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?

The effect of continuous monoculture of sorghum, mungbean, oats, greenpanic and luceren on the nitrogen status of a brown clay soil from Narayen, South East Queensland was studied using biological and chemical methods. the soil nitrogen status was estimated by using indices of nitrogen availability i.e. waterlogged incubation method as the biological method and 2 M KCL, phosphate-borate buffer and 0.01 M CaCl_2 as rapid chemical methods. Total soil nitrogen and organic carbon were also included as estimates of soil nitrogen status. The results obtained by the waterlogged (WL) method were used to evaluate the results obtained by the three rapid chemical methods. The results show that of the three rapid chemical methods 2 M KCL was the most closely correlated with the waterlogged incubation method. Total N and organic C were also highly correlated with the WL method and they may have value as indices of nitrogen availability. The available N, total N and organic C contents in the 0-5 cm and 5-15cm layer soils were consistently higher under greenpanic and lucerne than for the annual crop treatments. The available N contents as determined by the WL method in the 0-5 cm and 5-15 cm soil layers under greenpanic and lucerne ranged from 75.6 to 126.5 ug N/g soil and 53.2 to 106.7 ug N/g soil, respectively, whereas the values under the annual crop treatments ranged from 13.2 to 75.3 ug N/g soil and 25.6 to 66.1 ug N/g soil, respectively. The total N contents in the 0-5 cm and 5-15 cm layer soils under the greenpanic and lucerne ranged from 0.29 to 0.38 % and 0.20 to 0.33 %, respectively, whereas the values under the annual crop treatments ranged from 0.17 to 0.31 % and 0.17 to 0.25 %, respectively. The availability of the total N as indicated by the available N as a percentage of the total N in the 0-5 cm and 5-15 cm layer soils under the greenpanic and lucerne ranged from 2.6 to 4.0 % and 2.1 to 3.2 %, respectively, whereas the values under the annual crop treatments ranged from 0.8 to 3.8 % and 1.5 to 2.4 %, respectively. In addition the organic C contents in the 0.5 cm and 5-15 cm layer soils under the greenpanic and lucerne range from 2.4 to 4.0 % and 2.0 to 3.5 %, respectively, whereas the values under the annual crop treatments ranged from 1.4 to 3.3 % and 1.7 to 2.7 %, respectively.

Population dynamics of plants is the study of the recruitment and longevity of plants. Of the many tropical pasture legumes now in use, only Siratro (Macroptilium) is understood in simple mixtures. Walker (1980) found that rapid changes occurred in the populations of some tropical perennial legumes in response to grazing by cattle. The study investigated initial effects of cattle grazing on the dynamics of five perennial, tropical legumes in association with two contrasting grass species.

The prospects of sustainable crop production technologies in East Timor were discerned with relevant case studies and experimental data. An overview of the agricultural development in East Timor with particular emphasis on the traditional farming and cropping systems was presented complemented by the discussion on the aspects of agricultural mechanization and technological change and their socioeconomic ramifications on food security. Empirical data from tillage trials, established both in East Timor and New Zealand, were gathered and discussed in the quest for a better understanding of tillage effects on soil structure and crop production environment. The agro-climatic zones of East Timor provide a well-defined set of ecological boundaries upon which further collaborative research work can be developed. Given land resources as one of the major capital investments in agriculture development, the drive towards improvement and technical change in agriculture should be directed in a balanced combination, whenever appropriate, between technologies of land-saving (hybrid seeds, irrigation, and drainage) or labour-saving (mechanization, herbicides, varieties and cropping techniques) characteristics. Moreover, the justification for acquiring an improved technology for traditional farmers, to some extent, needs to conform to the features of their subsistence mode of farming. The emphasis in technology dissemination, therefore, will have to shift from communication to education. Experimental results of this study on the effects of tillage, and no-tillage in Particular as a form of conservation tillage, on the edaphic changes affecting cropping environment generally concur with the findings known in the literature. Organic carbon levels are generally restored with cropping in East Timor. In addition, soil bulk density and crop grain and biomass yield were not affected by tillage treatments. Soil compaction was significantly affected by tillage as shown by data from the Palmerston North experiment. Soil aggregate stability in the 0-10 cm topsoil was similar under all the tillage treatments. Manual tillage (MT) had the greatest number of soil aggregates on sieve after a 30-minute wet-sieving (68.3%) followed by no-tillage (NT) (65.1), permanent pasture (PP) (62.6) and conventional tillage (CT) (56.5). Similarly, the top 0-10 cm soil under MT had significantly larger macroporosity (16.4%) than CT (9.23), NT (11.5), and PP (10.6). MT and CT significantly reduced the total C whereas N levels were significantly decreased by tillage (CT, MT and NT) compared to permanent pasture at the top 0-10 cm soil layer. Barley grain and biomass were unaffected by tillage whereas potato tuber yield and biomass were significantly less under no-tillage. Conventional tillage significantly increased water runoff but produced less leachate compared to no-till and permanent pasture. Total soil sediment loss was significantly lower under PP (95.8 kg/ha) and NT (132.9) compared to CT (3556.7) and MT (4652.2). pH of water runoff was significantly reduced under tillage treatments compared to that from permanent pasture whereas nitrogen losses were unaffected. There are at least four major public policy components that will play vital roles in the development of sustainable crop production technologies in East Timor: (i) Agricultural research and development (ii) Agricultural extension (iii) International and regional networking (iv) Shift of policy focus. The policy approach needs to be decentralized and broad-based and conservation agriculture should be promoted as opposed to conventional production agriculture. Three major areas for the future research agenda include: (i) Integrated Farming Systems (ii) Soil tillage and erosion (iii) Applied science and technology. The last component may cover disciplines such as: food policy analysis, farm machinery selection and testing, soil testing and mapping, land evaluation and GIs, bio-energy technologies, improved local seed varieties, adaptive fodder crops for improved grazing and pasture management, appropriate agro-forestry and soil and water conservation technologies and cash crop initiatives.

