There is a need to shorten the selection process for sugarcane (Saccharum hybrids) in Mauritius in order to improve the efficiency of the varietal improvement programme. On average six to seven ratoon crops are grown in Mauritius and selection for ratooning ability is of major importance. The current selection cycle lasts around 15 years and ratooning ability is tested on five occasions. Data (estimates of sucrose content, cane and sugar yields) from the Mauritius Sugar Industry Research Institute's selection trials planted in 1986–90, representing 85 trials (9680 genotypes) in Stage 3 (one-line stage) and 141 trials (2620 genotypes) in Stage 4 (two-line stage) were analysed. It was hypothesized that 1st ratoon (1R) data in Stage 3 and 2nd ratoon (2R) in Stage 4 were effectively redundant and that the cycle could be shortened by two years without loss of precision. Repeatability estimates, between plant cane (P) and the mean of P and 1R (P + 1R) in Stage 3, and between (P + 1R) and the mean of plant cane, 1st and 2nd ratoon (P + 1R + 2R) in Stage 4, were found to be positive and highly significant for all characters indicating that the extra ratoon data were unnecessary.

Present and proposed selection scenarios were studied further using differential-selection methodology. The coincidence indices (CI) obtained with the two scenarios were extremely high (63–82% in Stage 3 and 91–96% in Stage 4) again indicating that the additional ratoon data were not cost effective. Realized gains from selection in Stage 4 based on (P + 1R + 2R) as opposed to (P + 1R) were shown to be small or even negative. The results concur extremely well with published data from Australia and the USA. It was therefore recommended that the cycle be reduced by two years and that the resources be more usefully allocated to test genotypes over more sites and more replicates.

The developmental and scientific impacts of research carried out intermittently over a thirty year period on the tea crop (Camellia sinensis) in southern Tanzania are reported. It is an attempt to demonstrate to questioning donors that research can contribute, in many ways, to the alleviation of poverty in developing countries. During Phase I (1966–1972) the work was funded in large part by the UK Department for International Development (DFID), as it is now known, with the support of the tea industry in East Africa. During Phase II (1985–1991) a regional study in eastern Africa was largely funded by DFID with local field experimentation in Tanzania paid for by tea growers. In Phase III (1992–1997) the work was funded almost entirely by a consortium of commercial producers.

Throughout this period, despite political and economic uncertainties in Tanzania, the close contact with industry meant that the results of the research were exploited to commercial advantage whenever circumstances allowed. These interventions enabled productivity on a unit area basis to rise over time and companies to remain profitable. More recently major investments in new projects have taken place in southern Tanzania, again supported by the results of the research. All of this has led to the creation of new jobs and to continuity of employment in rural areas that have few other sources of paid work. The financial return on the research investment, although very difficult to quantify with precision, has been immense.

The science has not been neglected either. Over the same period more than 30 refereed papers have been published in the international scientific literature. These cover such topics as the responses of tea to climate and weather, including drought and irrigation. Scientists have also been trained in modern research techniques. In addition there have been ancillary benefits including the introduction of technical and management training programmes for staff in the tea industry. Frustration has been caused by the lack of continuity in funding due to changes in policies, and in the priority research topics, even within one donor organization, which have often put the work at risk. Ingenuity, patience and commitment have all been pre-requisites to ensure that the research continued.

The partnership with industry has been beneficial to all the stakeholders. It has led directly to the creation of the new, commercially managed Tea Research Institute of Tanzania serving both small- and large-scale producers throughout the country. Researchers, with the support of the tea industry and in partnership with the Tanzanian Government and DFID, can continue to play a significant role in the fight against poverty. Research for development is a continuing process: it can be successful.

Input-responsive, high yielding rice varieties and associated technologies responsible for the doubling of yields on irrigated lands in Asia have not suited the area of more than 40 million hectares of Asian rainfed lowland rice. These environments are home to some of the poorest rural populations in South and Southeast Asia, and the rice crops are subject to drought, prolonged submergence from uncontrolled flooding and nutrient deficiencies. Farmers grow unimproved varieties and these, combined with abiotic stresses and low inputs, result in grain yields often less than 2 t ha−1. The International Rice Research Institute (IRRI) and National Agricultural Research Systems (NARS) have recently joined to form the Rainfed Lowland Rice Research Consortium in order to identify, prioritize and execute strategic research that addresses critical yield and productivity constraints. Principal intervention points for achieving sustainable yield increases are in developing drought- and submergence-tolerant germplasm with good yield potential, improved nutrient management under stress conditions, water use-efficient crop establishment practices, and understanding farmers' approaches to risk management. Multidisciplinary teams of IRRI and NARS scientists execute research at sites selected across the region to represent the key sets of constraints.

