Successful irrigation management is one of the most important agronomic practices for achieving profitable yield and maximizing crop water productivity (CWP) while maintaining environmental quality by minimizing water losses to runoff and deep drainage. This study was conducted to compare the influence of two irrigation frequencies on crop water use (CWU) and CWP of sugarbeet (Beta vulgaris L.), malt barley (Hordeum vulgare L.), and potato (Solanum tuberosum L.) on a sandy loam soil in the semiarid northern Great Plains. The irrigation frequencies compared were: high frequency (HF) irrigation with biweekly application of small irrigation quantities, and the conventional low frequency (LF) with weekly application of large irrigation quantities. Irrigation frequency was varied based on either 15 mm (HF) or 30 mm (LF) cumulative crop evapotranspiration replacements. Seasonal CWU amounts were determined using the water balance equation of sugarbeet, malt barley, and potato under HF and LF irrigations for 2007, 2008, 2009, 2010, and 2011. No significant differences due to irrigation frequency were found for yield, CWU, and CWP of sugarbeet (root and sucrose), malt barley, or potato. Small differences in CWU values between HF and LF irrigations were due to variations in soil moisture content in the soil profile and drainage losses below the 0.91-m soil depth. Conventional LF irrigation thus can sustain yield, improve water use, and reduce net economic input as feasibly as HF irrigation practices when a self-propelled automated sprinkler system is used on a sandy loam soil.

Low water use efficiency is a challenge to crop production in Sub-Sahara African countries. Water is getting continuously scarce due to increased demand and shrinking availability induced mainly by climate change. As agriculture is the major consumer of water, improving crop water productivity is among the ways of overcoming the challenge. Crop production under rainfed system is the major livelihood strategy for smallholder farmers in Ethiopia. The major objective of this study is, therefore, to estimate water productivity of major crops grown under rainfed system in Meja watershed as influenced by management practices and local agro-ecology. The research work mainly depends upon house hold survey and field measurement conducted from July 2011 to February 2012. Agronomic practices used for major crops were monitored on randomly selected farmers’ fields, and biomass and grain yield were determined at harvest. Crop water requirement was simulated by CROPWAT model from which the average consumptive water use (m3) by each crop was calculated. In a mixed crop livestock farming system, farmers obtain benefit not only from grain but also from straw (primarily as animal feed). In line with this demand, the average biomass water productivity magnitudes for barley (Hordeum vulgare), wheat (Triticum Vulgare), teff (Eragrostis tef), sorghum (Sorghum bicolor), potato (Solanum tuberosum) and maize (Zea mays) were found to be 3.57, 4.82, 2.31, 6.45, 14.61 and 6.68kg/m3, respectively while the corresponding grain water productivity were 1.32, 1.42, 0.65, 0.98, 14.25 and 1.42kg/m3 in that order. Based on the local market values of the crops’ biomass, economic water productivity of barley, wheat, teff, sorghum, potato and maize were determined to be 10.09, 10.84, 8.45, 8.05, 28.82 and 10.18 Birr/m3, respectively. The mean biomass water productivity showed significant variation across the three local agro-ecological zones due to variations in seeding rate, tillage frequency, fertilizer rates and other agronomic practices. Hence, farmers can enhance economic benefit from the land and water resources they are endowed with rainfed by using improved technologies that could enhance grain and biomass yield. Moreover, implementation of integrated crop-soil-water management strategy is crucial to bring sustainable agricultural production and ensure food security in the long run. The correlation test between some management practices and major crops water productivity also indicated no significance but tended to correlate indicating a need to have detailed further study.

The viability of commercial potato production is influenced by spatial and temporal variability in soils and agroclimate, and the availability of water resources where supplementary irrigation is required. Soil characteristics and agroclimatic conditions greatly influence the cultivar choice, agronomic husbandry practices and the economics of production. Using the latest (UKCP09) scenarios of climate change for the UK, the present paper describes a methodology using pedo-climatic functions and a geographical information system (GIS) to model and map current and future land suitability for potato production in England and Wales. The outputs identify regions where rainfed production is likely to become limiting and where future irrigated production would be constrained due to shortages in water availability. The results suggest that by the 2050s, the area of land that is currently well or moderately suited for rainfed production would decline by 88 and 74%, respectively, under the ‘most likely’ climate projections for the low emissions scenario and by 95 and 86%, respectively, for the high emissions scenario, owing to increased likelihood of dry conditions. In many areas, rainfed production would become increasingly risky. However, with supplementary irrigation, c. 0·85 of the total arable land in central and eastern England would remain suitable for production, although most of this is in catchments where water resources are already over-licensed and/or over-abstracted; the expansion of irrigated cropping is thus likely to be constrained by water availability. The increase in the volume of water required due to the switch from rainfed- to irrigated-potato cropping is likely to be much greater than the incremental increase in water demand solely on irrigated potatoes. The implications of climate change on the potato industry, the adaptation options and responses available, and the uncertainty associated with the land suitability projections, are discussed.

