Browsing by Author "Carr, M. K. V."
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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 Evaluation of simple hand-held Mechanical systems for harvesting tea (Camellia Sinensis)(Cambridge University Press, 2006-04-01T00:00:00Z) Burgess, Paul J.; Carr, M. K. V.; Mizambwa, F. C. S.; Nixon, D. J.; Lugusi, J.; Kimambo, E. I.Over an eight-year period, harvesting methods based on simple mechanical aids (blade and shear) were evaluated against hand harvesting on mature morphologically contrasting tea clones in Southern Tanzania. The effects of shear step height (5-32 mm) and the harvest interval (1.8-4.2 phyllochrons) were also examined. Except in the year following pruning, large annual yields (5.7- 7.9 t dry tea ha[minus sign]1) were obtained by hand harvesting at intervals of two phyllochrons. For clones K35 (large shoots) and T207 (small shoots), the mean harvested shoot weights were equivalent to three unfurled leaves and a terminal bud. The proportions of broken shoots (40-48 %) and coarse material (4- 6 %) were both relatively high. Using a blade resulted in similar yields to hand harvesting from K35 but larger yields from T207 (+13 %). The yield increase from clone T207 was associated with the harvest of more shoots and heavier shoots, smaller increases in canopy height, and a higher proportion (7-9 %) of coarse material compared to hand harvesting. On bushes, which had been harvested by hand for two years following pruning, using flat shears (no step) supported on the tea canopy resulted, over a three year period, in yields 8-14 % less than those obtained by hand harvesting and, for clone K35, a reduction in the leaf area index to below 5. The development of a larger leaf area index is made possible by adding a step to the shear. However, since annual yields were reduced by 40-50 kg ha[minus sign]1 per mm increase in step height, the step should be the minimum necessary to maintain long-term bush productivity. As mean shoot weights following shear harvesting were about 13 % below those obtained by hand harvesting, there is scope, when using shears, to extend the harvest interval from 2 to 2.5 phyllochrons.Item Open Access The management of tea research(Cranfield University, 1996-02) Huq, Mainul; Morris, Joe; Carr, M. K. V.Sponsors and clients of agricultural R&D are showing increasing concern about research costs and benefits. R&D organisations need to assess the impact of research to justify spending, obtain continuous technical and financial support from donors, and research sponsors. Further, impact assessment for R&D organisations are essential to assess their management systems in order to optimise the benefits from scarce research resources. At present criteria to assess the performance, objective verifiable indicators and means of verification are not available. No systematic method is in practice to assess the research management performance. Therefore, a study was under taken to develop tea R&D management criteria and incorporated these in a methodology to assess performance of research management in the tea sector. A case study approach was adopted. Six case studies were conducted on Tea Research Institutes of Asia and Africa. Case studies were grouped into two phases. Phase One was exploratory in nature and developed the conceptual framework for the research. This enabled the identification of research management criteria, objective verifiable indicators and means of verification. These can be used to improve in R&D management decision making. In addition, a scoring model was developed to assess the performance of research management in tea. Phase Two applied the developed conceptual model to four tea R&D organisations and analysed their performance. This clearly showed that the identified criteria and developed conceptual model can be used to analyses the performance of tea R&D management. Results indicated that there is lack of a structured approach to organising and conducting R&D activities. Research is carried out without any systematic approach for research prioritisation. Appraisal and resource allocation are inadequately addressed. Management information systems for rational, quick and effective decision making for the most part are weak and unorganised. Data on resource utilisation and benefits derived by individual research projects are rarely recorded and maintained properly. There is a lack of general awareness especially regarding importance of studying the rate of uptake of technology. A good correlation, however, was observed between organisations adopting best practices and suggested guidelines and the performance of tea R&D organisations in terms of perceived benefit