Long-term indicators of soil fertility were assessed by measuring grain yield, soil organic carbon (SOC) and soil Olsen phosphorous for a P-deficient soil. In one set of treatments, goat manure was applied annually for 13 years at 0, 5 and 10 t ha−1, and intercrops of sorghum/cowpea, millet/green gram and maize/pigeonpea were grown. Yield depended on rainfall and trends with time were not identifiable. Manure caused an upward trend in SOC, but 10 t ha−1 manure did not give significantly more SOC than 5 t ha−1. Only 10 t ha−1 manure increased Olsen P. Measurements of both SOC and Olsen P are recommended. In another set of treatments, manure was applied for four years; the residual effect lasted another seven to eight years when assessed by yield, SOC and Olsen P. Treatment with mineral fertilizers provided the same rates of N and P as 5 t ha−1 manure and yields from manure and fertilizer were similar. Fertilizer increased Olsen P but not SOC. Management systems with occasional manure application and intermediate fertilizer applications should be assessed. Inputs and offtakes of C, N and P were measured for three years. Approximately 16, 25 and 11% of C, N and P respectively were stabilized into soil organic matter from 5 t ha−1 a−1 manure. The majority of organic P was fixed as soil inorganic P.

A maize-breeding programme was targeted at resource-poor farmers of eastern India using a client-oriented approach (often called participatory plant breeding). Farmers tested a range of varieties in a participatory varietal selection programme but none proved to be very popular. Information from these trials was used in a breeding programme to develop a broadly-based population from three yellow- and three white-grained maize varieties that were either identified in the trials or had traits liked by farmers. The population was subjected to several cycles of random mating. In the C3, C4 and C6 cycles, subpopulations were extracted and subjected to mass selection over several generations in environments that represented well the target population of environments of resource-poor farmers' fields in eastern India for traits identified by farmers. To identify better the required traits, in some generations the selection was carried out by farmers on a research farm under fertility levels that approximated farmers' practice. The improvement of the subpopulations resulted in several varieties that performed well in research station and on-farm trials. One of them, BVM 2, was released in Jharkhand state, India. In multilocational research station trials, it yielded more than the control variety BM 1 but silked earlier. In the less favourable environments of on-farm trials, its yield superiority, in percentage terms, was higher. Farmers perceived BVM 2 to have better grain quality and stover yield than the local varieties. BVM 2 was specifically bred to meet the needs of the clients (resource-poor farmers with no access to irrigation) and has earlier maturity combined with higher grain yield. The returns were higher from this highly client-oriented approach, than by classical breeding, mainly because uptake was faster as a result of research and extension being done in tandem.

Soil deficiencies of zinc (Zn) and boron (B) limit crop production in Nepal. Improving the micronutrient status of plants would increase yield and increase micronutrient content of the seeds, leading to better nutrition of the progeny crop and to improved human micronutrient nutrition. The primary micronutrient problem in grain legumes is B deficiency, while in rice (Oryza sativa), Zn deficiency is more important, and wheat (Triticum aestivum) suffers from both deficiencies. A series of field experiments was carried out over two seasons to compare soil fertilization and micronutrient seed priming as methods of improving Zn and B nutrition of each crop. Micronutrient treatments were evaluated for their effect on grain yield and grain micronutrient content. Soil B fertilization increased B content of the grain of lentil (Lens culinaris), chickpea (Cicer arietinum), and wheat by a factor of two to five, while increasing the yield of chickpea only. Soil fertilization with Zn had no effect on yield of any crop, but resulted in a small increase in Zn in wheat grain. Sowing micronutrient-primed seeds had no effect on yield or micronutrient content of the progeny seeds in most cases. During the first season, the primed chickpea seeds failed to emerge at either site, causing complete yield loss, but this negative effect was not observed in the second season with similar priming treatments at nearby sites, and no effect of priming on yield was observed with any other crop in either season.

Organic coffee is one of several types of speciality coffees selling at a premium over mainstream coffees because of distinct origin and flavour, environment-friendly production or socio-economic concerns for the smallholder coffee growers. The demand for organic coffee in Western Europe, North America and Japan exceeds the present supply, which is still small (<1% of annual world production). More than 85% of organic coffees come from Latin America and practically all is (washed) arabica coffee. The production of certified organic coffee follows the principles of organic farming developed in Europe and the United States out of concern for the perceived negative effects of conventional high-input agriculture on health and environment. It claims superior ecological sustainability in combination with sound economic viability. A rather complex and expensive system of certification has to be passed before such coffees can be sold as truly organic. Growers adhering to the strict rules of organic coffee production may to some extent share the concern of the health- and environment-conscious consumers, but they are motivated primarily by the economic benefits from the premium received for certified organic coffee. Nevertheless, there appears to be considerable injustice between the extreme preconditions demanded for ‘organics’ by the largely urban consumer of the industrialized world and the modest rewards received by the organic coffee growers for their strenuous efforts. From an agronomic point of view, there is also considerable ground for criticism on the principles of organic farming when applied to coffee. For instance, to sustain economically viable yield levels (1 t green coffee ha−1 year−1) large additional amounts of composted organic matter will have to come from external sources to meet nutrient requirements (especially N and K). Most smallholders will be unable to acquire such quantities and have to face declining yields. Organic farming does not necessarily reduce incidence of diseases and pests below economically harmful thresholds, while the humid conditions of heavily shaded coffee may actually stimulate the outbreak of others. These and other aspects peculiar to the preconditions of organic coffee production are addressed in this review. It is concluded that the concept of organic farming in its strict sense, when applied to coffee, is not sustainable and also not serving the interests of the producer and consumer as much as the proponents would like us to believe. On the other hand, agronomically and economically sustainable coffee production is feasible by applying best practices of crop production and post-harvest processing.

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.

This paper documents the yield gains attributable to the breeding and distribution of new cocoa varieties in Ghana, using data from a 2002 survey of 192 fields in the country's key cocoa producing regions. We find that planting the more recently-released varieties is associated with at least 42% higher yields, and that genetic improvement accounts for much but not all of the observed correlation between tree age and cocoa yield. Fertilizer use is also very important, being associated with 19% higher cocoa yield per 50 kg bag of fertilizer. We find no evidence that varieties differ in their response to fertilizer, pesticide use or labour, and no evidence of a decline in the yield advantage of new varieties over the 17-year age span observed in the sample.