Mircen Journal of Applied Microbiology and Biotechnology, 1987
... experienced. The distillates are titrated against a sulphuric acid solution (0.05-0.25 N), th... more ... experienced. The distillates are titrated against a sulphuric acid solution (0.05-0.25 N), this acid being standardized by titration against a solution of tris (hydroxymethyl) methylamine (THAM) as suggested by Keeney & Nelson (1982). ...
... Juliane Lilienfein 1 ,; Wolfgang Wilcke ,; Lourival Vilela 2 ,; Samuel do Carmo Lima 3 ,; Ric... more ... Juliane Lilienfein 1 ,; Wolfgang Wilcke ,; Lourival Vilela 2 ,; Samuel do Carmo Lima 3 ,; Richard Thomas 4 ... Lilienfein, J., Wilcke, W., Vilela, L., do Carmo Lima, S., Thomas, R. and Zech, W. (2000 ... electrical conductivity (EC) of the soil solution, and the concentrations of Al, C, Ca, Cl ...
Four cultivars of Phaseolus vulgaris L., Carioca, Venezuela‐ 350, Rio Tibagi and Negro Argel, wer... more Four cultivars of Phaseolus vulgaris L., Carioca, Venezuela‐ 350, Rio Tibagi and Negro Argel, were grown to maturity in a glass house with a low (1 mol m) and a high (4.5 mol m) potassium supply. Potassium stimulated nitrogenase activity (acetylene reduction) and the accumulation of ureides in pod walls of Carioca and Negro Argel, cultivars which had the highest
The accumulation of humus in soils under Pinus caribaea Morelet forests may increase the availabi... more The accumulation of humus in soils under Pinus caribaea Morelet forests may increase the availability of organically bound N, P, and S to plants and thus improve soil fertility. To test this hypothesis, we compared C, N, P, and S concentrations and forms in soil solid phase and soil solution under Pinus (PI) and natural savanna vegetation (Cerrado, CE). We sampled the 0± 0.15, 0.15±0.3, 0.3±0.8, 0.8±1.2, and 1.2±2 m soil depth layers of Oxisols from three spatially separated plots under CE and PI; at each plot, soil solution at 0.15, 0.3, 0.8, 1.2, and 2 m soil depth and under PI additionally below the organic layer was collected during two rainy seasons (21 October±28 April 1997.
The United Nations University (UNU) is an organ of the United Nations established by the General ... more The United Nations University (UNU) is an organ of the United Nations established by the General Assembly in 1972 to be an international community of scholars engaged in research, advanced training, and the dissemination of knowledge related to pressing global problems of human survival, development and welfare. Its activities focus mainly on environment and sustainable development, and peace and governance. The UNU International Network on Water, Environment and Health (UNU-INWEH) is a member of the UNU family of organizations. It was created by the UNU Governing Council in 1996 to strengthen water management capacity, particularly of developing countries, and to provide on-the-ground project support, with its core funding provided by the Government of Canada. It is hosted by McMaster University, Canada.
Knowledge of the phosphorus (P) dynamics in the soil-plant system, and especially of the short- a... more Knowledge of the phosphorus (P) dynamics in the soil-plant system, and especially of the short- and long-term fate of P fertiliser in relation to different management practices, is essential for the sustainable management of tropical agroecosystems. A series of field trials was conducted in the tropical savannas and Andean hillsides in Colombia to follow the dynamics of P under different
In this study, we investigated the spatial distribution of an earthworm community together with t... more In this study, we investigated the spatial distribution of an earthworm community together with the heterogeneity of selected soil properties in a gallery forest (GF) of the Colombian "Llanos". We performed fine-scale spatial variability by intensively sampling 100 points distributed in the nodes of a regular grid with 5 m inter-sample distance. Non-parametric statistics were used and included SADIE analysis and partial Mantel test, in addition to geostatistics (semi-variograms) and correlogram computation. Our results indicated that the spatial distribution of earthworms was characterized by areas of presence (patches) and absence (gaps), although the general pattern was random at the scale of this study (<5 m), while soil physico-chemical characteristics showed a clumped spatial distribution. Contrary to previous results reported for the nearby savanna, a significant spatial association was found for two competing endogeic species Andiodrilus sp. and Glossodrilus sp. in the GF. Semi-variograms of soil environmental factors were adjusted to model families most commonly used (spherical and linear), and correlograms for earthworms showed significant positive and negative spatial autocorrelation for lag distances <15 m and >30 m, respectively. Partial Mantel test revealed specific significant relationships between soil variables and some species. The earthworm community of the GF displayed a random structure in a spatially clumped soil environment, and our results suggested that spatial distribution observed for some species could be the result of preferential selection of soil environmental factors. In other words, soil heterogeneity contributed to the formation of population patches for some earthworm species. The variability of suitable sites (resource availability patchiness) exerted an influence in the spatial distribution of earthworms at the scale used in this study, and we identified the spatial scale at which both environmental heterogeneity could influence and express earthworm impact on soil properties.
