A bio-economic modelling project for small-scale milk production systems in South-East Brazil: Part 2—refinement and use of the model to analyse some short- and long-term management strategies

The further development and use of a bio-economic model to simulate small-scale dairy enterprises in South-East Brazil are reported.The account of animal nutrition has been refined to take account of protein requirements in addition to energy balance. A new version has been developed which allows for the inheritance of production traits.The model has been used to analyse the effects of short-term management decisions on feeding strategies and longer term breeding policies for herd development. It has been used, also, to examine the possibilities of culling for reproductive performance and the effects of a range of growth rates of replacement heifers on overall herd performance.     

Multiple objective programming: An approach to planning and evaluation of agroforestry systems: Part 2—An illustrative example and analysis

Four methods representing four different multiple objective programming (MOP) approaches are described in this paper. Some theoretical and computational characteristics of these methods are illustrated using an agroforestry planning problem. The solutions generated by each method correspond to alternative land allocation schemes identified by land compartment, site quality and management regime which specifies the cropping system used, the length of the timber rotation and the thinning schedule.     

Simulation of peak-demand hydrographs in pressurized irrigation delivery systems using a deterministic–stochastic combined model. Part II: model applications

A deterministic–stochastic combined model named HydroGEN was developed, as described in a companion paper (Part I: Model development), to enable the simulation of demanded daily volumes and hourly flow rates during peak periods in pressurized irrigation delivery networks. The model was applied to a pilot large-scale irrigation system located in southern Italy for calibration and for testing its reliability in analyzing the operation of large-scale pressurized delivery systems through the simulated flow configurations. Daily input data on rainfall, temperature, solar radiation, wind speed and relative humidity were gathered from a meteorological station located within the study area, whereas information on local irrigation management practices were collected through interviews with farmers and from extension specialists. The model was tested at different management levels, from district to sector and hydrants. The model testing was supported by the use of high-resolution remote-sensing imagery acquired on a single overpass date in 2006 and then classified and recoded following a ground-truthing campaign conducted during the same year. Simulations were performed to identify the 10-day peak-demand period and to generate the hydrographs of daily volumes and of hourly flow rates. Results from the different simulations were compared with historical datasets of irrigation volumes and discharges recorded during the 2008 and 2009 seasons at the upstream end of the irrigation network under study, at a sector level during the 2007 season and at selected delivery hydrants during the 2005 season. Some discrepancies between simulated and recorded data were noted that can be related to small errors in estimating crop and soil parameters, application efficiency at field level, as well as to large variability in irrigation management practices followed by local farmers. Overall, the results from testing showed that the model is capable of forecasting with good accuracy the timing of peak-demand periods, the irrigation volumes demanded during the season, as well as the hydrographs of daily volumes and hourly flow rates withdrawn by farmers during these peak-demand periods, especially when it is applied to large multi-cropped command areas.     

Fate and risks of potentially toxic elements in wastewater-fed food production systems—the examples of Cambodia and Vietnam

Non-treated wastewater is used for irrigation of aquatic food production systems in the peri-urban areas of the major cities in Southeast Asia. This paper complement the knowledge on agricultural soil-based crops irrigated with low quality water, by reviewing the research findings on the wastewater-fed aquatic productions with special focus on heavy metals and other potentially toxic elements (PTEs) in the production systems of Hanoi in Vietnam and Phnom Penh in Cambodia. In Hanoi, sediments in the wastewater exposed rivers of Hanoi were reported to be polluted with PTEs, in particular with Cadmium (Cd). The river sediment had a high retention capacity for PTEs which seems to prevent the transport of PTEs to the wastewater-fed production systems. In Phnom Penh, domestic and industrial wastewater is pumped into the Cheung Ek Lake located south of the city. A major part of the water spinach (Ipomoea aquatica Forssk.) consumed in the city is produced in the lake. The concentrations of some PTEs were elevated at the wastewater inlets to the lake compared to concentrations at the lake outlet and at the control site. Water spinach is by far the major vegetable produced in the wastewater-fed systems in Hanoi and Phnom Penh, but did only contain PTEs in concentrations within or slightly above the concentration range observed for water spinach grown in agricultural soil not exposed to wastewater. PTE concentration in fish grown in wastewater-fed systems in Hanoi and Phnom were low. However, mean PTE concentrations in liver and skin of some fish were high. Consumption of muscle tissue from fish produced in wastewater-fed systems in Hanoi and Phnom Penh resulted in an estimated intake of PTEs amounting to less than 9% of the tolerable intake. It was concluded, that the PTE concentrations in fish and water spinach from Hanoi and Cheung Ek Lake in Phnom Penh constituted low food safety risks for consumers.     

Examples of the use of “CARTA”—A computer program to predict transport vehicle performance and costs in developing countries

A questionnaire, designed to obtain information about rural transport conditions in developing countries, is tested and the results are examined. It is found that a set of typical conditions can be drawn up and used in a computer program which predicts vehicle performance and operating costs.The predicted performance and costs of a 1 t and a 4·7 t truck when operated in the specified conditions are compared with survey results obtained in Kenya, and are found to be similar.Conditions corresponding to those existing on a land development programme in Central Africa are derived and the predicted costs of a number of vehicles when operated in those conditions are examined.It is concluded that low speed industrial/agricultural vehicles with payloads in the range 0·7–2 t are most likely to offer a satisfactory compromise between capital cost, fuel used and cost per tonne-kilometre.     

Effects of the measures envisaged in “Agenda 2000” on arable crop producers and beef and veal producers: an application of Positive Mathematical Programming to representative farms of a Spanish region

The authors analyse the possible effects of the measures envisaged in “Agenda 2000”, approved by the Berlin European Council of March 1999, on representative farms specialised in arable crop production and beef and veal production. Three economic sizes are considered for each of these types of farming (4–16 European Size Units [ESU], 16–40 ESU and >40 ESU). The analysis is made by means of Positive Mathematical Programming, utilising quadratic cost functions. The results show that the increase in compensatory payments and premiums would not offset a possible decrease in market prices, and therefore, for most of the agricultural holdings studied, the economic results worsen. It is worth noting that the total subsidies share in agricultural incomes is notably increased.