ALBERT

Description:    Seasonal drought in tropical agroecosystems may affect C and N mineralization of organic residues. To understand this effect, C and N mineralization dynamics in three tropical soils (Af, An 1 , and An 2 ) amended with haricot bean (HB; Phaseolus vulgaris L.) and pigeon pea (PP; Cajanus cajan L.) residues (each at 5 mg g −1 dry soil) at two contrasting soil moisture contents (pF2.5 and pF3.9) were investigated under laboratory incubation for 100–135 days. The legume residues markedly enhanced the net cumulative CO 2 –C flux and its rate throughout the incubation period. The cumulative CO 2 –C fluxes and their rates were lower at pF3.9 than at pF2.5 with control soils and also relatively lower with HB-treated than PP-treated soil samples. After 100 days of incubation, 32–42% of the amended C of residues was recovered as CO 2 –C. In one of the three soils (An 1 ), the results revealed that the decomposition of the recalcitrant fraction was more inhibited by drought stress than easily degradable fraction, suggesting further studies of moisture stress and litter quality interactions. Significantly ( p  〈 0.05) greater NH 4 + –N and NO 3 − –N were produced with PP-treated (C/N ratio, 20.4) than HB-treated (C/N ratio, 40.6) soil samples. Greater net N mineralization or lower immobilization was displayed at pF2.5 than at pF3.9 with all soil samples. Strikingly, N was immobilized equivocally in both NH 4 + –N and NO 3 − –N forms, challenging the paradigm that ammonium is the preferred N source for microorganisms. The results strongly exhibited altered C/N stoichiometry due to drought stress substantially affecting the active microbial functional groups, fungi being dominant over bacteria. Interestingly, the results showed that legume residues can be potential fertilizer sources for nutrient-depleted tropical soils. In addition, application of plant residue can help to counter the N loss caused by leaching. It can also synchronize crop N uptake and N release from soil by utilizing microbes as an ephemeral nutrient pool during the early crop growth period. Content Type Journal Article Pages 1-16 DOI 10.1007/s00374-011-0607-8 Authors Girma Abera, Department of Plant and Environmental Sciences, Norwegian University of Life Sciences, P.O. Box 5003, 1432 Ås, Norway Endalkachew Wolde-meskel, Department of Plant and Horticultural Sciences, Hawassa University, P.O. Box 05, Hawassa, Ethiopia Lars R. Bakken, Department of Plant and Environmental Sciences, Norwegian University of Life Sciences, P.O. Box 5003, 1432 Ås, Norway Journal Biology and Fertility of Soils Online ISSN 1432-0789 Print ISSN 0178-2762

Description:    Plant growth-promoting rhizobacteria (PGPR) naturally occur in the rhizospheres of pasture, but still little is understood regarding how soil agricultural practices affect them. Here, we examined the effects of long-term nitrogen (N) fertilisation on the occurrence of potential culturable PGPR in rhizosphere soils from pastures grown in Chilean Andisols. We also evaluated in vitro the effects of organic acids (citric, malic and oxalic acids), metals (Al and Mn) and N supply (urea and ammonium sulphate) on indole acetic acid (IAA) production and phosphorus (P) liberation by selected strains. Compared with non-N-fertilised pasture, N fertilisation significantly increased (30%) the occurrence of culturable phosphobacteria but decreased (7%) the occurrence of IAA-producing rhizobacteria. Most efficient IAA-producing phosphobacteria were identified as Bacillus , Enterobacter , Pseudomonas and Serratia . At low pH (4.8), the assays showed that the IAA production by Serratia sp. N0-10LB was increased (31–74%) by organic acids. On the other hand, the IAA production by Pseudomonas sp. N1-55PA was increased two- to fivefold by metals. In all strains, the growth and IAA production were significant decreased by 500 μM of Al, except Serratia sp. N0-10LB, suggesting its potential as PGPR for Chilean Andisols. When urea was added as main N source, the bacterial growth and P utilisation significantly increased compared with ammonium sulphate. The influence of environmental factors that are typical of Chilean Andisols on rhizobacterial communities will provide better management practices to enhance their PGPR functions as well as a better selection biofertilisers to be used in Chilean Andisols. Content Type Journal Article Pages 1-11 DOI 10.1007/s00374-011-0593-x Authors Oscar A. Martínez, Programa de Doctorado en Ciencias de Recursos Naturales, Universidad de La Frontera, Avenida Francisco Salazar, 01145 Temuco, Chile Milko A. Jorquera, Center of Plant, Soil Interaction and Natural Resources Biotechnology, Scientific and Technological Bioresource Nucleus, Universidad de La Frontera, Avenida Francisco Salazar, 01145 Temuco, Chile David E. Crowley, Department of Environmental Sciences, University of California, Riverside, CA 92521, USA María de la Luz Mora, Center of Plant, Soil Interaction and Natural Resources Biotechnology, Scientific and Technological Bioresource Nucleus, Universidad de La Frontera, Avenida Francisco Salazar, 01145 Temuco, Chile Journal Biology and Fertility of Soils Online ISSN 1432-0789 Print ISSN 0178-2762

