The Experts below are selected from a list of 294 Experts worldwide ranked by ideXlab platform
Chris Picone - One of the best experts on this subject based on the ideXlab platform.
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Diversity and Abundance of Arbuscular-Mycorrhizal Fungus Spores in Tropical Forest and Pasture1
Biotropica, 2006Co-Authors: Chris PiconeAbstract:As Neotropical forests are increasingly converted to agriculture (especially Pastures), little is known about the impacts on microbial biodiversity. To assess such impacts, I compared spore abundance and diversity of arbuscular mycorrhizal fungi (AMF) in soils from lowland evergreen forests and Pastures in Nicaragua and Costa Rica. Species composition, dominance–diversity curves, and Simpson's diversity indices were similar for both forest and Pasture soils. Of 28 distinct fungus morphospecies, 11 produced more spores in Pasture, while only 1 produced more spores in forest. According to species–accumulation curves, local AMF species richness did not significantly decline following conversion of forest to Pasture. Because Pastures contained a surprising abundance and diversity of AMF spores compared to native forest, a lack of mycorrhizal fungi is unlikely to limit plant succession, restoration, or reforestation in the Pastures studied. At the regional scale, however, species-accumulation curves showed significantly greater gamma (G) diversity of spores in forest. In addition to these trends in diversity, species that sporulated more in Pasture tended to have small spores, while the one species that sporulated more in forest had the largest spores. Similarly, only largespored fungi (>300 Μm) showed any seasonal variation in spore abundance, being more common in the wet season
Christopher M. Picone - One of the best experts on this subject based on the ideXlab platform.
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Diversity and Abundance of Arbuscular-Mycorrhizal Fungus Spores in Tropical Forest and Pasture1
BIOTROPICA, 2000Co-Authors: Christopher M. PiconeAbstract:Abstract As Neotropical forests are increasingly converted to agriculture (especially Pastures), little is known about the impacts on microbial biodiversity. To assess such impacts, I compared spore abundance and diversity of arbuscular mycorrhizal fungi (AMF) in soils from lowland evergreen forests and Pastures in Nicaragua and Costa Rica. Species composition, dominance–diversity curves, and Simpson's diversity indices were similar for both forest and Pasture soils. Of 28 distinct fungus morphospecies, 11 produced more spores in Pasture, while only 1 produced more spores in forest. According to species-accumulation curves, local AMF species richness did not significantly decline following conversion of forest to Pasture. Because Pastures contained a surprising abundance and diversity of AMF spores compared to native forest, a lack of mycorrhizal fungi is unlikely to limit plant succession, restoration, or reforestation in the Pastures studied. At the regional scale, however, species-accumulation curves s...
K R Helyar - One of the best experts on this subject based on the ideXlab platform.
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Pasture and sheep responses to lime application in a grazing experiment in a high-rainfall area, south-eastern Australia. I. Pasture production
Australian Journal of Agricultural Research, 2006Co-Authors: K R Helyar, S. J. Welham, Mark Conyers, Ljc. Castleman, R.p. Fisher, C. M. Evans, Brian R. Cullis, Peter CreganAbstract:‘Managing Acid Soils Through Efficient Rotations (MASTER)’ is a long-term Pasture–crop rotation experiment commenced in 1992. One of the objectives was to demonstrate the extent of crop, Pasture, and animal responses to lime on a typical acidic soil in the 500–800 mm rainfall zone in south-eastern Australia. Two types of Pastures (perennial v. annual Pastures) with or without lime application were established in 1992. This paper presents the results of the Pasture dry matter (DM) responses to lime application over 6 years from 1992 to 1997. Results showed that both perennial and annual Pastures responded positively to lime on a highly acidic soil on the south-west slopes of New South Wales. Averaged across Pasture types and 5 growing seasons, the limed Pastures produced 18% more Pasture DM (520 kg/ha, P < 0.05) than the unlimed Pastures. Significant responses to lime were detected on perennial Pastures (610 kg DM/ha, P < 0.05), but not on annual Pastures, although the limed annual Pastures produced more DM (420 kg/ha, P = 0.20) than the unlimed annual Pastures. There was a large seasonal variation in Pasture growth rate with the significant lime responses in winter and spring on both perennial Pastures (P < 0.05) and annual Pastures (P < 0.10 in winter and P < 0.05 in spring), but no responses in autumn and summer on either perennial or annual Pastures. The extra growth in winter is of importance as winter is the period when feed is normally inadequate and limits stocking rates. It is recommended that perennial-based Pastures should be promoted for the purposes of productivity, in terms of increasing Pasture production and improving feed quality, and for the environmental benefits in terms of alleviating the soil acidity problem and reducing the risk of dryland salinity in the high-rainfall zone in south-eastern Australia.
