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  • Nitrogen
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  • 1
    Language: English
    In: Plant and Soil, 2011, Vol.341(1), pp.179-192
    Description: The integration of multipurpose legumes into low-input tropical agricultural systems is needed because they are a nitrogen (N) input through symbiotic fixation. The drought-tolerant cover legume canavalia ( Canavalia brasiliensis ) has been introduced for use either as forage or as a green manure into the crop-livestock system of the Nicaraguan hillsides. To evaluate its impact on the subsequent maize crop, an in-depth study on N dynamics in the soil-plant system was conducted. Microplots were installed in a 6-year old field experiment with maize-canavalia rotation. Direct and indirect 15 N-labelling techniques were used to determine N uptake by maize from canavalia residues and canavalia-fed cows’ manure compared to mineral fertilizer. Litter bags were used to determine the N release from canavalia residues. The incorporation of N from the amendment into different soil N pools (total N, mineral N, microbial biomass) was followed during the maize cropping season. Maize took up an average of 13.3 g N m −2 , within which 1.0 g N m −2 was from canavalia residues and 2.6 g N m −2 was from mineral fertilizer, corresponding to an amendment N recovery of 12% and 32%, respectively. Recoveries in maize would probably be higher at a site with lower soil available N content. Most of the amendment N remained in the soil. Mineral N and microbial N were composed mainly of N derived from the soil. Combined total 15 N recovery in maize and soil at harvest was highest for the canavalia residue treatment with 98% recovery, followed by the mineral fertilizer treatment with 83% recovery. Despite similar initial enrichment of soil microbial and mineral N pools, the indirect labelling technique failed to assess the N fertilizer value of mineral and organic amendments due to a high N mineralization from the soil organic matter.
    Keywords: Canavalia brasiliensis ; N ; Indirect and direct labelling techniques ; Microplot study ; Organic amendments
    ISSN: 0032-079X
    E-ISSN: 1573-5036
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  • 2
    Language: English
    In: Agriculture, Ecosystems and Environment, 30 January 2011, Vol.140(1-2), pp.155-163
    Description: ▶ We describe how legume proportion modifies N acquisition from different sources. ▶ Symbiotic N fixation was stimulated in mixtures compared to monocultures. ▶ Uptake of N from soil N pools was stimulated in mixtures compared to monocultures. ▶ The acquired N was used more efficiently by mixtures for biomass production. Concerted use of legumes and of functional diversity in grassland forage systems can provide major contributions to the challenges of agricultural systems being productive yet environmental friendly. Acquisition and transformation of nitrogen (N) resources by legumes and grasses were studied in a temperate grassland experiment near Zurich (Switzerland) to investigate mechanisms driving effects of functional diversity in mixed swards and to optimise mixtures for efficient resource use. Grass–legume interactions and N availability were varied by manipulating legume percentage of the sward (0–100%) and N fertiliser application (50, 150 or 450 kg of N ha year ). N technology quantified N derived from symbiotic (Nsym) and non-symbiotic (Nnonsym) sources. Generally, acquisition of Nsym by the entire mixture was stimulated by grasses. As a result, strong overyielding of Nsym occurred (e.g. 75 and 114% for year 1 and 2 at N150) and mixtures with only 60% and 37% legumes (year 1 and 2) already attained the same Nsym yield as pure legume stands. Legumes stimulated Nnonsym acquisition by the entire mixture, largely via increased uptake by the grass component. Thus, overyielding of Nnonsym of 31% occurred in year 1 (N150). Mutual grass–legume interactions stimulated acquisition of Nsym, acquisition of Nnonsym and efficient transformation of N into biomass compared to either monocultures. These effects of functional diversity can substantially contribute to productive and resource efficient agricultural grassland systems and were maximised in mixtures with 40–60% legumes.
