Pearl millet [Pennisetum glaucum (L.) R. Br.] is grown as a forage, cover and grain crop in Brazil. Historically, forage production has the most important use, but during the last 30 years, the use as a cover crop in no-till soybean [Glycine max (L.) Merrill] production systems has expanded greatly and is currently used on over 5 million ha. Grain production as livestock feed is presently of minor importance but expanding. This review cites 125 references and documents pearl millet research conducted in Brazil which is largely published in Portuguese. The review addresses recommended pearl millet production practices for different uses, including stand establishment, row spacing and plant population, fertiliser and pest management, and the use of pearl millet in rotation and as a cover crop between soybean or maize (Zea mays L.) production to reduce crop losses from nematode infestation. It is concluded that greater research investment in crop improvement, fertiliser and pest management, nematode management, and forage/grain utilisation is needed to fully take advantage of pearl millet to meet feed, food and soil improvement needs in Brazil. In addition, creation of a database on pearl millet production, marketing and utilisation to assist farmers and grain merchandisers, and increased extension programming on pearl millet production is needed.

Temperature is the major environmental variable affecting the yield of tea, but within the framework of a temperature model shoot extension is severely depressed when daily maximum vapour pressure deficits rise above 2.3 kPa. Day length does not affect shoot extension when the nights are cool (10°C), but growth rate is depressed by short days (11 h) when nights are warm (20°C). Soil temperatures between 18–25°C do not affect shoot extension.

This paper places the participatory approaches to research presented in the six following papers into the broader debate on priorities in agricultural research and on the role of specific approaches to research. It reviews the principal features of the approaches outlined, the extent to which they have been incorporated into existing institutions such as national agricultural research services, and their implications for support services. Key issues which future participatory research should address are highlighted.

Crop yield response to soil moisture deficiency varies for different crops and also depends on the time of its occurrence in the growth cycle. Many attempts have been made to derive a single relationship between total water consumption and yield for various crops, but this has proved of limited use, because the effect of time was omitted from such production functions. Jensen (1968) derived two expressions, for determinate and indeterminate crops, bringing the time element into his expressions indirectly by a parameter (λi) which defines the relative sensitivity of the crop to soil moisture stress at different growing stages. The usefulness of this approach depends on the accuracy with which this parameter can be determined. The aim of this paper is to derive λi for a number of crops from available experimental data and subsequently to find a way of computing the quantitative contribution of each single irrigation application to the crop yield. This should lead to a more rational use of irrigation water resources.

Soil inoculation was tried in field experiments during two seasons using different concentrations and amounts of bacterial suspension and compared with direct seed inoculation of chemically protected and unprotected peanut seed. Soil inoculation gave significantly better results than direct inoculation of chemically protected or unprotected seed.

Large yields of high quality peanuts, which compared favourably with highly nitrogen-fertilized peanuts, were obtained after the application of relatively small amounts (10–40 gm.) of enriched peat inoculant in 5 litres of water per dunam (1/10 ha).

Pasture experiments may be grazed using either variable (put-and-take) or fixed stocking rates. Considerations such as the risks of introducing bias, the reliability of the data, and the resources required for these methods of grazing are discussed, and criteria are described for choosing between the methods.

Mineral fertilizer application and consequent plant nutrition has long been observed to influence associated plant-parasitic nematode population densities, offering the potential as a nematode management option. Observations were made on the influence of mineral fertilizer application on nematode populations on three separate long-term rice experiments, (differential mineral application on upland and on lowland rice, and P application on upland rice) undertaken between 1994 and 1997 in Côte d'Ivoire. In 1995, on upland rice, treatments with K or N withheld from the comprehensive mineral application treatment (range of elements including N, P, K, Ca, Mg and Zn) led to lower densities of Pratylenchus zeae at harvest than the comprehensive mineral application. By withholding K or Mg, Helicotylenchus pseudorobustus densities were greater than with either the control (no mineral application) or comprehensive mineral application in the same year. No differences were observed between treatments in 1994, or between treatments for densities of other nematode species present (Meloidogyne incognita, Criconemella tescorum) or for total nematode density. In the lowland rice trial, no treatment effects on nematode species (Hirschmanniella oryzae and Uliginotylenchus palustris) were observed. In the P application trial on a P-deficient Ultisol, Heterodera sacchari densities were lower in treatments receiving 180 kg P ha−1, than untreated in 1995; in 1996 no differences were observed between untreated and 135 kg P ha−1, while in 1997 higher densities of H. sacchari were present in 135 kg P ha−1 than untreated. Regression analysis of nematode densities against the mineral straw content in the P application trial revealed a negative correlation between M. incognita and Mn and Ca, and between P. zeae and Zn or Fe. A positive correlation was observed between Helicotylenchus spp. and Mg. This study provides strong arguments for taking plant parasitic nematodes into account when planning and executing long-term research trials.