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Effects of lime on the botanical composition of Pasture over nine years in a field experiment on the south-western slopes of New South Wales
Australian Journal of Experimental Agriculture, 2003Co-Authors: K R Helyar, Ljc. Castleman, R.p. Fisher, C. M. Evans, Brian R. Cullis, M. C. Wilson, Mark ConyersAbstract:Two permanent Pastures (annual Pasture v. perennial Pasture) were established in 1992 as part of the long-term field experiment, MASTER — Managing Acid Soils Through Efficient Rotations. The primary objective of the experiment was to develop an agricultural system that is economically viable and environmentally sustainable on the highly acidic soils in south-eastern Australia. This paper reports on the effects of lime on the botanical composition changes of annual and perennial Pastures over 9 years. In general, lime increased the proportion of the desirable species, such as phalaris (Phalaris aquatica) in perennial Pasture and subterranean clover (Trifolium subterraneum) in annual Pastures, and decreased the proportion of the undesirable species, such as Vulpia spp., in both annual and perennial Pastures, ultimately improving the quality of feed-on-offer to animals. As a result, the limed Pastures carried 24% more sheep than the unlimed Pastures, while maintaining individual animal performance similar for both limed and unlimed Pastures. The phalaris-based perennial Pasture was more stable in terms of maintaining the sown species than the annual Pasture. Lime improved the persistence of phalaris and the longevity of the phalaris-based Pasture should be at least 10 years. Lime changed the direction of plant succession of annual Pastures. Without lime, Vulpia spp. gradually became more dominant while ryegrass and subterranean clover became less dominant in annual Pastures. With lime, barley grass (Hordeum leporinum) gradually invaded the sward at the expense of ryegrass, thus reducing the benefits of lime, but this effect was less for the perennial Pastures than for annual Pastures. Liming perennial Pastures should be more beneficial than liming annual Pastures because of the beneficial effects on Pasture composition. In addition, previously published work reported that liming perennial Pastures improved sustainability through better use of water and nitrogen.
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Seasonal differences in the soil water balance under perennial and annual Pastures on an acid Sodosol in southeastern Australia
European Journal of Soil Science, 2001Co-Authors: L K Heng, K R Helyar, R Fisher, Rob White, Deli ChenAbstract:Summary Replacement of native deep-rooted grasses by shallow-rooted ones has resulted in greater losses of water and nitrogen by drainage. To counter this effect we have tested the hypothesis that liming, and the conversion of annual grass Pastures to perennial grass Pastures, could improve the sustainability of grazing systems in the high rainfall zone (> 600 mm per annum) in southeastern Australia, through better use of water and nitrogen. A field experiment consisting of sixteen 0.135 ha (30 m × 45 m) grazed paddocks representing four Pasture combinations (annual Pasture (mainly Lolium rigidum) without lime (AP–); annual Pasture with lime (AP+); perennial Pasture (mainly Phalaris aquatica) without lime (PP–), and perennial Pasture with lime (PP+)) was carried out from 1994 to 1997 on an acid Sodosol (Aquic Hapludalf) in southern New South Wales, Australia. Measurements were made of surface runoff, subsurface flow (on top of the B horizon) and soil water content. The results showed that perennial grass Pastures, especially PP+, extracted approximately 40 mm more soil water each year than the annual grass Pastures. As a result, surface runoff, subsurface flow and deep drainage were at least 40 mm less from the perennial Pastures. These measurements were further supported by a simulation of soil water deficit and deep drainage for AP– and PP+ paddocks, using 10 years' past meteorological records. Overall, the results suggested that well-grown, phalaris-based Pastures could reduce recharge to groundwater and make pastoral systems more sustainable in the high rainfall zone.
