Soil Nutrient Deficiency Research Articles

Peranan Fosfor dalam Meningkatkan Toleransi Tanaman Sorgum terhadap Cekaman Aluminium

The management of P nutrition can be a good solution for aluminum toxicity and P nutrient deficiency in acid soil. This study aimed to determine the role of phosphorus in improving the tolerance of sorghum to Al stress in nutrient culture. This research was conducted at green house of IPB Bogor, tissue culture laboratory in the Department of AGH IPB and Balai Besar Pasca Panen Cimanggu Bogor, from January to November 2014. A completely randomized factorial design was used in three experiments. The results revealed that addition of P improved the tolerance of two sorghum genotypes to Al stress as indicated by the reduction in root length inhibition by Al, where P was more effective in tolerant genotype Numbu. Addition of P reduced the accumulation of Al in the root tissues as shown by the lighter intensity of hematoxylin staining, especially in Numbu. Aluminum stress increased the secretion of oxalate acid in both sorghum genotypes, where P lowered oxalate acid secretion in both genotypes. These facts showed that the role of P in improving the tolerance of sorghum to Al stress might be associated with the inhibition of Al absorption into the root tissues, although the mechanism is not yet known.Keywords: Al stress, organic acid secretion, role of P, root staining method, sorghum

English

Reforestation of native Acacia confusa Merr. on landslide areas in Taiwan is important for agroforestry and soil conservation. To ensure high survival and growth vigor, A. confusa seedlings must develop a strong root system. Inoculating of acacia with symbiotic nitrogen-fixing bacteria (NFB) may ameliorate the problems associated with soil nutrient deficiency on landslide sites. In this study, under plastic house condition, a NFB was isolated from the root nodules of native A. confusa and identified as Bradyrhizobium elkanii, and its effects on growth, root system morphology and pullout resistance of acacia seedlings were investigated. Our results revealed that the growth of inoculated seedlings is significantly more vigor than that of the noninoculated controls. The enhancements in height, tap root length, shoot biomass and root biomass were 40, 100, 140 and 130%, respectively. Also, inoculated seedlings had significantly longer total root length (150%), larger external root surface area (130%), larger root volume (70%), and more root tip number (60%) than the controls. Moreover, the inoculated seedlings developed significantly stronger root functional traits, that is, root density (130%), root length density (60%) and specific root length (60%), than the controls. Consistently, the root pullout resistance of inoculated seedlings was significantly higher than that of the noninoculated ones. These results demonstrate that B. elkanii is an effective nitrogen-fixing bacterium capable of enhancing growth, root development and pullout resistance of A. confusa. Key words: Fabaceae, inoculation, nodules, pullout resistance, root morphology.

Selenium deficiency in subtropical littoral pampas: environmental and dietary aspects.

Se deficiency has a critical effect on human health. The littoral near Patos Lagoon in the south of Brazil is composed of Quaternary sandy deposits and nutrient-deficient soils, which contribute to Se deficiency in the surrounding environment. The average concentration of Se in littoral soils is six times lower than the metalloid deficiency threshold of 0.5mgkg-1 and is close to that in countries where Keshan disease is registered. The sediments in the Patos Estuary are also notably lower in Se than near-shore marine sediments. Foodstuffs produced in the littoral pampas are characterised by extremely low Se concentrations compared with the same alimentary products reported worldwide. The total daily dietary intake of Se in the region is 24μgday-1, which is half the Estimated Average Requirement for adults. Black beans in the local diet provide over 40% of daily Se intake. Prescriptive addition of Se to prevalent products seems the most effective solution to the problem of metalloid dietary deficiency in the region. Similar environmental conditions and significant concentration of the population in the littoral zone suggest that the problem of Se deficiency probably affects a large proportion of the population along the Atlantic coast of Brazil.

