulation among metallicolous (from As-contaminated soils) and nonmetallicolous populations (from uncontaminated soils) and the related mechanisms is still not clear.

Materials and methods

Pot trials, hydroponic culture, and manual simulation were conducted to investigate the roles of arsenate reductase and root exudates in accumulating As in P. vittata, which were collected from two uncontaminated sites including Sun Yat-sen University campus, Guangdong Province (ZD), and a botanical garden in Guangxi Academy of Forestry Sciences, Nanning City, Guangxi Province (NN), and two As and Pb/Zn mining and/or smelting sites located in Shaoguan of Guangdong Province (SG) and Guiyang of Hunan Province (GY).

Results and discussion

The nonmetallicolous populations (ZD and NN) possessed more efficient uptake of arsenate and arsenite than the metallicolous populations (SG and GY). There were significant (p?<?0.05) difference in arsenate reductase activities in roots among the four populations of P. vittata and that the higher arsenate reductase activities were recorded in the nonmetallicolous populations (110 nkat mg^?1 protein for ZD, 160 nkat mg^?1 protein for NN) compared with the metallicolous populations (62.9 nkat mg^?1 protein for SG, 78.1 nkat mg^?1 protein for GY). Root exudates from the nonmetallicolous population (NN) and the metallicolous population (GY) of P. vittata contained similar compositions of organic acids including oxalic, malic, and succinic acids, of which oxalate were dominant (>?67%). The NN population exuded 4.23 times more oxalate than the SG population. Root exudates from the NN population mobilized significantly (p?<?0.05) more As from As-contaminated soils than those from the SG population, of which oxalate had the most effective in As mobilization.

Conclusions

The present study suggests that higher arsenate reductase activities and oxalate exudation in the nonmetallicolous populations may play an important role in increasing their efficiency in phytoremediation of As-contaminated soils.

     

Are the biogeochemical cycles of carbon,nitrogen, sulfur,and phosphorus driven by the “Fe<Superscript>III</Superscript>–Fe<Superscript>II</Superscript> redox wheel” in dynamic redox environments?

Purpose  

Iron’s fluctuation between the II (ferrous) and III (ferric) oxidation states has been coined as the “Fe^III–Fe^II redox wheel.” Numerous studies have coupled the “iron redox wheel” with the biogeochemical cycle of carbon (C), nitrogen (N), sulfur (S), or phosphorus (P) individually in soils or sediments, but evidence suggests that the Fe^III–Fe^II redox wheel drives the biogeochemical cycles interactively in a fluctuating redox microenvironment. The interactions of the Fe^III–Fe^II redox wheel with the biogeochemical cycles of C, N, S, and P in the fluctuating redox environments were reviewed in this paper.     

<Emphasis Type="Italic">Manihot fortalezensis</Emphasis> Nassar,Ribeiro, Bomfim et Gomes a new species of <Emphasis Type="Italic">Manihot</Emphasis> from Ceará, Brazil

A new species of Manihot has been collected from Fortaleza, Ceará state, Brazil. It was grown at the living collection in the experimental station, University of Brasilia since 1980 and left for natural reproduction. It bred true during all these years giving rise to identical typical plants of the ancestor one. The closest species to it is M. glaziovii. Apparently this new species was formed by sporadic hybridization between M. glaziovii and cassava itself in its natural habitat, Ceará. It possesses morphological marker gene of the latter one which is ribbed fruit that is found only in cassava. Interspecific hybrids produced experimentally between M. glaziovii and cassava showed similar morphological markers. Exam of its ovules revealed formation of multiple embryos, an indicator of apomixis. Grafting it with common cassava was compatible, giving increased root size up to seven times.     