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soil factors affecting the sustainability and productivity of perennial and annual Pastures in the high rainfall zone of south eastern australia
Australian Journal of Experimental Agriculture, 2000Co-Authors: R E White, K R Helyar, A M Ridley, Deli Chen, L K Heng, J Evans, R Fisher, J R Hirth, Pauline M Mele, G R MorrisonAbstract:A field study was carried out in the high rainfall zone (HRZ, >600 mm p.a.) of southern Australia from March 1994 to August 1997 to test the hypothesis that sown perennial grasses and liming could make the existing Pastures more sustainable through better use of water and nitrogen. The site, on an acid duplex soil at Book Book near Wagga Wagga in southern New South Wales, was typical of much of the HRZ grazing country in southern New South Wales and north-east Victoria. The experiment consisted of 4 replicate paddocks (each 0.135 ha) of 4 treatments: annual Pasture (mainly ryegrass Lolium rigidum, silver grass Vulpia spp., subterranean clover Trifolium subterraneum and broadleaf weeds) without lime, annual Pasture with lime, perennial Pasture (phalaris Phalaris aquatica, cocksfoot Dactylis glomerata and subterranean clover T. subterraneum) without lime, and perennial Pasture with lime. Soil pH (0–10 cm) in the limed treatments was maintained at 5.5 (0.01 mol/L CaCl2), compared to 4.1 in the unlimed treatments. The Pastures were rotationally grazed with Merino ewe or wether hoggets at a stocking rate which varied with the season, but was 10–25% higher on the limed Pastures [14.8–17.3 dry sheep equivalent (dse)/ha] than the unlimed Pastures. One replicate set of Pasture treatments was intensively monitored for surface runoff, subsurface flow (at the top of the B horizon), water potential gradients and ammonium volatilisation. Other measurements of nitrogen inputs, transformations and losses were made on all paddocks. In a normal to wet year, surface runoff, subsurface flow and deep drainage (>180 cm depth) were about 40 mm less from the perennial than the annual Pastures. The reduction in deep drainage under the perennials was about one-third to one-half (20–29 mm/year). The smaller loss of solution NO3– from the perennial Pastures (up to 12 kg N/ha.year) suggested soil acidification under perennials was reduced by about 1 kmol H+/ha.year. Denitrification and volatilisation losses of N were small (1–12 kg N/ha.year). Nitrogen fixed by subterranean clover (above ground parts) ranged from 2–8 kg N/ha in the drought of 1994–95 to 128 kg N/ha in a normal year (1996). The soil-Pasture nitrogen balance was positive for all treatments and averaged 76 kg N/ha.year over 2 years. The abundance of introduced and native earthworms increased from 85 to 250/m2 in the limed Pastures between 1994 and 1997. Introduced species, such as Aporrectodea trapezoides, were especially responsive to lime. Animal production per hectare was 10–25% higher on Pastures with lime. Critical gross margins per dse were lowest ($16/ha) for a long-lived perennial Pasture (>15 years), and highest ($20/ha) for a short-lived perennial (5 years). Overall, there were substantial benefits in animal production, improved soil quality and water use from establishing perennial grass Pastures with lime on these strongly acid soils.
Deli Chen - One of the best experts on this subject based on the ideXlab platform.
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Seasonal differences in the soil water balance under perennial and annual Pastures on an acid Sodosol in southeastern Australia
European Journal of Soil Science, 2001Co-Authors: L K Heng, K R Helyar, R Fisher, Rob White, Deli ChenAbstract:Summary Replacement of native deep-rooted grasses by shallow-rooted ones has resulted in greater losses of water and nitrogen by drainage. To counter this effect we have tested the hypothesis that liming, and the conversion of annual grass Pastures to perennial grass Pastures, could improve the sustainability of grazing systems in the high rainfall zone (> 600 mm per annum) in southeastern Australia, through better use of water and nitrogen. A field experiment consisting of sixteen 0.135 ha (30 m × 45 m) grazed paddocks representing four Pasture combinations (annual Pasture (mainly Lolium rigidum) without lime (AP–); annual Pasture with lime (AP+); perennial Pasture (mainly Phalaris aquatica) without lime (PP–), and perennial Pasture with lime (PP+)) was carried out from 1994 to 1997 on an acid Sodosol (Aquic Hapludalf) in southern New South Wales, Australia. Measurements were made of surface runoff, subsurface flow (on top of the B horizon) and soil water content. The results showed that perennial grass Pastures, especially PP+, extracted approximately 40 mm more soil water each year than the annual grass Pastures. As a result, surface runoff, subsurface flow and deep drainage were at least 40 mm less from the perennial Pastures. These measurements were further supported by a simulation of soil water deficit and deep drainage for AP– and PP+ paddocks, using 10 years' past meteorological records. Overall, the results suggested that well-grown, phalaris-based Pastures could reduce recharge to groundwater and make pastoral systems more sustainable in the high rainfall zone.