A tied ridge system of hand cultivation has been practised successfully in parts of Tanzania for many years. Equipment to mechanize this system was devised and constructed by the National Institute for Agricultural Engineering, U.K., particularly for use in areas of marginal rainfall where water conservation is essential. Agronomic trials with this equipment were carried out on three soil types in Northern Tanzania. Records from resistance units showed much better penetration of rainfall under tied ridges than under flat cultivation. Corresponding yield responses in maize were only obtained when the increase in available water made an appreciable difference to conditions of water stress at the time of tasselling and silking. Weeding operations using a ridging body achieved a satisfactory control. After a few modifications to the equipment, especially the incorporation of a small tine to rip the bottom of the basins to improve infiltration, the system of cultivation based on ripping, ridging and tieing proved to be an adequate alternative to ploughing and harrowing for seed bed preparation, and a much more efficient method of water conservation.

Shifting agriculture is an ancient basis for maintaining soil fertility but pressures of population have caused it to give place in most countries to rotations and bare fallows which, in turn, have had to be reduced or modified. Research on various measures to shorten the duration of fallows and increase their effectiveness is reviewed. These measures include the use of organic manures and inorganic fertilizers, green manuring, mulches and the growing of legumes and grasses, which are discussed in relation to their effects on the soil and on crop yields. The increasing use of the factorially-designed experiment is recognized as a major contributor to this research.

Seedling emergence and stand establishment of crops following the allelopathic crops are often affected. When the crops are grown in rotation, they are influenced by allelopathy of preceding crop. In this study, consisting of three independent experiments, allelopathic effect of tobacco, rich in several allelochemicals, on the subsequent maize and mungbean crops was investigated. In first experiment, maize and mungbean were sown in field previously occupied by tobacco or was fallow. In second experiment, maize and mungbean were planted in pots after the harvest of tobacco. Whereas in third experiment, maize and mungbean seeds were soaked in water or 2 and 4 mM nicotine and were then sown in soil-filled pots. Stand establishment, leaf emergence and growth of maize were significantly improved when grown after tobacco, whereas in mungbean these characters were suppressed when grown after tobacco. Likewise external application of nicotine improved the emergence uniformity, seedling dry weight and chlorophyll contents in maize and suppressed these parameters in mungbean. Tobacco allelopathy also increased the total soil nitrogen, zinc, iron, nicotine and total phenolics. Nicotine-induced change in chlorophyll contents and α-amylase activity seems the possible reason of differential response of maize and mungbean to tobacco allelopathy. When grown in rotation with tobacco, stand establishment and growth of maize were improved, whereas mungbean stand and growth were suppressed. In crux, allelopathic nature of the crops must be considered while making the crop rotations.

An on-farm study was conducted from 2009 to 2012 with communities in the Manjawira, Mpingu and Zidyana Extension Planning Areas in the Ntcheu, Lilongwe and Nkhotakota districts of central Malawi. The aim of the study was to evaluate the effects of the principles (no-tillage and mulching) and components (fertilization and weeding) of conservation agriculture (CA) on crop productivity and weeds, and the interactions between principles and components, and to suggest strategies for introducing CA to smallholder farmers. The treatments consisted of tillage, fertilizer application, residues management and weed control strategies. While combined analysis showed that mulching is as effective as tillage in controlling weeds, the interaction between site and treatment revealed that in the more humid environment of Zidyana, weed dry matter obtained under no-tillage and residues plus fertilizer (NT+F+R) was 0.6 mg ha−1 lower than under CP+F. Results suggest that about 6.0 mg ha−1 of mulch is required to have a similar effect as tillage in controlling weeds. Fertilizer had an overriding effect on maize yield, regardless of tillage and crop residue management. Mulching was beneficial over tillage in the drier environment of Manjawira, where maize yield obtained under NT+F+R was 1.2 mg ha−1 greater than under CP+F. Our results show that the introduction of no tillage has benefits only if it is accompanied by fertilizer application, retention of crop residues as surface mulch, and improved weed control. Increasing availability and accessibility of inputs (fertilizers and herbicides) to farmers is critical for adoption of CA at scale in Malawi.

