Four hybrids of pearl millet (Pennisetutn typhoides) were screened for photoperiod sensitivity in a heated temperate glasshouse and the effects of 12 h short day induction on the reproductive development and plant morphology were examined. All the hybrids (BK 560, MBH 104, MBH 110 and ICH 105) responded to 14 short days by a considerable reduction in the time to anthesis, plant height and the final number of leaves produced, without any adverse effect on head development. In another experiment BK 560 required at least four short days for floral initiation and another four for subsequent development. Short day induction had no apparent effect on the rate of leaf appearance. The results were compared to those reported for millets in general and to millets grown in the tropics.

In a 2 row cereal: 1 row pigeonpea intercropping system, four sorghum and two millet genotypes were examined with four of pigeonpea on a medium-deep Alfisol during 1978 and 1979. The cereals usually produced a large proportion of their sole crop yields. Millets matured relatively early which allowed large yields of later-maturing pigeonpea. A tall millet gave the best total Land Equivalent Ratio (LER) of 1.78 and most monetary returns. Early and/or short sorghums produced large LERs (1.51–1.59) and combinations with an early hybrid also gave good returns. A tall late sorghum gave poor yields of both components, smallest total LER (1.30), and little return. Pigeonpea intercrop yields became larger as the maturity difference between the cereal and pigeonpea increased. A combination of a short, early but large-yielding cereal with a pigeonpea that is as late as possible without incurring undue risk of moisture stress may be ideal.

Seedling growth in the nursery and the magnitude of shock experienced by the seedlings after transplanting can affect subsequent growth and development of transplanted rice (Oryza sativa). These two processes have not been adequately represented by rice growth simulation models. In this study, seedling growth in the nursery was described with respect to endosperm mobilization, dry matter (DM) distribution and seed size. In addition, the transplanting shock process was represented describing the crop development and growth in relation to seedling age at transplanting. These relationships, as two sub-models, were incorporated into CERES-Rice, a rice growth model, and their performances compared with independent field data. The nursery growth sub-model was also evaluated with another model, RIBHAB. Results of the comparison showed that the nursery growth sub-model, either with CERES-Rice or RIBHAB, closely predicted observed seedling growth. On the other hand, CERES-Rice overestimated root and leaf DM and underestimated culm DM, while RIBHAB underestimated all the growth traits considered in the evaluation. Transplanting shock period predicted by the sub-model closely mimicked observation, whereas CERES-Rice highly overestimated it. It is concluded that the developed nursery growth and transplanting shock sub-models can be incorporated into CERES-Rice and other rice growth models for better simulation of those growth processes.

Rainfed wheat is frequently exposed to periods of water stress that generate low and variable grain yields. Field experiments (with studies in Tunisia and Morocco) carried out in the context of a European research project of co-operation with Mediterranean partner countries (WatNitMED) showed that nitrogen (N) fertilization may be a tool to increase productivity of rainfed wheat in Mediterranean environments. However, most farmers in Northern Africa do not fertilize their rainfed cereals. In the present study, we aimed to analyse whether the generally accepted positive yield response to N fertilization in rainfed Mediterranean conditions corresponds to actual advantages achieved in the fields of working farmers, attempting a further up-scaling of knowledge from field experiments to real fields. We attempted to apply research results to Tunisian working farmers’ fields by conducting a farm pilot experiment. The pilot experiment was conducted in two different regions (a low-yielding region and a relatively high-yielding region) of cereal production in Tunisia, where wheat production represents typical rainfed Mediterranean agro-ecosystems in North Africa. First, we compared the yield response to N fertilization against unfertilized conditions (a common situation for many of the farmers in North Africa), and secondly we compared what the farmers suggested as an optimal N fertilization practice in their fields against the WatNitMED's recommendation which was based on an N-fertilization scheme derived from field experiments from the European research project in Mediterranean conditions. The WatNitMED fertilization scheme suggested higher rates of fertilization than those considered optimal by farmers (on average 40 kg N ha−1 higher). Unfertilized grain yield across both locations ranged from about 1 to 3.5 Mg ha−1 (typical of farmers’ yields in the region), and fertilizing increased grain yields in most situations. Within the two alternative fertilization treatments, WatNitMED fertilization produced higher yields than the fertilization rate considered optimal by farmers. This trend was observed at the low-yielding location as well as at the high-yielding location. These responses demonstrated that fertilization in working farmers’ field conditions may be a reliable means of improving dryland wheat grain and straw yields. They also showed that rates of fertilization regarded as optimal by real farmers were below the optimum for these regions.

