Optimisation of Nitrogen Supply from Sugarcane Residues in the Wet Tropics

Retention of sugarcane leaves and tops on the soil surface after harvesting has almost completely replaced burning of crop residues in the Australian sugar industry. Long term retention of residue is believed to improve soil fertility to the extent that nitrogen (N) fertilizer applications might be reduced by up to 40 kg N/ha/y. However, the fate of N in the extreme environment of the wet tropics is not known with certainty. Indices of potential N mineralisation and nitrification were developed and indicate that potential N fertility is greater in the wet tropics compared to more southern cane growing areas, and is enhanced under residue retention. Field results from the wet tropics support this prediction, but indicate high soil ammonium-N concentrations relative to nitrate-N.

Farming under constrained budgets: Practices of agricultural credit users in central Lombok, Indonesia

There has been a long dependency on credit by Indonesian farmers as a result of the lack of capital to apply proper farming practices. This paper describes the farming activities applied by agricultural credit users in Central Lombok, Indonesia. A survey was conducted during July 2001- March 2002 of 65 farmers making use of government or private credit in three villages within the Regency. Data from the farmers were collected using face-to-face, semi-structured interviews. Survey results indicated that on average, farmers had some 20 years experience of farming, were aged 40 years, but lacked of formal education. Their main asset was cropping land with average landholding of 0.69 ha. As a consequence of their capital constraints, farmers were commonly making use of credit to finance their farming activities, including both production of rice as the main crop and secondary crops. Farmers generally applied less than recommended amount of inputs in their farming practices, since the amount of credit they obtained was limited. As a result, their farms become less productive and their repayment capability of loans diminished. Of 65 farmers interviewed, 54 could earn extra income by engaging in a variety of non-farm activities, which contributed on average some 36% to family incomes of over Rp 5 million (A$ 1 thousand). The average credit repayment rate made by agricultural producers was 60%. The repayment made did not always reflect farm production capacity, being sometimes supported by other borrowings. The greater role of credit is not in increasing agricultural production or improving farmers’ income, but in helping them to sustain farm production and their living. Farmers need a bigger amount of credit to make an impact on their livelihood. This should be accompanied by extension services for farmers to enable better use of credit and to change their attitude towards it. As well, farmers require to be equipped with technical and market skills to run a business. Interdisciplinarity, holistic analysis, and an expansion of traditional ‘agricultural’ interests to embrace the span of interests included in rural livelihood, are each critical features of revision of the existing system.

Adding constrained discontinuities to Gaussian process models of wind fields

Gaussian Processes provide good prior models for spatial data, but can be too smooth. In many physical situations there are discontinuities along bounding surfaces, for example fronts in near-surface wind fields. We describe a modelling method for such a constrained discontinuity and demonstrate how to infer the model parameters in wind fields with MCMC sampling.

Amplitude response of a unilaterally constrained nonlinear micromechanical resonator

Dynamical systems that involve impacts frequently arise in engineering. This Letter reports a study of such a system at microscale that consists of a nonlinear resonator operating with an unilateral impact. The microresonators were fabricated on silicon-on-insulator wafers by using a one-mask process and then characterised by using the capacitively driving and sensing method. Numerical results concerning the dynamics of this vibro-impact system were verified by the experiments. Bifurcation analysis was used to provide a qualitative scenario of the system steady-state solutions as a function of both the amplitude and the frequency of the external driving sinusoidal voltage. The results show that the amplitude of resonant peak is levelled off owing to the impact effect and that the bandwidth of impacting is dependent upon the nonlinearity and the operating conditions.

Loss of chance and the evaluation of hypothetical's in contractual claims

Analyses how to calculate damages for the loss of an opportunity by reason of a breach of contract, in the light of the House of Lords judgment in Gregg v Scott concerning clinical negligence. Discusses whether different principles apply to contract claims and torts.