Evaluation of Elemental Sulphur Application with Rhizobia Inoculation on Peanut Yield and its Quality Grown in Sandy Soil at Egypt

TWO field experiments were conducted during the summer of ….. two successive seasons of 2011 and 2012, to identify the response of peanut (Arachis hypogaea L., cv. Giza 5)to soil application of elemental sulphur (at rate of 15, 30 and 45 Kg s/fed before sowing) and Rhizobia(Bradyrhizobium japonicum) inoculation, individually or in combination, for determination of the yield criteria, pods yield, 100 seeds yield, seeds & straw yield and shilling percentage at harvest, as well as seed oil, oil yield, protein content and protein yield. The associated amelioration in plant macro and micronutrient contents and uptake, and soil biological activities (nodulation status, nitrogenase, dehydrogenase, CO2 evolution and total bacterial counts) were assessed in this study. The obtained results indicated that Rhizobium inoculation or S addition alleviated the adverse effect of soil nutrient deficiency and caused significant increases in all the studied parameters of peanut and soil. Rhizobium inoculation individually caused insignificant increases in all the studied parameters over S addition solely at 45 kgs/fed. The joint addition of sulphur at all rates with Rhizobium inoculation gave high significant increases in all prior studied parameters and soil biological parameters at 50 and 80 days after peanut sowing followed by the individual treatments.

植被砼技术在京港澳高速鸡公山段砾石土边坡上的应用

鸡公山地区为国家4A级自然保护区，大量高填深挖方法建设的高速公路产生了许多裸露路基边坡，不仅破坏生态环境，还可能危及高速公路的安全。该课题实施对象为砾石土边坡，营养缺乏，不适合植被生长，雨季造成了水土流失，坡面产生一定程度的垮落和小冲沟，侵蚀明显。为保护高速公路的安全，恢复当地生态环境，通过系统对比研究，本课题利用植被砼技术对高速公路鸡公山区域某示范段裸露边坡实施植被防护。结果显示，通过合理调配植被砼中水泥含量、混播草种的比例以及营养成分等，采用适当的施工方法，在冬季施工的情况下，边坡植被恢复良好，护坡效果显著，极大提高了高速公路的安全性，对当地高速公路生态恢复起到很好的示范作用。 Jigong Mountain area is the state-level AAAA nature reserve; the construction of highway by high filling and deep digging method produces many unstable bare slope, which result in not only the destruction of the ecological environment, but also the safety problem of the highway. The slope of the project is gravel; the soil nutrient deficiency is not suitable for vegetation growth; the rainfalls cause obvious soil erosion, and a certain degree of collapse and small gullies. For highway safety and restoring the local ecological environment through comparative study, this subject tried to build a restoration project of exposed slope using vegetation-growing concrete technology. The results show that slope protection effects have been greatly improved by adjusting the proportion of cement and mixed sowing grass species, and adopting proper construction methods in winter construction. It is a role model for local ecological restoration.

Screening of efficient phosphate solubilizing fungi from mine soil and effect of phosphofungi on seed germination and vigour index of ground nut (arachis hypogaea L.) and green gram (vigna radiata L.)

Background: The use of chemical fertilizers to solve the problem of nutrient deficiency in soil has been associated with a number of environmental problems.Objective: The aim of this study was to perform an isolation and screening of native phosphofungi from mine soil. To evaluate the effect of phosphofungi on seed germination and seedling vigour index of Ground nut and Green gram.Materials and Methods: The phosphofungi were screened using Pikovskaya’s agar medium with tricalcium phosphate (Ca3 (PO4)2) as the phosphorus source. The soluble phosphorus, Phosphate solubilizing activity, titrable acidity, pH and fungal biomass were determined. Mineral phosphate solubilizing (MPS) activities of fungal isolates were tested in tricalcium phosphate medium.Results: Five promising phosphate solubilizing fungal species were screened. Aspergillus niger (13±1.0 mm) and Aspergillus flavus (8±0.6mm) showed the more phosphate solubilising index than compared to other fungal isolates. Analyzing the possible phosphorus released, from 3rd, 6th, 9th, and 12th day of incubation. Antagonistic effect of phosphofungi Aspergillus flavus (65±11 mm) and Aspergillus niger (60±13 mm) showed more effective against Colletotrichum sp. than compared to other fungal isolates. Aspergillus flavus (745±20µg/ml) and Penicillium spinulosum (600±20 µg/ml) showed maximum phosphate solubilizing activity on 3rd and 12th day of incubation. Fusarium redolens showed the more effectiveness on seed germination and seedling vigour than compared to other fungal isolates. Aspergillus flavus showed positive result for the production of Indole 3 acetic acid and remain four fungal strains are negative result.Conclusion: Biofertilizers from native phosphofungi could be used alongside reduced levels of inorganic fertilizers to enhance soil available Phosphorous.