Changes in CO<Subscript>2</Subscript>, <Superscript>13</Superscript>C abundance,inorganic nitrogen, β-glucosidase,and oxidative enzyme activities of soil during the decomposition of switchgrass root carbon as affected by inorganic nitrogen additions

This study was conducted to investigate the effect of inorganic nitrogen (N) and root carbon (C) addition on decomposition of organic matter (OM). Soil was incubated for 200 days with nine treatments (three levels of N (no addition (N0) = 0, low N (NL) = 0.021, high N (NH) = 0.083 mg N g⁻¹ soil) × three levels of C (no addition (C0) = 0, low C (CL) = 5, high C (CH) = 10 mg root g⁻¹ soil)). The carbon dioxide (CO₂) efflux rates, inorganic N concentration, pH, and potential activities of β-glucosidase and oxidative enzyme were measured during incubation. At the beginning and the end of incubation, the native soil organic carbon (SOC) and root-derived SOC were quantified by using a natural labeling technique based on the differences in δ ¹³C between C3 and C4 plants. Overall, the interaction between C and N was not significant. The decomposition of OM in the NH treatment decreased. This could be attributed to the formation of recalcitrant OM by N because the potentially mineralizable C pool was significantly lower in the NH treatment (3.1 mg C g⁻¹) than in the N0 treatment (3.6 mg C  g⁻¹). In root C addition treatments, the CO₂ efflux rate was generally in order of CH > CL > C0 over the incubation period. Despite no differences in the total SOC concentration among C treatments, the native SOC in the CH treatment (18.29 mg C g⁻¹) was significantly lower than that in the C0 treatment (19.16 mg C g⁻¹).     

Sorption of Uranium on a Bifunctional Polymer of Diethylenetriaminepentaacetic Acid Cross-Linked <Emphasis Type="Italic">β</Emphasis>-Cyclodextrin in the Presence of Humic Acid: Kinetics,Isotherms, and Thermodynamics

Humic acid (HA) plays an important role in the migration and transformation of uranium in natural waters. To effectively remove uranium in the presence of HA, a bifunctional polymer, diethylenetriaminepentaacetic acid cross-linked β-cyclodextrin (DTPA-β-CD), was synthesized by polycondensation reaction. The sorption performance of DTPA-β-CD in functions of pH, ionic strength, contact time, initial time, and temperature were explored batch wise. Experimental results showed that DTPA-β-CD could concurrently sorb uranium and HA around pH of 3.0. The sorption strongly depended on pH and on ionic strength, demonstrating outer-sphere surface complex in nature. Two sorption kinetics well followed pseudo-second-order model. Sorption isotherm accorded with Sips model. Increasing temperature facilitated uranium and restrained HA sorption. This work demonstrated that DTPA-β-CD was a promising material for sorbing uranium in the presence of HA.     

Tolerance of durum wheat lines to an acid,aluminum‐toxic subsoil

Durum wheat, Triticum durum Desf., is reportedly more sensitive to aluminum (Al) toxicity in acid soils than hexaploid wheat, Triticum aestivum L. em. Thell. Aluminum‐tolerant genotypes would permit more widespread use of this species where it is desired, but not grown, because of acid soil constraints. Durum wheat germplasm has not been adequately screened for acid soil (Al) tolerance. Fifteen lines of durum wheat were grown for 28 days in greenhouse pots of acid, Al‐toxic Tatum subsoil at pH 4.5, and non‐toxic soil at pH 6.0. Aluminum‐tolerant Atlas 66 and sensitive Scout 66 hexaploid wheats were also included as standards. Based on relative shoot and root dry weight (wt. at pH 4.5/wt. at pH 6.0 X 100), durum entries differed significantly in tolerance to the acid soil. Relative shoot dry weight alone was an acceptable indicator of acid soil tolerance. Relative dry weights ranged from 55.1 to 15.5% for shoots and from 107 to 15.8% for roots. Durum lines PI 195726 (Ethiopia) and PI 193922 (Brazil) were significantly more tolerant than all other entries, even the Al‐tolerant, hexaploid Atlas 66 standard. Hence, these two lines have potential for direct use on acid soils or as breeding materials for use in developing greater Al tolerance in durum wheat. Unexpectedly, the range of acid soil tolerance available in durum wheat appears comparable to that in the hexaploid species. Hence, additional screening of durum wheat germplasm for acid soil (Al) tolerance appears warranted. Durum lines showing least tolerance to the acid soil included PI 322716 (Mexico), PI 264991 (Greece), PI 478306 (Washington State, USA), and PI 345040 (Yugoslavia). The Al‐sensitive Scout 66 standard was as sensitive as the most sensitive durum lines. Concentrations of Al and phosphorus were significantly higher in shoots of acid soil sensitive than in those of tolerant lines, and these values exceeded those reported to cause Al and phosphorus (P) toxicities in wheat and barley.     