The objective of the study was to map sweet potato value chain linkages between actors, processes and activities in Tanzania. The study is cross sectional in design.The study was conducted in Shinyanga rural and Mwanza urban districts. The study used individual interviews, focused group discussions; review of relevant practical documents and discussions with key informants. A total of 150 actors in the value chain participated. Data collected was summarized using Statistical Package of Social Science (SPSS) and content analysis. Analysis of data shows that “<em>Michembe” </em>and<em> </em><em>“Matobolwa”</em> were two main local made value added products derived from sweet potatoes preferred by producers. In general sweet potatoes production is marked with low production and productivity. Low productivity is a result of poor agronomic practices and low level of production technology application among others. Three main marketing channels exist in the study area: Producers selling directly to consumer; producers to retailers to consumer; and producers to hawkers/village vendors to consumer. Moreover data revealed that (50.7%) of sampled producers set prices after hearing from their fellow farmers. About (44%) of the sampled producers sell their produce direct to the market. The sub sector in general faces a number of structural and technological problems that need immediate attention to revamp agricultural sector development.

Potato (Solanum tuberosum L.) is one of the most important vegetable tuber crops produced in Ethiopia. Yield and productivity of the crop has been far below the world average owing to several factors including lack of high yielding varieties and inappropriate agronomic practices observed in most farmers’ fields. Thus, a 3x5 factorial experiment arranged in Randomized Complete Block Design (RCBD) with three replications was conducted at Bure Woreda, western Zone of Gojjam from December 2010 to April 2011 to assess the effect of variety and earthing-up frequency on growth, yield and quality of potato. Three different varieties (Belete, Zengena and Gera) and five earthing-up frequencies (no earthing-up, one time, two times, three times and four times earthing-up) were used in the experiment. The results revealed that varieties and earthing-up frequency significantly (P<0.05) affected total tuber number per plant. The maximum total tuber number per plant (15.82) was recorded by Zengena variety and three times earthing-up frequency (15.58),while the lowest tuber number per plant (11.46) was recorded by Gera variety and, from plants grown without earthing-up (11.13). Significantly the highest total tuber yield and the maximum tuber yield per ha (38.32 and 34.05 t/ha) were recorded by variety Belete and three times earthing-up frequency, respectively, while the lowest (24.43 and 30.07 t/ha) was recorded by Gera variety and no earthing-up, respectively. Significantly maximum marketable tuber number (8.9 and 10.5/plant) was obtained by Belete variety and three times earthing-up frequency, respectively. Variety and earthing-up frequency also showed significant effect on marketable yield per ha. The maximum marketable yield (27.27 and 27.23 t/ha) was recorded by Belete variety and three times earthing-up frequency, respectively. The maximum unmarketable yield (11.06 t/ha) was recorded by Belete variety and no earthing-up (10.72 t/ha), while the lowest unmarketable yield (4.39 t/ha) was recorded by Gera variety and four times earthing up frequency (6.03 t/ha). Total yield per hectare was highly significantly and positively correlated with marketable yield per hectare (r=0.86**), total tuber number per hectare (r=0. 57**) and number of marketable tuber per ha (r=0.39**). Significantly (P<0.05) the highest leaf area index (3.17) was recorded by Belete variety, while the lowest (2.30) was obtained from Gera variety. Similarly, leaf area index was highly significantly and positively correlated with tuber yield per ha (r=0.71**), total tuber number per hectare (r=0.46**), and marketable yield per ha (r=0.51**). The result of this study verified that growth, yield and quality of potato are influenced by variety and earthing up frequency. It can be concluded that Belete variety and three times earthing-up frequency produced higher total yield and marketable yield per hectare than other varieties and earthingup frequencies. Thus, variety Belete and three times earthing-up frequency after complete plant emergence can be used at the study area, for the better marketable yield and quality potato production. Since the experiment was conducted for one season and in one location, further research, involving different varieties, growing seasons and location, may be suggested to come up with conclusive result.