Quinoa biomass production capacity and soil nutrient deficiencies in pastures, tree plantations and native forests in the Andean Highlands of Southern Ecuador

Life Cycle Assessment is a trendsetter methodology in order to assess environmental and social impacts associated to an entire productive cycle in a vision “Cradle to Grave” or in a new one “Cradle to Cradle”, taking in count every single component of these impacts or almost all. In particular, agroproductive chains have unique components and considerations, which need to be counted in the assessment process. These have been commented in the text and some calculation considerations were explained.

Seasonal changes in antioxidative/oxidative profile of mining and non-mining populations of Syrian beancaper as determined by soil conditions

Soil pollution by heavy metals/metalloids (HMMs) is a problem worldwide. To prevent dispersion of contaminated particles by erosion, the maintenance of a vegetative cover is needed. Successful plant establishment in multi-polluted soils can be hampered not only by HMM toxicities, but also by soil nutrient deficiencies and the co-occurrence of abiotic stresses. Some plant species are able to thrive under these multi-stress scenarios often linked to marked fluctuations in environmental factors. This study aimed to investigate the metabolic adjustments involved in Zygophyllum fabago acclimative responses to conditions prevailing in HMM-enriched mine-tailings piles, during Mediterranean spring and summer. To this end, fully expanded leaves, and rhizosphere soil, of three contrasting mining and non-mining populations of Z. fabago grown spontaneously in south-eastern Spain were sampled in two consecutive years. Approximately 50 biochemical, physiological and edaphic parameters were examined, including leaf redox components, primary and secondary metabolites, endogenous levels of salicylic acid, and physicochemical properties of soil (fertility parameters and total concentration of HMMs). Multivariate data analysis showed a clear distinction in antioxidative/oxidative profiles between and within the populations studied. Levels of chlorophylls, proteins and proline characterized control plants whereas antioxidant capacity and C- and S-based antioxidant compounds were biomarkers of mining plants. Seasonal variations were characterized by higher levels of alkaloids and PAL and soluble peroxidase activities in summer, and by soluble sugars and hydroxycinnamic acids in spring irrespective of the population considered. Although the antioxidant systems are subjected to seasonal variations, the way and the intensity with which every population changes its antioxidative/oxidative profile seem to be determined by soil conditions. In short, Z. fabago displays a high physiological plasticity that allow it to successfully shift its metabolism to withstand the multiple stresses that plants must cope with in mine tailings piles under Mediterranean climatic conditions.

The Alleviation of Nutrient Deficiency Symptoms in Changbai Larch (Larix olgensis) Seedlings by the Application of Exogenous Organic Acids

Exogenous organic acids are beneficial in protecting plants from the stress of heavy metal toxins (e.g., Pb) in soils. This work focuses on the potential role of organic acids in protecting Changbai larch (Larix olgensis) seedlings from the stress of growing in nutrient deficient soil. The seedlings were planted in a nutrient rich or deficient soil (A1 horizon of a Haplic Cambisol without organic acid as the nutrient rich control, or fully-mixed A1 + B horizons in a proportion of 1:2 as deficient) in pots in a greenhouse. In A1 + B horizons the seedlings were treated daily with concentrations of oxalic or citric acid (OA or CA) at a rate approximately equivalent to 0, 0.04, 0.2, 1.0, or 2.0 mmol·kg−1 of soil for 10, 20, and 30 days. Nutrient deficiency stressed the seedlings as indicated by lipid peroxidation and malondialdehyde (MDA) content in leaves significantly increasing, and superoxide dismutase (SOD) activities, proline, photosynthetic pigment contents, and chlorophyll fluorescence (Fv/Fm) decreasing. The stress increased in controls over the application periods. When nutrient deficient plants were exposed to an organic acid (especially 5.0 or 10.0 mmol·L−1 for 20 days), the stress as indicated by the physiological parameters was reversed, and survival rate of seedlings, and biomass of root, stem, and leaf significantly increased; CA was more effective than OA. The results demonstrate that exogenous organic acids alleviate nutrient deficiency-induced oxidative injuries and improve the tolerance of L. olgensis seedlings to nutrient deficiency.