In the Oxisols of the eastern plains of Colombia, the large native anecic earthworm Martiodrilus ... more In the Oxisols of the eastern plains of Colombia, the large native anecic earthworm Martiodrilus sp. is an abundant ecosystem engineer producing long-lasting casts and burrows. Casts deposited in the soil by this species have been estimated at several tonnes per hectare per year. The physical and chemical processes occurring in these casts have never been studied. In this study, we compared the dynamics of water content (WC), total C (C tot ), and available N (N avail ) contents, and the distribution in size of aggregates in ageing below-ground casts of this species and in the bulk soil. In a native herbaceous savannah and a sown grass/legume pasture (Brachiaria humidicola, Arachis pintoi, Desmodium ovalifolium and Stylosanthes capitata), fresh surface casts were experimentally injected into artificial burrows of 1 cm Ø and 10 cm depth and sampled at different dates during a total period of 120 days. The injection procedure used resulted in a 34% decrease in WC of the casts from the sown pasture and reduced the mean mass diameter (MMD) of the aggregates of casts from the savannah by 19%. Other properties were not significantly affected by the procedure.
The proportion of nitrogen derived from fixation was measured by 15N isotope dilution in three tr... more The proportion of nitrogen derived from fixation was measured by 15N isotope dilution in three tropical grass-legume pastures on two Oxisols differing in texture over a 3 year period using three non-fixing controls. The use of the companion pasture grass, Brachiaria dictyoneura, was satisfactory as a non-fixing control when compared with a non-fixing Panicum maximum ecotype KK16 and native savanna grasses. Amounts of nitrogen fixed ranged from 0.3 to 40 kg N ha−1 12 weeks−1 during the wet season and were greatest with Stylosanthes capitata followed by Centrosema acutifolium and Arachis pintoi mainly as a result of greater legume biomass in the former compared with the latter two species. There were little or no differences amongst the three legumes in kg N fixed t legume DM−1. Amounts of nitrogen fixed per unit area decreased over the 3 year period mainly as a result of a loss of legume biomass. The % N derived from fixation (%Ndfa) was generally greater than 80% in all legumes on b...
We aimed to determine how root decomposition is affected by soil texture and weather conditions, ... more We aimed to determine how root decomposition is affected by soil texture and weather conditions, and to produce a data set for calibrating or validating litter decomposition models. Roots of tropical grasses and legumes were buried in the field in two acid Oxisols of widely differing textures during either the dry or the wet season. Results were analyzed, using four decay models: single exponential, single exponential with residue, double exponential, and a model in which the relative decomposition rate (RDR) decreases non-linearly as a function of the litter fraction left: l/X.dX/dt = -k(X/XoJ'ib. In the dry season, the RDR of all roots decreased steeply with a declining fraction of leftover root weight. This indicates a rapid loss of a small fraction of easily decomposable material, leaving behind a large fraction of recalcitrant material. In the wet season, RDR decreased more gradually. The basic pattern of decomposition was the same for both clay loam and sandy soil, although the absolute values for RDR and the steepness of its decrease differed. Given that the two soils differed widely in texture and consequent water retention characteristics, the differences in RDR may have resulted from differences in soil water regime. The very high C-to-P ratios in the roots (up to 1780) reflect low P availability in these strongly P-sorbing Oxisols. Because microbial C-to-P ratios in these soils ranged from 34 to 50, considerable P immobilization may be needed for decomposition to proceed.
