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Item Open Access Climate change and land suitability for potato production in England and Wales: impacts and adaptation(Cambridge University Press, 2012-04-01T00:00:00Z) Daccache, Andre; Keay, Caroline A.; Jones, Robert J. A.; Weatherhead, E. K.; Stalham, M. A.; Knox, Jerry W.The viability of commercial potato production is influenced by spatial and temporal variability in soils and agroclimate, and the availability of water resources where supplemental irrigation is required. Soil characteristics and agroclimatic conditions greatly influence the cultivar choice, agronomic husbandry practices and the economics of production. Using the latest (UKCP09) scenarios of climate change for the UK, this paper describes a methodology using pedo-climatic functions and a GIS to model and map current and future land suitability for potato production in England and Wales. The outputs identify regions where rainfed production is likely to become limiting and where future irrigated production would be constrained due to shortages in water availability. The results suggest that by the 2050s, the area of land that is currently well or moderately suited for rainfed production would decline by 74 and 95% under the "most likely" climate projections for the low and high emissions scenario respectively, owing to increased droughtiness. In many areas, rainfed production would become increasingly risky. However, with supplemental irrigation, around 85% of the total arable land in central and eastern England would remain suitable for production, although most of this is in catchments where water resources are already over-licensed and/or over-abstracted; the expansion of irrigated cropping is thus likely to be constrained by water availability. The increase in volumetric water demand due to the switch from rainfed to irrigated potato cropping is likely to be much greater than the incremental increase in water demand solely on irrigated potatoes. The implications of climate change on the potato industry, the adaptation options and responses available, and the uncertainty associated with the land suitability projections, are discussed.Item Open Access A comparison of the responses of mature and young clonal tea to drought.(Cambridge University Press, 2001-01-01T00:00:00Z) Nixon, D. J.; Burgess, Paul J.; Sanga, B. N. K.; Carr, M. K. V.To assist commercial producers with optimising the use of irrigation water, the responses to drought of mature and young tea crops (22 and 5 years after field planting respectively) were compared using data from two adjacent long-term irrigation experiments in Southern Tanzania. Providing the maximum potential soil water deficit was below about 400-500 mm for mature, and 200-250 mm for young plants (clone 6/8), annual yields of dry tea from rainfed or partially irrigated crops were similar to those from the corresponding well-watered crops. At deficits greater than this, annual yields declined rapidly in young tea (up to 22 kg (ha mm)-1) but relatively slowly in mature tea (up to 6.5 kg (ha mm)- 1). This apparent insensitivity of the mature crop to drought was due principally to compensation that occurred during the rains for yield lost in the dry season. Differences in dry matter distribution and shoot to root ratios contributed to these contrasting responses. Thus, the total above ground dry mass of well-irrigated, mature plants was about twice that for young plants. Similarly, the total mass of structural roots (>1 mm diameter), to 3 m depth, was four times greater in the mature crop than in the young crop and, for fine roots (<1 mm diameter), eight times greater. The corresponding shoot to root ratios (dry mass) were about 1:1 and 2:1 respectively. In addition, each unit area of leaf in the canopy of a mature plant had six times more fine roots (by weight) available to extract and supply water than did a young plant. Despite the logistical benefits resulting from more even crop distribution during the year when crops are fully irrigated, producers currently prefer to save water and energy costs by allowing a substantial soil water deficit to develop prior to the start of the rains, up to 250 mm in mature tea, knowing that yield compensation will occur later.Item Open Access Description, diagnosis, prescription: a critique of the application of co- evolutionary models to natural resource management.(Cambridge University Press, 2006-12-01T00:00:00Z) Jeffrey, Paul; McIntosh, Brian S.To support moves towards more sustainable modes of natural resource management, the research community has been engaged in an evaluation of paradigms, theories and methods which might provide useful and usable insights into such a complex problem set. A particularly influential family of theoretical models concerned with the processes and dynamics of species evolution has been adopted from the fields of biology and ecology. This paper scrutinizes the relevance of biological evolutionary theory to sustainable natural resource management beyond identification of the core analogy, namely that both natural resource management and ecological systems are characterized by multiple interacting elements requiring systemic interpretation. A review of the workings of co-evolutionary theory within its intellectual homeland of biology and ecology leads to a critical evaluation of its use as a descriptive model outside of these domains. Findings from this assessment identify a number of fractures in meaning as the co-evolutionary model is transferred between disciplinary fields, suggesting that the transposition has been conducted without sufficient rigour or consistency. A measured reinterpretation of the applicability of the co- evolutionary model to natural resources management is thereby undertaken. Using water management as a context, the paper posits a series of phenomena which might provide a focus for the application of the co-evolutionary model outside of biology and ecology. In conclusion, the paper argues that the research community needs to move beyond a consideration of the complex implications of co-evolutionary processes to the establishment of a firm, process-based definition of co-evolution as a type of change.Item Open Access Modelling energy metabolism of Friesians in Kenya smallholdings shows how heat stress and energy deficit constrain milk yield and cow replacement rate(Cambridge University Press, 2006-06-14T00:00:00Z) King, J. M.; Parsons, David J.; Turnpenny, J. R.; Nyangaga, J.; Bakari, P.; Wathes, C. M.The 2002 World Summit on Sustainable Development focussed attention on agricultural sustainability and biodiversity in developing countries. These goals are relevant for livestock production in Kenya, where development agencies encourage resource-poor smallholders to acquire large, exotic, high-yielding