Farmers in the mid-hills of Nepal have a mix of rainfed land on which millet is grown in relay after maize (maize/millet), and irrigated land on which wheat is grown sequentially after rice (wheat–rice). Double cropping is the norm but the diminishing quantities of organic materials, coupled with the trend towards increased use of inorganic fertilizers, have raised questions about the long-term productivity and sustainability of the cropping systems. The aim of this work was to examine the long-term effects (eight years) on grain yield of additions of manure and fertilizer either singly or in combination. Maize/millet and wheat–rice rotations were established on a Dystochrept at Pakhribas Agricultural Centre at about 1450 m altitude. Manure and fertilizer applications were applied to the maize (eight combinations in May) and the wheat (different rates in seven combinations in November) every year with the succeeding crops (millet and rice) utilizing residual nutrients. Yields of maize, millet and rice were greater when manure rather than fertilizer was applied but yields of wheat were less. The combined application of manure and fertilizer significantly increased yields of maize and wheat compared with applications of either manure or fertilizer alone. However, for the subsequent crops (millet and rice) there was either a small residual benefit of the combined application when compared with fertilizer alone, or no benefit when compared with manure alone. Overall, the combined application increased total grain yields by about 35% in the maize/millet rotation and by 16% in the wheat–rice rotation. There was no trend in yields in response to treatment with time.

Land and crop management practices were studied to determine yield stability and feasible measures to improve productivity of dry-seeded rice. Variability of yields among farms that had grown dry-seeded rice on the entire farm every season during the period 1991–95 was lower than among farms that had consistently grown transplanted rice during the same period. Weed control is a major challenge for dry-seeded rice and almost all farmers used herbicides to control weeds. Farmers who grew a non-rice crop before the rice season had better weed control than those who did not. Ploughing intensity and the type of implement used for land preparation were not significant factors for weed control. Field bund management was one determinant of productivity differences among farmers. The use of cross-bunds or periphery- and cross-bunds improved the efficiency of rainwater conservation and input use, and increased yields. Fields with higher levelling precision had lower water stress and produced better yields. On average, a farmer lost 0.93 t ha−1 yield due to land-levelling deficiency. The division of large and medium farms into a number of smaller plots improved levelling precision and water control, resulting in higher yields.

Poor crop establishment was identified as a major constraint on rainfed crop production by farmers in the tribal villages of Rajasthan, Gujarat and Madhya Pradesh served by the Krishak Bharati Cooperative (KRIBHCO) Indo-British Rainfed Farming Project (KRIBP). On-farm seed priming with water was chosen as a low cost, low risk intervention appropriate to the farmers' needs. In vitro screening of the effects of priming on the germination of seeds of local and improved varieties of maize, upland rice and chickpea provided ‘safe limits’ – the maximum length of time for which farmers should prime seeds and which, if exceeded, could lead to seed or seedling damage. Recommended safe limits were 24 h for maize and rice and 10 h for chickpea, with only minor varietal differences. These recommendations were then tested in on-station trials in Dahod, Gujarat. Farmer-managed trials were conducted for chickpea in three villages in the rabi (post-monsoon) season in 1995–96; for maize and upland rice in eight villages in the kharif (monsoon) season in 1996; and for maize and chickpea in 15 villages in the 1996--97 rabi season. Farmers modified these recommendations to ‘overnight’ for all three crops. Evaluation of the technology by farmers involved focus group discussions, matrix ranking exercises and two workshops.

Direct benefits in all three crops included faster emergence, better stands and a lower incidence of re-sowing, more vigorous plants, better drought tolerance, earlier flowering, earlier harvest and higher grain yield. Indirect benefits reported were earlier sowing of rabi crops because of the shorter duration of the preceding kharif crop, earlier harvesting of rabi crops that allowed earlier migration from the area, with better chance of obtaining off-season work, and increased willingness to use fertilizers because of reduced risk of crop failure. In matrix ranking exercises in four villages in the kharif 1996, 95% of farmers indicated that, even after only one exposure to the technology, they would prime seed in the following season. Similar exercises in four villages in rabi 1996–97 revealed that 100% of collaborating farmers intended to continue seed priming. From 21 villages, 246 farmers attended two workshops to share their experiences of seed priming and resolved to continue with the technology.

