A comparison of the responses of mature and young clonal tea to drought.

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

Modelling the Impact of Credit on Intensification in Mixed Crop-Livestock Systems: A Case Study from Ethiopia

Access to credit is one strategy for promoting the adoption of yield-enhancing technologies. However, advancing credit to smallholder farmers for encouraging technology adoption is a complex policy issue. The objective of this paper is to identify appropriate and sustainable credit repayment policies to encourage intensification in the Ethiopian Highlands. Using a household model, we analyze the impact of advancing in-kind credit in the form of fertilizer and seed to smallholder farmers in the Ethiopian highlands and alternative credit repayment strategies. The results indicate that in kind input credit of fertilizer and seed provided to farmers in the highland of Ethiopia increased the value of household crop output moderately and hence allowed the household to increase its consumption. This scheme requires borrowers to sell their crop immediately at harvest to repay their credit. An alternative repayment scheme of extending the repayment period to allow households to capture seasonal price variation is proposed. The amount repaid is also tied to yields of wheat.Agricultural Finance,

Paramagnetic magnetization signals and curious metastable behaviour in field-cooled magnetization of a single crystal of superconductor 2H-NbSe2

We present here some newer characteristics pertaining to paramagnetic Meissner effect like response in a single crystal of the low Tc superconducting compound 2H-NbSe2 via a detailed study of effects of perturbation on the field-cooled magnetization response. In the temperature range, where an anomalous paramagnetic magnetization occurs, the field-cooled magnetization response is found to be highly metastable: it displays a curious tendency to switch randomly from a given paramagnetic value to a diamagnetic or to a different paramagnetic value, when the system is perturbed by an impulse of an externally applied ac field. The new facets revealed in a single crystal of 2H-NbSe2 surprisingly bear a marked resemblance with the characteristics of magnetization behaviour anticipated for the giant vortex states with multiple flux quanta predicted to occur in mesoscopic-sized superconducting specimen and possible transitions amongst such states.Comment: 12 pages, 9 figures, submitted to Journal of Physics: Condensed Matte

An overview of tea research in Tanzania - with special reference to the Southern Highlands.

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

Ferroelectric Phase Transitions in Ultra-thin Films of BaTiO3

We present molecular dynamics simulations of a realistic model of an ultrathin film of BaTiO$_3$ sandwiched between short-circuited electrodes to determine and understand effects of film thickness, epitaxial strain and the nature of electrodes on its ferroelectric phase transitions as a function of temperature. We determine a full epitaxial strain-temperature phase diagram in the presence of perfect electrodes. Even with the vanishing depolarization field, we find that ferroelectric phase transitions to states with in-plane and out-of-plane components of polarization exhibit dependence on thickness; it arises from the interactions of local dipoles with their electrostatic images in the presence of electrodes. Secondly, in the presence of relatively bad metal electrodes which only partly compensate the surface charges and depolarization field, a qualitatively different phase with stripe-like domains is stabilized at low temperature

Studies on riverine flora of Pamba river basin, Kerala

Riparian forests are ecotonal assemblage of aquatic and terrestrial habitats. The composition of riparian forests of Pamba River is an amalgamation of riverine, evergreen, deciduous and wetland flora. The floristic investigation of the riparian forests of Pamba river basin revealed taxonomically 433 species which include 410 angiosperms, 3 gymnosperms and 20 pteridophytes. The dominant families based on the number of species are Poaceae, Euphorbiaceae, Rubiaceae, Cyperaceae and Fabaceae. The flora consists of a diverse blend of 99 evergreen, 36 deciduous, 50 wetland, 15 shola-grassland, 46 cultivated and 44 riverine components. The river basin holds 17.5 % endemism and 17 RET species. The riparian tree species identified in the present investigation are _Barringtonia racemosa_, _Calophyllum inophyllum_, _Crateva magna_, _Dillenia indica_, _Elaeocarpus tuberculatus_, _Garcinia gummi-gutta_, _Humboldtia vahliana_, _Largestromea speciosa_, _Neolamarkia kadamba_, _Ochrenauclea missionis_, _Syzigium salicifolium_, _Talipatri tiliaceaum_ and _Trewia nudiflora_. It is assumed that these potential tree species might have a crucial role to maintain the ecological integrity of the riparian zones and floodplain for the restoration of Pamba river