Lentil is generally grown as a rainfed crop in areas of West Asia and North Africa where rainfall is highly variable. This study aimed to measure genetic responses to variation in moisture supply in the yield of seed and straw, evapotranspiration and water use efficiency, to guide the lentil breeding programme. The response of 25 diverse lentil lines to a soil water gradient was studied in 1987/88 and 1988/89 at Breda, northern Syria, using a line-source sprinkler system. The coefficient of determination between rainfed and irrigated seed yield in the dry 1988/89 season was r2 = 0.26, and the genotypes that were well adapted to dry conditions were different from those well adapted to wet conditions. However, there were also widely adapted genotypes that yielded well under both wet and dry conditions. The selection of such genotypes might be appropriate for the region receiving 300–400 mm annual rainfall, in contrast with the approach to selection suggested for drier areas (less than 300 mm annual rainfall) in a companion article. Soil moisture extraction from the time of maximum profile recharge to maturity in 1987/88 and cumulative crop evapotranspiration in the 1987/88 rainfed crop did not differ among lentil lines. In the irrigated treatment, however, evapotranspiration in the medium to late maturing lines exceeded that in the early maturing lines towards maturity.

Manganese (Mn) is one important microelement for plants and the human beings. This study was conducted to evaluate the potential of Mn nutrition in improving the productivity and grain biofortification of wheat. For optimization of Mn seed treatments, seeds were primed with 0.1 and 0.01 M Mn solution, or were coated with 250 and 500 mg Mn kg−1 seed. The optimized treatments were used in the second experiment replicated over time and space. In the first experiment conducted at Faisalabad during 2012–2013, maximum grain yield was recorded with Mn seed priming (0.1 M Mn solution), while maximum grain Mn concentration was recorded with foliar application of 0.75 M Mn solution and seed coating with 250 mg Mn kg−1 seed. In the second experiment, conducted at Faisalabad and Sheikhupura during 2013–2014, and at Faisalabad during 2014–2015, maximum grain yield and grain Mn concentration were recorded from seed priming with 0.1 M Mn solution. Regardless of method, Mn application improved the productivity and grain biofortification of wheat. Overall order of improvement in grain yield was seed priming (3.87 Mg ha−1) > foliar application (3.74 Mg ha−1) > seed coating (3.57 Mg ha−1). Regarding grain Mn concentration, the best treatment was seed priming (41.40 µg g−1) followed by seed coating (39.87 µg g−1) and foliar application (36.94 µg g−1). Maximum net returns and benefit-cost ratio were obtained with Mn seed priming, while maximum marginal rate of return was obtained with Mn seed coating. In conclusion, Mn application through seed treatments was cost effective for improving the productivity and grain biofortification of bread wheat in alkaline calcareous soil.

Agricultural production in southern Africa is constrained by numerous factors, including low soil fertility, frequent droughts and flooding, limited access to fertilizers and the use of unsustainable management techniques that increase soil erosion rates. Conservation agriculture (CA) is based on the principles of minimum soil disturbance, crop residue retention and crop rotations. CA systems have been proposed to alleviate the negative externalities associated with conventional crop management systems. This study was conducted to examine the riskiness of economic returns of CA technologies based on maize grain yield evaluated in 12 target communities in Malawi from 2005–2011. On average, maize grain yields on both CA treatments exceeded the conventional control treatment by 22.1–23.6%, with differences more distinct in low altitude areas with low rainfall and frequent seasonal dry spells. Stochastic dominance analysis suggest that CA technologies would be preferred by risk-averse farmers, with corresponding differences in risk premiums (compared to conventional maize production systems) ranging between US$40 and US$105. However, these rankings are sensitive to the agroecological zones where the experiments were conducted. The risk premiums associated with the CA technologies in low elevation regions are unambiguous. Risk-averse farmers in higher elevations may need substantial incentives to adopt some CA technologies.