    Keywords: Competition ; Cost 852 ; Facilitation ; N Uptake ; Symbiotic N2 Fixation ; Transgressive Overyielding ; Agriculture ; Environmental Sciences
    ISSN: 0167-8809
    E-ISSN: 1873-2305
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  • 3
    Language: English
    In: PLoS ONE, 01 January 2016, Vol.11(8), p.e0160729
    Description: Zinc (Zn) nutrition is of key relevance in India, as a large fraction of the population suffers from Zn malnutrition and many soils contain little plant available Zn. In this study we compared organic and conventional wheat cropping systems with respect to DTPA (diethylene triamine pentaacetic acid)-extractable Zn as a proxy for plant available Zn, yield, and grain Zn concentration. We analyzed soil and wheat grain samples from 30 organic and 30 conventional farms in Madhya Pradesh (central India), and conducted farmer interviews to elucidate sociological and management variables. Total and DTPA-extractable soil Zn concentrations and grain yield (3400 kg ha-1) did not differ between the two farming systems, but with 32 and 28 mg kg-1 respectively, grain Zn concentrations were higher on organic than conventional farms (t = -2.2, p = 0.03). Furthermore, multiple linear regression analyses revealed that (a) total soil zinc and sulfur concentrations were the best predictors of DTPA-extractable soil Zn, (b) Olsen phosphate taken as a proxy for available soil phosphorus, exchangeable soil potassium, harvest date, training of farmers in nutrient management, and soil silt content were the best predictors of yield, and (c) yield, Olsen phosphate, grain nitrogen, farmyard manure availability, and the type of cropping system were the best predictors of grain Zn concentration. Results suggested that organic wheat contained more Zn despite same yield level due to higher nutrient efficiency. Higher nutrient efficiency was also seen in organic wheat for P, N and S. The study thus suggests that appropriate farm management can lead to competitive yield and improved Zn concentration in wheat grains on organic farms.
    Keywords: Sciences (General)
    E-ISSN: 1932-6203
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  • 4
    Language: English
    In: Soil Biology and Biochemistry, 2010, Vol.42(4), pp.558-566
    Description: Soil microorganisms are key regulators of the biogeochemical phosphorus (P) cycle. Microbial P limitation in highly weathered tropical soils has been reported, but whether it affects the cellular P content of indigenous soil microorganisms and its biochemical composition is unknown. We investigated the effect of microbial P limitation by measuring respiration, microbial growth, community composition and P content of microbial cells in a Ferralsol with low amounts of available P as affected by amendments with C substrates with ample nitrogen (CN) with and without extra phosphate (P). Microbial biomass and community composition were quantified by phospholipid fatty acid (PLFA) analyses. Cellular P content and P pools (PLFA, DNA and RNA per cell) were determined after extraction of microbial cells from soil by density gradient centrifugation. The apparent microbial growth rate during exponential increase in respiration rates in response to CNP addition was 0.072 h , compared to 0.017 h for the CN amendment (no extra P added). This suggests that the microbial growth after a combined C and N addition was retarded by P limitation in the native soil (without added P). The net increase in microbial biomass, however, reached similar levels for both the CN and CNP treatment (measured at the point in time when respiration rates peaked). This outcome was unexpected since maximum respiration rates were about three times higher in the CNP compared to the CN treatment. Total P in extracted cells ranged from 2.1 to 8.9 fg P cell (microscopic counts), with a tendency for lower values for treatments without C amendments. Only 10–25% of the measured total P in extracted cells was accounted for by the measured RNA, DNA and PLFA. This low percentage could partly be due to underestimation of the RNA pool (degradation during extraction). PLFA analyses showed that substrate induced growth, regardless of P addition, led to a change in microbial community composition and was dominated by fungi. The extraction of microbial cells from soil by density gradient centrifugation, however, discriminates against fungi. Accordingly, the extracted cells were not fully representative for the entire soil microbiota regarding the community composition and metabolic state. Nevertheless, for the first time microbial cell P content and P pools are reported for microorganisms that actually grew in soil and not in chemostat or batch cultures.
    Keywords: Cell Extraction ; Density Gradient Centrifugation ; Ferralsol ; Soil Microorganisms ; Substrate Induced Respiration ; Nutrient Limitation ; Phosphorus ; Chemical Composition ; Plfa ; DNA ; RNA ; Agriculture ; Chemistry
    ISSN: 0038-0717
    E-ISSN: 1879-3428
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  • 5
    Language: English
    In: Plant and Soil, 2016, Vol.408(1), pp.15-30
    Description: Background and Aims Soil microbial communities contribute to organic phosphorus cycling in a variety of ways, including secretion of the PhoD alkaline phosphatase. We sampled a long-term grassland fertilization trial in Switzerland characterized by a natural pH gradient. We examined the effects of phosphate depletion and pH on total and active microbial community structures and on the structure and composition of the total and active phoD-harboring community. Methods Archaeal, bacterial and fungal communities were investigated using T-RFLP and phoD-harboring members of these communities were identified by 454-sequencing. Results Phosphate depletion decreased total, resin-extractable and organic phosphorus and changed the structure of all active microbial communities, and of the total archaeal and phoD-harboring communities. Organic carbon, nitrogen and phosphorus increased with pH, and the structures of all total and active microbial communities except the total fungal community differed between the two pH levels. phoD-harboring members were affiliated to Actinomycetales, Bacilliales, Gloeobacterales, Planctomycetales and Rhizobiales. Conclusions Our results suggest that pH and associated soil factors are important determinants of microbial and phoD-harboring community structures. These associated factors include organic carbon and total nitrogen, and to a lesser degree phosphorus status, and active communities are more responsive than total communities. Key players in organic P mineralization are affiliated to phyla that are known to be important in organic matter decomposition.
