Library

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Biology and fertility of soils 23 (1996), S. 229-235 
    ISSN: 1432-0789
    Keywords: Key words Denitrification ; N2-fixation ; Fermentation ; N2O/N2 ratio ; C-availability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Nitrate and glucose additions were investigated for their role in the C and N dynamics during anaerobic incubation of soil. A gas-flow soil core method was used, in which the net production of N2, N2O, NO, CO2, and CH4 under a He atmosphere could be monitored both accurately and frequently. In all experiments clayey silt loam soil samples were incubated for 9 days at 25°C. Addition of nitrate (50 mg KNO3-N kg–1 soil) had no effect on total denitrification and CO2 production rates, while the N2O/N2 ratio was affected considerably. The cumulative N2O production exceeded the cumulative N2 production for 6 days in the treatment with nitrate addition, compared to 1.2 days in the unamended treatment. Glucose addition stimulated the microbial activity considerably. The denitrification rates were limited by the growth rate of the denitrifying population. During denitrification no significant differences were observed between the treatments with 700 mg glucose-C kg–1 and 4200 mg glucose-C kg–1, both in combination with 50 mg KNO3-N kg–1. The N2 production rates were remarkably low, until NO3 – exhaustion caused rapid reduction of N2O to N2 at day 2. During the denitrification period 15–18 mg N kg–1 was immobilised in the growing biomass. After NO3 – shortage, a second microbial population, capable of N2-fixation, became increasingly important. This change was clearly reflected in the CO2 production rates. Net volatile fatty acid (VFA) production was monitored during the net N2-fixation period with acetate as the dominant product. N2-fixation faded out, probably due to N2 shortage, followed by increased VFA production. In the high C treatment butyrate became the most important VFA, while in the low C treatment acetate and butyrate were produced at equal rates. During denitrification no VFA accumulation occurred; this does not prove, however, that denitrification and fermentation appeared sequentially. The experiments illustrate clearly the interactions of C-availability, microbial population and nitrate availability as influencing factors on denitrification and fermentation.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 1432-0789
    Keywords: Key words Carbon dioxide production ; Nitrous oxide ; production ; Ammonia volatilization ; Pig slurry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Dynamics of nitrogen (N) and carbon (C) were investigated in a loamy soil amended or injected with pig slurry. Treatments were with or without acetylene C2H2 (which is assumed to inhibit reduction of nitrous oxide (N2O) to dinitrogen (N2), and soil cores were conditioned for 15 days at 25°C while pH, production of CO2 and N2O, ammonia (NH3) emission and (nitrate) (NO3 –) and (ammonium) (NH4 +) concentrations were monitored. There was no significant difference in CO2 production between the injected and surface applied pig slurry treatments, and within 15 days ca. 5% of the C applied had been mineralized, if no priming effect was assumed. Neither the production of N2O nor the total gaseous production of the denitrification process (N2O plus N2) were affected by the way the pig slurry was added to the soil. NH3 volatilization, however, decreased by 90% when pig slurry was injected. The addition of C2H2 significantly increased the CO2 production and the concentration of NH4 +, but significantly decreased the concentration of NO3 –. It was concluded that the injection of pig slurry to a dry soil was an acceptable alternative to its application to the soil surface, as not only was NH3 volatilization reduced, but the production of N2O and N2 through denitrification was not stimulated. It is also suggested that the composition of the organic C fraction in the pig slurry, most likely the concentration of fatty acids, had an important effect on the dynamics of N and C in the soil.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 3
    ISSN: 1432-0789
    Keywords: Key words Alley cropping ; Nitrogen availability ; Olsen phosphorus ; Particulate organic matter