Photosynthetic rates were monitored during the warm dry season in tea Clone 6/8 in a line-source irrigation × fertilizer experiment in the Southern Highlands of Tanzania. Irrigation and fertilizer increased photosynthetic rate both by enhancing photosynthetic rate per unit leaf area (A) in healthy leaves and by increasing the proportion of sunlight intercepted by photosynthetically efficient leaves. Irrigation-induced increases in A could be accounted for by increases in stomatal conductance (g) and associated reductions in leaf temperature. Fertilizer at an annual application rate of 225 kg N ha-1 caused increases in A associated with increases in g and improved responses to ambient CO2 concentration and illuminance (photon flux density, PFD). However, a further increase in fertilizer application rate to 375 kg N ha-1 a-1 decreased A in spite of increasing g. Light-saturation of photosynthesis occurred only at the higher fertilizer application rate. In unfertilized tea or tea fertilized at the lower rate, A decreased at a PFD of between 1400 and 2000 μmol m-2 s-l. These results are discussed in terms of the relation between photosynthesis and yield in tea.

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This study examines the role, structure and effectiveness of informal seed systems in the diffusion of new barley varieties. It uses data collected by tracing farmers who received new barley varieties and other farmers who purchased seeds through farmer-to-farmer seed trade over a period of five years. The principal finding was that informal farmer-to-farmer seed dissemination was an important vehicle for the diffusion of new barley varieties, which were grow on 27% of the barley area of monitored farmers, despite a complete lack of extension support. Almost all seed exchanges were undertaken through purchases at market prices, highlighting the importance of markets in informal seed systems. The second main finding was the high concentration of seed sales among a few key seed suppliers, who established reputations as reliable sources of seed and had contacts with research organizations. The importance of market-based local seed transactions implies that farmers specializing in seed sales can invest in local seed enterprises and provide sustainable services at affordable prices. The results of this study indicate great potential for supporting local seed suppliers in order to ensure a sustainable flow of new crop varieties to smallholder farmers in the dry areas. The study also examined farmers' criteria in evaluating and eventually adopting a new variety. These criteria depend on agro-ecological zones with more complex criteria in drier areas with high rainfall variability. These findings will help plant breeding programmes to target dry and marginal areas, where access to new varieties is low, more effectively.

Field measurements with a pressure chamber showed that the water potential of tea shoots was more closely related to the atmospheric saturation deficit than to the amount of water in the soil. Records for shoot growth and weather then revealed that, within a narrow range of mean temperature, the weekly rate of shoot extension was inversely related to mean saturation deficit measured at 1400 h. During periods when saturation deficit did not rise above 20 mbar, the rate of shoot extension varied linearly with mean temperature above a base temperature of 12.5–13.0°C. These correlations suggested that seasonality of shoot growth in tea can be explained largely by the independent effects of temperature and humidity. The effect of mean air temperature on the rate of shoot extension was confirmed in a glasshouse built over an established crop.

Farmers in the Lake Alaotra region of Madagascar are currently evaluating a range of conservation agriculture (CA) cropping systems. Most of the expected agroecological functions of CA (weed control, erosion control and water retention) are related to the degree of soil cover. Under farmers’ conditions, the grain and biomass productivity of these systems is highly variable and the biomass is used for several purposes. In this study, we measured biomass production of cover crops and crops in farmers’ fields. Further, we derived relationships to predict the soil cover that can be generated for a particular quantity of mulch. We used these relationships to explore the variability of soil cover that can be generated in farmers’ fields, and to estimate how much of the biomass can be removed for use as livestock feed, while retaining sufficient soil cover. Three different kinds of cropping systems were investigated in 91 farmers’ fields. The first two cropping sequences were on the hillsides: (i) maize + pulse (Vigna unguiculata or Dolichos lablab) in year 1, followed by upland rice in year 2; (ii) the second crop sequence included several years of Stylosanthes guianensis followed by upland rice; (iii) the third crop sequence was in lowland paddy fields: Vicia villosa or D. lablab, which was followed by rice within the same year and repeated every year. The biomass available prior to rice sowing varied from 3.6 t ha−1 with S. guianensis to 7.3 t ha−1 with V. villosa. The relationship between the mulch quantity (M) and soil cover (C) was measured using digital imaging and was well described by the following equation: C = 1 − exp(−Am × M), where Am is an area-to-mass ratio with R2 > 0.99 in all cases. The calculated average soil cover varied from 56 to 97% for maize + V. unguiculata and V. villosa, respectively. In order to maintain 90% soil cover at rice sowing, the average amount of biomass of V. villosa that could be removed was at least 3 t ha−1 for three quarters of the fields. This quantity was less for other annual or biennial cropping systems. On average the V. villosa aboveground biomass contained 236 kg N ha−1. The study showed that for the conditions of farmers of Malagasy, the production and conservation of biomass is not always sufficient to fulfil all the above-cited agroecological functions of mulch. Inventory of the soil cover capacity for different types of mulch may help farmers to decide how much biomass they can remove from the field.