Two series of trials were initiated to compare different lengths of crop cycles for sugarcane harvested every 12 months under the local conditions over a six-year period. The first series involved harvesting cane every 24 months and in the second series cane was harvested after 16 or 20 months alternately. All trials included four cane varieties except one in the second series where only three varieties were planted. Cumulative results for both series of trials showed a difference in favour of the 12-month cane crop. In the first series after six years, cane and sugar yields were reduced by 19–48% and 22–60% respectively in the 24-month-old canes compared with 12-month-old crops. The level of reduction varied with cane variety. In the second series, the declines in cane and sugar yields were smaller, 5–44% and 7–49% respectively. Cane lodging, which increased with length of crop cycle, led to greater weed infestation, increased damage by rats and rendered manual harvest more difficult.

Four surface sterilization agents and two hot-water treatments were evaluated with a view to eliminating bacterial contamination in sugarcane (Saccharum hybrids) buds used for in vitro initiation. None of the treatments achieved total elimination of contaminants. Disinfection in either a 2.7% solution of sodium hypochlorite (pH 6) or 1% mercuric chloride were equally good, resulting in 46.8% and 56.3% clean cultures respectively. However, sterilization with 2.7% sodium hypochlorite (pH 6) was most phytotoxic and 100% tissue necrosis and bud death were recorded. The Australian cold-soak hot-water treatment (consisting of a 48-h soak in running water followed by hot-water treatment at 50 °C for 3 h on the following day) reduced contamination from 70% to 25%. With the dual hot-water treatment (setts immersed in water at 52 °C for 20 min and then at 50 °C for 3 h on the following day) a decrease to 45% was observed. Bacterial contaminants were identified by fatty acid profiling and were found to belong mainly either to the Enterobacteriaceae family or the genus Bacillus.

The extent by which fertilizer nitrogen (N) may be reduced by the use of drip-fertigation in sugarcane was determined using 15N-labelled fertilizer in a field experiment in Mauritius. The data showed that, under the soil and climatic conditions that prevailed at the study site, fertilizer N could be reduced by 30%. Indeed, with 80 kg N ha−1 a−1 by drip-fertigation, total or fertilizer N recovered, growth pattern (as reflected by tiller density and leaf area development) and sugarcane yields were not inferior to those obtained with the standard practice of burying 120 kg N ha−1 a−1 along the cane rows. Applying more N than needed by the sugarcane in anticipation of a higher yield with drip irrigation would be wasteful of fertilizer N resources.

Floodwater was characterized through field surveys over three years in rainfed lowland and deepwater rice areas of Eastern India. Measurements focused on dissolved O2 and CO2, pH and irradiance during flash floods in rice fields. Over locations and time, dissolved O2 concentrations ranged from zero to 0.28 mol m−3 (0–1.1 times air-saturated water at 30 °C) while dissolved CO2 ranged from 0.28 to 1.96 mol m−3 (31–217 times air-saturated water). Floodwater pH varied from 6.6 to 9.7. Irradiance decreased with depth in the water profile to an extent depending on turbidity. Turbidity varied greatly over locations and time. The significance of these measurements in assessing rice submergence tolerance is discussed.

One of the major research activities of the Mauritius Sugar Industry Research Institute (MSIRI) is the breeding and selection of sugarcane varieties adapted to the different agro-climatic environments. Most of the on-farm experimentation is carried out in the fields of miller-planters (planters who own the sugar mills), where resources in terms of land, labour and other inputs are usually easily available. The non-miller-planters are operating in environments which are not always similar to those of the miller-planters. There is a need for on-farm experimentation under these conditions in order to improve productivity. Variety trials, observation plots and industrial trials to compare commercial varieties with promising and newly released ones have been established on-farm in order to improve the adoption rate of new varieties. The paper elaborates on the objectives of this major extension activity during the last decade. A major inference is that the planters obtain first-hand information on promising varieties prior to their release for commercial plantation, hence influencing their decision for adoption or rejection. Moreover, additional information on the performance and behaviour of these promising varieties is made available to research staff.

Groundnut (Arachis hypogaea) cannot be grown economically on unamended acid soils because of poor pod-filling resulting from an inadequate supply of calcium. Gypsum improves pod-filling but in Mauritius it is now too expensive.