Changes in the anatomy, morphology and mycorrhizal infection of fine root systems ofCryptomeria japonicain relation to stand ageing

Biomass allocation to fine roots often increases under soil nutrient deficiency, but the fine root biomass does not often increase in old stands, even under nutrient limitation. Therefore, in old stands, the morphology, anatomy, branching architecture and mycorrhization of fine roots may compensate efficiently for nutrient acquisition by the low fine root biomass. In this study, changes in the morphology, anatomy and arbuscular mycorrhizal infection at each branching position of fine root clusters were evaluated in relation to stand age. A chronosequence (6–90 years of age) of stands in a Cryptomeria japonica D. Don plantation was used for these analyses. The fine root size parameters, such as length, weight and tip numbers of fine root clusters, increased with stand age. The specific root tip length (SRTL) decreased with increasing stand age, suggesting that the allocation to root active portions decreased with stand age. From the anatomical observation, the ephemeral root tips increased with stand age, suggesting that root tip turnover within a root cluster was high in old stands. The proportions of proto-xylem groups among branching positions indicated that the life cycles in branching hierarchy should be clearer in old stands than that in younger stands. The increasing in the mycorrhizal infection of root tips in old stands should enhance the root tip absorptive functions. The SRTL was correlated with the wood/needle ratio, suggesting that carbon limitation as the stand ages may result in decline of carbon allocation to maintain active root tips. However, increasing of the ephemeral tips and mycorrhizal infection rates may compensate the declines of tip allocation in old stands.

Association of plant growth-promoting Serratia spp. with the root nodules of chickpea

Serratia species-affiliated DNA sequences have recently been discovered in the root nodules of two chickpea cultivars; however, little is known about their potential influence on chickpea plant growth. All Serratia-affiliated sequences (1136) could be grouped into two clusters at 98% DNA similarity. The major cluster, represented by 96% of sequences, was closely associated with Serratia marcescens sequences from GenBank. In the current study, we isolated two Serratia strains, 5D and RTL100, from root nodules of a field-grown Desi cultivar from Faisalabad and Thal areas, respectively. In vitro, strain 5D showed significantly higher phosphate (P) solubilization and lactic acid production than RTL100, whereas a comparable concentration of phytohormone was produced by both isolates. The application of Serratia strain 5D as an inoculum resulted in 25.55% and 30.85% increases in the grain yield of crops grown on fertile soil in irrigated areas and nutrient-deficient soil in rainfed areas, respectively, compared to the non-inoculated control. Results of plant inoculations indicated that Serratia sp. 5D and RTL100 can serve as effective microbial inoculants, particularly in nutrient-deficient soils in rainfed areas, where chickpea is the only major crop grown during the entire year.

MAPAS TEMÁTICOS DE COMPONENTES PRINCIPAIS PARA CARACTERIZAÇÃO DE PROPRIEDADES QUÍMICAS DO SOLO - DOI: 10.13083/1414-3984/reveng.v23n6p529-540

A agricultura na região Oeste do Paraná tem destaque por intensa atividade agrícola, na qual busca altas produtividades. A produtividade das áreas de cultivo está diretamente relacionada com a fertilidade. O uso intensivo do solo tende à acidificação e diminuição nos teores de nutrientes nele armazenados, o que, por consequência, limita também o desenvolvimento radicular, contribuindo para redução da produtividade. O presente trabalho foi desenvolvido com o intuito de investigar a relação entre as propriedades químicas do solo: acidez potencial, cálcio, magnésio, potássio, pH do solo, teor de matéria orgânica, soma de bases, capacidade de troca de cátions total e saturação por bases, na camada de 0,0 a 0,20 m. A exploração do solo na região se faz de forma intensiva com cultivos de soja, milho, trigo e feijão em sucessão de culturas. A amostragem de solo para análise das referidas variáveis foi georreferenciada (grid de 2 ha), sendo utilizadas técnicas de geoestatística e análise de componentes principais, com o intuito de identificar regiões que possuam maior acidez e deficiência de nutrientes que possam ser supridos por meio de calagem. Os resultados permitiram evidenciar a relação da acidez do solo com variáveis como cálcio e magnésio o que sugere a correção desses nutrientes nas regiões de elevada acidez. A classificação dos mapas em classes permite o direcionamento de ações em campo nas unidades com características similares, sendo importante para o trato localizado destas sub-regiões na área de estudo.