On-farm participatory varietal selection (PVS) trials are often of two types: mother trials (with all of the entries) and baby trials (each having one, or very few of the entries from the mother trials). We conducted PVS trials on 17 wheat varieties in 12 villages of four districts of Bangladesh over three years but the data were highly unbalanced. Both quantitative and qualitative traits were measured in the on-farm trials. The factors in the trials were both fixed effects (varieties and districts) and random (years and farmers). We used the residual or restricted maximum likelihood (REML) analysis for the mixed model for quantitative traits. For qualitative data on farmers' perceptions, logistic regression procedures were used that are equally applicable to balanced and unbalanced data sets. The REML analysis provided adjusted mean values for quantitative traits for all the varieties, for the mother and baby trials separately, using the data from all years and all locations. It identified varieties BAW 1006 and BAW 1008 that yielded 19–30% more than the control Kanchan and also had a higher 1000-grain weight, were at least as early to flower and had a high overall ranking by farmers in the mother trials. The logistic regression analysis of perception data agreed with the results of the REML analysis as these varieties were most preferred by farmers for grain yield, earlier maturity and better chapatti making quality. The less labour-intensive method of recording qualitative perceptions can usefully replace actual yield measurements, particularly when validated by other participatory measures such as intended and actual adoption. In 2005, BAW 1006 was released as BARI Gom 23 or Bijoy and BAW 1008 as BARI Gom 24 or Prodip for the whole of Bangladesh. The validity of the results of the REML analysis was confirmed by the high early adoption trends of the identified varieties. Since REML is an effective analysis for unbalanced PVS trial data using a mixed model, its wider use by researchers would increase the value of the PVS process.

The nutritive value and yield of forage legumes and barley harvested as immature herbage, hay and straw were measured in two experiments. The voluntary feed intake of peas at all stages of maturity and immature herbage from woollypod vetch was substantially lower than that of common vetch and chickling. At each stage of maturity barley was less digestible than all the forages except immature peas. Despite exceptionally cold weather in February/March 1985, yields of common vetch were higher in 1984/85 than in 1985/86 when there was less rain. Peas yielded the most hay, and chickling yielded less seed and straw than common vetch, peas and barley. Yields of digestible dry matter from straw and seed exceeded those from hay but protein yield at the two stages was similar. Mechanical baling substantially reduced the yields of baled hay but these losses would be reduced to less than 10% if the residues were grazed.

This study investigated the feasibility of using sole organics or a combination of organics with inorganic fertilizer to improve maize production in on-station and on-farm experiments in central Kenya. In the on-station experiment, combined application of Calliandra calothyrsus, Leucaena trichandra and Tithonia diversifolia at 30 kg N ha−1 plus inorganic fertilizer (30 kg N ha−1) consistently gave significantly higher maize grain yields than the recommended rate of inorganic fertilizer (60 kg N ha−1). Sole application of calliandra, leucaena and tithonia also increased maize yields more than the recommended rate of inorganic fertilizer. In the on-farm experiment, calliandra, leucaena, tithonia and cattle manure either alone or combined with inorganic fertilizer increased maize yields with a similar magnitude to that of inorganic fertilizer. These organic resources could therefore be used to supplement inorganic fertilizer as a whole or in part. There was a yield gap between on-station and on-farm trials with on-station yields having, on average, 65% greater yields than the on-farm yields. There is therefore potential for increasing yields at the farm level by closing the yield gap.

This paper assesses farmer adoption of rice varieties and new genotypes introduced through participatory varietal selection (PVS) in villages which represent submergence- and drought/submergence-prone villages in eastern Uttar Pradesh, India. It focuses on the involvement of women farmers in participatory research for screening improved varieties for areas which suffer from abiotic stresses. It further assesses the impact on the decision-making authority (or women's empowerment) on rice varietal choice, seed acquisition and disposal, and crop management after participating in PVS trials. It suggests strategies to empower women farmers in making sound and timely decisions on farm-related matters and to enhance their roles in accelerating the adoption of new varieties.

Under rainforest vegetation, the central Amazonian Ferralsols are characterized by relatively high availability of N in relation to other nutrients. After forest clearing, several tree crops also have not shown yield responses to N fertilizer. To elucidate the mechanisms of this apparent N sufficiency, the mineralization of soil N was measured under three tree crops and a leguminous cover crop (Pueraria phaseoloides) in a multi-strata agroforestry system at two fertilizer input levels on a Xanthic Ferralsol in central Amazonia. In situ incubations of topsoil (0–10 cm) were carried out using the buried-bag method on five occasions over ten months. The highest mineralization rates were found under the cover crop, intermediate rates under rubber trees (Hevea brasiliensis) where the soil was also covered by the cover crop, and lowest rates under peach palm (Bactris gasipaes) and cupuaçu (Theobroma grandiflorum) with no cover crop. The increased N mineralization under the cover crop was due to more total N in the soil, higher soil moisture and, presumably, a larger pool of readily mineralizable soil N compared with the soil under the tree crops. Other fertility parameters also differed significantly between sampling positions within the plots, but this had no major influence on net N mineralization. Also, the input of NPK fertilizer and dolomite had no significant influence on N mineralization, indicating that N mineralization was not nutrient-limited. High total N mineralization rates in the soil (approximately 350 kg ha−1 a−1 at 0–10 cm depth) explained earlier observations of nitrate leaching into the subsoil under multi-strata agroforestry at this site. Considering the spatial patterns of N mineralization with maximum values under the cover crop, the exploration of the soil volume by crop roots should be maximized to increase the uptake of mineralized soil N by the crops and reduce nitrate leaching. Appropriate measures are narrow tree spacing, use of annual and semi-perennial intercrops and encouragement of the lateral root development of the trees. In addition, the mineralization of soil N close to the tree crops can be influenced through the management of the cover crop. In view of the high total N mineralization rates in the system and unclear yield responses of tree crops to N fertilizer, the application of N fertilizer to tree crops with well-developed root systems and a well-managed cover crop may often be unnecessary on this soil type. This may facilitate the further development of tree crop agriculture in the region.