Description:    Organic fractions from farm yard manure (FYM), vermicompost, municipal sludge, mustard cake, and surface soil of West Bengal, which was arsenic (As)-contaminated, were extracted and fractionated into fulvic and humic acid (FA and HA, respectively) fractions following standard procedures. These HA and FA samples were characterized by pH-potentiometric titrations, viscometric measurements and visible spectrophotometry. The stability constant (log K ) of the complexes formed by these natural with As in aqueous phase was evaluated by the ion-exchange method. The log K values suggest that the organo-As complexes were quite stable. The release isotherm of As from the HA/FA complexes extracted from vermicompost and FYM was assayed in the presence of molybdate, nitrate, phosphate, sulfate and borate. The greatest tendency to displace As from the complexes was shown by sulfate, molybdite, and nitrate. Content Type Journal Article Pages 1-8 DOI 10.1007/s00374-011-0589-6 Authors Bishwajit Sinha, Department of Agricultural Chemistry and Soil Science, Bidhan Chandra Krishi Viswavidyalaya, Kalyani-741235, Mohanpur, Nadia, West Bengal, India Kallol Bhattacharyya, Department of Agricultural Chemistry and Soil Science, Bidhan Chandra Krishi Viswavidyalaya, Kalyani-741235, Mohanpur, Nadia, West Bengal, India Journal Biology and Fertility of Soils Online ISSN 1432-0789 Print ISSN 0178-2762

Description:    The effects of increasing levels of metals (10 and 20 mg of Cr kg -1 and 25 and 50 mg of Cd, Pb, and Ni kg -1 soil) and arbuscular mycorrhizal (AM) fungi Glomus intraradices on the yield, chemical composition of volatile oil, and metal accumulation in sweet basil ( Ocimum basilicum L.) were investigated in a pot experiment. The shoot yield, content of essential oil, and root yield of sweet basil were increased by the application of low dose of Cd, Pb, and Ni as compared to control. The application of high level of metals had deleterious effect on the yield. In soil with low dose of metal applied, AM fungi inoculation significantly enhanced the metal concentration in shoots and had adverse effect on the yield, whereas in soil with high dose of metal applied, AM fungal inoculation reduced the metal concentration in shoot and had beneficial effect on the yield. The content of linalool in basil oil was decreased and that of methyl chavicol was increased by the application of Cr, Cd, and Pb in soil as compared to control. Similarly, the level of linalool and methyl chavicol was decreased and that of methyl eugenol was increased by the application of Ni as compared to control. However, AM fungal inoculation led to maintain the content of linalool, methyl chavicol, and methyl eugenol in volatile oil, which were either increased or decreased by the application of metals. We conclude that the AM–sweet basil symbiosis could be used as a novel approach to enhance the yield and maintain the quality of volatile oil of sweet basil under metal-contaminated soils. Content Type Journal Article Pages 1-9 DOI 10.1007/s00374-011-0590-0 Authors Arun Prasad, Central Institute of Medicinal and Aromatic Plants, P.O. CIMAP, Lucknow, 226015 India Sanjay Kumar, Central Institute of Medicinal and Aromatic Plants, P.O. CIMAP, Lucknow, 226015 India Abdul Khaliq, Central Institute of Medicinal and Aromatic Plants, P.O. CIMAP, Lucknow, 226015 India Ankit Pandey, Central Institute of Medicinal and Aromatic Plants, P.O. CIMAP, Lucknow, 226015 India Journal Biology and Fertility of Soils Online ISSN 1432-0789 Print ISSN 0178-2762

