The residual effects of three years' mulch application and the associated erosion processes, such as soil loss or deposition, on pearl millet (Pennisetum glaucum) growth have been investigated on a Sahelian sandy soil in field and pot studies. The smallest millet yields were found on unmulched eroded plots despite mineral phosphorus (P) applications, whereas stover mulching or manure and urine consistently resulted in larger yields. Bioassays revealed that aluminium (Al) by itself was not growth-limiting. Neither nematodes nor lack of micronutrients contributed to the small millet yields. On soil from eroded plots, millet dry matter yield tripled after P addition, and increased by a factor of 13.5 when additional nitrogen (N) was applied. High P availability was found to be the key to reversing decline in yields on erosion-affected fields, but the addition of organic material is a prerequisite to prevent acidification. Manure was more effective than straw because of the large amounts of N and P it contained. The addition of small quantities of lime (CaCO3) may partly compensate for organic matter addition by increasing soil pH and reducing P fixation. P-Bray was not a suitable indicator of plant available P on degraded sandy acid soils.

Information on the influence of date of planting on protein, oil and fatty acid composition of soybean seeds is meagre, whilst similar studies on lipoxygenase isozymes and trypsin inhibitor contents are lacking. A field experiment was conducted with nine Indian genotypes and three planting dates (spread over 23 days) to study the influence of planting dates on these seed traits. Results based upon a one-year study indicated that oil content declined with delays in planting. Oleic acid content increased from the first to third planting, while the reverse trend was observed for linolenic acid. Lipoxygenase-1 activity was reduced by delayed plantings. Protein content was the lowest and trypsin inhibitor content was the highest for the second planting. However, no differences were observed for protein and trypsin inhibitor contents between the first and third planting. Significant interactions. observed between genotype and planting date for most of the seed compositional characters suggest that the influence of late planting is genotype-dependent.

The practice and management of subsurface drip irrigation (SDI) on heavy clay soils is poorly understood. Over-irrigation can lead to excessive runoff and drainage, with associated negative environmental consequences. Experiments were conducted in 2001/2002 and 2002/2003 on cotton (Gossypium hirsutum) in a Vertisol in Australia to evaluate the effect of SDI at various application rates on cotton yield and quality, and the results were compared with those for conventional furrow irrigation. Irrigating with SDI that supplied 50% or 75% of daily crop evapotranspiration (ETc) maintained a dry upper soil profile throughout the season. SDI at 50% ETc could potentially capture 250mm more rain during the season compared to SDI 90% ETc, and even more than furrow irrigation. However, supplying only 50% ETc with SDI hastened the maturity of the crop by on average 25 days compared with furrow irrigation and higher SDI rates, fewer bolls were set and yields were lower than in the other treatments. Nevertheless, a shorter season, if yield sacrifice is acceptable, favours logistics when integrating winter crops with summer cotton. It also reduces the number and cost of pesticide sprays and irrigation. Yield plateaued when 75% or more of daily ETc was supplied by SDI. The two drier treatments (SDI at 50% and 75% of ETc) had consistently higher water use efficiencies (WUE) for lint production compared with those of the two wetter SDI treatments (SDI at 90% and 105/120% ETc). All SDI treatments were also more efficient in the first year in the use of water for lint production than was furrow irrigation, but improved irrigation management in the form of faster irrigation and reduction of tail water in the second year obviated the advantage of SDI. Irrigation of cotton with SDI at 75% ETc offered significant benefits in terms of saved irrigation water over wetter SDI treatments, resulted in the highest average WUE for lint production over the two years, and reduced drainage and runoff compared with higher SDI rates and furrow irrigation.

Asynchrony between nitrogen (N) released by organic materials and N demand by the crop leads to low N use efficiency. Optimizing the time of application could increase the N recovery. A field experiment was designed to determine the effects of time of application of Gliricidia sepium prunings and of the addition of small doses of inorganic N fertilizer on N recovery and yield of maize. Six split applications of gliricidia prunings (in October, December and February) were compared. The prunings were incorporated into the soil while fresh. The application in October was done four weeks before planting the maize. Higher N uptake and maize yields were obtained when gliricidia prunings were applied in October than when applied in December and February. The corresponding substitution values were 0.66, 0.32 and 0.20. Split applications of prunings prolonged mineral N availability in the soil until March but did not increase N uptake and maize grain yield compared to a sole application in October. Combinations of gliricidia prunings and inorganic fertilizer increased N uptake and maize yield over prunings alone but the effect was only additive. We concluded that application of gliricidia prunings in October was more efficient than application in December and February.

The response of germination and early seedling growth to levels of salinity (0, 50, 100, 150, 200 and 250 mM NaCl) were examined in single seed lots of ten modern rice genotypes. Unaged and deteriorated rice seeds were germinated in rolled paper towels and in Petri dishes. Initial seed quality, final germination, germination rate and early seedling growth were assessed. The samples of the rice genotypes differed in their initial seed quality (measured in terms of Ki). The effect of deterioration varied depending upon the initial seed quality and the severity of the treatment imposed. Ageing (using the technique of controlled deterioration, CD) for up to 24 h had no effect on final germination levels. Although CD for 30 h only reduced final germination slightly, ageing for 36 or 48 h reduced it greatly. Controlled deterioration for 36 h or longer reduced the final length and the rate of extension of both the plumule and radicle. Combining information about germination in salt solution with that about seed quality enabled a distinction to be made between varieties which performed poorly because they were genetically salt-susceptible from those which germinated poorly due to poor seed quality. It is argued that the seed vigour of seed lots used in genotype evaluation should be assessed in order to avoid discarding potentially useful genotypes because of poor physiological seed quality.

Many public-sector breeding programmes do not use explicit techniques to orient their programmes close to their clients' needs. Participatory techniques can be used to achieve high client orientation but these techniques do not have to involve farmers making selections during the segregating generations. This particularly applies when a sound initial market survey has been made or the learning from a participatory varietal selection (PVS) programme provides feedback to scientists. However, some published results on selection by farmers in the segregating generations (collaborative selection) indicate that it can produce appropriate varieties more effectively than less collaborative research. There is also evidence, from the few cases reported in the literature, that it is cost-effective. Alternative, less collaborative, approaches are also effective. Consultative forms of farmer participation, i.e. where farmers evaluate material grown by scientists, to aid selection in the segregating generations are more widely applicable because they demand fewer resources than collaborative methods. For more time-consuming tasks, such as in the selection of aromatic rice in segregating material, the most appropriate from of participation is contractual i.e., farmers are paid for their work. Mainly using examples from our research in Nepal, we present the particular circumstances in which the involvement of farmers in selection in the segregating generations is desirable or essential. These include: the occurrence of market failure (where the usual mechanisms of supply and demand have failed so there is no incentive to breed new varieties) and supply can only be met by actively involving farmers in the breeding process; when there are cost advantages to involving farmers – this is determined by the particular resources available to the institute undertaking the plant breeding research; when grain quality is both important and determined by a complex set of factors that are difficult to measure in the laboratory; when the objective is to learn in more detail about farmers' selection criteria to better orient the breeding programme to client needs; and when the goal is to empower farmers.

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 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.