Energizing marginal soils – The establishment of the energy crop Sida hermaphrodita as dependent on digestate fertilization, NPK, and legume intercropping

Growing energy crops in marginal, nutrient-deficient soils is a more sustainable alternative to conventional cultivation. The use of energy-intensive synthetic fertilizers needs to be reduced, preferably via closed nutrient loops in the biomass production cycle. In the present study based on the first growing season of a mesocosm experiment using large bins outdoors, we evaluated the potential of the energy plant Sida hermaphrodita to grow in a marginal sandy soil. We applied different fertilization treatments using either digestate from biogas production or a commercial mineral NPK-fertilizer. To further increase independence from synthetically produced N-fertilizers, the legume plant Medicago sativa was intercropped to introduce atmospherically fixed nitrogen and potentially facilitate the production of additional S. hermaphrodita biomass. We found digestate to be the best performing fertilizer because it produced similar yields as the NPK fertilization but minimized nitrate leaching. Legume intercropping increased the total biomass yield by more than 100% compared to S. hermaphrodita single cropping in the fertilized variants. However, it negatively influenced the performance of S. hermaphrodita in the following year. We conclude that a successful establishment of S. hermaphrodita for biomass production in marginal soils is possible and digestate application formed the best fertilization method when considering a range of aspects including overall yield, nitrate leaching, nitrogen fixation of M. sativa, and sustainability over time.

Noncoding RNAs, Emerging Regulators in Root Endosymbioses

Endosymbiosis interactions allow plants to grow in nutrient-deficient soil environments. The arbuscular mycorrhizal (AM) symbiosis is an ancestral interaction between land plants and fungi, whereas nitrogen-fixing symbioses are highly specific for certain plants, notably major crop legumes. The signaling pathways triggered by specific lipochitooligosaccharide molecules involved in these interactions have common components that also overlap with plant root development. These pathways include receptor-like kinases, transcription factors (TFs), and various intermediate signaling effectors, including noncoding (nc)RNAs. These latter molecules have emerged as major regulators of gene expression and small ncRNAs, composed of micro (mi)RNAs and small interfering (si)RNAs, are known to control gene expression at transcriptional (chromatin) or posttranscriptional levels. In this review, we describe exciting recent data connecting variants of conserved si/miRNAs with the regulation of TFs, such as NSP2, NFY-A1, auxin-response factors, and AP2-like proteins, known to be involved in symbiosis. The link between hormonal regulations and these si- and miRNA-TF nodes is proposed in a model in which different feedback loops or regulations controlling endosymbiosis signaling are integrated. The diversity and emerging regulatory networks of young legume miRNAs are also highlighted.

Effects of arbuscular mycorrhizae on growth and mineral nutrition of greenhouse propagated fruit trees from diverse geographic provenances

Description of the subject. Arbuscular mycorrhizal (AM) fungi are known to promote plant growth by enhancing mineral uptake in nutrient deficient soils. These beneficial effects on plant growth may vary considerably between cultivars of a given species and between plant species originating from different locations. Objectives. The present experiment evaluated the response of three Sahelian fruit trees: néré (Parkia biglobosa [Jacq.] G.Don), tamarind (Tamarindus indica L.), and jujube (Ziziphus mauritiana Lam.), originating from five different geographic provenances, to mycorrhizal colonization, evaluate their respective mycorrhizal dependency (MD) and analyze their leaf and stem mineral composition. Method. Trees were cultivated in a nursery on pre-sterilized soil substrate low in available P (2.18 μg·g-1) with or without inoculum of Glomus aggregatum (Schenck & Smith emend. Koske). The experiment was arranged in a factorial design for each fruit tree species separately: 5 provenances x 2 AM treatments (inoculated and non-inoculated [control]) with 10 replicates per treatment. Plants were harvested six months after inoculation and different parameters were measured. Results. Overall, the results showed significant provenance variations in the plant response to mycorrhizal inoculation. Néré mycorrhizal plants, from two seed sources, tamarind and jujube plants from one seed source had significant higher dry weight and shoot height than those from other provenances. Jujube plants from 3 out of the 5 provenances showed significant higher MD. It then appears that seed provenance happened to be determinant even though AM-root colonization levels (80-90%) do not vary much from one provenance to another. In all cases, the fruit trees benefited from AM fungi with increased N, P and K mineral uptake in aerial parts. In particular P uptake was proportional to MD concentration in AM-jujube plants. Conclusions. These results demonstrate the importance of considering seed provenance when performing pre-selection of mycotrophic plant candidates prior to large-scale fruit tree propagation in orchards and agroforestry systems.