Description:    Little information is available about the effects of cover crops on soil labile organic carbon (C), especially in Australia. In this study, two cover crop species, i.e., wheat and Saia oat, were broadcast-seeded in May 2009 and then crop biomass was crimp-rolled onto the soil surface at anthesis in October 2009 in southeastern Australia. Soil and crop residue samples were taken in December 2009 to investigate the short-term effects of cover crops on soil pH, moisture, NH 4 + –N, NO 3 − –N, soluble organic C and nitrogen (N), total organic C and N, and C mineralization in comparison with a nil-crop control (CK). The soil is a Chromic Luvisol according to the FAO classification with 48.4 ± 2.2% sand, 19.5 ± 2.1% silt, and 32.1 ± 2.1% clay. An exponential model fitting was employed to assess soil potentially labile organic C ( C 0 ) and easily decomposable organic C for all treatments based on 46-day incubations. The results showed that crop residue biomass significantly decreased over the course of 2-month decomposition. The cover crop treatments had significantly higher soil pH, soluble organic C and N, cumulative CO 2 –C, C 0 , and easily decomposable organic C, but significantly lower NO 3 − –N than the CK. However, no significant differences were found in soil moisture, NH 4 + –N, and total organic C and N contents among the treatments. Our results indicated that the short-term cover crops increased soil labile organic C pools, which might have implications for local agricultural ecosystem managements in this region. Content Type Journal Article Pages 1-6 DOI 10.1007/s00374-011-0594-9 Authors Xiaoqi Zhou, Environmental Futures Centre, Griffith School of Environment, Griffith University, Nathan, 4111 Australia Chengrong Chen, Environmental Futures Centre, Griffith School of Environment, Griffith University, Nathan, 4111 Australia Shunbao Lu, Environmental Futures Centre, Griffith School of Environment, Griffith University, Nathan, 4111 Australia Yichao Rui, School of Biomolecular and Physical Sciences, Griffith University, Nathan, 4111 Australia Hanwen Wu, EH Graham Centre for Agricultural Innovation, Wagga Wagga Agricultural Institute, Industry & Investment NSW, Pine Gully Road, Wagga Wagga, NSW 2650, Australia Zhihong Xu, Environmental Futures Centre, Griffith School of Environment, Griffith University, Nathan, 4111 Australia Journal Biology and Fertility of Soils Online ISSN 1432-0789 Print ISSN 0178-2762

Description:    Poultry ( Gallus gallus domesticus L.) litter (PL) is a readily available nutrient source for crop production in the Southeast USA. Long-term PL application may alter availability of N and the effect may be dependent on tillage practice. Tillage [no till (NT) vs. conventional (CT)] and N source (PL vs. commercial fertilizer CF) effects on N availability and plant uptake were evaluated in years 9, 10, and 11 of a long-term cropping systems study at the United States Department of Agriculture, Agricultural Research Service, J. Phil Campbell Sr. Natural Resource Conservation Center, Watkinsville, GA, USA. Mineral N in the top 10 cm, measured in situ, varied each year and was influenced by time, tillage, and N source. In 2003 (year 9), soil mineral N content was greater in CT–CF (100 kg ha −1 ) than in NT–PL (95 kg ha −1 ) but in 2004 (year 10) and 2005 (year 11) it was lower in CT–CF (93 and 60 kg ha −1 ) compared to NT–PL (140 and 71 kg ha −1 ). Nitrogen mineralization rates were generally greater for PL than for CF treatments with the difference being almost 1 kg ha −1  day −1 in 2003. Mineralization rates were greater for NT–PL compared to CT–CF in 2004 and 2005. Across the three growing seasons, corn ( Zea mays L.) aboveground biomass was consistently greater in the NT–PL treatment than in the NT–CF and CT–CF treatments. Correlation between aboveground biomass and N mineralization was greater for PL than for CF (0.75 vs. 0.48). Patterns of N mineralization and total soil mineral N indicated that the distribution of N through the growing season more closely matched corn N demand in PL treatments. Results indicate that improved N availability through the growing season, by combining NT and PL, can result in more profitable corn production in the southeast. Content Type Journal Article Pages 1-9 DOI 10.1007/s00374-011-0582-0 Authors Harry H. Schomberg, US Department of Agriculture, Agricultural Research Service, Watkinsville, GA, USA Dinku M. Endale, US Department of Agriculture, Agricultural Research Service, Watkinsville, GA, USA Michael B. Jenkins, US Department of Agriculture, Agricultural Research Service, Watkinsville, GA, USA Dwight S. Fisher, US Department of Agriculture, Agricultural Research Service, Watkinsville, GA, USA Journal Biology and Fertility of Soils Online ISSN 1432-0789 Print ISSN 0178-2762