to the client industry. The most effective R&D was associated with committee culture, problem identification, monitoring, evaluation, publication, technology dissemination and feedback. The developed model was applied in specific context of Bangladesh Tea Research Institute. Specific suggestions are made on how to improve the linkages with the industry, better ways of problem identification, evaluation and technology dissemination, and there by increased contribution to the productivity of the tea sector. A research management cycle (RPCM) was developed which proposes to carry out research in an organised way emphasising the participation of the beneficiary. Best practices for all the identified criteria and guidelines for major research management criteria were developed to support in R&D decision making. The study recommends further work to monitor and evaluate the application of the guidelines in practice.Item Open Access An overview of tea research in Tanzania - with special reference to the Southern Highlands.(1992-10-09T00:00:00Z) Carr, M. K. V.; Ndamugoba, D. M.; Burgess, Paul J.; Myinga, G. R.; Ekpere, J. A.; Rees, D. J.; Mbwile, R. P.; Lyino, N. G.The history of tea development in Tanzania from the early part of this century to the present is summarised. Average yields of made tea from well managed estates in the Mufindi district have increased from around 600 kg ha-1 in the late 1950s to 3000 kg ha-1 at the present time: by comparison, yields from smallholder farms have remained much lower, averaging only 400-500 kg ha-1. There have been a large number of technical, economic and other changes over the last 30 to 40 years. The removal of shade trees, the use of herbicides, the application of NPK compound fertilisers, the introduction of irrigation (on some estates) and changes in harvesting policy have all contributed to the increases in yield. Financial and infrastructural problems have contributed to the low yields from many smallholders and others, and have limited the uptake of new technology. The contribution of research is reviewed, from the start of the Tea Research Institute of East Africa in Kenya in 1951, through to the development of the Marikitanda Tea Research Centre in Amani in 1967; the Ngwazi Tea Research Unit in Mufindi (1967 to 1970, and from 1986), and lastly the Kifyulilo Tea Research Station, also in Mufindi in 1986. The yield potential of well fertilized and irrigated clonal tea, grown at an altitude of 1800 m, is around 6000 kg ha-1. This potential is reduced by drought, lack of fertilizer, bush vacancies and inefficient harvesting practices. The corresponding potential yields at high (2200 m) and low (1200 m) altitude sites range from 3000-3500 kg ha-1 up to 9000-10000 kg ha-1 and are largely a function of temperature. The opportunities for increasing yields of existing tea, smallholder and estate, are enormous. Tea production in the Southern Highlands of Tanzania is about to expand rapidly. Good, appropriate research is needed to sustain this development over the long term, and suggestions on how best this is done in order to assist the large scale producers as well as the smallholders, are discussed.Item Open Access Responses of tea clones to drought in Southern Tanzania(1992-02) Burgess, Paul John; Carr, M. K. V.A line-source experiment, planted in August 1988, was used to quantify the yield responses of six tea (Camellia sinensis) clones to drought in Southern Tanzania. The selected clones (1, 6/8, SFS150, S15/10, 207 and K35) are scientifically and/or commercially important in eastern Africa. Drought treatments were imposed during the latter part of 1989 and 1990. Soil water deficits were estimated using a water balance model, validated using a neutron probe. The maximum yield of made tea, from June 1990 to May 1991, was 3760 kg ha⁻¹ for clone S15/10, compared to 2210-2640 kg ha⁻¹ for the other clones. Drought resistances, assessed from the relative yield reduction below the maximum, were greatest for clones 1 and SFS150. The clonal attributes determining these responses were examined in terms of dry matter production and partitioning,components of yield, and plant water status, and were used to determine selection criteria for high yielding and/or drought resistant clones. The high yield of clone S15/10 resulted from greater partitioning of dry matter to leaf and harvested shoots (51%) than the other five clones (34-39%). The conversion efficiency for four of the fully irrigated clones was 0.33-0.55 g MJ-⁻¹ intercepted total solar radiation. Drought resistance was related with leaf measurements of photosynthetic rate per unit stomatal conductance (A/g). In a comparison of droughted plants, resistance was related