Potato late blight caused by the pathogen Phytophthora infestans is one of the most dreaded diseases to this culture. So far, chemical control is the most widespread method used against the pathogen. In turn, the amount of fungicides used to control this disease makes potato the crop with the highest Treatment Frequency Index of all arable crops. The use of resistant varieties, including specific resistance genes, has also demonstrated an effective limitation of injuries that this disease can cause. Still, specific resistances lack durability as there is an average span of 4 years before the emergence of a resistance breakdown phenomenon by more virulent strains. It is therefore necessary to develop control strategies that combine a set of methods (genetic, cultural, physical and chemical) to meet agronomic, environmental and socio-economic criteria. A model named SIPPOM (Simulator for Integrated Pathogen POpulation Management), was developed to address these issues for the control of phoma stem canker on oilseed rape. The present work consisted in adapting the generic structure of SIPPOM for the integrated control of potato late blight by designing specific sub-models using existing models or specifically developed models. A crop model (Spudgro), an epidemiologic model (Guntz-Divoux/Milsol), a damage model (Shtienberg's model) and a dispersal function (Scherm's model) were selected in the literature, adapted, and embedded in SIPPOM's generic structure. This set of sub-models led to an operational prototype of SIPPOM-de-terre under the RECORD modelling platform. A new model, named VOLPONE, was designed to simulate potato volunteer dynamics in a field or on a waste pile. This model permits to simulate inoculum sources at the territory scale under the influence of climate and cropping practices. The predictive quality of the damage model was assessed with data generated in specific field experimentations and proved to be good. Simulation examples produced with the first prototype of SIPPOM-de-terre illustrate the capacity of the model to represent epidemiological dynamics at the field scale or at a small regional scale under the influence of cropping practices and climate. However, further work is required before to totally achieve the design and the implementation of SIPPOM-de-terre under the modelling platform RECORD. The conducted study illustrates the genericity of the model SIPPOM and produced knowledge, references and tools for the integrated management of the disease. The outputs of this work will help design integrated, collective and durable control strategies of potato late blight. | Le mildiou de la pomme de terre, causé par l'agent pathogène Phytophthora infestans est l'une des maladies les plus préjudiciables de la culture. Jusqu'à présent, la lutte chimique reste le moyen de contrôle le plus utilisé pour la maîtriser, classant la pomme de terre au premier rang en termes d'Indices de Fréquence de Traitement en grande culture. Par ailleurs, l'utilisation de variétés résistantes, comportant notamment des gènes de résistances spécifiques, a également démontré son efficacité pour limiter les dégâts engendrés par cette maladie. Mais leur efficacité est peu durable avec une durée moyenne de 4 ans avant l'apparition du phénomène de contournement par les isolats plus virulents. Il est donc nécessaire de développer des stratégies de contrôle de la maladie en combinant un ensemble d'approches génétiques, culturales, physiques, et chimiques afin de satisfaire au mieux les objectifs agronomiques, environnementaux et socio-économiques. Un modèle, nommé SIPPOM (Simulator for Integrated Pathogen POpulation Management), avait été développé dans le cas de la gestion durable du phoma du colza. Le présent travail a consisté à adapter la structure générique de SIPPOM au cas de la gestion intégrée du mildiou de la pomme de terre en développant des modules spécifiques à partir de modèles préexistants ou développés spécifiquement. Un modèle de culture (Spudgro), un modèle épidémiologique (Guntz-Divoux / Milsol), un modèle de nuisibilité (modèle de Shtienberg) et une fonction de dispersion (modèle de Scherm) ont été identifiés dans la littérature, adaptés et intégrés dans la structure générique de SIPPOM. Cet ensemble de modules a donné lieu à la réalisation du premier prototype opérationnel de la version informatisée de SIPPOM-de-terre sur la plate-forme de modélisation RECORD. Un nouveau modèle, appelé VOLPONE, a été développé pour représenter les dynamiques de repousses de pomme de terre dans une parcelle et sur un tas de déchets. Ce modèle permet de représenter les sources d'inoculum primaire à l'échelle du territoire sous l'influence du climat et des pratiques agricoles. La qualité prédictive du modèle de nuisibilité a été estimée à partir d'un jeu de données expérimentales générées au cours du travail de thèse et s'est montrée correcte. Des exemples de résultats issus de simulations réalisées à l'aide du premier prototype montrent la capacité du modèle, en fonction d'une combinaison de pratiques culturales et de conditions climatiques variables, à prédire la dynamique épidémique de la maladie, ainsi que les dégâts et dommages associés à l'échelle de la parcelle ou sur un parcellaire simple. Néanmoins, d'autres tâches restent à accomplir afin de disposer d'une version achevée de SIPPOM-de-terre sur la plate-forme RECORD. Le travail réalisé illustre la généricité du modèle d'origine SIPPOM et contribue à la production de connaissances et de références permettant l'optimisation d'outils existants tels Mileos®. Les avancées réalisées pourront contribuer à la conception de stratégies de gestion intégrée, collectives et durables pour cette maladie.