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  The impact of land use (unfertilized continuous maize cropping, unfertilized and fertilized alley cropping with maize, Gliricidia sepium tree fallow, natural fallow) on the soil organic matter (SOM) status and general soil fertility characteristics were investigated for a series of soils representative for the West African moist savanna zone. Three soils from the humid forest zone were also included. In an associated pot experiment, relationships between maize N and P uptake and SOM and general soil characteristics were developed. Soils under natural fallow contained the highest amount of organic C (1.72%), total N (0.158%), and had the highest effective cation exchange capacity (ECEC) [8.9 mEq 100 g–1 dry soil], while the Olsen P content was highest in the fertilized alley cropping plots (13.7 mg kg–1) and lowest under natural fallow (6.3 mg kg–1). The N concentration of the particulate organic matter (POM) was highest in the unfertilized alley cropping plots (2.4%), while the total POM N content was highest under natural fallow (370 mg N kg–1) and lowest in continuously cropped plots (107 mg N kg–1). After addition of all nutrients except N, a highly significant linear relationship (R 2=0.91) was observed between the total N uptake in the shoots and roots of 7-week-old maize and the POM N content for the savanna soils. POM in the humid forest soils was presumably protected from decomposition due to its higher silt and clay content. After addition of all nutrients except P, the total maize P uptake was linearly related to the Olsen P content. R 2 increased from 0.56 to 0.67 in a multiple linear regression analysis including the Olsen P content and clay content (which explained 11% of the variation in P uptake). Both the SOM status and N availability were shown to be improved in land-use systems with organic matter additions, while only the addition of P fertilizer could improve P availability.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Biology and fertility of soils 32 (2000), S. 234-242 
    ISSN: 1432-0789
    Keywords: Key words Imperata ; Mulch ; Lablab ; Maize ; Mucuna
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  Reliable estimates of symbiotically fixed N2 in herbaceous legumes are important in order to determine their role in maintaining or improving N levels in tropical low-external-input farming systems. We have studied the effects of different management systems on the suitability of two non-N2-fixing reference crops, imperata [Imperata cylindrica (L.) Rauescel] and maize (Zea mays L.), for estimating N2 fixation in mucuna [Mucuna pruriens (L.) DC var. utilis (Wright) Bruck] and lablab [Lablab purpureus (L.) Sweet] in the field. The total-N-difference (TND) method of estimating N2 fixation was compared to the 15N-isotope-dilution (ID) technique. The two methods did not differ with respect to estimates of N2 fixation under in situ mulch (IM) systems. In contrast, under live-mulch (LM) systems the TND method underestimated N2 fixed in mucuna by 29% and in lablab by 40% compared to estimates made with the ID method. Irrespective of the treatment, estimates of N derived from fixation in both herbaceous legumes were not influenced by either of the reference plants. Using the ID technique, the proportion of N2 derived from fixation in mucuna and lablab at 12 weeks varied from 52% to 90% depending on whether the treatments were N fertilized, inoculated or uninoculated, cover-crop systems. In view of the nature of cover-crop systems in the derived savanna of West and Central Africa, where imperata is usually present as a weed or maize is grown in IM or LM systems, imperata or maize could be used to estimate N2 fixation and N contributions of the legumes to soil fertility and subsequent crop improvements.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Biology and fertility of soils 5 (1987), S. 126-132 
    ISSN: 1432-0789
    Keywords: Residual soil 14C ; Microbial biomass ; Root-derived organic matter ; Fluorescent pseudomonads ; Rhizosphere ; Nutrient levels
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Maize plants were grown for 42 days in a sandy soil at two different mineral nutrient levels, in an atmosphere containing 14CO2. The 14C and total carbon contents of shoots, roots, soil and soil microbial biomass were measured 28, 35 and 42 days after germination. Relative growth rates of shoots and roots decreased after 35 days at the lower nutrient level, but were relatively constant at the higher nutrient level. In the former treatment, 2% of the total 14C fixed was retained as a residue in soil at all harvests while at the higher nutrient level up to 4% was retained after 42 days. Incorporation of 14C into the soil microbial biomass was close to its maximum after 35 days at the lower nutrient level, but continued to increase at the higher level. Generally a good agreement existed between microbial biomass, 14C contents and numbers of fluorescent pseudomonads in the rhizosphere. Numbers of fluorescent pseudomonads in the rhizosphere were maximal after 35 days at the lower nutrient level and continued to increase at the higher nutrient level. The proportions of the residual 14C in soil, incorporated in the soil microbial biomass, were 28% to 41% at the lower nutrient level and 20%6 – 30% at the higher nutrient level. From the lower nutrient soil 18%6 – 52%6 of the residual soil 14C could be extracted with 0.5 N K2SO4, versus 14%6 – 16% from the higher nutrient soil. Microbial growth in the rhizosphere seemed directly affected by the depletion of mineral nutrients while plant growth and the related production of root-derived materials continued.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 6