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The effect of continuous monoculture of sorghum, mungbean, oats, greenpanic and luceren on the nitrogen status of a brown clay soil from Narayen, South East Queensland was studied using biological and chemical methods. the soil nitrogen status was estimated by using indices of nitrogen availability i.e. waterlogged incubation method as the biological method and 2 M KCL, phosphate-borate buffer and 0.01 M CaCl_2 as rapid chemical methods. Total soil nitrogen and organic carbon were also included as estimates of soil nitrogen status. The results obtained by the waterlogged (WL) method were used to evaluate the results obtained by the three rapid chemical methods. The results show that of the three rapid chemical methods 2 M KCL was the most closely correlated with the waterlogged incubation method. Total N and organic C were also highly correlated with the WL method and they may have value as indices of nitrogen availability. The available N, total N and organic C contents in the 0-5 cm and 5-15cm layer soils were consistently higher under greenpanic and lucerne than for the annual crop treatments. The available N contents as determined by the WL method in the 0-5 cm and 5-15 cm soil layers under greenpanic and lucerne ranged from 75.6 to 126.5 ug N/g soil and 53.2 to 106.7 ug N/g soil, respectively, whereas the values under the annual crop treatments ranged from 13.2 to 75.3 ug N/g soil and 25.6 to 66.1 ug N/g soil, respectively. The total N contents in the 0-5 cm and 5-15 cm layer soils under the greenpanic and lucerne ranged from 0.29 to 0.38 % and 0.20 to 0.33 %, respectively, whereas the values under the annual crop treatments ranged from 0.17 to 0.31 % and 0.17 to 0.25 %, respectively. The availability of the total N as indicated by the available N as a percentage of the total N in the 0-5 cm and 5-15 cm layer soils under the greenpanic and lucerne ranged from 2.6 to 4.0 % and 2.1 to 3.2 %, respectively, whereas the values under the annual crop treatments ranged from 0.8 to 3.8 % and 1.5 to 2.4 %, respectively. In addition the organic C contents in the 0.5 cm and 5-15 cm layer soils under the greenpanic and lucerne range from 2.4 to 4.0 % and 2.0 to 3.5 %, respectively, whereas the values under the annual crop treatments ranged from 1.4 to 3.3 % and 1.7 to 2.7 %, respectively.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The objective was to evaluate concentrate substitution by corn silage on steers performance, as well as carcass and meat characteristics. The animals were organized according to the following treatments: 0% Sil: supplementation with 100% of corn grain; 33% Sil: supplementation with 66% of corn grain and 33% of corn silage; 50% Sil: supplementation with 50% of corn grain and 50% of corn silage; 66% Sil: supplementation with 33% of corn grain and 66% of corn silage; 100% Sil: supplementation with 100% of corn silage. The animals were slaughtered with average weight and body condition of 426.1 kg and 3.21 points, respectively. No significant interaction was observed between treatments and periods for forage mass, daily weight gain and stoking rate. The average forage mass was increased with the inclusion of roughage as supplement, providing higher stoking rate. The daily weight gain, weight gain per area and body condition didn t differ between treatments (P>.05). Treatments 66% Sil and 100% Sil had presented minor carcass length. Also significant correlation between amount of muscle and bone was verified (P= 0,0012 and r=0,67). Carcass and meat characteristics didn t show significant variations that can infer problems in animal commercialization. / O objetivo do experimento foi avaliar a substituição do concentrado pela silagem de milho no desempenho de novilhos de corte, bem como na carcaça e na carne. Os animais foram organizados de acordo com os seguintes tratamentos: 0% Sil: suplementação com 100% de grão de milho; 33% Sil: suplementação com 66% de grão de milho e 33% de silagem de milho; 50% Sil: suplementação com 50% de grão de milho e 50% de silagem de milho; 66% Sil: suplementação com 33% de grão de milho e 66% de silagem de milho; 100% Sil: suplementação com 100% de silagem de milho. Os novilhos foram abatidos com peso médio e escore corporal de 426,1 kg e 3,21 pontos, respectivamente. Houve interação significativa entre tratamentos e período para as variáveis massas de forragem (MF), taxa de crescimento diário (TC) e carga animal (CA) e peso final. A MF média foi superior frente aos tratamentos com maior inclusão de volumoso suplementar à dieta, principalmente com relação ao 100% Sil, promovendo, assim, aumento na CA para os mesmos. O ganho de peso médio diário, o ganho de peso vivo por hectare e o escore corporal não apresentaram variação significativa entre tratamentos (P>0,05). Os tratamentos 66% Sil e 100% Sil apresentaram menor comprimento de carcaça. Também foi verificada correlação significativa entre quantidade de músculo e osso (P= 0,0012 e r=0,67). Contudo não houve variações significativas que possam inferir problemas no momento da comercialização dos animais junto aos frigoríficos.