The aim of this study was to provide an ex ante assessment of the sustainability of genetically modified (GM) crops under the agricultural conditions prevailing in Switzerland. The study addressed the gaps in our knowledge relating to (1) the agronomic risks/benefits in production systems under Swiss conditions (at field and rotation/orchard level), (2) the economic and socio-economic impacts associated with altered farming systems, and (3) the agro-ecological risks/benefits of GM crops (at field and rotation/orchard level). The study was based on an inventory of GM crops and traits which may be available in the next decade, and on realistic scenarios of novel agricultural practices associated with the use of GM crops in conventional, integrated, and organic farming systems in Switzerland. The technology impact assessment was conducted using an adapted version of the matrix for “comparative assessment of risks and benefits for novel agricultural systems” developed for the UK. Parameter settings were based on information from literature sources and expert workshops. In a tiered approach, sustainability criteria were defined, an inventory of potentially available, suitable GM crops was drawn up, and scenarios of baseline and novel farming systems with GM crops were developed and subsequently submitted to economic, socio-economic, and agro-ecological assessments. The project had several system boundaries, which influenced the outcomes. It was limited to the main agricultural crops used for food and feed production and focused on traits that are relevant at the field level and are likely to be commercially available within a decade from the start of the project. The study assumed that there would be no statutory restrictions on growing GM crops in all farming systems and that they would be eligible for direct payments in the same way as non-GM crops. Costs for co-existence measures were explicitly excluded and it was assumed that GM foods could be marketed in the same way as non-GM foods at equal farm gate prices. The following model GM crops were selected for this study: (1) GM maize varieties with herbicide tolerance (HT), and with resistance to the European corn borer (Ostrinia nubilalis) and the corn rootworm (Diabrotica virgifera); (2) HT wheat; (3) GM potato varieties with resistance to late blight (Phytophthora infestans), to the nematode Globodera spp., and to the Colorado beetle (Leptinotarsa decemlineata); (4) HT sugar beet with resistance to “rhizomania” (beet necrotic yellow vein virus; BNYVV); (5) apples with traditionally bred or GM resistance to scab (Venturia inaequalis), and GM apples with stacked resistance to scab and fire blight (Erwinia amylovora). Scenarios for arable rotations and apple orchards were developed on the basis of the model crops selected. The impact assessments were conducted for the entire model rotations/orchards in order to explore cumulative effects as well as effects that depend on the farming systems (organic, integrated, and conventional). In arable cropping systems, herbicide tolerance had the most significant impact on agronomic practices in integrated and conventional farming systems. HT crops enable altered soil and weed management strategies. While no-till soil management benefited soil conservation, the highly efficient weed control reduced biodiversity. These effects accumulated over time due to the high proportion of HT crops in the integrated and conventional model rotations. In organic production systems, the effects were less pronounced, mainly due to non-use of herbicides. Traits affecting resistance to pests and diseases had a minor impact on the overall performance of the systems, mainly due to the availability of alternative crop protection tools or traditionally bred varieties. The use of GM crops had only a minor effect on the overall profitability of the arable crop rotations. In apple production systems, scab and fire blight resistance had a positive impact on natural resources as well as on local ecology due to the reduced need for spray passages and pesticide use. In integrated apple production, disease resistance increased profitability slightly, whereas in the organic scenario, both scab and fire blight resistance increased the profitability of the systems substantially. In conclusion, the ecological and socio-economic impacts identified in this study were highly context sensitive and were associated mainly with altered production systems rather than with the GM crops per se.