    ISSN: 1432-0789
    Keywords: Decomposition ; N release ; Rainfall pattern ; Residue quality ; Hedgerow species
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In alley-cropping systems, hedgerow trees are regularly cut back. Losses of N released from the decomposing prunings are minimized when N release is synchronized with crop N demand. In this study, the sensitivity of the decomposition of Leucaena leucocephala, Senna siamea, and Dactyladenia barteri leaf litter to the nature of the rainfall regime is correlated with the residue quality. The litterbag technique was used to measure decomposition. Four periods of 115 days, each starting at a time when hedgerow trees are normally pruned, were selected and the rain that fell during each of these periods in 1986 was simulated on a day-to-day basis by applying irrigation water on the litterbags. The number of rainfall events was better correlated with the percentage dry matter loss than with the total amount of precipitation. The relationship consisted of two lines. The slope of the first line, indicative of the sensitivity of the decomposition to varying numbers of rainfall events, correlated well with the watersoluble fraction (P〈0.05), the C:N ratio (P〈0.05), and the polyphenol: N ratio (P〈0.01) of the residues. The decomposition process was shown to be dominated by microbial catabolism, rather than leaching. Because the decomposition of the higher quality residues is affected by varying rainfall patterns and because rainfall may often be unpredictable in frequency and intensity, synchronization of N released from a significant part of the decomposing residue with crop N demand may require additional management practices.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Biology and fertility of soils 31 (2000), S. 261-269 
    ISSN: 1432-0789
    Keywords: Key words Cover crops ; Mixed residues ; Microbial biomass ; N-mineralization ; Soil organic matter fractions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  The fate of 15N-labeled plant residues from different cover-cropping systems and labeled inorganic N fertilizer in the organic, soil mineral, microbial biomass and soil organic matter (SOM) particle-size fractions was investigated in a sandy Lixisol. Plant residues were from mucuna (legume), lablab (legume), imperata (grass), maize (cereal) and mixtures of mucuna or lablab with imperata or maize, applied as a surface mulch. Inorganic N fertilizer was applied as 15N-(NH4)2SO4 at two rates (21 and 42 mg N kg–1 soil). Total N release from mucuna or lablab residues was 2–3 times higher than from the other residues, whereas imperata immobilized N throughout the study period. In contrast, 15N was mineralized from all the plant residues irrespective of the mineralization–immobilization pattern observed for total N. After 168 days, 69% of soil mineral N in mucuna- or lablab-mulched soils was derived from the added residues, representing 4–8% of residue N, whereas 9–30% of inorganic N was derived from imperata, maize and the mixed residues. At the end of the study, 4–19% of microbial biomass N was derived from the added residue/fertilizer-N, accounting for 1–3% of added residue-N. Averaged across treatments, particulate SOM fractions accounted for less than 1% of the total soil by weight but contained 20% of total soil C and 8% of soil N. Soils amended with mucuna or lablab incorporated more N in the 250–2000 μm SOM pool, whereas soil amended with imperata or the mixed residues incorporated similar proportions of labeled N in the 250–2000 μm and 53–250 μm fractions. In contrast, in soils receiving the maize or inorganic fertilizer-N treatments, higher proportions of labeled N were incorporated into the 53–250 μm than the 250–2000 μm fractions. The relationship between these differences in residue/fertilizer-N partitioning into different SOM particle-size fractions and soil productivity is discussed.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Biology and fertility of soils 31 (2000), S. 254-260 
    ISSN: 1432-0789