area of native savanna on an acid, strongly P-sorbing Oxisol in the Eastern Plains of Colombia wa... more area of native savanna on an acid, strongly P-sorbing Oxisol in the Eastern Plains of Colombia was opened and sown to various rotations of grass pasture with rice, grass-legume pasture with rice or rice monocrop. After 4.5 y, the soil under each cropping system was sampled and analysed for total organic matter, microbial C, N and P content, and mineralization rate of C and N. Microbial biomass C did not vary much among treatments, whereas the N and P contents of the biomass were considerably lower in rice monocrop than in any crop-pasture treatment. Biomass P was also low under native savanna. The contribution of microbial N or P to soil-organic-matter N or P was lowest under the rice monocrop and highest under the grass-legume pasture. Microbial C-to-N ratios fell in ranges commonly reported, but C-to-P ratios were rather wide (34-50), indicating that the microbes may have adapted themselves to the low-P conditions of these soils. The contribution of microbial P to soil-organic-matter P, however, was about the same as usually found in soils of much higher P fertility. As microbial biomass nutrients cycle relatively rapidly and P availability in these strongly P-sorbing soils is low, the microbial biomass may play an important role in supplying P to plants growing in these soils. A similar conclusion was reached for N. The microbial respiration rate per unit of microbial biomass C (qCO& as determined during an ll-day incubation, was higher under rice-pasture rotations-particularly in the presence of a legume-than under rice monocropping. This suggests that a greater fraction of microbes was active under rice-pasture rotations, probably because of a more continuous and higher input of fresh organic matter. The fraction of organic matter mineralized during the incubation was also highest for the rice-pasture treatments. 0 1997 Published by Elsevier Science Ltd Biology and Biochemistry 22, 251-255. Zeitschriff fur Pflanzenerniihrung und Bodenkunde 157, 359-367.
Establishment of improved tropical pastures on acid savanna soils of low fertility can increase t... more Establishment of improved tropical pastures on acid savanna soils of low fertility can increase the soil organic matter (SOM) content and soil fertility. Our objective was to follow the quantitative and qualitative changes of SOM associated with sand-, silt-and clay-sized separates after establishment of a grass-alone (Brachiaria decumbens) and a grass-legume (Brachiaria decumbens + Pueraria phaseoloides) pasture on isohyperthermic savanna soils of Colombia. Additionally, earthworm casts of anecic and endo-anecic species derived from the grass-legume pasture were investigated. Whole soil and size separates were analyzed for C, N, lignin-derived phenols (alkaline CuO-oxidation) and carbohydrates (4 M trifluoroacetic acid hydrolysis). For native savanna, grass-alone and grass-legume pasture the C content increased in the order sand (1.63.3 g C kg-') 4 silt (25.8-32.1 g C kg-l) < clay (38843.0 g C kg-'); the C-to-N ratio decreased in the same order. Fifteen years of pasture establishment resulted in an increase of C by factors ofca. 2 (sand), 1.3 (silt) and 1.1 (clay) compared to native savanna. Decreasing yields of phenolic CuO-oxidation products and increasing side-chain oxidation of the remnant lignin indicated progressive lignin alteration with decreasing particle size. Soil under savanna was substantially lower in intact lignin structures than soil under grass-alone and grass-legume pastures. Enrichment factors, E = (mg kg-' soil under pasture/mg kg-' soil under savanna), for lignin-derived phenolics after establishment of B. decumbens and B. decumbens + P. phaseoloides were 3.9 and 2.7,4.3 and 2.4, and 2.6 and 2.6 in sand-, silt-and clay-sized separates, respectively. Clay-bound SOM was rich in microbially-derived sugars, whereas the SOM of the sand-sized separates contained large amounts of plant-derived sugars. Silt-associated SOM had low concentrations of both. Establishment of grass-alone and grass-legume pasture increased the amount of easily-degradable plant-derived sugars by factors of 3.0 and 3.5 (sand), 1.9 and 1.3 (silt), and 1.1 and 1.1 (clay). SOM distribution across size separates suggested an increasing amount of unprotected macro-OM after establishment of grass-alone and grass-legume pastures. Concurrently, lignin and carbohydrate signature indicated higher contents of relatively undegraded plant-derived SOM, notably in the sand-sized separates. 1 t was concluded that the increase of this SOM fraction has beneficial effects on the soil internal N cycle as far as N mineralization and N immobilization is concerned. Earthworm casts were characterized by a tremendous enrichment of C, intact lignin and plant-derived sugars in the sand-sized separates, compared with the surrounding soil. This suggested a pronounced incorporation of fresh litter into the mineral soil (anecic effect), that decomposition processes were dramatically slowed in the casts, and a pool of relatively labile, but physically-protected SOM was built up.
