The results of research on the water relations and irrigation needs of sugar cane are collated and summarized in an attempt to link fundamental studies on crop physiology to irrigation practices. Background information on the centres of production of sugar cane is followed by reviews of (1) crop development, including roots; (2) plant water relations; (3) crop water requirements; (4) water productivity; (5) irrigation systems and (6) irrigation scheduling. The majority of the recent research published in the international literature has been conducted in Australia and southern Africa. Leaf/stem extension is a more sensitive indicator of the onset of water stress than stomatal conductance or photosynthesis. Possible mechanisms by which cultivars differ in their responses to drought have been described. Roots extend in depth at rates of 5–18 mm d−1 reaching maximum depths of > 4 m in ca. 300 d providing there are no physical restrictions. The Penman-Monteith equation and the USWB Class A pan both give good estimates of reference crop evapotranspiration (ETo). The corresponding values for the crop coefficient (Kc) are 0.4 (initial stage), 1.25 (peak season) and 0.75 (drying off phase). On an annual basis, the total water-use (ETc) is in the range 1100–1800 mm, with peak daily rates of 6–15 mm d−1. There is a linear relationship between cane/sucrose yields and actual evapotranspiration (ETc) over the season, with slopes of about 100 (cane) and 13 (sugar) kg (ha mm)−1 (but variable). Water stress during tillering need not result in a loss in yield because of compensatory growth on re-watering. Water can be withheld prior to harvest for periods of time up to the equivalent of twice the depth of available water in the root zone. As alternatives to traditional furrow irrigation, drag-line sprinklers and centre pivots have several advantages, such as allowing the application of small quantities of water at frequent intervals. Drip irrigation should only be contemplated when there are well-organized management systems in place. Methods for scheduling irrigation are summarized and the reasons for their limited uptake considered. In conclusion, the ‘drivers for change’, including the need for improved environmental protection, influencing technology choice if irrigated sugar cane production is to be sustainable are summarized.

The results of research on the water relations and irrigation needs of coconut are collated and summarized in an attempt to link fundamental studies on crop physiology to drought mitigation and irrigation practices. Background information on the centres of origin and production of coconut and on crop development processes is followed by reviews of plant water relations, crop water use and water productivity, including drought mitigation. The majority of the recent research published in the international literature has been conducted in Brazil, Kerala (South India) and Sri Lanka, and by CIRAD (France) in association with local research organizations in a number of countries, including the Ivory Coast. The unique vegetative structure of the palm (stem and leaves) together with the long interval between flower initiation and the harvesting of the mature fruit (44 months) mean that causal links between environmental factors (especially water) are difficult to establish. The stomata play an important role in controlling water loss, whilst the leaf water potential is a sensitive indicator of plant water status. Both stomatal conductance and leaf water potential are negatively correlated with the saturation deficit of the air. Although roots extend to depths >2 m and laterally >3 m, the density of roots is greatest in the top 0–1.0 m soil, and laterally within 1.0–1.5 m of the trunk. In general, dwarf cultivars are more susceptible to drought than tall ones. Methods of screening for drought tolerance based on physiological traits have been proposed. The best estimates of the actual water use (ETc) of mature palms indicate representative rates of about 3 mm d−1. Reported values for the crop coefficient (Kc) are variable but suggest that 0.7 is a reasonable estimate. Although the sensitivity of coconut to drought is well recognized, there is a limited amount of reliable data on actual yield responses to irrigation although annual yield increases (50%) of 20–40 nuts palm−1 (4–12 kg copra, cultivar dependent) have been reported. These are only realized in the third and subsequent years after the introduction of irrigation applied at a rate equivalent to about 2 mm d−1 (or 100 l palm−1 d−1) at intervals of up to one week. Irrigation increases female flower production and reduces premature nut fall. Basin irrigation, micro-sprinklers and drip irrigation are all suitable methods of applying water. Recommended methods of drought mitigation include the burial of husks in trenches adjacent to the plant, mulching and the application of common salt (chloride ions). An international approach to addressing the need for more information on water productivity is recommended.