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soil factors affecting the sustainability and productivity of perennial and annual Pastures in the high rainfall zone of south eastern australia
Australian Journal of Experimental Agriculture, 2000Co-Authors: R E White, K R Helyar, A M Ridley, Deli Chen, L K Heng, J Evans, R Fisher, J R Hirth, Pauline M Mele, G R MorrisonAbstract:A field study was carried out in the high rainfall zone (HRZ, >600 mm p.a.) of southern Australia from March 1994 to August 1997 to test the hypothesis that sown perennial grasses and liming could make the existing Pastures more sustainable through better use of water and nitrogen. The site, on an acid duplex soil at Book Book near Wagga Wagga in southern New South Wales, was typical of much of the HRZ grazing country in southern New South Wales and north-east Victoria. The experiment consisted of 4 replicate paddocks (each 0.135 ha) of 4 treatments: annual Pasture (mainly ryegrass Lolium rigidum, silver grass Vulpia spp., subterranean clover Trifolium subterraneum and broadleaf weeds) without lime, annual Pasture with lime, perennial Pasture (phalaris Phalaris aquatica, cocksfoot Dactylis glomerata and subterranean clover T. subterraneum) without lime, and perennial Pasture with lime. Soil pH (0–10 cm) in the limed treatments was maintained at 5.5 (0.01 mol/L CaCl2), compared to 4.1 in the unlimed treatments. The Pastures were rotationally grazed with Merino ewe or wether hoggets at a stocking rate which varied with the season, but was 10–25% higher on the limed Pastures [14.8–17.3 dry sheep equivalent (dse)/ha] than the unlimed Pastures. One replicate set of Pasture treatments was intensively monitored for surface runoff, subsurface flow (at the top of the B horizon), water potential gradients and ammonium volatilisation. Other measurements of nitrogen inputs, transformations and losses were made on all paddocks. In a normal to wet year, surface runoff, subsurface flow and deep drainage (>180 cm depth) were about 40 mm less from the perennial than the annual Pastures. The reduction in deep drainage under the perennials was about one-third to one-half (20–29 mm/year). The smaller loss of solution NO3– from the perennial Pastures (up to 12 kg N/ha.year) suggested soil acidification under perennials was reduced by about 1 kmol H+/ha.year. Denitrification and volatilisation losses of N were small (1–12 kg N/ha.year). Nitrogen fixed by subterranean clover (above ground parts) ranged from 2–8 kg N/ha in the drought of 1994–95 to 128 kg N/ha in a normal year (1996). The soil-Pasture nitrogen balance was positive for all treatments and averaged 76 kg N/ha.year over 2 years. The abundance of introduced and native earthworms increased from 85 to 250/m2 in the limed Pastures between 1994 and 1997. Introduced species, such as Aporrectodea trapezoides, were especially responsive to lime. Animal production per hectare was 10–25% higher on Pastures with lime. Critical gross margins per dse were lowest ($16/ha) for a long-lived perennial Pasture (>15 years), and highest ($20/ha) for a short-lived perennial (5 years). Overall, there were substantial benefits in animal production, improved soil quality and water use from establishing perennial grass Pastures with lime on these strongly acid soils.
L K Heng - One of the best experts on this subject based on the ideXlab platform.