Competition and growth of a grass–legume mixture fertilised with nitrogen and phosphorus: effect on nutrient acquisition, root morphology and symbiosis with soil microorganisms

Achieving a fast initial growth is crucial for legumes because grasses grow more rapidly and compete much better with forbs. In a pot experiment with a nutrient-deficient soil, we added nitrogen (N), phosphorus (P) and N + P to pure and mixed stands of Lotus tenuis and Festuca arundinacea and investigated the effects of on plant growth, nutrient uptake and symbiotic associations with arbuscular mycorrhizae and rhizobia. Plant yield, N and P acquisition, mycorrhizal colonisation, rhizobial nodulation and root length were measured and root diameter and root surface area were calculated after two harvests. Species responded differently to specific nutrients when grown pure or mixed. Comparing pure with mixed stands in soils fertilised with P and N + P, L. tenuis showed decreased shoot and particularly root biomass, whereas F. arundinacea showed increases in both biomasses. This suggests that the competitiveness of the grass with the legume increased upon P and N + P addition. In mixed stands, F. arundinacea produced 51–64% of the total shoot biomass and 69–74% of the total root biomass with P and N + P, respectively. Root length and root surface area were greater and the roots thinner in F. arundinacea than in L. tenuis. Addition of P and N + P increased rhizobial nodulation in legume roots but decreased mycorrhizal colonisation in both plants. Supply of N does not necessarily favour grasses, whereas P supply favours legumes. Optimisation of P nutrition might help to maximise N inputs into grasslands by symbiotic N-fixation and decrease inputs of inorganic N by fertilisation.

Mapas Temáticos de Componentes Principais para Caracterização de Propriedades Químicas do Solo

THEMATIC MAPS OF PRINCIPAL COMPONENTS FOR CHARACTERIZATION OF SOIL CHEMICAL PROPERTIES The western region of Parana is known for its intensive agricultural activity seeking high productivity. Productivity of crop cultivation areas is directly related to soil fertility, and intensive soil use gives rise to acidification and a reduction in nutrient levels, in turn limiting root development and contributing to reduced productivity. This study was conducted with the aim of investigating relationships between the following chemical soil properties: potential acidity; calcium; magnesium; potassium; soil pH; organic matter; sum of bases; total cation exchange capacity and base saturation in the layer from 0.0 (zero) to 0.2 m. Soil use in the region is intensive, with cultivation of soybeans, corn, wheat and beans. Soil sampling for parameter analysis was georeferenced (on a grid of 2 ha), and geostatistical techniques and principal component analysis were employed to identify regions of highest soil acidity and nutrient deficiency treatable by liming at different levels. The results showed the relationship between soil acidity with variable such that calcium and magnesium which indicates the need to fix these nutrients in the soil in areas with higher acidity. The maps have five classes that allow us to select sub regions in study area to field actions, being important to localized treatment in the area.

Mixed planting with a leguminous plant outperforms bacteria in promoting growth of a metal remediating plant through histidine synthesis

ABSTRACTThe effectiveness of plant growth promoting bacteria (PGPB) in improving metal phytoremediation is still limited by stunted plant growth under high soil metal concentrations. Meanwhile, mixed planting with leguminous plants is known to improve yield in nutrient deficient soils but the use of a metal tolerant legume to enhance metal tolerance of a phytoremediator has not been explored. We compared the use of Pseudomonas brassicacearum, Rhizobium leguminosarum, and the metal tolerant leguminous plant Vicia sativa to promote the growth of Brassica juncea in soil contaminated with 400 mg Zn kg–1, and used synchrotron based microfocus X-ray absorption spectroscopy to probe Zn speciation in plant roots. B. juncea grew better when planted with V. sativa than when inoculated with PGPB. By combining PGPB with mixed planting, B. juncea recovered full growth while also achieving soil remediation efficiency of >75%, the maximum ever demonstrated for B. juncea. μXANES analysis of V. sativa suggested possible root exudation of the Zn chelates histidine and cysteine were responsible for reducing Zn toxicity. We propose the exploration of a legume-assisted-phytoremediation system as a more effective alternative to PGPB for Zn bioremediation.

