The lack of good quality planting material of farmers' cassava varieties, produced locally and at low cost, is a major constraint limiting the expansion of cassava production in Colombia. This article describes the adaptation of conventional cassava propagation to a low-input scheme for rural tissue-culture multiplication, developed and run by small, resource-poor farmers (referred in this article as an informalfarmers' seed production system). Developed through a two-phase participatory process by a group of women farmers, a non-governmental organization and International Center for Tropical Agriculture scientists in a farmers' community in the hillsides of southern Colombia, the project resulted in alternative, economical and readily available sources of tissue-culture material and equipment. Rates of multiplication achieved with the system were as high as with conventional tissue-culture procedures.

In maximizing productivity levels in oilseed sesame (Sesamum indicum) one of the major constraints is the large-scale shedding of buds, flowers and capsules. The present study examines the reproductive behaviour of five sesame genotypes with a view to ascertaining the extent of production, shedding and retention of different reproductive organs. Sesame genotypes produce 250–350 flower buds per plant but shed most of them at different stages of development. Shedding is thus excessive, and 86–91% of the reproductive potential was not realized in this study, thus limiting yield. Improvement in yield through increased fruit retention is essential.

Seed yield in two soyabean varieties—one tall (Improved Pelican) and one short (V/1)—was mainly determined by the total number of main stem and branch pods produced when plant population density varied from 5·4 to 16·2 plants/m2. An increasing percentage of the pods was found on the main stems of Improved Pelican as the crop stand became denser.

Under rainfed conditions in north west India, intercropping with soyabean, peanut, greengram and clusterbean reduced sunflower yields by 25–50%. The number of pods per plant and grain yield of the leguminous intercrops were also reduced. The maximum LER (1.05) was obtained from the sunflower–greengram mixture. Intercropping increased the protein percentage of the sunflower but decreased that of the companion legumes. It had no effect on percentage oil content of sunflower.

The study of livestock in farming systems research presents several challenges. Factors such as the small number of observations, high statistical variability in measurements, and the difficulty in valuing non-market inputs and outputs make it difficult to evaluate on-farm research. Regular Research Field Hearings (RRFH) can improve communication between scientists and farmers, thereby increasing mutual understanding, willingness to collaborate in evaluation, potential technologies, and also improving test results. Of three groups of sheep and goat farmers involved in on-farm testing in northeast Brazil, the group which participated in RRFH experienced a significantly higher level of success with the technology as measured according to performance criteria such as weight gains and farmers' perceptions of their animals' performance. The results confirm the importance of farmers' participation in agricultural research.

The Sudanese local onion cultivar Wad Ramli has a markedly long rest period (60 days) and a long dormant period of up to six months. It has high dry matter (16 per cent), high soluble solids (15 per cent) and strong pungency, factors which contribute to its good storability under conditions that are usually adverse for good storage.

Biophysical and socio-economic variability have several impacts on farmers' cropping strategies in dryland areas of Africa. This study examines data from a communal area in southern Zimbabwe over a seven year period. Variation in the output of different crops, in the pattern of crop mixes, in the diversity of cropping patterns and the level of crop sales is explored. Through contrasts between ecological zones and household wealth status, the analysis helps to explain the range of farm-level risk management strategies employed. Finally, the importance for research and extension approaches of understanding variability, through a differentiated analysis of cropping strategies, is emphasized.

Dry matter and tuber yields of potato grown in a sub-tropical environment were estimated employing simple radiation-based models which require meteorological information on air temperature and solar radiation. Two versions of the MacKerron and Waister (1985) model, in which estimation of dry matter accumulation relies on a single composite parameter, radiation use efficiency (RUE), were compared with the Versteeg and Van Keulen (1986) model, which explicitly accounts for temperature and radiation effects on dry matter accumulation. In the original version of the MacKerron and Waister model, a linear change in the radiation interception factor with leaf area index is assumed; in the modified version an exponential change in the interception factor with leaf area index is considered. The accumulation of dry matter estimated from all three models was close to the measured values throughout the growing season, but estimates of tuber yield differed widely. Our analysis showed that the best agreement with measured values was obtained using the MacKerron and Waister linear model with RUE values adjusted according to the incident radiation level.