Summary Sheep urine was applied once in August to 1 m2 plots of a N-deficientLolium perenne-domin... more Summary Sheep urine was applied once in August to 1 m2 plots of a N-deficientLolium perenne-dominated sward at a rate equivalent to a single urination (48 g N m−2) at an upland site. After 17 days herbage dry matter (DM) and total N were increased 19- and 63-fold respectively compared with a control receiving water only. Soil mineral N (NH
The fate of sheep urine-N applied to an upland grass sward at four dates representing widely diff... more The fate of sheep urine-N applied to an upland grass sward at four dates representing widely differing environmental conditions, was followed in soil (0–20 cm) and in herbage. Urine was poured onto 1-m2 plots to simulate a single urination in August 1984 (warm and dry), May (cool), July and August 1985 (cool and wet) at rates equivalent to 40–52 g
Mircen Journal of Applied Microbiology and Biotechnology, 1987
... experienced. The distillates are titrated against a sulphuric acid solution (0.05-0.25 N), th... more ... experienced. The distillates are titrated against a sulphuric acid solution (0.05-0.25 N), this acid being standardized by titration against a solution of tris (hydroxymethyl) methylamine (THAM) as suggested by Keeney &amp; Nelson (1982). ...
... Juliane Lilienfein 1 ,; Wolfgang Wilcke ,; Lourival Vilela 2 ,; Samuel do Carmo Lima 3 ,; Ric... more ... Juliane Lilienfein 1 ,; Wolfgang Wilcke ,; Lourival Vilela 2 ,; Samuel do Carmo Lima 3 ,; Richard Thomas 4 ... Lilienfein, J., Wilcke, W., Vilela, L., do Carmo Lima, S., Thomas, R. and Zech, W. (2000 ... electrical conductivity (EC) of the soil solution, and the concentrations of Al, C, Ca, Cl ...
Four cultivars of Phaseolus vulgaris L., Carioca, Venezuela‐ 350, Rio Tibagi and Negro Argel, wer... more Four cultivars of Phaseolus vulgaris L., Carioca, Venezuela‐ 350, Rio Tibagi and Negro Argel, were grown to maturity in a glass house with a low (1 mol m) and a high (4.5 mol m) potassium supply. Potassium stimulated nitrogenase activity (acetylene reduction) and the accumulation of ureides in pod walls of Carioca and Negro Argel, cultivars which had the highest
The accumulation of humus in soils under Pinus caribaea Morelet forests may increase the availabi... more The accumulation of humus in soils under Pinus caribaea Morelet forests may increase the availability of organically bound N, P, and S to plants and thus improve soil fertility. To test this hypothesis, we compared C, N, P, and S concentrations and forms in soil solid phase and soil solution under Pinus (PI) and natural savanna vegetation (Cerrado, CE). We sampled the 0± 0.15, 0.15±0.3, 0.3±0.8, 0.8±1.2, and 1.2±2 m soil depth layers of Oxisols from three spatially separated plots under CE and PI; at each plot, soil solution at 0.15, 0.3, 0.8, 1.2, and 2 m soil depth and under PI additionally below the organic layer was collected during two rainy seasons (21 October±28 April 1997.