Straws and stovers are often called ‘by-products’ of grain production even though they are increasingly important, e.g. for animal feed, thatching, soil improvement, mushroom production and industrial use. As a result, plant breeders, agronomists, economists and animal nutritionists have to pay more attention than before to the total value of crops, i.e. whole plant value in which straws and grain both play a part. This paper reviews literature about the technical potential of breeding and/or management for more or better straw. It then discusses issues of the economic value (EV) and nutritional value (NV) of straw and stovers for livestock feed to guide research and development in cereal breeding and management. It is mainly based on experiences from the Indian subcontinent and semi-arid regions of the Near and Middle East. The paper shows that the quantity and quality of straw produced has changed considerably over recent decades as a result of breeding policies, new cultivation patterns and choice of cultivars. Both EV and NV depend on type of grain, animal production system and access to other feeds. A classification of these factors is provided and suggests that the EV of straw is particularly important in low-input systems with stovers from coarse grains.

In many parts of Pakistan, availability of green forage is critical to livestock farmers. Forage production is often conducted with two succeeding crops grown within one year and it is highly affected by uncertain availability of irrigation water and low levels of applied mineral fertilisers. The objectives of the present study were to (i) evaluate the effects of crop species, fertiliser type and irrigation level on yield, (ii) determine the corresponding water use efficiency and (iii) investigate relationships between chlorophyll content and crop yield as a basis for a simple sensor-based prediction of crop yield for on-farm use. To this end a two-year field experiment was conducted in Faisalabad, Pakistan, with a completely randomised design with four replications in a split plot arrangement. A combination of fertiliser treatment (control, farm yard manure and mineral fertiliser) and irrigation (recommended irrigation, half recommended irrigation) were assigned to main plot whereas subplots were assigned to cropping systems (common (CCS): Egyptian clover (Trifolium alexandrinum L.) followed by corn (Zea mays L.), drought-adapted (DACS): Oat (Avena sativa L.) followed by Sudangrass (Andropogon sorghum subsp. drummondii). Yield and irrigation water use efficiency of DACS was higher than CCS (14.8 and 26% respectively), the differences were bigger with reduced irrigation and fertilised crops used the available water better than the control. Positive linear relationships were found between chlorophyll concentration estimated by a chlorophyll meter and yield for all crops (r 2 = 0.63–0.96), suggesting this technique as a fairly accurate approach to predict yields of crops in vegetative growth stage.

Cowpea (Vigna unguiculata L. Walp) is the most important food grain legume in Africa. Cowpea is nodulated by rhizobium bacteria in almost all soils of the tropics, but studies performed in the 1970s and 1980s in Nigeria suggested only modest responses of grain yield in the field to inoculation of selected rhizobium strains. More recently, experiments performed in Brazil have shown that cowpea responded to inoculation of rhizobium selected locally and grain yields increased by up to 30%. We tested some of the Brazilian strains on cowpea at a site in northern Mozambique and at several sites in Northern Ghana. At all sites phosphorus fertilizer (26 kg P ha−1) was added to all plots. At the site in Mozambique despite considerable damage to the crop by the parasitic yellow witchweed (Alectra vogelii), grain yields were more than doubled by inoculation of one of the Brazilian strains and reached 1.4 Mg ha−1. In on-station experiments conducted in 2012 in June and August in northern Ghana using the local cowpea variety Padi-Tuya as the test crop, nodule weight at 35 days after planting (dap) tripled with rhizobium strain BR 3299 (530 mg plant−1) in August with the other inoculants (BR 3267 and a mixture of BR 3267 and BR 3299) also increased nodule weight to over 300 mg plant−1. In the first on-station experiment, grain yields were doubled by the inoculation of any of the three rhizobium strains, and in the second experiment, significant increases in grain yield ranged from 39% to 57% and reached over 2.0 Mg ha−1. Similar increases in nodulation and grain yield due to inoculation were observed in 22 on-farm trials. Nitrogen fertilizer application promoted vegetative growth but did not increase grain yield and nodulation. Inoculating cowpea with highly effective rhizobium strains can therefore enhance grain yield of smallholder farmers in Africa.

