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  • 1
    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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  • 2
    Language: English
    In: Agriculture, Ecosystems and Environment, 01 July 2018, Vol.261, pp.161-171
    Description: Cowpea ( L. Walp.) is an important African food legume suitable for dry regions. It is the main legume in two contrasting agro-ecological regions of Kenya as an important component of crop rotations because of its relative tolerance to unpredictable drought events. This study was carried out in an effort to establish a collection of bacterial root nodule symbionts and determine their relationship to physicochemical soil parameters as well as any geographical distributional patterns. spp. were found to be widespread in this study and several different types could be identified at each site. Unique but rare symbionts were recovered from the nodules of plants sampled in a drier in-land region, where there were also overall more different bradyrhizobia found. Plants raised in soil from uncultivated sites with a natural vegetation cover tended to also associate with more different bradyrizobia. The occurrence and abundance of different bradyrhizobia correlated with differences in soil texture and pH, but did neither with the agro-ecological origin, nor the origin from cultivated (n = 15) or uncultivated (n = 5) sites. The analytical method, protein profiling of isolated strains by Matrix-Assisted Laser Desorption Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS), provided higher resolution than 16S rRNA gene sequencing and was applied in this study for the first time to isolates recovered directly from field-collected cowpea root nodules. The method thus seems suitable for screening isolate collections on the presence of different groups, which, provided an appropriate reference database, can also be assigned to known species.
    Keywords: Bradyrhizobium Distribution ; Cowpea (Vigna Unguiculata L. Walp) ; Maldi-Tof MS ; Agro-Ecology ; Agriculture ; Environmental Sciences
    ISSN: 0167-8809
    E-ISSN: 1873-2305
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  • 3
    Language: English
    In: Agriculture, Ecosystems and Environment, 01 February 2019, Vol.270-271, pp.65-75
    Description: Phosphorus (P) accumulated in soil after surplus P applications can potentially serve as a P source for subsequent crop production. This study investigated residual P availability after long-term surplus P application with different organic waste products. Topsoil samples from a long-term field trial treated with different types of organic wastes were subjected to P characterization, including determination of total P, water-soluble P, and isotopically exchangeable P pools. The waste products were applied for 12 years before sampling, at rates according to crop nitrogen demand and thus typically in excess of crop P requirements. Residual waste P in soil was determined based on the difference between total soil P measured in the different specific waste-treated plots and a balanced reference treatment. After 12 years of surplus P balance (inputs – crop offtake) of 79–598 kg P ha yr with waste, significant amounts of P (636–4177 kg ha ) had accumulated in the soil as residual P. The average fraction of residual waste P which could be recovered as rapidly exchangeable P (within 1 min) followed the order: composted household waste P (2.1%) 〈 sewage sludge P (5.1%) 〈 cattle manure P (10.9%), indicating that type of waste has an impact on residual P availability after long-term surplus P application. Unaccounted P (surplus P balance – residual P, i.e., P potentially lost from the topsoil) followed the same order, so compost P was better retained in the soil, but with a less clear difference between sewage sludge and cattle manure. For the latter two wastes, approximately half the surplus P balance could not be accounted for in the topsoil and was assumed to be transported down the soil profile. Three years after waste application was terminated, the fraction of rapidly exchangeable residual P had not declined significantly, suggesting sustained availability of residual P in the soil after long-term application of organic waste. Overall, the availability and mobility of residual P after applying composted household waste to soil was significantly lower than that of residual P from sewage sludge and cattle manure.
    Keywords: Composted Household Waste ; Sewage Sludge ; Cattle Manure ; Organic Waste, Isotopic Exchange Kinetics ; P Balance ; Unaccounted P ; Agriculture ; Environmental Sciences
    ISSN: 0167-8809
    E-ISSN: 1873-2305
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