Letter from the Editors-in-Chief

An issue of USURJ takes form through case-by-case selection of exceptional student work, without consideration for theme; this is in keeping with the nature of a multidisciplinary journal. It is a pleasant inadvertency that, although issue 2.1 is penned by a diverse academic community, it yields notable thematic cohesion.In fact, cohesion is itself variously focused upon by issue 2.1, through its authors' research into issues of personal and societal well being. One researcher supports the incorporation of culturally meaningful healing processes into mainstream medical care. Another highlights the importance of the patientdoctor relationship and long-term, consistent health care, by proposing a tool for improving continuityof-care during medical professionals' residency training. We learn about the potential of combining GIS mapping, soil test data, and socioeconomic survey results to boost West African smallholder farmers' profitability and community well-being, by enabling efficient enrichment of nutrient-deficient soil. Finally, the politically and socially unifying power of music with a cause is demonstrated, through punk band D.O.A.'s part British Columbia's labour movement in the 1980s.We hope you will be as delighted as we are by the work of our featured visual artist, Stephanie Mah, as she explores breaks and connections between human and nature, and delicately twists them into powerful moments for us to experience.The knowledge and ideas shared in issue 2.1 certainly demonstrate the relevance and power of publicly engaged undergraduate research. Similarly, as the collaborative product of student editors, researchers, faculty, and reviewers, USURJ represents our desire to improve, to disseminate knowledge, and to contribute meaningfully to a larger community of research.Thanks to the diligence and initiative of our contributors, USURJ has established itself as part of the University of Saskatchewan academic community. Consequently, both volunteers and research submissions are increasing in number and, for the first time, we are now able to release two issues in one academic year.We have many contributors to thank for building up USURJ, and we do so with genuine appreciation. We hope that our hardworking authors, reviewers, and editors are as proud as we are of their promotion of valuable undergrad research! Thanks are particularly due to Liv Marken (staff advisor) and Kathleen James-Cavan (faculty advisor), who have been with USURJ since its inception, providing stability and expertise to the journal and its volunteers.Happy reading!Nicole Haldoupis, Graduate Editor-in-Chief& Caitilin Terfloth, Undergraduate Editor-in-Chief

Experiments Testing the Causes of Namibian Fairy Circles

The grasslands on the sandy soils of the eastern edge of the Namib Desert of Namibia are strikingly punctuated by millions of mostly regularly-spaced circular bare spots 2 to 10 m or more in diameter, generally with a margin of taller grasses. The causes of these so called fairy circles are unknown, but several hypotheses have been advanced. In October 2009, we set up experiments that specifically tested four hypothesized causes, and monitored these 5 times between 2009 and 2015. Grass exclusion in circles due to seepage of subterranean vapors or gases was tested by burying an impermeable barrier beneath fairy circles, but seedling density and growth did not differ from barrier-less controls. Plant germination and growth inhibition by allelochemicals or nutrient deficiencies in fairy circle soils were tested by transferring fairy circle soil to artificially cleared circles in the grassy matrix, and matrix soil to fairy circles (along with circle to circle and matrix to matrix controls). None of the transfers changed the seedling density and growth from the control reference conditions. Limitation of plant growth due to micronutrient depletion within fairy circles was tested by supplementing circles with a micronutrient mixture, but did not result in differences in plant seedling density and growth. Short-range vegetation competitive feedbacks were tested by creating artificially-cleared circles of 2 or 4 m diameter located 2 or 6 m from a natural fairy circle. The natural circles remained bare and the artificial circles revegetated. These four experiments provided evidence that fairy circles were not caused by subterranean vapors, that fairy circle soil per se did not inhibit plant growth, and that the circles were not caused by micronutrient deficiency. There was also no evidence that vegetative feedbacks affected fairy circles on a 2 to 10 m scale. Landscape-scale vegetative self-organization is discussed as a more likely cause of fairy circles.