The United Nations University (UNU) is an organ of the United Nations established by the General ... more The United Nations University (UNU) is an organ of the United Nations established by the General Assembly in 1972 to be an international community of scholars engaged in research, advanced training, and the dissemination of knowledge related to pressing global problems of human survival, development and welfare. Its activities focus mainly on environment and sustainable development, and peace and governance. The UNU International Network on Water, Environment and Health (UNU-INWEH) is a member of the UNU family of organizations. It was created by the UNU Governing Council in 1996 to strengthen water management capacity, particularly of developing countries, and to provide on-the-ground project support, with its core funding provided by the Government of Canada. It is hosted by McMaster University, Canada.
Knowledge of the phosphorus (P) dynamics in the soil-plant system, and especially of the short- a... more Knowledge of the phosphorus (P) dynamics in the soil-plant system, and especially of the short- and long-term fate of P fertiliser in relation to different management practices, is essential for the sustainable management of tropical agroecosystems. A series of field trials was conducted in the tropical savannas and Andean hillsides in Colombia to follow the dynamics of P under different
In this study, we investigated the spatial distribution of an earthworm community together with t... more In this study, we investigated the spatial distribution of an earthworm community together with the heterogeneity of selected soil properties in a gallery forest (GF) of the Colombian "Llanos". We performed fine-scale spatial variability by intensively sampling 100 points distributed in the nodes of a regular grid with 5 m inter-sample distance. Non-parametric statistics were used and included SADIE analysis and partial Mantel test, in addition to geostatistics (semi-variograms) and correlogram computation. Our results indicated that the spatial distribution of earthworms was characterized by areas of presence (patches) and absence (gaps), although the general pattern was random at the scale of this study (<5 m), while soil physico-chemical characteristics showed a clumped spatial distribution. Contrary to previous results reported for the nearby savanna, a significant spatial association was found for two competing endogeic species Andiodrilus sp. and Glossodrilus sp. in the GF. Semi-variograms of soil environmental factors were adjusted to model families most commonly used (spherical and linear), and correlograms for earthworms showed significant positive and negative spatial autocorrelation for lag distances <15 m and >30 m, respectively. Partial Mantel test revealed specific significant relationships between soil variables and some species. The earthworm community of the GF displayed a random structure in a spatially clumped soil environment, and our results suggested that spatial distribution observed for some species could be the result of preferential selection of soil environmental factors. In other words, soil heterogeneity contributed to the formation of population patches for some earthworm species. The variability of suitable sites (resource availability patchiness) exerted an influence in the spatial distribution of earthworms at the scale used in this study, and we identified the spatial scale at which both environmental heterogeneity could influence and express earthworm impact on soil properties.
In the Oxisols of the eastern plains of Colombia, the large native anecic earthworm Martiodrilus ... more In the Oxisols of the eastern plains of Colombia, the large native anecic earthworm Martiodrilus sp. is an abundant ecosystem engineer producing long-lasting casts and burrows. Casts deposited in the soil by this species have been estimated at several tonnes per hectare per year. The physical and chemical processes occurring in these casts have never been studied. In this study, we compared the dynamics of water content (WC), total C (C tot ), and available N (N avail ) contents, and the distribution in size of aggregates in ageing below-ground casts of this species and in the bulk soil. In a native herbaceous savannah and a sown grass/legume pasture (Brachiaria humidicola, Arachis pintoi, Desmodium ovalifolium and Stylosanthes capitata), fresh surface casts were experimentally injected into artificial burrows of 1 cm Ø and 10 cm depth and sampled at different dates during a total period of 120 days. The injection procedure used resulted in a 34% decrease in WC of the casts from the sown pasture and reduced the mean mass diameter (MMD) of the aggregates of casts from the savannah by 19%. Other properties were not significantly affected by the procedure.