A three-year trial was conducted on a degraded soil in the moist Guinea savanna of northern Nigeria to assess the possibility of improving productivity and economic viability of maize-based systems by incorporating short-season legumes and green manure crops into the cropping pattern. Treatments included double cropping legume-maize systems, full-season sole maize receiving various amounts of nitrogen, green manure crop mucuna (Mucuna pruriens var. utilis) followed by sole maize and a legume-maize system receiving additional rice mill waste. In comparison with full-season maize, the use of early-season cowpea followed by maize improved productivity as well as economic returns of the cropping system, while the use of mucuna, grown as an early-season crop or full-season crop, resulted in poor overall productivity of the system. The addition of rice mill waste as a soil amendment in cowpea–maize systems stimulated maize yields and rice mill waste can form a cheap source of organic inputs for farmers living nearby rice mills. Given the limited growing season of the northern Guinea savanna, it is concluded that timing of field operations is crucial for the successful application of double cropping systems. In addition, high labour requirements are a serious constraint for wide-scale adoption of double cropping systems by small-scale farmers, stressing the need to reduce soil cultivation operations, for example by maintaining a uniform ridge distance for all crops in the rotation.

Sorghum (Sorghum bicolor (L.) Moench) is a major staple crop of Burkina Faso where farmers continue to cultivate photoperiod-sensitive guinea landraces as part of the strategy to minimize risk and ensure yield stability. In the Boucle du Mouhoun region, however, sorghum farmers appear to have insufficient varietal choice due to cropping systems having shifted towards more intensive cultivation of cotton and maize, and rainfall patterns having decreased over the past decade. In search for new varietal options that can respond to this changing context, researchers decided to give farmers access to ex-situ national collections along with the opportunity to evaluate recent improved varieties. From 2002 to 2007, researchers and farmers worked closely together to implement on-farm testing, including varietal selection trials, crop management and multi-locational trials. Farmers’ choices tend to differ among groups, villages and years, with the exception of four particular landraces: two originating from a collection carried out in the Mouhoun region more than 30 years previous to this research, and two other landraces that came from the dissimilar agro-ecological zones of Burkina Faso. These four were the most commonly selected landraces out of 36 cultivars that covered both improved and landrace varieties. Farmers’ selection criteria were focused on adaptation to agro-climatic conditions as well as specific grain qualities for processing and consumption. The potential usefulness of each variety was verified via multi-locational trials. The paper also shows that wide dissemination of experimental seed, not just across the Mouhoun region but also at a national scale, was largely achieved through collaboration with a strong farmer organisation in conjunction with farmer training programs focused on the on-farm seed production and the commercialisation of this seed.

Tillage and use of organic manure are important agronomic practices that sustain high crop and soil productivity. Hence, a three-year (2007 to 2009) study was conducted to evaluate the effect of site, tillage and poultry manure (PM) treatments on soil and plant nutrients composition, growth and yield of cocoyam (Xanthosoma sagittifolium). The study was a 2 × 5 × 5 factorial experiment with two sites (Owo – site 1 and Obasooto – site 2), five tillage methods; manual clearing (MC), manual ridging (MR), manual mounding (MM), ploughing plus harrowing (P+H) and ploughing plus harrowing twice (P+2H) and five levels of PM (0, 2.5, 5.0, 7.5, 10.0 t ha−1). Treatments were replicated thrice. Soil OM, N, P, K, Ca, Mg and leaf nutrients reduced with increase in tillage intensity, thus MC conserved soil nutrients the most, and increased nutrient uptake. Soil and plant nutrient concentration was lowest under the P+2H treatment. The MC, MR and MM treatments led to faster growth and higher tuber yield. As PM increased from 0 to 10.0 t ha−1 soil pH, OM, soil and plant N, P, K, Ca and Mg increased. The 7.5 t ha−1 PM gave the highest leaf K, Ca and Mg values. Owo site had significantly higher yield and growth parameters of cocoyam compared with Obasooto site. Yield and growth parameters of cocoyam increased with increase in PM level up to 7.5 t ha−1. Out of all tillage cum manure treatments, MC+7.5 t ha−1 PM gave the highest values of yield and growth parameters.

A long-term trial with Leucaena leucocephala was initiated in 1982 to test the sustainability of Leucaena-based alley farming compared to a conventional cropping system without trees and with continuous cultivation of maize. It assessed the integration of short grazed fallows in rotation within Leucaena alleys and their effect on soil fertility and crop yields.

The various treatments had no effect on soil pH during the four-year period of the trial. The organic carbon and total nitrogen contents of the soils under conventional cropping were lower by the end of the fourth year than those under alley cropping and alley grazing treatments, whereas soil phosphorus levels were lower in the alley cropping and grazing plots. Foliage dry matter production of Leucaena under alley cropping management ranged from 6.0 to 6.7 t ha−1 a−1 under continuous cropping and reached 8 t ha−1 when alley cropping was preceded by a grazed fallow. Crop yields were consistently higher with alley cropping than with conventional cropping. Alley cropping plots in rotation with two year grazed fallows gave significantly higher crop yields during cropping years than those under continuous cultivation.