Field trials were conducted at two locations in 1994–95 and at four locations in 1995–96 to find out if cement could be used instead of gypsum. In three trials where the soil pH ranged from 5.4 to 6.3 and the soil calcium level from 2.4 to 6.9 cmol kg−1, there were few empty pods and no response to gypsum or cement was observed. At the remaining three sites, the soil pH was 5.5, 4.9 and 4.3 and the soil calcium levels were 1.8, 0.39 and 0.92 cmol kg−1, respectively. In the untreated plots at the three sites 17.4%, 27.5% and 50.6% of the pods were empty. Cement at rates of 525 and 700 kg ha−1 and gypsum at 1000 kg ha−1 applied to the foliage at flowering reduced the number of empty pods to less than 10% and significantly increased seed yield, shelling percentage and commercial-grade kernels. However, cement was not as effective when placed in the furrows at planting. At current prices, the use of cement was cost effective whereas that of gypsum was not. Cement may therefore be proposed as a replacement for gypsum for the improvement of pod-filling in groundnut.

This study demonstrates a relationship between earliness of ripening and stalk elongation which could be useful in a sugarcane selection programme. Sixty-four sugarcane genotypes with contrasting ripening behaviour were grown in a quadruple-lattice design and ordinary logistic curves were shown to give the best fit between stalk height and time. Genotypes with early high sucrose contents gave logistic curves with earlier inflection points and steeper slopes at the point of inflection. The inflection point was shown to be a reliable indicator of time of ripening and it was suggested that stalk height per se could be considered as a selection criterion for earliness of ripening in sugarcane.

Microclimate and soil fertility were measured under and away from the canopies of small and large scattered trees of néré (Parkia biglobosa) and karité (Vitellaria paradoxa) to explain their influence on pearl millet (Pennisetum glaucum). During the rainy season, photosynthetically active radiation under both tree canopies was reduced to 24% of incident radiation but, surprisingly, millet biomass was not significantly different from that in the open. Millet seedlings under the tree canopies experienced only 1–9 h week−1 of supra-optimal temperatures (>40 °C) compared with 27 h week−1 in the open. Reduction in windspeed and soil evaporation was observed under the trees but was unlikely to have a significant influence on millet growth since water was not limiting (rainfall = 920 mm).

Exchangeable potassium, percentage carbon and pH were significantly higher and δ13C lower in soil under trees than in the open. Nitrogen levels were not significantly higher than in the open except for large néré trees. Carbon derived from C3 plants, calculated from δ13C, was significantly higher in soils under trees than in the open and is recommended as a good indicator of the influence of trees on soils. These results show that the combined beneficial effects of temperature modifications and soil fertility could exceed the negative effect of tree shade.

Crop residue management is posing a serious problem in the rice (Oryza sativa)–wheat (Triticum aestivum) cropping system, which is widely practised in the Indian Subcontinent and China, and covers about 22.5 × 106 ha. The problem is serious because there is very little turn-around time between rice harvest and wheat sowing. Three practices, namely, residue removal, residue burning and residue incorporation were compared in two field experiments, one with the rice residues and the other with the wheat residues. Results obtained showed that both rice and wheat residues can be safely incorporated without any detrimental effects on the crops of rice or wheat grown immediately after incorporation. Incorporation of crop residue also improved soil fertility status as judged by organic carbon and available phosphorus and potassium contents. Residue incorporation should be preferred over residue burning, which results in the loss of valuable plant nutrients and is both an environmental and a health hazard.

A study was conducted from October 1994 to March 1996 to assess groundwater dynamics and quality in relation to landuse and farm input of nitrogen fertilizer in a highly diversified and intensive agricultural area at Magnuang, Batac, Ilocos Norte. Monthly groundwater depths, nitrate-nitrogen (NO3-N), chloride (Cl−), bicarbonate (HCO3−), electrical conductivity (EC) and pH were determined in 19 agricultural and domestic wells. In the dry season, sweet pepper (Capsicum annuum) had a higher irrigation requirement and caused more groundwater level decline than other crops. EC (700–3000 μmho cm−1) and HCO3− (90–500 ppm) in all wells exceeded the FAO threshold quality for irrigation but were not related to farm management practices. Eight wells showed near or above the World Health Organization NO3-N limit (10 ppm) for drinking water. High nitrogen fertilizer input increased the mean NO3-N (r2 = 0.45, p < 0.002). The percentage of the wells' service area under rice cultivation in the wet season accounted for 84% (p < 0.001) of the variation in NO3-N among the wells. The mean NO3-N declined as the percentage of service area under rice increased. This was related to the denitrification process in the flooded fields and the lower levels of nitrogen fertilizer for rice compared with other crops.