Description:    In two studies, we assessed the mass balance of added 14 C-labelled sucrose and 15 NH 4 15 NO 3 by measuring 14 CO 2 , 14 C and 15 N in soil microbial biomass (SMB) and 14 C and 15 N in soil solution. Specifically, we assessed the potential of recently added 14 C to be re-mobilised by cryptic growth using subsequent additions of sucrose and cellulose and the effect of physical protection on the stabilisation of the labelled substrate. We used both a constructed soil with low soil organic matter content and varied the clay content as well as a natural soil. We observed a substantial initial as well as a later stage transfer of 14 C into unidentifiable form, hypothesised to be microbial residues. When using a standard k EC value of 0.45, only roughly 50% of the added labelled substrates were accountable and therefore we explored the full range of reported k EC values to assess the mass balance. Subsequent application of unlabelled sucrose and cellulose did not substantially increase turnover 14 C and 15 N. Contrary to our expectation, there was no effect of clay content on the amount of unidentified 14 C and 15 N. The unidentified 14 C and 15 N is ascribed to formation of soil microbial residue. The low recovery of added isotope suggests that our mechanistic models are missing a large and important pool in order to realistically simulate organic matter turnover in soil. Content Type Journal Article Pages 1-12 DOI 10.1007/s00374-011-0592-y Authors Supathida Aumtong, Department of Agriculture and Ecology, Faculty of Life Sciences, University of Copenhagen, Thorvaldsensvej 40, 1871 Frederiksberg C, Denmark Andreas de Neergaard, Department of Agriculture and Ecology, Faculty of Life Sciences, University of Copenhagen, Thorvaldsensvej 40, 1871 Frederiksberg C, Denmark Jakob Magid, Department of Agriculture and Ecology, Faculty of Life Sciences, University of Copenhagen, Thorvaldsensvej 40, 1871 Frederiksberg C, Denmark Journal Biology and Fertility of Soils Online ISSN 1432-0789 Print ISSN 0178-2762

Description:    Successful exploitation of bacterial inoculants in agriculture requires that the inoculant can colonize the crop rhizosphere and then express the gene(s) of interest. This study focuses on two glucose-metabolizing genes that are associated with the inorganic phosphate solubilization phenotype of Pseudomonas fluorescens : gcd , which encodes glucose dehydrogenase, and pqqB , which encodes a cofactor required for Gcd activity. Tn5- lux -gene fusions were created to assess the expression of these genes in situ on roots of two maize hybrids, DK315 and PR37Y15. Expression was compared to in vitro levels in the presence of root exudates and different carbon sources. Although root exudates from both varieties triggered similar levels of expression in in vitro cultures, there was a marked difference in situ, where significantly higher expression levels of both genes were observed on DK315 roots. This correlates with a higher level of rhizosphere colonization by the inoculant on this hybrid (over PR37Y15) and illustrates the importance of monitoring both colonization and expression levels in tandem. In addition to demonstrating expression of these important genes in the rhizosphere, this study also illustrates that variation can exist between cultivars or varieties and demonstrates a methodology to monitor the expression of genes of interest in the rhizosphere of the selected crop variety on which the inoculant is to be applied. Content Type Journal Article Pages 1-4 DOI 10.1007/s00374-011-0586-9 Authors Olivia Rice, BIOMERIT Research Centre, Microbiology Department, University College Cork, Cork, Ireland Simon H. Miller, BIOMERIT Research Centre, Microbiology Department, University College Cork, Cork, Ireland John P. Morrissey, BIOMERIT Research Centre, Microbiology Department, University College Cork, Cork, Ireland Fergal O’Gara, BIOMERIT Research Centre, Microbiology Department, University College Cork, Cork, Ireland Journal Biology and Fertility of Soils Online ISSN 1432-0789 Print ISSN 0178-2762