Estimatión del rendimiento del tubérculo de la patata

Consider a field experiment laid out in a randomized complete block design in which you study three types of fertilizers for two winter wheat cultivars. One year, one location – the experiment is not repeated. You design it and then spend a lot of time and money to conduct it. You cultivate the soil and take care of the plants; you worry about them; you never know what can happen, so you cannot wait for the crop to be harvested. And that day finally comes. The crop is harvested, and everything is fine. And here you are, all went great, you have the data in hands, and now a simple thing to do – analyse them. Well, yes, the experiment was conducted in one year, and you are aware you cannot be sure the outcome would be the same next year or elsewhere, but whatever – suffice it to consider the conclusions as preliminary and get on with the interpretation. Why should you not? It was a properly designed experiment that took samples from the underlying infinite populations of the two winter wheat cultivars in the three water regimes studied. Statistics is here to help you out, is not it? Well, it is not. Statistics will not help you out whether the experiment was poorly designed. Agricultural science literature seldom explains what populations are studied and what types of samples are taken in designed experiments. To fill this gap, we discuss various aspects of the sampling process in designed experiments. In doing so, we look at the survey sampling methodology, a statistical framework for studying finite populations – we do this because survey sampling has developed into the advanced theory of sampling processes, and this background can help us understand the intrinsic aspects of sampling in designed experiments.

Crop rotations under no-till (NT) have been a strategy to increase soil organic carbon (SOC) and mitigate greenhouse gas (GHG) emissions, enhancing the cropping system efficiency. However, there is still controversy on the role of grasses and legumes, and species diversity and their impacts. This study aimed to assess the GHG emissions, SOC, and Nitrogen (TN) in a soybean production system managed under NT in rotation with different species in the fall–winter and the spring seasons. Main plots during the fall–winter were (1) Triticale (x Triticosecale) and (2) Sunflower (Helianthus annuus). Subplots established in the spring were (a) Sunn hemp (Crotalaria juncea), (b) Sorghum (Sorghum bicolor), (c) Pearl millet (Pennisetum glaucum), plus a (d) Fallow treatment. Soybean was grown every year in the summer, in sub-subplots. The GHG emission was affected according to crop species. In the spring, Sunn hemp emitted more nitrous oxide (N2O) (0.82 kg ha−1) than fallow (0.58 kg ha−1); however, the high C and N inputs by the legume and also other cover crop residues reduced the relative emissions compared with fallow. Growing pearl millet or Sunn hemp as a spring cover crop increases SOC by 7% on average compared with fallow. The N2O emission of Sunn hemp accounted for only 0.28% of the total N accumulated in the legume residues, notably lower than IPCC estimates. In the fall–winter, Triticale increased SOC by 7%, decreased CO2 emission by 18%, and emitted 20% lower GHG to produce the same soybean yield compared with sunflower. Soybean rotation with triticale in fall–winter and Sunn hemp or pearl millet in spring decreases GHG emissions. Our results indicate that the right choice of species in rotation with soybean under NT increases SOC and may offset GHG emissions from tropical soils. It may be an important tool in mitigating potential global warming.

Laboratory experiments and field tests were used to study the effects of seven anti-microbial agents and a trace element salt mixture (TEM) on the decay of cut pieces of seed potatoes. The effect of a mixture of gibberellic acid and ethrel (GA + E), TEM, and TEM with GA + E on the sprouting behaviour and yield of tubers was also studied. All the anti-microbial agents inhibited decay, although TEM and oxine were superior to other treatments. There was an increase in crop yield when seed tubers were treated with TEM. In laboratory tests, the GA + E mixture and TEM were effective in breaking dormancy.

