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Sun H.Y.,Northwest University, China | Sun H.Y.,Institute of Soil Ecology | Wang C.X.,Northwest University, China | Wang C.X.,Hainan Academy of Agricultural science | And 2 more authors.
Soil Use and Management

Over the past 20 years, conservation tillage has been used on the loess plateau of north-west China to improve the sustainability of local agriculture. There had been particular concern about loss of soil organic matter associated with traditional tillage. We examined the influence of four tillage treatments: conventional tillage (CT), subsoiling tillage (SST), rotary tillage (RT) and no-tillage (NT), with two straw residue management treatments (return and removal) on the distribution with soil depth (0-20 cm, 20-40 cm) of total organic carbon, labile organic carbon (KMnO4-C) and bound organic carbon. The study was carried out on a Loutu soil (Earth-cumuli-Orthic Anthrosol) over seven consecutive years of a winter wheat (Triticum aestivum L.)-summer maize (Zea mays L.) crop rotation. By the end of this period, conservation tillage (SST, RT and NT) led to greater storage of soil organic carbon (SOC) (22.7, 14.9 and 16.3% with straw return in contrast to 21.4, 15.8 and 12.3% with no straw return, respectively) compared with CT in the surface soil (0-20 cm). The reduced tillage treatments (SST and RT) both increased significantly the highly labile organic carbon (HLOC) content of the surface soil (50% in both SST and RT) and mildly labile organic matter (MLOC) (49.4 in SST and 53.5% in RT) when straw was removed. The largest pool of bound carbon was observed in the Humin-C pool, and the smallest in the free humic acids C (FHA-C) in each tillage treatment. Conservation tillage led to an increased content of FHA-C and CHA-C. Results from correlation analyses indicate that SOC enrichment might have resulted from the increase in HLOC, MLOC, FHA-C and CHA-C over a short period. Labile organic carbon was associated with the organic carbon that was more loosely combined with clay (FHA-C and CHA-C). We conclude that both SST and RT are effective in maintaining or restoring organic matter in Loutu soils in this region, and the effect is greater when they are used in combination with straw return. © 2013 British Society of Soil Science. Source

Wanat N.,CNRS Research Group on Water, Soil and Environment | Austruy A.,University dAuvergne | Joussein E.,CNRS Research Group on Water, Soil and Environment | Soubrand M.,CNRS Research Group on Water, Soil and Environment | And 7 more authors.
Journal of Geochemical Exploration

Mining activities produce a huge amount of contaminated wastes inducing potential risks for groundwater and/or food chain. As classical remediation solutions are very expensive, the necessity to find alternative rehabilitation is needed. The aim of this study was to assess the growth of Miscanthus×. giganteus (high lignocellulosic biomass used as biofuel) on highly contaminated mining media. In the way to control the parameters, experiments were conducted during 3. months in phytotron from composite mining soils without inputs developed from a former gold mine rich in arsenic (As), lead (Pb) and antimony (Sb). Results gave evidence of a clear aerial biomass reduction, whereas no real impact on physiological activity and development, as well as a very low translocation factor of contaminants to aerial parts are effective. The major conclusions are (i) the capacity of Miscanthus×. giganteus to grow on highly contaminated soils, and (ii) its short-term use as soils phytostabilizer by cropping the plant without any inputs. © 2013 Elsevier B.V.. Source

Kastl E.-M.,Helmholtz Center Munich | Schloter-Hai B.,Helmholtz Center Munich | Buegger F.,Institute of Soil Ecology | Schloter M.,Helmholtz Center Munich
Biology and Fertility of Soils