The incidence of rotting among three varieties of yams (Dioscorea rotunda, D. alata and D. cayenensis), stored in a yam barn at Ibadan for about four months, was between 0·6 and 68·5 per cent. The micro-organisms which caused rotting on experimental re-inoculation into yam tubers were the fungi, Botryodiplodia theobromae, Penicillium sp., Marcophomina phaseoli, Hendersonula toruloidea and a motile gram-negative orange-red pigmented bacterim, probably Serratia sp. This is the first record of the ability of M. phaseoli, and H. toruloidea to cause rotting in yam.

Participatory variety selection (PVS) was carried out in two of the major tef-growing woredas (districts) of Ethiopia, Ada and Akaki, in 2003 and 2004. The objectives were to identify farmers' selection criteria, to increase farmers' awareness and their access to improved tef varieties, to enable farmers to assess the performances of improved tef varieties of their choice and to accelerate seed dissemination of farmers' chosen varieties through farmer-to-farmer exchange mechanisms. Seed colour was the overriding selection criterion. Farmers overwhelmingly selected the very white seed variety DZ-01-196 (Magna) for market purposes, indicating that tef is a cash crop. Farmers also selected brown-seeded tef, but for home consumption. There was no evidence of connection between seed colour and desirable agronomic traits, or nutritional quality (protein content). Factors other than seed-colour were of secondary concern to farmers. When market demands become the dominant selection criteria, PVS should not be an end by itself: rather, it complements the formal breeding system. The results imply that tef performance evaluation trials need to be separated on a colour-group basis, and any new successful variety in the two woredas should be superior to DZ-01-196 not only in grain yield but also in seed-colour quality. A faster, more efficient and reliable pure-seed supply system than the traditional farmer-to-farmer exchange mechanism is required in order for farmers to continue planting improved varieties, which might be better achieved through small-scale commercial producers and/or cooperatives.

The results of research on the water relations and irrigation need of pineapple are collated and summarised in an attempt to link fundamental studies on crop physiology to irrigation practices. Background information on the centres of origin (northern South America) and of production (Brazil, Thailand and the Philippines) of pineapple is followed by reviews of crop development, including roots, plant water relations, crop water requirements and water productivity and irrigation systems. The majority of the recent research published in the international literature on these topics has been conducted in the United States (Hawaii) and Brazil. Pineapple differs from most other commercial crops in that it has a photosynthetic adaptation (crassulacean acid metabolism (CAM)) that facilitates the uptake of carbon dioxide at night, and improves its water-use efficiency under dry conditions. The crop is propagated vegetatively. The succulent leaves collect (and store) water in the leaf axils, where it is absorbed by surrounding tissue or by aerial roots. There is little published information on the effects of water deficits on vegetative growth, flowering or fruiting. Water stress can reduce the number of fruitlets and the fruit weight. After harvest, one or two ratoon crops can follow. Roots originate from just behind the stem-growing point, some remaining above ground (aerial roots), others entering the soil, reaching depths of 0.85–1.5 m. Root growth ceases at flowering. The ratoon crop depends on the original (plant crop) root system, including the axillary roots. Stomata are present on the abaxial leaf surfaces at relatively low densities (70–85 mm−2). They are open throughout the night, and close during the day before reopening in mid-afternoon. The degree to which CAM attributes are expressed depends in part on the location (e.g. tropics or subtropics), and possibly the cultivar, with the total amount of carbon fixed during the night varying from <3% to >80%. There are surprisingly few published reports of field measurements of crop water use and water productivity of pineapple. Two reports show evapotranspiration only occurring during the daytime. There is more uncertainty about the actual water use of pineapple, the value of crop coefficient (Kc) and relative rates of water loss (transpiration) and carbon gain (net photosynthesis), during the daytime and at night, under different water regimes. This is surprising given the amount of fundamental research reported on photosynthesis of CAM plants in general. Although pineapple is mainly a rainfed crop, it is widely irrigated. Drip irrigation is successfully used where the water supply is restricted, the cost of labour is high and cultivation techniques are advanced. Micro-jets can also be used, as can any of the overhead sprinkler systems, provided wind distortion is not a problem. There is a lack of reliable published data quantifying where irrigation of pineapple is likely to be worthwhile, how it is best practised and the benefits that can be obtained. This is remarkable considering the importance of pineapple as an internationally traded commodity.