An on-farm field experiment was conducted in northeastern Thailand to assess the effects of different eucalyptus biochar (BC) application rates, in combination with mineral fertilizers, on upland rice and a succeeding crop of sugarcane on sandy soil. Soil mineral N and greenhouse gas emissions were also evaluated. The field experiment consisted of three treatments: no biochar (BC0), 3.1 Mg ha−1 of biochar (BC1), and 6.2 Mg ha−1 of biochar (BC2). All treatments received the same recommended fertilizer rate. Soil mineral N, and emissions of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) were monitored after BC application. The results revealed that the BC2 treatment caused lower soil mineral N content than that of the BC0 treatment during the upland rice period. During the sugarcane period, the BC2 treatment induced a greater soil mineral N content than the BC1 treatment but had no significant difference from the BC0 treatment. The BC2 treatment resulted in significantly lower cumulative CH4 and N2O emissions than the BC0 treatment during the upland rice period. In conclusion, we found that the BC2 treatment alleviated the global warming potential from CH4 and N2O emissions throughout the experiment, causing slight changes in soil N availability in the upland rice–sugarcane cropping system.

Prolonged inability of yam tubers to sprout/germinate is associated with the expression of tuber dormancy, and the start of dormancy in tubers is linked to the onset of tuber formation. Although the plant hormone, abscisic acid (ABA) is known to regulate the onset and maintenance of dormancy in tubers, there are no known method(s) of inducing shoot growth (sprouting) on seed yam tubers that are harvested at 240 days after vine emergence or earlier. Therefore, this study was conducted to: (1) determine whether the absorption of fluridone, a reputed ABA inhibitor, prior to or during early seed yam tuber formation would induce sprouting, and (2) determine the effect of fluridone on early shoot growth. The study was a 2×4 factorial experiment arranged in a Completely Randomized Design (CRD) with eight treatment combinations replicated three times. Two species of yam with long dormancy durations were used: D. rotundata var TDr 131 and D. alata var TDa 98/01166; and three concentrations of fluridone were tested (30, 50, 100 µM). Young plants (69 days after vine emergence) of TDr 131 and TDa 98/01166 were grown in a coco coir medium hydroponics system using Hoagland's Nutrient Solution, with or without the test fluridone concentrations. In all fluridone treatments, most leaves of both species of yam had 30–90% of their surface bleached while the stems appeared purplish. In both Controls, all the newly formed seed tubers that were harvested at 90 and 104 days after vine emergence were dormant (devoid of any new shoots/sprouts). In contrast, over 70% of the seed tubers that developed in 30 and 100 µM fluridone had at least one new shoot, particularly in TDa 98/01166. The fluridone treatments did not significantly affect tuber weight or vegetative growth parameters like dimensions and number of leaves. This study has shown that the duration from vine emergence of the old tuber to sprouting of the new tuber can be reduced by more than half if young plants absorbed fluridone during early tuber development.

The paper describes value chain actors and institutional arrangements along value chains, and identifies major determinants of farmers’ decision making to work with middlemen/traders ‘jabbans’ (or cheese makers), and based on those identify short implications for research, development and policy processes. We hypothesize that small-scale sheep producers are more dependent on middlemen for market and loans than larger holders, leading to welfare losses. Our empirical findings based on a Heckman model applied for 120 farming households conducted in Khanasser region (Syria) show that despite unequal benefits, local arrangements are more blessing than curse for the poor. Small-scale sheep producers and middlemen developed intricate institutional arrangements that are mutually beneficial. Producers act collectively to pool sufficient quantity of milk to be attractive to traders (jabban) while gaining access to market and cash loans mainly for feed. This provides the middlemen needed supplies with reduced transaction costs. This suggests that development organizations should support local capacity of producing organizations to work together, small-scale producers to organize, develop small scale dairy processing workshops for pooling and possibly processing milk, support training for direct market access and facilitate access to loans. Finally, supporting organizations such as rural financial services and micro-finance need to ensure up-to-date market information is available to ensure fair prices are paid. They should also be able to negotiate favourable conditions for loans and reach out to these resource-poor rural populations where formal credit systems are absent.

