Ethiopia has a long history in which the food demands of rapidly growing population have periodically outstripped the productive capacity of the land, and this is particularly true in the dryland areas of the country. This has led to a decrease agricultural productivity and environmental degradation of the natural resource base. As the main source of economic activity in SSA is the agricultural production, declining soil productivity means not only less food is grown but also that production of cash crops and income are endangered. Thus, rectifying land degradation and enhancing productivity through appropriate soil management and conservation can play a major role in achieving farm household food security and agricultural development. This publication reviews issues related to land degradation, with focus on problems of soil fertility management in SSA. It highlights some successful experiences in the region, constraints and possible solutions specific to the major agro-ecological zones and the importance of holistic and participatory approaches for soil productivity improvement. The need for action and collaborative efforts of all stakeholders, within the framework of ongoing initiatives are emphasized. It is hoped that his document will contribute to increasing awareness of senior specialists and police-makers about the problems and alternative solutions towards enhanced and sustained soil productivity. This article assesses the major crop production constraints and their causes as related not only to the physical environment (climate, soils) but also in light of some of the important socioeconomic and policy problems. Details of some of the major crop production problems including drought (water stress), low soil fertility, pest infestation, lack of appropriate farm implements, and both socioeconomic and policy problems are indicated. The article also gives some examples of the available technologies and assess their practicality in relation to the low technology adoption by the smallholder farmers. Based on this research gaps are identified and future research strategies for sustainable crop production is proposed. Finally recommendation and suggestions on requirements in terms of capacity building in research and extension including trained manpower and facilities and other improvements in socioeconomic and policy issues required to improve crop production on sustainable basis for the resource poor smallholder farmers of the dry land areas of Ethiopia are forwarded.

Genetically diabetic (type II) KK-Ay mice, male and 5 wk of age, were divided into four groups and fed test diets containing 2(2F). 5(5F). 10(10F), or 20(20F)% fat for 4 wk. and then the 5F group and one-half of the 20F group continued to be fed the corresponding diet and the other half of the latter group was given the 20F (20FHWE) diet with 5% hot-water extracts (HWE) from woody ear (Auricularia auricula-judae Quel.) for a further 3 wk. Remarkable changes in body weight were unfound among the dietary groups. The food intake generally decreased according to the increase in dietary fat content, but the energy expenditure was hardly different among the dietary groups except for the 20FHWE group. That of the 20FHWE group was further decreased compared to the 20F group. Water consumption dropped in the order of the 20F. 5F, and 20FHWE groups. The plasma glucose concentration was the highest in the 20F group, followed in order by the 10F and 5F groups, and the lowest in the 2F and 20FHWE groups. The contents of dietary fat were most positively correlated with the plasma glucose level. The present results using KK-Ay mice confirm that dietary fat levels control postprandial glycaemia. and suggest that the hypoglycemic effect of HWE is primarily caused by a reduction in food ingestion.

Three experimental devices (joined cylinders, dry salting and a drying cell) were used to generate moisture and sodium chloride (NaCl) profiles in gels (gelatin, different starch/gelatin ratios) maintained at constant temperature (10 and 20°C). The moisture and chloride concentrations profiles were measured by a destructive method (slicing: 1 and 5 mm of thickness / analysis of moisture (oven) and chloride (potentiometric titration)). A drying cell was set up in order to generate salt and moisture gradients in salt added gelatin gels maintained at constant temperature and to obtain a large range of moisture fluxes (from 0,00003 to 0,0003 kg water per square meter and per second). For those investigated moisture fluxes, binary diffusion of moisture and chlorides seems to be the predominant phenomenon. Apparent diffusivities were either estimated by applying a direct data treatment method to measured profiles or identified by using a mathematical model taking the retraction of the gel into account. The direct data treatment method does not require any assumption on the D=f(X) relation. It can be applied to profiles with relatively few measurements - approximately 10 - when smoothing the experimental points by using a neural network. The two methods provided similar estimations of apparent moisture and chlorides diffusivities. The values depend neither on the strengh of gelatin gels (Bloom) nor on the anhydrous composition of the gel (ratio starch/gelatin). Apparent chloride diffusitivity is relatively constant and lower than mutual salt-water diffusivity. Apparent moisture diffusitivity decreases with moisture content when measured on gels during dehydration but, increases with decreasing moisture content in the gels during re-hydration. The addition of sodium chloride causes an increase of the apparent moisture diffusivity by a factor 10. | Trois dispositifs expérimentaux (cylindres accolés, salage à sec, cellule de séchage) ont été utilisés pour générer des profils de teneurs en eau et en chlorure de sodium (NaCl) dans des gels (gélatine, mélanges amidon/gélatine) à 10 et 20 °C. Ces profils ont été mesurés par analyses chimiques après découpe de tranches de gel d'épaisseurs 1 et 5 mm. Dans le cas du séchage, un dispositif original a permis de maintenir la température du gel constante et de faire varier la densité de flux d'eau évaporée de 0,00003 à 0,0003 kg d'eau par mètre carré et par seconde. Dans cette gamme, aucun effet d'entraînement du sel par l'eau n'a pu être mise en évidence. Les diffusivités apparentes ont été estimées soit en appliquant un traitement direct aux profils mesurés soit par identification avec un modèle de transfert couplé eau-sel qui tient compte de la rétraction du gel. Le traitement direct ne nécessite aucune hypothèse sur la forme de la relation D=f(X) ; il peut être appliqué à des profils constitués d'un nombre limité de mesures - environ 10 - grâce à un lissage par un réseau de neurones. Les deux méthodes ont fourni des estimations concordantes des diffusivités apparentes de l'eau et des chlorures. Elles ne dépendent ni de la force du gel (Bloom) ni de la composition du gel anhydre (ratio amidon/gélatine). Celle des chlorures est relativement constante et inférieure à la diffusivité mutuelle sel-eau. Celle de l'eau dépend de la teneur en eau initiale du gel, diminue avec la diminution de la teneur en eau en déshydratation mais augmente en réhydratation. L'ajout du chlorure de sodium provoque une augmentation de la diffusivité apparente de l'eau d'un facteur 10.

