Cranfield University at Silsoe (1975-2008)
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Browsing Cranfield University at Silsoe (1975-2008) by Type "Conference paper"
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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 Subsoil Compaction: A hidden form of Soil Sealing in Europe(Joint Research Centre, 2001-06) Jones, Robert J. A.; Montanarella, LucaThere are two definitions of ‘soil sealing’: (I) ‘covering (sealing) the soil surface by impervious materials, e.g. concrete, metal, glass, tarmac and plastic’; and (II) ‘changing the nature of the soil such that it behaves as an impermeable medium, e.g. by compaction’. The main causes of soil sealing according to the first definition (I) are building development (e.g. industrial and residential premises) and transport (e.g. roads). Changing the nature of the soil such that it behaves as an impermeable medium (definition II) is an extension to include the potential effects of the passage of machinery (mostly agricultural) and the effects of heavy rainfall. Intensification of agriculture is now recognised as often having a detrimental effect on soils, not least the widespread development of compaction. The worst effects of compaction at the surface can be rectified relatively easily by cultivation but once subsoil compaction occurs, it can be extremely difficult and expensive to alleviate. It is now clear that the detrimental effects of subsoil compaction go far beyond agricultural concerns of a decrease in yield and increase in management costs. Environmental impacts include increased erosion risk, accelerated runoff and increased pollution. A preliminary attempt to assess the susceptibility of subsoils in Europe to compaction is presented here in the context of soil sealing. The resulting distribution is only the first stage in assessing the vulnerability of subsoils in Europe to compaction. The biggest problem with soil sealing as an environmental indicator is the difficulty of establishing the true extent at the regional and larger scales. However, subsoil compaction should not be ignored because it probably affects a larger area in Europe than urbanisation (land consumption) and in this respect it must be regarded as an important process of soil sealing.