Leaf gas exchange and leaf water potential (Ψleaf) were measured seasonally on non-grafted and grafted Coffea arabica on Coffea canephora in the field to investigate whether grafting would be able to protect the carbon balance against the rise of in vapour pressure deficit (VPD) and air temperature (Tair) under future climate change. The net maximum photosynthetic rate obtained from the net photosynthesis (PN) curve as a function of photosynthetic photon flux density (PPFD) in wet and dry periods was used to estimate the integrated potential diurnal net CO2 assimilation (IPPN) around midday. The difference between IPPN and the integrated values of PN during diurnal courses (IPN) was measured to test grafting as suitable practice for minimizing midday depression of PN. Higher values of PN in grafted plants around midday showed that grafting was important even when environmental conditions were favourable in field conditions. Reduced susceptibility of grafted plants to midday depression was revealed by lower values of Ψleaf associated with higher values of PN and leaf transpiration (E) on sunny days in summer and spring, and by higher values of stomatal conductance (gs) around midday in autumn, winter and spring. The differences of E, gs, PN and Ψleaf between non-grafted and grafted plants were higher in dry periods in winter and spring. In addition, the ratio IPN/IPPN in grafted was double that in non-grafted plants around midday in sunny summer and in spring. Indeed, PN and gs of non-grafted plants showed higher dependence on VPD than grafted ones. The lower susceptibility of grafted plants to water stress demonstrated the graft efficiency for increasing positive components of leaf carbon balance of C. arabica in the field, especially under high VPD in projected future climate conditions.

To assess genotype adaptability to variable environments, we evaluated five irrigated rice genotypes, three new varieties, WAS161, a NERICA, IR32307 and ITA344, and two controls: Sahel 108, the most popular short-duration variety in the region, and IR64. In a field experiment conducted at two locations, Ndiaye and Fanaye, along the Senegal River, rice was sown on 15 consecutive dates at one month intervals starting in February 2006. Yield (0–12.2 t ha−1) and crop cycle duration (117–190 days) varied with sowing date, genotype and site. Rice yield was very sensitive to sowing date and the associated temperature regimes. Spikelet sterility due to cold stress (T < 20 °C) was observed when the crops were sown in August (Ndiaye), September (Ndiaye and Fanaye) and October (Ndiaye and Fanaye), and heat stress (T > 35 °C) resulted in spikelet sterility when sowing took place in April (Ndiaye and Fanaye) and May (Fanaye). For all experiments the source and sink balance was quantified and showed that yield was most limited by sink size when sowing between July and October. Variety WAS 161 was least affected by genotype × environment interactions, resulting in lower interactive principal component values. An increase in minimum temperature of 3 °C could decrease spikelet sterility from 100 to 45%. These changes in temperature are likely to force rice farmers in the Senegal River to adjust the cropping calendar, e.g. to delay planting or to use heat-tolerant genotypes.

Over a decade after the forest-savanna transition zone of Nigeria was deemed suitable for production of sorghum (Sorghum bicolor), no research has been undertaken on the crop's tillage requirements in the southeastern part of the zone. This study evaluated the effects of tillage-mulch practices on soil moisture, water use (WU), grain yield and water use efficiency (WUE) of the crop in a Typic Paleustult (sandy loam) at Nsukka during 2006 and 2007 growing seasons. In a split-plot design, no-till (NT) and conventional tillage (CT) treatments were left bare (B) or covered with mulch (M) at 5 Mg ha−1. The ensuing treatments (NTB, NTM, CTB, and CTM) represented four tillage methods, which were replicated four times in a randomized complete block. In the monitored root zone, NTB and CTM significantly (p ≤ 0.05) enhanced the soil moisture status over NTM and CTB, but the main effects of the tillage and the mulch factors were not significant. The crop WU was uninfluenced by the treatments throughout the study. Although the grain yield showed higher values with NT than with CT, the differences were significant (p ≤ 0.05) only in 2007 that was marked with erratic rainfall and relatively low mean yield. Mulch significantly (p ≤ 0.05) enhanced the grain yield in 2006, with greater effect in CT than NT. On average, the mulch plots out-yielded their bare counterparts by about 26%. The tillage × mulch interaction was significant (p ≤ 0.01), and showed higher grain yields in NTB, NTM and CTM than in CTB. In the year-weighted average, yield increments in NTB, NTM and CTM over CTB were 53, 53 and 67% respectively, a pointer to the relevance of mulch with the CT but not the NT. Relative WU showed that the crop's water demand was met under all treatments. Hence, the yield reduction in the CTB was not due to water shortage. The WUE varied among the treatments in the same pattern as grain yield. In summary, NTB and CTM proved superior to NTM only in soil moisture status but to CTB in all measured parameters. From a socio-economic viewpoint, however, NTB would be preferable to CTM for growing sorghum in this area.