In two cultivar × density trials for oil palms (Elaeis guineensis) planted in Indonesia, single leaf area, number of green leaves per tree, leaf opening rate per year and rachis length of leaves were followed over fourteen years. The data were analysed to determine the time course of canopy leaf area and to predict the moment of canopy closure.

Growth functions were fitted to the observed data. Estimates of leaf area index (L) were based on single leaf area, number of green leaves, leaf opening and planting density. The time course of L was modelled on the basis of the fitted functions to the components. The moment of canopy closure was calculated from the planting density and the functions fitted for rachis length.

The modelled time course of L was considerably different from the function fitted to the single leaf area data. The expansion of L was not as rapid as expected from the area growth of single leaves and, after maximum L was reached, a steady decline was observed. The continuously declining number of green leaves was the main cause of these two observations.

The time course of L differed considerably between the two experiments. Not only were there large differences in the number of green leaves maintained per tree in the experiments but also the final area of single leaves differed between both experiments. The first factor was a result of the management of the experiments, whereas the second factor was most likely influenced by a difference in soil-related factors at the two locations.

Leaf areas and numbers of leaves per tree were different for each cultivar, as was L. This was also the parameter most sensitive to planting density. Individual leaf area and leaf number per tree were not affected by planting density, but rachis length was affected by the planting density treatment. The moment of canopy closure was similar in both experiments. Planting density was the main factor that determined the onset of canopy closure.

The possibility of growing grasses of higher quality than tall fescue (Festuca arundinacea) in a continental climate with cold winters, hot summers and low precipitation was investigated with and without irrigation at Taigu, Shanxi, China. Tall fescue was compared with perennial ryegrass (Lolium perenne), meadow fescue (Festuca pratensis) and a perennial ryegrass × meadow fescue hybrid cultivar in field swards, managed by cutting, during the year of sowing and in the three subsequent years. Tall fescue persisted satisfactorily throughout the experiment, even without irrigation. With irrigation, the other three grasses persisted satisfactorily to the end of the second harvest year and fairly satisfactorily to the end of the third harvest year. Without irrigation, the other three grasses had incomplete ground cover in the second harvest year and did not recover from the third winter.

The main objective of this study was to determine the best soil amendment and tillage practices for sustainable millet yield and grain and stover quality. The treatments included tillage practices (immediate-, late- and no-till) and soil amendments (sheep manure plus urine, manure, millet stover (stalks, leaf blades and leaf sheaths) and millet stover ash) in factorial combinations with fertilizer nitrogen levels of 0, 15 and 30 kg ha−1 plus controls. Results showed that (i) higher yields were obtained in tilled plots than in no-till plots; (ii) tillage timing may not be a significant yield determining factor; (iii) the application of animal urine resulted in significantly higher yield and greater nitrogen, phosphorus and potassium uptake than the application either of manure alone or of millet stover. Urine application (ruminant urine contains virtually no phosphorus), which elevates soil pH especially during the first week after application, may have resulted in the dissolution of phosphorus from the aluminium–iron complexes of kaolinitic clays. This is corroborated by the significantly higher phosphorus uptake from the manure-plus-urine plots than from plots amended with either manure alone or millet stover. Long-term implications of ‘mining’ soil phosphorus with repeated applications of animal urine in these fragile ecosystems remains unclear.

Low concentrations of phosphorous were added to the floodwater of submerged rice in an attempt to regulate algal growth, so as to increase floodwater O2 concentration and plant survival during submergence for up to 12 days. Increasing the phosphorus concentration of the floodwater by 1 ppm increased algal growth by at least 4-fold based on chlorophyll concentrations, and increased floodwater O2 concentrations to over twice air saturation. However, additions of phosphorus reduced rice plant survival during submergence by up to 35%. The adverse effects of a high phosphorus concentration in the floodwater were mainly attributed to competition between the algae and the submerged rice for CO2 and, perhaps, light. The importance of photosynthesis during the submergence of rice was supported by the results of experiments in which floodwater CO2 concentration was manipulated by altering pH. The survival of an intolerant rice cultivar during submergence increased from 0 to 17 and 62% at pH 8, 7 and 5 respectively, while floodwater CO2 concentrations at these pHs would have increased from 0.02 to 0.3 and 1.0 mol m−3 respectively. The results were used to question the importance of floodwater O2 concentrations above anoxia for submergence tolerance of rice.