Three experimental devices (joined cylinders, dry salting and a drying cell) were used to generate moisture and sodium chloride (NaCl) profiles in gels (gelatin, different starch/gelatin ratios) maintained at constant temperature (10 and 20°C). The moisture and chloride concentrations profiles were measured by a destructive method (slicing: 1 and 5 mm of thickness / analysis of moisture (oven) and chloride (potentiometric titration)). A drying cell was set up in order to generate salt and moisture gradients in salt added gelatin gels maintained at constant temperature and to obtain a large range of moisture fluxes (from 0,00003 to 0,0003 kg water per square meter and per second). For those investigated moisture fluxes, binary diffusion of moisture and chlorides seems to be the predominant phenomenon. Apparent diffusivities were either estimated by applying a direct data treatment method to measured profiles or identified by using a mathematical model taking the retraction of the gel into account. The direct data treatment method does not require any assumption on the D=f(X) relation. It can be applied to profiles with relatively few measurements - approximately 10 - when smoothing the experimental points by using a neural network. The two methods provided similar estimations of apparent moisture and chlorides diffusivities. The values depend neither on the strengh of gelatin gels (Bloom) nor on the anhydrous composition of the gel (ratio starch/gelatin). Apparent chloride diffusitivity is relatively constant and lower than mutual salt-water diffusivity. Apparent moisture diffusitivity decreases with moisture content when measured on gels during dehydration but, increases with decreasing moisture content in the gels during re-hydration. The addition of sodium chloride causes an increase of the apparent moisture diffusivity by a factor 10. | Trois dispositifs expérimentaux (cylindres accolés, salage à sec, cellule de séchage) ont été utilisés pour générer des profils de teneurs en eau et en chlorure de sodium (NaCl) dans des gels (gélatine, mélanges amidon/gélatine) à 10 et 20 °C. Ces profils ont été mesurés par analyses chimiques après découpe de tranches de gel d'épaisseurs 1 et 5 mm. Dans le cas du séchage, un dispositif original a permis de maintenir la température du gel constante et de faire varier la densité de flux d'eau évaporée de 0,00003 à 0,0003 kg d'eau par mètre carré et par seconde. Dans cette gamme, aucun effet d'entraînement du sel par l'eau n'a pu être mise en évidence. Les diffusivités apparentes ont été estimées soit en appliquant un traitement direct aux profils mesurés soit par identification avec un modèle de transfert couplé eau-sel qui tient compte de la rétraction du gel. Le traitement direct ne nécessite aucune hypothèse sur la forme de la relation D=f(X) ; il peut être appliqué à des profils constitués d'un nombre limité de mesures - environ 10 - grâce à un lissage par un réseau de neurones. Les deux méthodes ont fourni des estimations concordantes des diffusivités apparentes de l'eau et des chlorures. Elles ne dépendent ni de la force du gel (Bloom) ni de la composition du gel anhydre (ratio amidon/gélatine). Celle des chlorures est relativement constante et inférieure à la diffusivité mutuelle sel-eau. Celle de l'eau dépend de la teneur en eau initiale du gel, diminue avec la diminution de la teneur en eau en déshydratation mais augmente en réhydratation. L'ajout du chlorure de sodium provoque une augmentation de la diffusivité apparente de l'eau d'un facteur 10.