The proportion of nitrogen derived from fixation was measured by 15N isotope dilution in three tr... more The proportion of nitrogen derived from fixation was measured by 15N isotope dilution in three tropical grass-legume pastures on two Oxisols differing in texture over a 3 year period using three non-fixing controls. The use of the companion pasture grass, Brachiaria dictyoneura, was satisfactory as a non-fixing control when compared with a non-fixing Panicum maximum ecotype KK16 and native savanna grasses. Amounts of nitrogen fixed ranged from 0.3 to 40 kg N ha−1 12 weeks−1 during the wet season and were greatest with Stylosanthes capitata followed by Centrosema acutifolium and Arachis pintoi mainly as a result of greater legume biomass in the former compared with the latter two species. There were little or no differences amongst the three legumes in kg N fixed t legume DM−1. Amounts of nitrogen fixed per unit area decreased over the 3 year period mainly as a result of a loss of legume biomass. The % N derived from fixation (%Ndfa) was generally greater than 80% in all legumes on b...
We aimed to determine how root decomposition is affected by soil texture and weather conditions, ... more We aimed to determine how root decomposition is affected by soil texture and weather conditions, and to produce a data set for calibrating or validating litter decomposition models. Roots of tropical grasses and legumes were buried in the field in two acid Oxisols of widely differing textures during either the dry or the wet season. Results were analyzed, using four decay models: single exponential, single exponential with residue, double exponential, and a model in which the relative decomposition rate (RDR) decreases non-linearly as a function of the litter fraction left: l/X.dX/dt = -k(X/XoJ'ib. In the dry season, the RDR of all roots decreased steeply with a declining fraction of leftover root weight. This indicates a rapid loss of a small fraction of easily decomposable material, leaving behind a large fraction of recalcitrant material. In the wet season, RDR decreased more gradually. The basic pattern of decomposition was the same for both clay loam and sandy soil, although the absolute values for RDR and the steepness of its decrease differed. Given that the two soils differed widely in texture and consequent water retention characteristics, the differences in RDR may have resulted from differences in soil water regime. The very high C-to-P ratios in the roots (up to 1780) reflect low P availability in these strongly P-sorbing Oxisols. Because microbial C-to-P ratios in these soils ranged from 34 to 50, considerable P immobilization may be needed for decomposition to proceed.
area of native savanna on an acid, strongly P-sorbing Oxisol in the Eastern Plains of Colombia wa... more area of native savanna on an acid, strongly P-sorbing Oxisol in the Eastern Plains of Colombia was opened and sown to various rotations of grass pasture with rice, grass-legume pasture with rice or rice monocrop. After 4.5 y, the soil under each cropping system was sampled and analysed for total organic matter, microbial C, N and P content, and mineralization rate of C and N. Microbial biomass C did not vary much among treatments, whereas the N and P contents of the biomass were considerably lower in rice monocrop than in any crop-pasture treatment. Biomass P was also low under native savanna. The contribution of microbial N or P to soil-organic-matter N or P was lowest under the rice monocrop and highest under the grass-legume pasture. Microbial C-to-N ratios fell in ranges commonly reported, but C-to-P ratios were rather wide (34-50), indicating that the microbes may have adapted themselves to the low-P conditions of these soils. The contribution of microbial P to soil-organic-matter P, however, was about the same as usually found in soils of much higher P fertility. As microbial biomass nutrients cycle relatively rapidly and P availability in these strongly P-sorbing soils is low, the microbial biomass may play an important role in supplying P to plants growing in these soils. A similar conclusion was reached for N. The microbial respiration rate per unit of microbial biomass C (qCO& as determined during an ll-day incubation, was higher under rice-pasture rotations-particularly in the presence of a legume-than under rice monocropping. This suggests that a greater fraction of microbes was active under rice-pasture rotations, probably because of a more continuous and higher input of fresh organic matter. The fraction of organic matter mineralized during the incubation was also highest for the rice-pasture treatments. 0 1997 Published by Elsevier Science Ltd Biology and Biochemistry 22, 251-255. Zeitschriff fur Pflanzenerniihrung und Bodenkunde 157, 359-367.