In the Sahelian zone of Niger, there is a need to develop guidelines for integrated nutrient management, which relies on the potential nutrient sources of manure, pearl millet residue and mineral fertilizers. A fully factorial on-station experiment was conducted during the 1994 and 1995 rainy seasons at Sadoré, Niger, combining application of: (i) broadcast millet residue (300, 900 and 2700 kg ha−1), (ii) broadcast cattle manure (300, 900 and 2700 kg ha−1) and (iii) mineral fertilizer (unfertilized control, 15 kg N ha−1 + 4.4 kg P ha−1 and 45 kg N ha−1 + 13.1 kg P ha−1). Manure and fertilizer increased millet yields in both years whereas residue was effective in 1995 only. The effect of manure and residue were additive, as was the effect of manure and fertilizer but only up to 50 kg N ha−1. However in 1995, the response to fertilizer was approximately doubled in the presence of 900 or 2700 kg residue ha−1 compared to fertilizer with 300 kg ha−1 residue, indicating a strong synergistic effect. This synergistic effect was reflected in the partial factor productivity of nitrogen and phosphorous in both years. Two treatment combinations stand out as particularly relevant based on yield, partial factor productivity and nutrient balance criteria: 2700 kg manure ha−1 combined with (i) 300 kg residue and no fertilizer (95% grain yield increase); (ii) 900 kg residue ha−1 and 15 kg N + 4 kg P ha−1 (132% grain yield increase). There is a need for similar, long-term experiments to confirm the present results.

Tea yields of 1 to 4 t ha−1y−1 of dry shoot tips are much less than those of other vegetative crops like grasslands or forests growing in similar conditions, partly because plucking restricts tea biomass production, but mainly because the harvest index of tea is small. In Kenya, plucked tea produced 36% less biomass per hectare per year than unplucked tea, and 64% less wood. Only 8·3% of the total annual biomass increment was harvested. This proportion might be increased by plucking older leaves, increasing the shoot:root ratio, and by lowering the plucking table so that less wood was produced.

Assessment of the relative advantages or otherwise of inter-cropping compared with sole cropping needs to be done over a wide range of plant populations. Systematic spacing designs lend themselves to this, and the paper discusses the interpretation of the yield/plant population curves which can be so derived.

Maize was grown for six years on two soil series in annual rotation with groundnuts, soyabean, lab-lab and sunflowers, and for up to four years after two year crops of pigeonpea. Nitrogen left by the annual legumes was estimated to vary from 0.0 to 52.2 kg ha−1 depending on year, soil and species. Summed over three successive maize crops, nitrogen left by two year crops of pigeonpea varied from 23.5 to 109.6 kg ha−1. Vigorous vegetative growth and low seed yield in the legume were associated with increased residual nitrogen. Groundnuts left more nitrogen on the more fertile soil. High rainfall at the beginning of the maize cropping season was associated on one soil series with the complete disappearance of residual nitrogen from the immediately preceding legume crop.

Crop Growth Rate, Leaf Area Index, Net Assimilation Rate and Harvest Index were estimated for oil palms in nine age groups growing on coastal alluvial soils in Malaysia. The mean Crop Growth Rate of mature palms was 29·83 t./ha./yr, with a Leaf Area Index of 3·61, and Net Assimilation Rate was 0·16 gm./dm.2/wk. Photosynthetic efficiency was about 2·2 per cent. Oil constituted about 17 per cent of total dry matter production. Possibilities for improving the yield of oil are briefly discussed.