Description:    Grain legume production with rhizobial inoculation has drawn attention not only because of the economic value of nitrogen (N) fixation by grain legumes, but also because of the concern that N 2 fixation by grain legumes may enhance emissions of nitrous oxide (N 2 O), a powerful greenhouse gas. However, the relationship between N 2 O emissions and biological N 2 fixation by grain legumes is not well understood. The objective of this study was to quantify N 2 O emissions associated with N 2 fixation by grain legumes as affected by wetting/drying cycles and crop residues. Two grain legumes, lentil ( Lens esculenta Moench) and pea ( Pisum sativum L.), either inoculated with two Rhizobium leguminosarum biovar viciae strains, 99A1 and RGP2, respectively, or fertilized with 15 N-labeled fertilizer were grown in a controlled environment under three wetting/drying cycles. Profile N 2 O concentrations and surface N 2 O emissions were measured from the soil–plant systems, which were compared with those from a cereal, spring wheat ( Triticum aestivum L. ac. Barrie ). After harvest, crop residues were incorporated into soils that were seeded to spring wheat to evaluate the effect of crop residues on N 2 O emissions. Results indicated that: (1) inoculating grain legumes with non-denitrifying rhizobia did not enhance N 2 O emissions and the presence of grain legumes did not increase N 2 O emissions compared with the cereal crop, and (2) profile N 2 O accumulation and surface emissions were not related to the type of crop residues added to the soil, but related to the residual N applied previously as N fertilizer. This suggests that N 2 O emissions are not directly related to biological N 2 fixation by grain legumes, and on a short time scale, N rich residues of N 2 -fixing crops have a limited impact on N 2 O emissions compared with N fertilization. Content Type Journal Article Pages 1-13 DOI 10.1007/s00374-011-0575-z Authors Zhaozhan Zhong, Department of Soil Science, University of Saskatchewan, Saskatoon, SK, Canada Louise M. Nelson, Biology and Physical Geography, University of British Columbia Okanagan, Kelowna, BC, Canada Reynald L. Lemke, Agriculture & Agri-Food Canada, Saskatoon, SK, Canada Journal Biology and Fertility of Soils Online ISSN 1432-0789 Print ISSN 0178-2762

Description:    Rose-scented geranium ( Pelargonium sp.) is a highly valued aromatic crop. Its growth is limited by soil salinity and sodicity stress. Arbuscular mycorrhizal (AM) fungus, phosphate-solubilizing bacteria (PSB), and P fertilizers may enhance the growth and secondary metabolism in geranium plants. In this context, a pot experiment was conducted to study the effects of PSB, AM fungi ( Glomus intraradices ), and P fertilizer on the yield, chemical composition of essential oil, and mineral element acquisition of geranium. The dry matter yield of shoot and essential oil yield, and mineral element (P, K, Ca, Mg, Na, Fe, Cu, and Zn) uptake in shoot tissues of geranium were significantly increased by the inoculation with AM fungi, co-inoculation with AM fungi and PSB, and P fertilization as compared to control. While the co-inoculation of geranium with AM fungi and PSB significantly enhanced the content of the monoterpenes such as citronellol, geraniol, geranial, and a sesquiterpene (10- epi -γ eudesmol), the P fertilization only enhanced the content of a sesquiterpene, 10- epi -γ eudesmol in the volatile oil. We conclude that the co-inoculation of PSB and AM fungi could be the best natural alternative to phosphate fertilizers to enhance the yield and quality of essential oil from geranium plants grown in sodic soils. Content Type Journal Article Pages 1-6 DOI 10.1007/s00374-011-0578-9 Authors Arun Prasad, Division of Agronomy and Soil Science, Central Institute of Medicinal and Aromatic Plants, P.O.-CIMAP, Lucknow, 226015 India Sanjay Kumar, Division of Agronomy and Soil Science, Central Institute of Medicinal and Aromatic Plants, P.O.-CIMAP, Lucknow, 226015 India Ankit Pandey, Division of Agronomy and Soil Science, Central Institute of Medicinal and Aromatic Plants, P.O.-CIMAP, Lucknow, 226015 India Sukhmal Chand, Division of Agronomy and Soil Science, Central Institute of Medicinal and Aromatic Plants, P.O.-CIMAP, Lucknow, 226015 India Journal Biology and Fertility of Soils Online ISSN 1432-0789 Print ISSN 0178-2762