Machair is a habitat found predominantly in coastal areas of the north–west of Scotland and is characterised by a low-input, rotational arable system interspersed with semi-natural grasslands. Land management is an essential part of the machair system as both intensification and abandonment threaten its future. Little is known about this system in terms of its below ground communities. A survey was conducted over a three season, two year period for molecular determination of bacterial, AM fungal and nematode community structure. Cropped, fallow and undisturbed grassland were sampled; soil and roots associated with two commonly occurring species and composite soil samples were collected. In addition the effect of edaphic factors and vegetation composition on soil communities was assessed, both in the field and in greenhouse experiments. Results show that although all of the examined factors impacted the community structure of the three soil groups to some degree, the strength of this effect varied between groups. Bacterial communities were mainly affected by temporal factors, particularly year, possibly due to variation in soil moisture content. AM fungal community structure also varied considerably with season, but the mechanisms behind this were less obvious, with both abiotic and plant factors playing a role. AM fungal community structure varied with different plant hosts but also with soil moisture content. In contrast to both bacteria and AM fungi, nematode communities showed a strong response to land use although temporal factors and differences between locations were also observed. Grasslands harboured a distinctly different community structure from cropped and fallow, largely as a result of variation in bacterivores and carnivores. Vegetation composition and soil moisture content were also found to affect nematode community structure. This study has revealed that machair soil communities seem to be highly complex, dynamic and adapted to the changeable conditions that persist.

Thesis (Ph. D.)--University of Adelaide, Waite Agricultural Research Institute, 1955. / Typewritten copy. Includes bibliographical references.

Based on periodic clipping of a fertilized pasture plot in the Peace River region in 1977 and 1979, accumulated dry matter production of a timothy, red fescue and alsike clover mix was found to be linearly related to accumulated transpiration during the active growing season, with a growth/transpiration ratio of 0.026 t ha⁻¹ /(mm H₂O)-The effect of fertilizer level and cutting management on dry matter production is discussed. Energy balance/Bowen ratio measurements of evapo-transpiration (E) in 1977, 1978 and 1979 showed that daytime E can be calculated for energy limiting conditions using the Priestley-Taylor formula with α = 1.26 ± 0.05. Daytime net radiation required in this formula was estimated to within 15%, using the Idso-Jackson longwave radiation equation and daily solar radiation data from a regional climate station 50 km away. During water supply limiting conditions E was found to be linearly related to root zone water storage. Root zone drainage was found to be negligible in this soil, which has a high bulk density subsoil. A simple model for calculating the course of pasture growth during the growing season at Sunset Prairie Community Pasture is described. The model is composed of a single-layer root zone water balance submodel and a relationship between dry matter production and transpiration. The water balance submodel estimates daily transpiration and requires daily values of rainfall, solar radiation and maximum and minimum air temperature. It also requires crop albedo and an estimate of the initial root zone water storage. Estimates of root zone water storage during the three growing seasons agreed well with gravimetric and neutron moisture probe measurements. The model, using the above growth/transpiration ratio, was found to estimate hay growth during the droughty growing season in 1978 to within 15% of measured values. An effective growth/transpiration ratio of 0.013 t ha ⁻¹/mm was required to account for the growth of pasture subjected to a simulated monthly grazing rotation. / Land and Food Systems, Faculty of / Graduate

Graduation date: 1996

Bibliography : leaves 150-158. / viii, 158 leaves, [7] leaves of plates : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Crop Protection, 1996?

A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfillment of the requirements for the degree of Master of Science. Johannesburg 1990. / No abstract provided.

Angus cows (Bos taurus) with calves and 1/2 Dorset, 1/4 Finn and 1/4 Rambouillet ewes (Ovis aries) with lambs grazed Kentucky bluegrass (Poa pratensis) - white clover (Trifolium repens) in a randomized block design with three replications during 3 yr, to investigate effects of grazing cattle and sheep together and separately on soils, plants and animals. Additionally, changes in stocking rate, seasonal distribution of cool-season forages and varying nutritional requirements of animals were examined. There were 6 cow-calf pairs or 6 ewes with 11 lambs per replication of cattle alone and sheep alone treatments. Six cows plus six ewes, with their offspring, were allotted to each replication of mixed grazed pastures. Initial stocking rates were equilibrated among treatments to 1 cow and calf per .45 ha. Grazing sheep alone increased (P < .05) percentage bluegrass (58%) but decreased white clover (6%) and weeds (36%), compared to pastures grazed only by cattle (30, 16 and 53%, respectively, which was similar to initial composition). Soils in mixed grazed pastures remained higher (P < .05) in plant nutrients, pH, and percent organic matter and were less (P < .05) compacted, compared to soils where sheep or cattle grazed alone. Total forage mass and quality were higher (P < .05) in mixed grazed pastures, compared to pastures grazed by cattle and sheep alone. Daily gain (.23 kg/d), total gain (23 kg), and weaning weights (43 kg) of lambs were higher (P < .01) in pastures grazed by both animal species, compared to sheep alone (.18 kg/d, 19 and 38 kg, respectively). These animals also reached target weaning weights (43 kg) 14 d earlier (P < .05) than those grazed alone. Body condition of ewes was improved by the breeding season, compared to ewes grazed alone. Five measuring techniques were investigated to determine forage mass and botanical composition. Measurements based on small plots permanently located within pastures were as accurate as those based on the entire pasture. Visual estimations of forage mass were lower, compared to hand clipping, but reflected canopy height. Visual evaluations more accurately estimated presence of individual plant species than hand separated samples. Grazing ewes and cows with associated spring-born offspring on bluegrass-white clover improved the balance between plant growth and animal forage requirements and improved sustainability of the soil-plant-animal system. / Ph. D.

[Truncated abstract] In southern Australian farming systems the replacement of deep-rooted perennial native vegetation with shallow-rooted annual crops and pastures has resulted in rising groundwater tables and an increased incidence of dryland salinity. It has been suggested that to address this issue by restoring hydrological balance, large areas of agricultural land need to be vegetated with perennial plants. One of the most agriculturally productive ways to do this is to introduce perennial pastures, both into upslope groundwater

Copy of author's previously published work inserted. Bibliography: leaves 261-306. The objectives of the project were: i. to determine whether there are competitive interactions between Aporrectodea trapezoides and A. caliginosa and A. rosea.--ii. to investigate compeditive interactions between A. calignosa, Microscolex dubius and A. trapezoides.--iii . to determine the likely impact of A. longa on soil fauna, especially the native earthworm, Gemascolex lateralis, in native ecosystems.

Copy of author's previously published work inserted. / Bibliography: leaves 261-306. / xxix, 308 leaves : ill. (some col.), maps ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / The objectives of the project were: i. to determine whether there are competitive interactions between Aporrectodea trapezoides and A. caliginosa and A. rosea.--ii. to investigate compeditive interactions between A. calignosa, Microscolex dubius and A. trapezoides.--iii . to determine the likely impact of A. longa on soil fauna, especially the native earthworm, Gemascolex lateralis, in native ecosystems. / Thesis (Ph.D.)--University of Adelaide, Dept. of Soil Science, 1996