The manure that is returned to croplands each year is an important resource in the subsistence farming systems of eastern Kenya. Measurements on several farms have shown that the manure being used is of very poor quality. Analyses of soil samples from beneath the bomas (small enclosures) where animals are kept indicate that substantial losses of nutrients occur through leaching; ammonia volatilization and denitrification may also be involved. Current practice is to apply the manure at rates that appear to make poor use of this scarce resource. The findings are discussed in terms of what changes to the system may be feasible to reduce losses of nutrients, and to improve the quality of the manure and the effectiveness of its use.

Cereal residues are an important feed source for ruminants in smallholder crop-livestock systems in the (sub)tropics. In many areas of India maize is a relatively new cash crop where farmers and development agents alike generally perceive maize stover to have limited utility, in contrast with the intensive feeding of other cereal residues in India and the intensive use of maize stover in sub-Saharan Africa and Latin America. A comparative assessment of maize stover quality (based on a brief review and a feeding trial) indeed confirms its potential as a ruminant feed according to its relative nutritive value. The paper then explores the apparent paradox through a scoping study of maize stover use (based on village surveys) in three contrasting maize-growing districts in India – including both traditional and non-traditional maize producers. The limited maize stover use appears to alleviate seasonal shortages, with tradition and technology helping explain the preferential use of other cereal residues. The paper thereby provides further impetus to India's apparent food-feed paradigm – whereby farmers’ staple food preferences coincide with crop residue feed preferences. The paper argues the case for investing in maize stover R&D in India and thus reigniting earlier feed research in general. Indeed, maize stover use is a relatively neglected area by India's agricultural R&D and merits more attention so as to exploit its potential contribution and alleviate eventual tradeoffs.

Phosphorus deficiency in tropical acid soils is a problem because soluble inorganic phosphorus is fixed by aluminium and iron. Organic amendments could be used to overcome phosphorus fixation in acid soils. Thus, the objectives of this study were to (i) improve soil phosphorus availability using biochar and compost produced from poultry manure and pineapple leaves respectively, and (ii) determine whether the use of biochar and compost could improve phosphorus, nitrogen, potassium, calcium and magnesium uptake and dry matter production of Zea mays L. cultivation on a tropical acid soil. Organic amendments significantly increased soil pH compared with non-organic amendments. Organic amendments also significantly reduced exchangeable acidity and exchangeable forms of aluminium and iron, and effectively fixed aluminium and iron instead of phosphorus. As a result, phosphorus availability in soil increased. Besides increasing the availability of nitrogen, potassium, calcium and magnesium in soil, organic amendments improved nutrients uptake and dry matter production of Zea mays L. Biochar and compost can be used to improve the productivity of Zea mays L. on acid soils by reducing phosphorus fixation.

Three levels of nitrogen (N) were applied to cotton grown in irrigated field trials at two locations in Zimbabwe in 1978. Dry matter (DM) production, total uptake and distribution of N among vegetative and reproductive components, and soil mineral-N contents were recorded about every 14 days. About 60% of total DM was produced, and 40% of total N taken up, between 10 and 16 weeks after sowing. Most N was present in vegetative parts, particularly leaves and branches, during early growth but, later, it accumulated in buds, flowers and bolls. At maturity, seeds and lint contained 42% of total above-ground plant N. N concentrations were similar in sympodial and mainstem leaves, petioles and branches. Inorganic N applied at sowing had little effect on plant N, but when given after 10 weeks it increased the N content of leaves, stems, branches, petioles and bolls.

Two glasshouse experiments were conducted at the Department of Plant Production, University of Helsinki, Finland, to study the effect of foliar application of aqueous 0.1 and 0.3M glycinebetaine on leaf growth of drought-stressed tobacco (Nicotiana tabacum L.) cv. Samsun. Leaf nitrogen and glycinebetaine concentrations were estimated periodically. After 16 days of treatment, leaves were harvested, and fresh and dry weights, and area determined. The number of total and green leaves was also recorded. Significant increases in leaf fresh and dry weights, and area were associated with glycinebetaine application, especially when drought was induced early. The application of 0.3M glycinebetaine reduced leaf area duration. Residual leaf glycinebetaine content remained high 16 days after application. The results indicate that exogenous glycinebetaine has the potential to improve the drought tolerance of leaf tobacco.