There are many reasons why agricultural researchers carefully evaluate approaches to experimental data analysis. Agricultural experiments are typically highly complex, with many types of variables often collected at a wide range of temporal and spatial scales. Furthermore, research in the developing world is often conducted on-farm where simple and conventional experimental designs are often unsuitable. Recently, a variant of stochastic dominance called stochastic efficiency with respect to a function (SERF) has been developed and used to analyse long-term experimental data. Unlike traditional stochastic dominance approaches, SERF uses the concept of certainty equivalents (CEs) to rank a set of risk-efficient alternatives instead of finding a subset of dominated alternatives. This study evaluates the efficacy of the SERF methodology for analysing conventional and conservation tillage systems using 14 years (1990–2003) of economic budget data collected from 36 experimental plots at the Iowa State University Northeast Research Station near Nashua, IA, USA. Specifically, the SERF approach is used to examine which of two different tillage systems (chisel plough and no-till) on continuous corn (Zea mays) and corn/soyabean (Glycine max) rotation cropping systems are the most risk-efficient in terms of maximizing economic profitability (gross margin and net return) by crop across a range of risk aversion preferences. In addition to the SERF analysis, we also conduct an economic analysis of the tillage system alternatives using mean-standard deviation and coefficient of variation for ranking purposes. Decision criteria analysis of the economic measures alone provided somewhat contradictive and non-conclusive rankings, e.g. examination of the decision criteria results for gross margin and net return showed that different tillage system alternatives were the highest ranked depending on the criterion and the cropping system (e.g. individual or rotation). SERF analysis results for the tillage systems were also dependent on the cropping system (individual, rotation or whole-farm combined) and economic outcome of interest (gross margin or net return) but only marginally on the level of risk aversion. For the individual cropping systems (continuous corn, rotation corn and rotation soyabean), the no-till tillage and rotation soyabean system was the most preferred and the chisel plough tillage and continuous corn system the least preferred across the entire range of risk aversion for both gross margin and net return. The no-till tillage system was preferred to the chisel plough tillage system when ranking within the continuous corn and the corn-soyabean rotation cropping systems for both gross margin and net return. Finally, when analysing the tillage system alternatives on a whole-farm basis (i.e. combined continuous corn and corn-soybean rotation), the no-till tillage system was clearly preferred to the chisel plough tillage system for both gross margin and net return. This study indicates that the SERF method appears to be a useful and easily understood tool to assist farm managers, experimental researchers and, potentially, policy makers and advisers on problems involving agricultural risk.

This paper analyses the organization of the rice seed sector in Guinea with the overall objectives to assess how organizational settings affect seed supply to small-scale farmers and to suggest institutional changes that would favour seed service and uptake of varieties. Data were collected in Guinea, West Africa, using focus group discussions with extension workers, farmers, representatives of farmers’ associations, agro-input dealers, researchers and non-governmental organization (NGO) staff, and surveys of 91 rice farming households and 41 local seed dealers. Findings suggest that the current institutional settings and perceptions of stakeholders from the formal seed sector inhibit smallholder farmers’ access to seed. Seed interventions in the past two decades have mainly relied on the national extension system, the research institute, NGOs, farmers’ associations and contract seed producers to ensure seed delivery. Although local seed dealers play a central role in providing seed to farmers, governmental organizations operating in a linear model of formal seed sector development have so far ignored their role. We discuss the need to find common ground and alternative models of seed sector development. In particular we suggest the involvement of local seed dealers in seed development activities to better link the formal and the informal seed systems and improve smallholder farmers’ access to seed from the formal sector.

Citrus clementine cv. ‘Nules’ is a seedless mandarin with excellent quality for consumption as fresh fruit; however, its poor fruit set leads to an excess of small-sized fruits. Currently, the only available practice to increase fruit set is the use of the growth regulator gibberellic acid (GA3) as a foliar spray. A trial was conducted to compare an environmentally friendly new bioregulator (MX), containing methyl-xanthine, to GA3 in terms of increasing fruit set and yield of clementine cv. Nules mandarin trees. Fruit yield was significantly increased in treated trees from 17.4 to 25.7% for GA3 and MX treatments, respectively, compared to untreated control trees, without any significant differences between the growth regulators. At the tested doses, MX performed similarly to GA3 in terms of fruit quality and nutrient content, while colour index was not affected significantly by this new bioregulator. A single foliar application of MX was enough to increase fruit set. Spray application of MX on clementine mandarins at the end of the flowering period, when all petals have fallen showed a similar response to GA3 treatments.