The effects of various intercropping patterns of maize and melon on soil temperature and moisture content and crop growth and yield were compared in field trials over a two year period. Intercropping raised soil temperature in the upper 10 cm at 0600 h and reduced it at 1000, 1400 and 1800 h, and also increased soil moisture content by about 30%, compared with maize sole cropping. Melon biomass and seed yields were reduced by intercropping but maize growth characters were unaffected. However, the reduction in melon yields was less when grown with maize in widely spaced rows. Maize intercropped with melon in alternate pairs of rows (2:2) gave the best land equivalent ratio (LER).

This paper addresses the preservation and use of minor root crop genetic resources, mostly aroids and yams. Conservation is fraught with difficulty: ex situ collections are expensive to maintain and methods for on-farm conservation have not been studied. Conventional breeding strategies present serious limitations when applied to these species. Furthermore, the evaluation and distribution of improved material are as problematical as its conservation. The similarities shared by these species regarding their domestication, breeding constraints and improvement strategies as well as farmers' needs, are briefly reviewed. Based on these biological constraints, we propose a practical alternative to current conservation and breeding strategies. This approach focuses on the geographical distribution of allelic diversity rather than localized ex situ and/or in situ preservation of genotypes. The practical steps are described and discussed. First, a core sample representing the useful diversity of the species is assembled from accessions selected for their diverse and distant geographic origins, wide genetic distances, quality, agronomic performances and functional sexuality. Second, the geographical distribution of this core sample, in vitro via a transit centre, allows the direct use of selected genotypes by farmers or for breeding purposes. Third, the distribution of genes is realized in the form of clones resulting from segregating progenies and, fourth, farmers select clones with local adaptation.

Modern maize varieties have been bred for drought tolerance and early maturity, to assist farmers in avoiding or escaping the effects of moisture stress in drought-prone areas. This study evaluates the prospects for widespread adoption of these modern maize varieties as a climate change adaptation strategy for smallholder farmers. Data are from a detailed household survey completed in four rural villages in Southern Malawi between May and July 2010. The empirical analysis involves estimation of an ordered logit regression model because the dependent variable is categorical, with one category for nonadoption (has never grown modern maize varieties) and three categories for the duration of growing a modern maize variety among adopters (this year only, 2 to 5 years and 6 years or more). The empirical findings indicate a positive association between a farmer's perception of drought risk and the adoption and continued use of modern maize. Regression results also show that farmers that value the traits of early maturity and drought tolerance are more likely to adopt modern maize varieties. There is evidence of some disadoption among farmers dissatisfied with maize genotype performance, in terms of poor storability and yield under drought conditions. Finally, the study highlights the urgent need for maize breeders interested in sustained use of modern varieties to simultaneously address robust drought tolerance, early maturity and storability. This underscores the importance of cognizance of local farmer preferences in crop breeding efforts.

The yields of eight grass species, Axonopus compressus, Brachiaria decumbens, B. humidicola, B. miliiformis, Dicanthium caricosum, Ischaemum aristatum, Paspalum conjugatum and Stenotaphrum secundatum, were compared at five sites under different coconut densities giving variations in shade. Light transmission (LT) values were approximimately 100 (adjacent open area), 70, 50, 40 and 20% of full sunlight. Soils were fertile, red-brown clays developed on uplifted coral limestone (typic arguidoll), with marginal K status. Brachiaria spp. yielded most in full sunlight, with B. decumbens giving 28 t ha−1 year−1. I. aristatum was less sensitive to shade than the Brachiaria spp., at least down to 40% LT. S. secundatum, although poor yielding at 100 and 70% LT, gave the best yield of all species at 20% LT. Shaded plants had thinner leaves and larger nitrogen concentrations than unshaded ones. B. decumbens and B. humidicola are recommended for open plantations (LT > 70%), I. aristatum for moderate shade (LT 45–70%) and S. secundatum for deeper shade (30–50%) on poor fertility soils.

Concentration of tea yields in Malawi into regular successive peaks within the main growing season is the cause of severe economic problems. A model of the causes of these peaks has been developed and its explanatory power is confirmed in the light of empirical tests of its component parts and predictions. A computer version of the model is presented and its predictive power demonstrated. Use of the model to explore relations between weather and yields is discussed, with indications of its limitations for this purpose.