Exploitative fast-growing plants have higher demands for nutrients compared to conservative slow-growing plants. We presume that these differences in nutrient uptake highly influence the microbial performance mainly in the rhizosphere of nutrient-poor soils. In order to investigate the influence of plants with contrasting exploitation types on microbial communities at the root–soil interface, we performed a greenhouse experiment in a N-poor, sandy soil using the fast-growing plant Dactylis glomerata and the conservative, slow-growing plant Festuca rubra. We applied four different amounts of the inorganic fertilizer ammonium nitrate (0, 50, 100, and 200 kg NH4NO3ha−1). After 6 weeks, the abundance of nitrifiers and denitrifiers was investigated in the root–rhizosphere complex (RRC) based on the quantification of the marker genes amoA, nirK, nirS, and nosZ. Furthermore, soil chemical properties and the plant biomass were determined. Independent from the investigated plant species, fertilizer applications up to 100 kg ha−1 resulted in a clear depletion of ammonium and nitrate in the RRC, with ammonium and nitrate concentrations <1 mg kg−1 dry weight (dw). Only the highest fertilizer rate increased both ammonium and nitrate concentrations in the RRC of both plants reaching concentrations of 9.5 mg kg−1 dw for ammonium and 92.5 mg kg−1 dw for nitrate. The abundance of bacterial ammonia oxidizers (AOB) followed this trend (increase in abundance in response to the highest fertilizer rate), and copy numbers up to 3.2×107 copies g−1 dw were measured in the RRC of treatments with F. rubra where 200 kg N ha−1 was applied. As the archaeal ammonia oxidizers (AOA) did respond neither to plant species nor to the fertilizer application, the AOA/AOB ratio decreased from 10 in the non-fertilized treatments to 2 in treatments with 200 kg N ha−1. Also the abundance of microbes involved in denitrification strongly increased in response to higher fertilization rates in the RRC of both plant species, although higher gene copy numbers were detected in the rhizosphere of D. glomerata mainly for nitrous oxide reducers (up to 2.7×108 copies g−1 dw). Surprisingly, the highest fertilization rates resulted in a 50 % decrease in abundance of microbes involved in nitrite as well as nitrous oxide reduction. © Springer-Verlag Berlin Heidelberg 2014. Source

Larionova A.A.,Russian Academy of Sciences | Zolotareva B.N.,Russian Academy of Sciences | Yevdokimov I.V.,Russian Academy of Sciences | Bykhovets S.S.,Russian Academy of Sciences | And 2 more authors.
Eurasian Soil Science

The intensity of decomposition of the organic matter in the particle-size fractions from a agrogray soil sampled in a 5-year-long field experiment on the decomposition of corn residues was determined in the course of incubation for a year. The corn residues were placed into the soil in amounts equivalent to the amounts of plant litter in the agrocenosis and in the meadow ecosystem. A combination of three methods-the particle-size fractionation, the method of 13C natural abundance by C3-C4 transition, and the method of incubation-made it possible to subdivide the soil organic matter into the labile and stable pools. The labile pool reached 32% in the soil of the agrocenosis and 42% in the meadow soil. Owing to the negative priming effect, the addition of C4 (young) carbon favored the stabilization of the C3 (old) carbon in the soil. When the young carbon was absent, destabilization or intense decomposition of the old organic matter was observed. This process was found even in the most stable fine silt and clay fractions. © 2011 Pleiades Publishing, Ltd. Source

Kuruthukulangarakoola G.T.,Institute of Biochemical Plant Pathology | Zhang J.,Institute of Biochemical Plant Pathology | Albert A.,Research Unit Environmental Simulation | Winkler B.,Research Unit Environmental Simulation | And 10 more authors.
Plant, Cell and Environment

Nitric oxide (NO) is an important signalling molecule that is involved in many different physiological processes in plants. Here, we report about a NO-fixing mechanism in Arabidopsis, which allows the fixation of atmospheric NO into nitrogen metabolism. We fumigated Arabidopsis plants cultivated in soil or as hydroponic cultures during the whole growing period with up to 3ppmv of NO gas. Transcriptomic, proteomic and metabolomic analyses were used to identify non-symbiotic haemoglobin proteins as key components of the NO-fixing process. Overexpressing non-symbiotic haemoglobin 1 or 2 genes resulted in fourfold higher nitrate levels in these plants compared with NO-treated wild-type. Correspondingly, rosettes size and weight, vegetative shoot thickness and seed yield were 25, 40, 30, and 50% higher, respectively, than in wild-type plants. Fumigation with 250ppbv 15NO confirmed the importance of non-symbiotic haemoglobin 1 and 2 for the NO-fixation pathway, and we calculated a daily uptake for non-symbiotic haemoglobin 2 overexpressing plants of 250mgN/kg dry weight. This mechanism is probably important under conditions with limited N supply via the soil. Moreover, the plant-based NO uptake lowers the concentration of insanitary atmospheric NOx, and in this context, NO-fixation can be beneficial to air quality. © 2016 John Wiley & Sons Ltd. Source

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