Integrating farmers’ preferences into the breeding and dissemination of new genotypes is a effective approach to enhance their successful adoption by farmers. In the case of sweet potato, a staple crop in many parts of West Africa, there is a need for more research on the selection criteria used by farmers when choosing which varieties to grow. This study aims to highlight farmers’ selection criteria for sweet potato varieties in the main production areas in Benin. A total of 480 farmers from the top three sweet potato production areas were surveyed. The relative importance of various traits for sweet potato farmers was evaluated using best-worst scaling methods. Latent class analysis was applied to find groups of farmers with similar preferences. Best-Worst Scaling analysis revealed that high root yield, root size, marketability, and early maturing were the most important variety selection criteria. Latent class analysis revealed three farmers’ groups referred to as ‘Yield potential’, ‘Market value’, and ‘Plant resilience’ classes. ‘Yield potential’ farmers were more likely to be from Atlantique and Alibori departments; they significantly committed more acreage to sweet potato production. The ‘Market value’ farmers highlighted the variety of root size and commercial value as the main selection criteria and consisted of farmers with primary education levels from the Ouémé department. ‘Plant resilience’ refers to a group of Alibori farmers who prioritize environmental issues and primarily grow sweet potatoes for self-consumption. Our findings shed light on farmers’ preferences and suggested that heterogeneity in sweet potato selection criteria was highly influenced by various socio-economic factors and location.

When the agricultural value chain involves profit making, it results in changes in the production and distribution relationships among men and women in terms of access to and control of markets, resources and benefits emanating from product value chain participation. This affects not only individual incomes but also gender equality. This study examined gender relationships in the cassava value chain in the Kigoma region of Tanzania. The aim was to assess gender participation in the cassava value chain. Multi-stage sampling was used to select the respondents in four districts. A structured questionnaire was administered to 384 randomly selected household heads. A chi-square test was used to test for significant relationships among the variables. Results indicated that gender was significantly related to socio-economic characteristics. About 34% of the women participating in the cassava value chain were young, some below 17 years of age. There were significant relationships between gender and access to resources (land, extension services and markets), control over resources (land, house and household assets) and benefits (revenue) generated from cassava value chains. Overall, there was gender disparity in participation along the cassava value chain. These results suggest that any intervention in the cassava value chain should consider gender relations to benefit men and women and alleviate household poverty.

A field study was conducted on vertisols to determine the effect of three watering regimes and two plant densities on growth and yield of groundnuts. Total water requirements ranged from 486 to 597 mm depending on treatments. Three quarters of the water depletion was from the upper 20–30 cm. Plants in the sparse population were more sensitive to water stress so that the watering interval could be lengthened in the dense population without seriously reducing yield.

A study was conducted in Suba area, central highlands of Ethiopia, to assess the net return, land and labour productivity, and the return to scale of cereal farming practice. Seventy-five farmers belonging to three local wealth classes (poor, medium and rich) were randomly selected and interviewed about inputs and outputs related to cereal farming for the production year 2007/2008. Farm soil properties were investigated to check the variability in soil quality among the wealth classes. Benefit:cost ratio (BCR), net returns and annual profit were used to indicate the worthiness of the cereal farming activity. The return to scale was estimated by using the Cobb–Douglas production function. The results show that cereal farming is a rewarding practice, with the rich households gaining more profit than the poor. Farm size was the most important variable that affects the net return. There is an increasing return to scale. However, it is unlikely that farmers will have more land than they own at present because of the land shortage problem in the country caused by the increasing human population. Thus, attention should be given to minimizing the costs of production through proper regulation of domestic fertilizer costs and increasing labour productivity especially for the poor and medium households. The use of manure and compost as an additional fertilizer should also be promoted.

Field experiments during the rainy seasons (July–October) of 1984 and 1985 at Hisar, India showed that removing weeds in pearl millet from 10 to 60 days after sowing led to fewer weeds at harvest, and significantly higher grain yields were obtained when weeds were removed 20 days after the crop was sown. All the weed control methods tried (hand hoeing, hand wheel hoeing, or application of terbutryne or atrazine) were successful and significantly increased crop growth and grain yield. The maximum grain yield was obtained with atrazine at 0.5 kg ha−1 and the minimum in the unweeded control.

The on-farm performance of more than 150 000 pre-basic potato (Solanum tuberosum) minitubers of 1–10 g was monitored over two years in contrasting environments in Nepal. Average minituber productivity (grams of basic seed produced per minituber planted) was 171 g in the southern plains and 116 g in the hills. Although the performance of minitubers varied between environments, minituber sizes and potato varieties, the overall results clearly indicated that minitubers can be successfully multiplied by small-scale farmers. This technology therefore allows for the highly decentralized production of basic seed which, in turn, will reduce farmers' dependence on an unreliable and costly supply of bulky conventional seed.