When differences are observed between genotypes in their response to low temperatures at germination, it has been generally assumed these are purely genetic. Laboratory experiments were carried out to evaluate the effects of physiological age on the temperature responses of 13 rice genotypes from Bangladesh in order to clarify whether (a) differences in seed germination at low temperature represented genetic differences or differences in the physiological state of the particular seed lot used and (b) whether genotype performance at higher temperatures was indicative of performance at lower temperatures. A higher initial seed moisture content (mc) was associated with lower initial viability (Ki). The base temperature for germination differed by less than 1 °C between genotypes. Seeds remaining ungerminated at low temperatures usually germinated when transferred to 21 °C. The thermal time requirement to reach t50 (θ) differed widely between genotypes. Lower optimum temperatures for germination were associated with lower thermal time requirements. Ageing seeds for 24 hours at 24 % mc and 45 °C significantly reduced final germination on a thermal gradient table at all temperatures below 20.8 °C in genotype BR29 but only below 16.5 °C in BR11. The rates of germination (seeds d−1) of aged seeds were also lower at all temperatures. Germination of high quality seeds of four genotypes were compared at 21 °C and 11 °C both before and after ageing (at 24 % mc and 45 °C). Ageing consistently reduced the rates of germination at both 21 °C and 11 °C. Increased ageing time progressively reduced the rate of germination of all seed lots at both temperatures. The rates of germination at 11 °C and 21 °C were positively and significantly (p < 0.01) related to final germination at the lower temperature of 11 °C. These results demonstrate that seed physiological quality as well as genotype might influence the final germination and rate of germination of rice genotypes at low temperatures. This information will be useful for breeders involved in selection of lines suitable for growing in cooler seasons.

In an on-station agroforestry experiment conducted in south-west Niger, the effects of seven windbreak species and of a soil mulch made from crop residue on wind erosion and pearl millet (Pennisetum glaucum) production were monitored. Within a distance of 20 m, strips of the perennial grass, Andropogon gayanus, reduced total annual soil flux by 6–55% and hedges of Bauhinia rufescens 2 m in height reduced soil flux by 47–77% compared with unsheltered control plots. No significant overall windbreak effect on millet stover and grain yields was found. In contrast, erosion reduction and yield increases due to mulch application were highly significant. Soil mulch is a promising alternative to complex windbreak–millet cropping systems in regions where direct economic benefits for farmers are not ensured by windbreaks.

Apparatus was built to screen sorghum and pearl millet for seedling emergence through a hot soil surface. Seeds were sown in soil in long clay pots arranged in a steel water tank so that the top 7 cm of the pots was above the water level. The soil in the pots was heated with infra-red lamps fitted to a frame above the tank. By adjusting the height of the frame the temperature of the soil could be changed. The system allows emerging plumules to be subjected to high soil temperatures (up to 50°C) but without water stress. Both crops exhibited genotypic differences in emergence.

Farmers grow vegetables widely during the dry season in wetlands known locally as dambos in southern Africa. Declining soil fertility is one of the major factors limiting smallholder vegetable production in the dambos of eastern Zambia. An experiment was initiated with 43 farmers with the objective of assessing the agronomic and economic feasibility of foliar biomass of gliricidia (Gliricidia sepium) and leucaena (Leucaena leucocephala) for production of cabbage, onion and a subsequent maize crop during the dry season. The treatments were, on a dry-matter basis, 8 and 12 t ha−1 gliricidia, 12 t ha−1 leucaena and 10 t ha−1 manure+half the recommended fertilizer rate, inorganic fertilizer at recommended rate, and a control without any inputs. Direct field measurements and informal enquiries were used for evaluating the effects of different treatments. The highest cabbage and onion yields were obtained from manure+half-rate fertilizer application. The gliricidia biomass transfer technology produced cabbage, onion and maize yields comparable with the full fertilizer application. In both cabbage and onion, manure+fertilizer gave generally higher net incomes. Biomass transfer also recorded higher net incomes than the control, and required lower cash inputs than the fully fertilized crop. Net incomes of the biomass treatments were substantially reduced by the labour costs for pruning and incorporation of the biomass. The results indicate that the gliricidia biomass transfer technology could be used as an alternative to inorganic fertilizers for vegetable production in dambos.