    Keywords: 454-sequencing ; Grassland ; Alkaline phosphatase ; DNA ; RNA ; T-RFLP
    ISSN: 0032-079X
    E-ISSN: 1573-5036
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  • 6
    Language: English
    In: PLoS ONE, 01 January 2014, Vol.9(7), p.e101487
    Description: Zinc (Zn) deficiency is a major problem for many people living on wheat-based diets. Here, we explored whether addition of green manure of red clover and sunflower to a calcareous soil or inoculating a non-indigenous arbuscular mycorrhizal fungal (AMF) strain may increase grain Zn concentration in bread wheat. For this purpose we performed a multifactorial pot experiment, in which the effects of two green manures (red clover, sunflower), ZnSO4 application, soil γ-irradiation (elimination of naturally occurring AMF), and AMF inoculation were tested. Both green manures were labeled with 65Zn radiotracer to record the Zn recoveries in the aboveground plant biomass. Application of ZnSO4 fertilizer increased grain Zn concentration from 20 to 39 mg Zn kg-1 and sole addition of green manure of sunflower to soil raised grain Zn concentration to 31 mg Zn kg-1. Adding the two together to soil increased grain Zn concentration even further to 54 mg Zn kg-1. Mixing green manure of sunflower to soil mobilized additional 48 µg Zn (kg soil)-1 for transfer to the aboveground plant biomass, compared to the total of 132 µg Zn (kg soil)-1 taken up from plain soil when neither green manure nor ZnSO4 were applied. Green manure amendments to soil also raised the DTPA-extractable Zn in soil. Inoculating a non-indigenous AMF did not increase plant Zn uptake. The study thus showed that organic matter amendments to soil can contribute to a better utilization of naturally stocked soil micronutrients, and thereby reduce any need for major external inputs.
    Keywords: Sciences (General)
    E-ISSN: 1932-6203
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  • 7
    Language: English
    In: Plant and Soil, 2004, Vol.259(1), pp.243-258
    Description: Water and nitrogen availability may limit the growth of the main crop competing with a cover crop in a living mulch system. Some aspects of the dynamics of water (soil water content and deep percolation) and nitrogen (concentration in soil solution and leachate) were studied in maize ( Zea mays L.) sown into a bare soil (BS, conventional cropping) or into a living Italian ryegrass ( Lolium multiflorum Lam.) mulch (LM) during three years. Eight lysimeters (1.0 by 1.0 m square surface area and 1.1 m deep) with ceramic suction cups, TDR probes and a drainage pipe were used each. In LM a 0.3 m wide strip was kept free of grass around the maize row. The living mulch reduced the soil water content between 0.3 and 0.9 m soil depth, which remained lower even after intense rainfall. Deep percolation over the entire maize crop season was at least 40% lower in the LM compared to the BS treatment. In LM the nitrate concentrations in the soil solution and in the leachate (usually 〈10 mg L −1 ) were very low. In BS the nitrate concentration in the leachate reached as much as 70 mg L −1 . Losses of N in LM did not reach 1% of the values observed in BS. Reduced water and N availability in LM contribute to explain the decrease in growth and yield of the maize plants, and are in good agreement with the dense root system developed in this cropping system as compared to BS. The challenge for the development of living mulch systems is to improve the uptake of water and nitrogen by the roots of the main crop in a competitive environment without affecting the capacity of the cover crop to prevent N losses by leaching.
    Keywords: living mulch ; Lam. ; nitrogen dynamics ; water dynamics ; L.