    Keywords: Key words Imperata ; Lablab ; Maize ; Soil fumigation ; Nematodes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  Populations of plant parasitic nematodes and their effects on symbiotic nitrogen (N) fixation in herbaceous legumes and on some selected characteristics of other plant species associated with such cover crops were studied. Two legume species [mucuna, Mucuna pruriens (L) DC. var. utilis (Wright) Bruck and lablab, Lablab purpureus L. Sweet], one grass/weed species [imperata, Imperata cylindrica (L.) Rauschel] and a cereal (maize, Zea mays L.) were used. There were three soil treatments (fumigation, fumigation plus inoculation with Meloidogyne species, and an untreated control). Plant parasitic nematode populations in soil, roots and nodules were determined at 4, 8 and 12 weeks after planting. The response of the phytoparasitic nematodes to soil treatments varied according to the plant species present. The predominant nematodes in soils, roots and nodules of legumes were of the genus Meloidogyne, whereas other genera of parasitic nematodes dominated the fauna in soils and roots of maize and imperata. Biomass yield of mucuna was not significantly affected by either Meloidogyne spp. or the other genera of phytoparasitic nematodes. In contrast, the dry matter yield of lablab measured at 12 weeks was reduced by 16% in inoculated compared with fumigated soils. Similarly, the biomass yields of maize and imperata were reduced by 10% and 29%, respectively, in unfumigated rather than fumigated soils. The amounts of N accumulated in mucuna, maize and imperata were not significantly affected by the two groups of plant parasitic nematodes. However, at 12 weeks, lablab grown on inoculated soils accumulated only 69% of the N found in plants grown on fumigated soils. Inoculation of soil with Meloidogyne spp. significantly increased the number of nodules on lablab roots compared with the non-inoculated treatments, whereas nodulation in mucuna was not affected by soil treatment. After 12 weeks, the quantity of N2 derived from symbiotic fixation in mucuna was not significantly affected by soil treatments whereas the amount of fixed N in lablab was 32% lower in inoculated than in fumigated soils. Possible mechanisms for the non-suppressive effect of plant parasitic nematodes on mucuna are discussed.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 9
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Soil use and management 17 (2001), S. 0 
    ISSN: 1475-2743
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract. Cashew soils of South Eastern Tanzania become acidified due to sulphur used for controlling powdery mildew disease (Oidium anacardii Noack). The buffering capacity of surface and subsurface horizons of 35 soil profiles of major cashew growing areas –- the Makonde plateau, its piedmont and inland plains –- was studied. The buffering capacity of surface and subsurface horizons was strongly correlated with clay content and weakly with organic carbon content. In addition, it was only weakly correlated with total exchangeable bases and available P of the surface horizon, but strongly with soil pH, base saturation and cation exchange capacity of the clay fraction of the subsurface horizon. Highly weathered sandy soils, dominant on the Makonde plateau and common on the Piedmont, had the lowest buffering capacity. Soils from the inland plains had better buffering capacities as they are generally more clayey or are less weathered. The risk of severe acidification and of a decline in productivity of cashew and of food crops is highest on the Makonde plateau. Further development and dissemination of methods which can reduce the use of sulphur are required.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 10
    ISSN: 1365-2389
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: In tropical cropping systems with few external inputs, efficient management of mineral N derived from added organic residues is essential for the proper functioning of the system. We studied the dynamics of mineral nitrogen (N) in the top 100 cm of soil with a system of tensiometers and suction cups after applying 15N-labelled Leucaena leucocephala and Dactyladenia barteri residues to bare and cropped microplots installed in the respective alley cropping systems, and followed the fate of the N for two maize-cowpea rotations (1992 and 1993).Fifty days after applying the residues (DDA), 20% of the added residue N was found in the soil profile of the bare Leucaena treatment, and 5% under Dactyladenia, compared with 5% and 1%, respectively, where cropped. All values decreased to about 1% after 505 days. In the cropped soil, no mineral N derived from the residues was lost by leaching during the first 6 weeks.As the maize grew, the soil profile was gradually depleted of nitrate to near Zero in the Dactyladenia treatment, whereas during the cowpea season the amount of nitrate N increased to 36 kg N ha−1 for the Leucaena treatment, and 26 kg N ha−1 for the Dactyladenia treatment. The soil of the bare microplots contained substantially more nitrate N (98 and 47 kg N ha-1 during the first year on average, under Leucaena and Dactyladenia, respetively) than that of the cropped microplots, except during the 1993 cowpea season. Nitrate residing in the subsoil (80–100 cm) in the bare treatments was not readily leached to deeper soil. The risk of losses of native mineral N was greatest during the first 50 DAA and to a lesser extent during the cowpea seasons. Improved management of the hedgerows could increase the potential of the hedgerow trees to recycle mineral N.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...