dairy cows, despite their poor performance, revealed in recent surveys in the highlands and at the coast. The performance of the cows is not in question. The debate relates to the diagnosis of the causes, their treatment and the prognosis for the production system. To improve our understanding of the dynamics of the system, models of nutrition and energy, modified for the tropics, were used to measure the thermal responses over 24 h of six pure or crossbred Friesians at a mean lactation of 54 (s.d. 21·6) days, in separate zero-grazing units. Four smallholdings were on the hot, humid coast and two in the cooler highlands. The output of the model runs was related to the subsequent lactation, calving interval and profitability of the cows. The model showed that the thermal load caused moderate stress for all cows during the day, which became severe in the sun in the highlands, but the drop in air temperature, from 27 °C to 13 °C, at night dissipated the gain in body heat. At the coast, where the night temperature remained above 24 °C and relative humidity above 0·85, there was no remission of heat stress for cows with a milk yield greater than 11 l/day. The lactation curve, in all cows, declined from an initial peak to a low profile of 5 l/day. Cows in both regions with initial yields above 20 l/day had the steepest decline and longest calving intervals (457 to 662 days). They had the largest lactation yields and lowest direct cost per litre, but their poor breeding record reduced cull sales and increased replacement cost, raising the total cost per litre. By contrast, the cow with the lowest daily and lactation yield had the highest direct cost, but lowest total cost per litre, because she produced 2 heifer calves at an interval of only 317 days. These case studies serve as a reminder that, where heat load depresses appetite or poor food cannot support lactation, the energy deficit and stress reduces cow fertility, fitness, and longevity, so that she fails to breed a heifer replacement during her shortened productive life. The model predicted that food intake, depressed by heat stress, would not support a milk yield above 14 l/day and 3000 l per annum at the coast, and 22 l/day and 5000 l per annum in the highlands. Therefore, although appearing profitable in the short term, the current policy of promoting cows with higher yields than the climate and production system can support, is unsustainable. This outcome has implications for smallholder dairy development policy in Kenya, and probably elsewhere in the tropics. Instead, one should reconsider smaller exotic breeds and crossbreds with improved indigenous dairy cows whose overall productivity from milk yield, fecundity, longevity, and disease tolerance 50 years ago was better than that of the modern Holstein-Friesian in a Kenya smallholding.Item Open Access Proceedings of the first meeting of the Operational Research (OR) Society's Special Interest Group on Agriculture and Natural Resources (SIG-ANR)(Cambridge University Press, 2010-04-30T00:00:00Z) Sandars, D. L.This group, which represents the reformed Operational Research (OR) Society's Agriculture and Related Industries group (http://www.orsoc.org.uk), promotes the use of OR (or the application of the scientific method) in solving management and governance problems within this sector. The theme of this meeting was to look at models concerned with making better decisions for the management or governance of the agricultural and natural resource industries. This first one day meeting was at Reading University, Berkshire, UK on the 2 April when the following papers were read.Item Open Access Proceedings of the Fourth Meeting of the EURO Working Group on Operational Research (OR) in Agriculture and Forest Management (EWG-ORAFM)(Cambridge University Press, 2009-04-27T00:00:00Z) Sandars, D. L.; Pla, L. M.The current paper will survey how things have changed over nearly 50 years of OR applied to agriculture. The first ‘OR group’ was set up at the National Institute of Agricultural Engineering by Dan Boyce in 1969 and is now at Cranfield University. The current paper will examine how, and what, factors have influenced the type of work and the methods used. What applications have stood the test of time and what are just distant memories in paper publications?Item Open Access The water relations and irrigation requirements of sugar cane (Saccharum officinarum): a review.(Cambridge University Press, 2011-01-01T00:00:00Z) Carr, M. K. V.; Knox, Jerry W.The results of research on the water relations and irrigation needs of sugar cane are collated and summarized in an attempt to link fundamental studies on crop physiology to irrigation practices. Background information on the centres of production of sugar cane is followed by reviews of (1) crop development, including roots; (2) plant water relations; (3) crop water requirements; (4) water productivity; (5) irrigation systems and (6) irrigation scheduling. The majority of the recent research published in the international literature has been conducted in Australia and southern Africa. Leaf/stem extension is a more sensitive indicator of the onset of water stress than stomatal conductance or photosynthesis. Possible mechanisms by which cultivars differ in their responses to drought have been described. Roots extend in depth at rates of 5-18 mm d- 1 reaching maximum depths of > 4 m in ca. 300 d providing there are no physical restrictions. The Penman-Monteith equation and the USWB Class A pan both give good estimates of reference crop evapotranspiration (ETo). The corresponding values for the crop coefficient (Kc) are 0.4 (initial stage), 1.25 (peak season) and 0.75 (drying off phase). On an annual basis, the total water-use (ETc) is in the range 1100-1800 mm, with peak daily rates of 6-15 mm d-1. There is a linear relationship between cane/sucrose yields and actual evapotranspiration (ETc) over the season, with slopes of about 100 (cane) and 13 (sugar) kg (ha mm)-1 (but variable). Water stress during tillering need not result in a loss in yield because of compensatory growth on re-watering. Water can be withheld prior to harvest for periods of time up to the equivalent of twice the depth of available water in the root zone. As alternatives to traditional furrow irrigation, drag- line sprinklers and centre pivots have several advantages, such as allowing the application of small quantities of water at frequent intervals. Drip irrigation should only be contemplated when there are well-organized management systems in place. Methods for scheduling irrigation are summarized and the reasons for their limited uptake considered. In conclusion, the ‘drivers for change', including the need for improved environmental protection, influencing technology choice if irrigated sugar cane production is to be sustainable are summarize