Intended to test broad hypotheses and arrive at unifying conclusions, meta-analysis is the process of extracting, assembling, and analyzing large quantities of data from multiple publications to increase statistical power and uncover explanatory patterns. This paper describes the ways in which meta-analysis has been applied to support claims and counter-claims regarding two topics widely debated in agricultural research, namely organic agriculture (OA) and conservation agriculture (CA). We describe the origins of debate for each topic and assess prominent meta-analyses considering data-selection criteria, research question framing, and the interpretation and extrapolation of meta-analytical results. Meta-analyses of OA and CA are also examined in the context of the political economy of development-oriented agricultural research. Does size matter? We suggest that it does, although somewhat ironically. While meta-analysis aims to pool all relevant studies and generate comprehensive databases from which broad insights can be drawn, our case studies suggest that the organization of many meta-analyses may affect the generalizability and usefulness of research results. The politicized nature of debates over OA and CA also appear to affect the divergent ways in which meta-analytical results may be interpreted and extrapolated in struggles over the legitimacy of both practices. Rather than resolving scientific contestation, these factors appear to contribute to the ongoing debate. Meta-analysis is nonetheless becoming increasingly popular with agricultural researchers attracted by the power for the statistical inference offered by large datasets. This paper consequently offers three suggestions for how scientists and readers of scientific literature can more carefully evaluate meta-analyses. First, the ways in which papers and data are collected should be critically assessed. Second, the justification of research questions, framing of farming systems, and the scales at which research results are extrapolated and discussed should be carefully evaluated. Third, when applied to strongly politicized topics situated in an arena of scientific debate, as is the case with OA and CA, more conservative interpretations of meta-analytical results that recognize the socially and politically embedded nature of agricultural research is are needed.

Most commonly, on-farm research has sought to validate and demonstrate technologies developed under controlled experimental conditions. It is argued here that on-farm research has a role in all stages of technology development, and that methodologies and objectives transplanted from the research station are inappropriate, particularly given the restrictions they impose on farmers' capacity to experiment with new technology. Drawing on experience with alley farming in W. Africa, it is shown how the farm and farm family can be incorporated fully throughout the process of technology development. The example is used to clarify the role of researchers in participatory technology development.

A long-term field experiment was conducted at the Qu-Zhou experimental station, China Agricultural University to study how the nematode community structure was influenced by compost and chemical fertilizer, using no amendment as the control. Soil samples were collected from 0–10 cm and 10–20 cm depths. The different treatments led to a significant difference in the total number of nematodes, bacterivores, plant parasites, omnivores-predators and nematode richness. The total number of nematodes, bacterivores, omnivores-predators and nematode richness were found to decrease in chemical fertilizer-treated plots. Although plant parasites were more abundant under compost treatment than under chemical fertilization, the relative abundance of plant parasites in the compost-treated plots was smaller. The application of chemical fertilizer decreased the number of genera of bacterivores and omnivores-predators. The numbers of total nematodes, bacterivores, plant parasites and omnivores-predators were significantly positively correlated with the contents of total organic carbon, total N, alkali-hydrolysable N, available P and available K. The compost-treated plots tended to have a greater diversity of nematodes than chemical fertilizer treated plots, so there was a healthy soil ecosystem under compost treatment.

Six genotypes of cowpea (Vigna unguiculata) of diverse origin were sown on various dates at five locations in Australia in order to provide a range of photothermal environments. Times from sowing to first flowering (f) ranged between 36 d and 145 d; pre-flowering temperature and photoperiod means varied from 15.7° to 29.2°C and from 11.6 to 15.5 h d−1. In five genotypes there was no effect of photoperiod on rate of progress towards flowering (1/f), but the relation between 1/f and mean temperature was always positive. The base temperatures (at which 1/f = 0) varied between 8.1° and 10.4°C. The rankings of parameter estimates among four photoperiod-insensitive genotypes common to this study and earlier research in controlled environments were almost identical, and there was generally good agreement between field observations and predictions from controlled environments once hourly temperatures were used to describe the natural environment. When cowpea plants were exposed to temperatures below 3°C, flowering was delayed beyond expected values, presumably as a result of chilling damage. In one genotype, rate of progress towards flowering was affected by both temperature and photoperiod, and relations between 1/f and the photothermal environment were described by a two-plane linear model of similar form to that determined in an earlier controlled environment study. These latest findings support the utility of such linear models for the prediction of crop phenology in the field and for the genetic characterization of photothermal flowering response in annual crops.