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Seasonal differences in the soil water balance under perennial and annual Pastures on an acid Sodosol in southeastern Australia
European Journal of Soil Science, 2001Co-Authors: L K Heng, K R Helyar, R Fisher, Rob White, Deli ChenAbstract:Summary Replacement of native deep-rooted grasses by shallow-rooted ones has resulted in greater losses of water and nitrogen by drainage. To counter this effect we have tested the hypothesis that liming, and the conversion of annual grass Pastures to perennial grass Pastures, could improve the sustainability of grazing systems in the high rainfall zone (> 600 mm per annum) in southeastern Australia, through better use of water and nitrogen. A field experiment consisting of sixteen 0.135 ha (30 m × 45 m) grazed paddocks representing four Pasture combinations (annual Pasture (mainly Lolium rigidum) without lime (AP–); annual Pasture with lime (AP+); perennial Pasture (mainly Phalaris aquatica) without lime (PP–), and perennial Pasture with lime (PP+)) was carried out from 1994 to 1997 on an acid Sodosol (Aquic Hapludalf) in southern New South Wales, Australia. Measurements were made of surface runoff, subsurface flow (on top of the B horizon) and soil water content. The results showed that perennial grass Pastures, especially PP+, extracted approximately 40 mm more soil water each year than the annual grass Pastures. As a result, surface runoff, subsurface flow and deep drainage were at least 40 mm less from the perennial Pastures. These measurements were further supported by a simulation of soil water deficit and deep drainage for AP– and PP+ paddocks, using 10 years' past meteorological records. Overall, the results suggested that well-grown, phalaris-based Pastures could reduce recharge to groundwater and make pastoral systems more sustainable in the high rainfall zone.
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soil factors affecting the sustainability and productivity of perennial and annual Pastures in the high rainfall zone of south eastern australia
Australian Journal of Experimental Agriculture, 2000Co-Authors: R E White, K R Helyar, A M Ridley, Deli Chen, L K Heng, J Evans, R Fisher, J R Hirth, Pauline M Mele, G R MorrisonAbstract:A field study was carried out in the high rainfall zone (HRZ, >600 mm p.a.) of southern Australia from March 1994 to August 1997 to test the hypothesis that sown perennial grasses and liming could make the existing Pastures more sustainable through better use of water and nitrogen. The site, on an acid duplex soil at Book Book near Wagga Wagga in southern New South Wales, was typical of much of the HRZ grazing country in southern New South Wales and north-east Victoria. The experiment consisted of 4 replicate paddocks (each 0.135 ha) of 4 treatments: annual Pasture (mainly ryegrass Lolium rigidum, silver grass Vulpia spp., subterranean clover Trifolium subterraneum and broadleaf weeds) without lime, annual Pasture with lime, perennial Pasture (phalaris Phalaris aquatica, cocksfoot Dactylis glomerata and subterranean clover T. subterraneum) without lime, and perennial Pasture with lime. Soil pH (0–10 cm) in the limed treatments was maintained at 5.5 (0.01 mol/L CaCl2), compared to 4.1 in the unlimed treatments. The Pastures were rotationally grazed with Merino ewe or wether hoggets at a stocking rate which varied with the season, but was 10–25% higher on the limed Pastures [14.8–17.3 dry sheep equivalent (dse)/ha] than the unlimed Pastures. One replicate set of Pasture treatments was intensively monitored for surface runoff, subsurface flow (at the top of the B horizon), water potential gradients and ammonium volatilisation. Other measurements of nitrogen inputs, transformations and losses were made on all paddocks. In a normal to wet year, surface runoff, subsurface flow and deep drainage (>180 cm depth) were about 40 mm less from the perennial than the annual Pastures. The reduction in deep drainage under the perennials was about one-third to one-half (20–29 mm/year). The smaller loss of solution NO3– from the perennial Pastures (up to 12 kg N/ha.year) suggested soil acidification under perennials was reduced by about 1 kmol H+/ha.year. Denitrification and volatilisation losses of N were small (1–12 kg N/ha.year). Nitrogen fixed by subterranean clover (above ground parts) ranged from 2–8 kg N/ha in the drought of 1994–95 to 128 kg N/ha in a normal year (1996). The soil-Pasture nitrogen balance was positive for all treatments and averaged 76 kg N/ha.year over 2 years. The abundance of introduced and native earthworms increased from 85 to 250/m2 in the limed Pastures between 1994 and 1997. Introduced species, such as Aporrectodea trapezoides, were especially responsive to lime. Animal production per hectare was 10–25% higher on Pastures with lime. Critical gross margins per dse were lowest ($16/ha) for a long-lived perennial Pasture (>15 years), and highest ($20/ha) for a short-lived perennial (5 years). Overall, there were substantial benefits in animal production, improved soil quality and water use from establishing perennial grass Pastures with lime on these strongly acid soils.
