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Differential adaptations of barley (Hordeum vulgare L.) and wheat (Triticum spp.) genotypes suggest that they be evaluated under multi-environmental conditions. The objectives of this study were to determine if small grain genotypes, bred for various moisture conditions, respond differently in terms of yield, water use, and rooting pattern to contrasting moisture conditions. Eight small grain genotypes were compared under a gradient of water from 89 to 404 mm (plus 254 mm of stored water) in a field study at Marana, AZ. A barley bred for low input conditions had greater root density in the subsoil and used moisture earlier in the season when compared to a high input barley (WestBred Gustoe). The cultivars bred for high input conditions required more water for optimum yield compared to those bred for low input conditions.

Bibliography: leaves 223-247. Effects of water availability during grain filling is examined in wheat (Triticum aestivum L.) and barley (Hordum vulgare L.) genotypes. The study tests the accumulation of dry matter (DM) and nitrogen (N) in the grain and also their remobilization from the shoot to the grain. Water stress during grain filling was found to reduce DM and N accumulation and also to increase N concentration in both wheat and barley grain.

Graduation date: 1994

Bibliography: leaves 223-247. / xiii, 247 p. : ill, maps ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Effects of water availability during grain filling is examined in wheat (Triticum aestivum L.) and barley (Hordum vulgare L.) genotypes. The study tests the accumulation of dry matter (DM) and nitrogen (N) in the grain and also their remobilization from the shoot to the grain. Water stress during grain filling was found to reduce DM and N accumulation and also to increase N concentration in both wheat and barley grain. / Thesis (Ph.D.)--University of Adelaide, Dept. of Plant Science, 1996

An understanding of the water use of different crops commonly grown in an area is essential for the implementation of integrated catchment management in South Africa. With increasing pressure on water resources, mainly due to the recent changes in the Water Act, it has become important to determine the actual water demands of agricultural and other crops. Policy makers require knowledge of whether forestry canopies use more water than grassland and other agricultural crops. The Bowen ratio and Penman-Monteith methods were used in a comparative study of the evaporation from Saccharum, Acacia and Eucalyptus. All of the research was conducted at marginal sites located in the KwaZulu-Natal Midlands of South Africa over a period of two years. The Bowen ratio energy balance (BREB) technique combines the Bowen ratio (J3) (the ratio between the sensible, H and latent heat flux density, XE), with the net irradiance (Rn) and soil heat flux densities (G) to calculate evaporation. A comparative study of the sitespecific energy balance components (Rn, G, H and AE), general climatic conditions (rainfall, solar irradiance and air temperature) and other site-specific parameters (leaf area index and average canopy height) was conducted on Saccharum and young commercial forests consisting of Acacia and Eucalyptus. The energy balance highlighted important differences in the energy balance components between the different canopies. The differences between the reflection coefficients at the three sites contributed mainly to the differences in the evaporation rates. The low reflection coefficients of the forest canopies (Acacia and Eucalyptus) (0.1 and 0.08 respectively) were smaller than of the sugarcane canopy (0.2). This resulted in more energy available (« 6 %) for partitioning between the sensible and latent heat flux densities and higher evaporation rates for the forestry canopies. Where low leaf area indices existed (Acacia and Eucalyptus sites) (LAI < 2), the soil heat flux density contributed up to 40 % of the net irradiance (G = 0.4 Rn). The evaporation rates for Saccharum, Acacia and Eucalyptus averaged 2 mm day"1 in winter and 5 mm day"1 in summer. The slightly higher summer evaporation rate for Eucalyptus (5.6 mm day"1), compared to Acacia (4.9 mm day"1), resulted from the lower reflection coefficients and canopy resistance (rc) for Eucalyptus (ocs = 0.08, rc = 35 s m"1) compared to Acacia (ocs = 0.1, rc = 45 s m"1). Automatic weather station data (solar irradiance, air temperature, water vapour pressure and windspeed) were applied to site-specific Penman-Monteith equations to predict evaporation for all three sites. Statistically significant relationships (slope, m « 1, r2 > 0.8) were found between the measured (Bowen ratio) and simulated (site-specific Penman-Monteith) evaporation estimates. The current study has demonstrated the effectiveness of applying the Penman-Monteith equation to forest and sugarcane canopies to predict evaporation, provided accurate net irradiance, soil heat flux densities and canopy resistances are used. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1999.

Call number: LD2668 .T4 1961 M59

Call number: LD2668 .T4 1985 M378 / Master of Science