Establishment of improved tropical pastures on acid savanna soils of low fertility can increase t... more Establishment of improved tropical pastures on acid savanna soils of low fertility can increase the soil organic matter (SOM) content and soil fertility. Our objective was to follow the quantitative and qualitative changes of SOM associated with sand-, silt-and clay-sized separates after establishment of a grass-alone (Brachiaria decumbens) and a grass-legume (Brachiaria decumbens + Pueraria phaseoloides) pasture on isohyperthermic savanna soils of Colombia. Additionally, earthworm casts of anecic and endo-anecic species derived from the grass-legume pasture were investigated. Whole soil and size separates were analyzed for C, N, lignin-derived phenols (alkaline CuO-oxidation) and carbohydrates (4 M trifluoroacetic acid hydrolysis). For native savanna, grass-alone and grass-legume pasture the C content increased in the order sand (1.63.3 g C kg-') 4 silt (25.8-32.1 g C kg-l) < clay (38843.0 g C kg-'); the C-to-N ratio decreased in the same order. Fifteen years of pasture establishment resulted in an increase of C by factors ofca. 2 (sand), 1.3 (silt) and 1.1 (clay) compared to native savanna. Decreasing yields of phenolic CuO-oxidation products and increasing side-chain oxidation of the remnant lignin indicated progressive lignin alteration with decreasing particle size. Soil under savanna was substantially lower in intact lignin structures than soil under grass-alone and grass-legume pastures. Enrichment factors, E = (mg kg-' soil under pasture/mg kg-' soil under savanna), for lignin-derived phenolics after establishment of B. decumbens and B. decumbens + P. phaseoloides were 3.9 and 2.7,4.3 and 2.4, and 2.6 and 2.6 in sand-, silt-and clay-sized separates, respectively. Clay-bound SOM was rich in microbially-derived sugars, whereas the SOM of the sand-sized separates contained large amounts of plant-derived sugars. Silt-associated SOM had low concentrations of both. Establishment of grass-alone and grass-legume pasture increased the amount of easily-degradable plant-derived sugars by factors of 3.0 and 3.5 (sand), 1.9 and 1.3 (silt), and 1.1 and 1.1 (clay). SOM distribution across size separates suggested an increasing amount of unprotected macro-OM after establishment of grass-alone and grass-legume pastures. Concurrently, lignin and carbohydrate signature indicated higher contents of relatively undegraded plant-derived SOM, notably in the sand-sized separates. 1 t was concluded that the increase of this SOM fraction has beneficial effects on the soil internal N cycle as far as N mineralization and N immobilization is concerned. Earthworm casts were characterized by a tremendous enrichment of C, intact lignin and plant-derived sugars in the sand-sized separates, compared with the surrounding soil. This suggested a pronounced incorporation of fresh litter into the mineral soil (anecic effect), that decomposition processes were dramatically slowed in the casts, and a pool of relatively labile, but physically-protected SOM was built up.
Summary Sheep urine was applied once in August to 1 m2 plots of a N-deficientLolium perenne-domin... more Summary Sheep urine was applied once in August to 1 m2 plots of a N-deficientLolium perenne-dominated sward at a rate equivalent to a single urination (48 g N m−2) at an upland site. After 17 days herbage dry matter (DM) and total N were increased 19- and 63-fold respectively compared with a control receiving water only. Soil mineral N (NH
The fate of sheep urine-N applied to an upland grass sward at four dates representing widely diff... more The fate of sheep urine-N applied to an upland grass sward at four dates representing widely differing environmental conditions, was followed in soil (0–20 cm) and in herbage. Urine was poured onto 1-m2 plots to simulate a single urination in August 1984 (warm and dry), May (cool), July and August 1985 (cool and wet) at rates equivalent to 40–52 g
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