to reduced incidence of Phomopsis theae, reduced leaf abscision and high xylem water potentials. Measurements of stomatalconductance highlighted calibration problems with transient and steady state porometers. Clone SFS150 had the lowest base temperature for shoot extension (8.9°C) and therefore a more even seasonal distribution of yield than the other clones. Base temperatures for shoot development were 1.7-3.5°C lower than those for extension. The dry matter content of harvested shoots typically ranged from 24.2% for clone 1 to 20.7% for clone SFS150. Partitioning of dry matter to leaves and green stem for high yield, a high A/g ratio for drought resistance, and low base temperatures for improved yield distribution are proposed as selection criteria.Item Open Access Responses of Young Tea (Camellia Sinensis) Clones to Drought and Temperature II: Dry Matter Production and Partitioning(Cambridge University Press, 1996-01-01T00:00:00Z) Burgess, Paul J.; Carr, M. K. V.The physiological basis for differences in yields from well-watered and droughted plants of four contrasting clones of tea were studied in terms of light interception, dry matter production and partitioning at a high altitude site in Southern Tanzania where there are marked seasonal variations in rainfall and temperature. The plant dry weights, including roots, were measured eight months after field planting and subsequently at intervals of three to four months, corresponding to the different seasons, during the following two years. Fully irrigated plants of one clone (S15/10) were also harvested after four years in the field. Clones differed in the rates of canopy spread and hence in their capacity to intercept solar radiation. The ‘radiation use efficiency’ (the net total dry matter production per unit of intercepted short-wave solar radiation) was similar for the four well-watered clones and ranged from 0.40 to 0.66 g MJ -1 , which corresponds closely to values reported for other woody tropical plants. A 16-week drought treatment imposed two years after planting reduced the mean light interception of the four clones by about 25% and the mean radiation use efficiency by 78% to 0.09 g MJ -1 . Clone S15/10, a cultivar from Kenya which produces large yields, partitioned a greater proportion of dry matter to leaves and harvested shoots than the other clones, and correspondingly less to large structural roots. This resulted in a maximum harvest index of 24%, substantially greater than other values reported in the literature. There were seasonal differences in partitioning with more dry matter being diverted to roots and less to shoots during the cool season. Although the drought treatments had no significant effect on root growth, the amount of dry matter partitioned to leaves, stems and harvested shoots declined by 80-95%. The roots of all four clones extended in depth at similar rates (about 2 mm d -1 ), those of Clone S15/10 reaching 2.8 m after four years. The results are discussed in terms of appropriate field cultural practices and possible selection criteria for high yielding cloItem Open Access Responses of Young Tea (Camellia Sinensis) Clones to Drought and Temperature. I. Yield and Yield Distribution(Cambridge University Press, 1996-07-01T00:00:00Z) Burgess, Paul J.; Carr, M. K. V.The yield responses to drought and temperature of six contrasting tea clones were studied in a line-source irrigation experiment in Southern Tanzania. The selected clones, all commercially and/or scientifically important in eastern Africa, embrace a range of morphological and physiological types. The bushes were planted in August 1988 and differential drought treatments were imposed for 16 and 13 weeks towards the end of the dry seasons in 1990 and 1991 respectively. The resulting soil water deficits were successfully simulated using a water balance model. Under well-watered conditions Clone S15/10 (from Kenya) gave the highest yield of dry tea reaching 5600 kg ha-1 in the fourth year after planting (1991/92) compared to 3640-4420 kg ha-1 for the other five clones. During the cool season Clone SFS150 (from Malawi) yielded more than Clones 1, 207, 6/8 and K35. Although annual yields decreased curvi-linearly as the maximum soil water deficit increased, single values for the drought sensitivity of each clone could be derived by using stress time as an index of drought. On this basis Clones S15/10 and 207 were identified as being the most sensitive to drought; Clones SFS150 and 1 were drought resistant. The reasons for these differences in yield responses and the importance of determining drought sensitivity over an appropriate time period are discussed.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