    ISSN: 0032-079X
    E-ISSN: 1573-5036
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  • 8
    Language: English
    In: Acta Agriculturae Scandinavica, Section B - Soil & Plant Science, 01 January 2012, Vol.62(1), pp.59-69
    Description: Non-sorted solid urban wastes (SUW) are used by periurban cereal farmers in Africa. There is however limited information on how these SUW affect soil quality and cereal production and quality. In order to answer this question we identified around...
    Keywords: Burkina Faso ; Heavy Metals ; Non-Sorted Solid Urban Wastes ; Periurban Agriculture ; Phosphate ; Soil and Crop Pollution ; Sorghum ; Agriculture
    ISSN: 0906-4710
    E-ISSN: 1651-1913
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  • 9
    Language: English
    In: Forest ecology and management, 2003, Vol.175, p.413–423
    Description: In a field experiment, lasting two years, an intensive monitoring of the nitrate reductase activity (NRA) of Norway spruce fine roots was used to investigate the question of whether the NRA is suitable as an indicator for nitrogen availability in the soil. The treatments were a liquid complete fertilisation containing 70–100 kg N (64% as nitrate), simulating a high N input to the soil, a non-treated control, and a water treatment as an additional control. Another treatment was the application of wood ash, which recycled mainly basic cations back into the forest soil (Ca, Mg, K). This treatment caused a mineralisation pulse leading to a shift in nitrate concentration in the soil solution. The NRA of the fine roots was increased by the liquid fertilisation (averages 34% compared to control), but also by the water treatment (averages 28% more than control) and most by the wood ash treatment (averages 82% more than control). Nitrate concentrations in the soil solution were enhanced during the irrigation with the fertiliser. The pH was distinctly elevated in the soil solution by the ash, but also by the liquid fertiliser treatment. The soil solution applied to the water treated plots was not monitored, but results from an investigation of soil extracts revealed an elevated pH in the soil of the water treated plots as well. The pH of the soil solution was significantly correlated with the NRA in the fine roots, while a correlation between the nitrate concentration in the soil solution and the NRA was not significant. When taking the spatial heterogeneity of the soil nitrate into account, a correlation between the nitrate concentration of the soil extract and the root NRA was found. Although only a weak correlation between the NRA and the actual soil nitrate was observed, the NRA is assumed to reflect the nitrate conditions in the soil, possibly only in a time scale of months. As shown with the wood ash and water treatments, an elevated NRA can also be caused from other environmental parameters which can change the nitrate availability in the soil and uptake properties of the roots. The conclusion is that the NRA of fine roots as a marker for nitrate concentrations in the soil is not suitable on a regional and short-term scale in the field if other environmental parameters (e.g. the soil pH) are subjected to pronounced changes. ; Includes references ; p. 413–423.
    Keywords: Forest Soils ; Nitrate Reductase ; Soil Ph ; Recycling ; Soil Solution ; Roots ; Field Experimentation ; Soil Heterogeneity ; Wood Ash ; Irrigation ; Nitrogen ; Soil Water ; Cations ; Mineralization ; Picea Abies ; Liquid Fertilizers
    ISSN: 0378-1127
    Source: AGRIS (Food and Agriculture Organization of the United Nations)
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  • 10
    Language: English
    In: Ambio, March 2015, Vol.44 Suppl 2, pp.S217-27
    Description: Urine contains about 50 % of the phosphorus (P) and about 90 % of the nitrogen (N) excreted by humans and is therefore an interesting substrate for nutrient recovery. Source-separated urine can be used to precipitate struvite or, through a newly developed technology, nitrified urine fertilizer (NUF). In this study, we prepared (33)P radioisotope- and stable (15)N isotope-labeled synthetic NUF (SNUF) and struvite using synthetic urine and determined P and N uptake by greenhouse-grown ryegrass (Lolium multiflorum var. Gemini) fertilized with these products. The P and N in the urine-based fertilizers were as readily plant-available in a slightly acidic soil as the P and N in reference mineral fertilizers. The ryegrass crop recovered 26 % of P applied with both urine-based fertilizers and 72 and 75 % of N applied as struvite and SNUF, respectively. Thus, NUF and urine-derived struvite are valuable N and P recycling fertilizers.
    Keywords: Nitrogen -- Metabolism ; Phosphorus -- Metabolism ; Urine -- Chemistry
    E-ISSN: 1654-7209
    Source: MEDLINE/PubMed (U.S. National Library of Medicine)
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