Does genetic diversity of grass improve yield,digestibility, and resistance to weeds,pests and disease infection?

ABSTRACT

Intraspecies genetic level diversity has the potential to improve ecosystem functions and services, similar to that by species-level diversity. Although yield, pollination, and pest and disease control have been enhanced by crop genetic diversity, mixing multiple cultivars of grass within a species in an agricultural field have not been fully tested by farmers.

We, therefore, tested whether multiple ecosystem functions are increased in a grass mixture of multiple cultivars compared to monoculture and whether this relationship differs with soil fertility. We performed monocultures of four Orchard Grass cultivars and a mixture of these cultivars with and without fertilizer application and examined the aboveground net primary productivity (ANPP), their stability, dry matter digestibility, and resistance to weed, pest, and disease. We found significant differences between cultivars in the second yield and disease lesion area on the leaf, but not between mixed culture and monoculture. Moreover, no significant difference was found in the first and third yields in terms of stability, dry matter digestibility, and leaf damage by insects, although the number of leaves damaged by insects for mixed culture was less than half of that on average for monoculture. Although genetic diversity is not always an important driver of ecological processes due to fluctuation among plots, it may play a role in pest control of agricultural land in the long term.     

Genetics of Wild and Managed Populations of <Emphasis Type="Italic">Leucaena esculenta</Emphasis> Subsp. <Emphasis Type="Italic">esculenta</Emphasis> (Fabaceae; Mimosoideae) in La Montaña of Guerrero,Mexico

Genetic consequences of silvicultural management of Leucaena esculenta subsp. esculenta were analyzed from eight allozyme loci in half-sib families of one wild and one managed in situ (selectively cleared) population from La Montaña de Guerrero region, Central Mexico. A reference sample (including wild, feral and cultivated individual plants) from the states of Morelos, Puebla and Guerrero, Mexico was also analyzed. Genetic variation, population structure and mating system were analyzed. All loci showed high variation (75–87.5% polymorphic loci at 95% level; 2.4–2.8 mean number of alleles per locus). All progenies showed heterozygous deficiency, but both wild and managed parental inbreeding coefficients were negative, suggesting heterosis. Progenies of managed populations differed from those of the wild and reference samples (Nei’s unbiased identities 0.874–0.934). Biparental inbreeding is suggested by Wright’s-statistics ( f = 0.313), and by outcrossing rate estimates: t_m = 0.644 (SE 0.094), and 0.645 (SE 0.193); t_s = 0.576 (SE 0.189), and 0.523 (SE 0.182), for managed and wild samples respectively. Population differentiation is significant (Θ = 0.210). The species is self-incompatible and deviations from the mixed mating model were found. Indirect estimates of products of effective population size (N_e) by the proportion of migrants (N_m) were moderate, as were the N _evalues. Variation due to ecotypic differentiation (related to altitude), prolonged artificial selection, and introduction from other areas is supported. A model of domestication of seed-propagated trees is suggested, based on extensive and in situ selection of locally adapted populations, and their diffusion to other areas.     

Changes in Physical,Chemical, and Microbiological Properties During the Two-Stage Composting of Green Waste due to the Addition of β-cyclodextrin

This research determined whether addition of β-cyclodextrin (β-CD; 0, 0.15, or 0.25%) improved the two-stage composting of green waste (GW). The following parameters were measured during composting or in the final product: moisture content; volume; biochemical and chemical oxygen demand; humic substances; C/N_solid and C/N_soluble; microbial numbers (culturable bacteria, actinomycetes, and fungi); enzyme activities (pectinase and xylanase); microbial biomass carbon and nitrogen; degradation of organic components; contents of phosphorus (available and total), potassium, sodium, calcium, and magnesium; and toxicity to germinating seeds. The two-stage composting of GW was optimal with the addition of 0.15% β-CD. A mature and stable compost was obtained in only 28?days with the optimized two-stage composting rather than in the 90–270?days typically required for traditional composting.