The use of remote sensing to quantify wetland loss in the Choke Mountain range, Upper Blue Nile basin, Ethiopia

Wetlands provide multiple ecosystem services such as storing and regulating water flows and water quality, providing unique habitats to flora and fauna, and regulating micro-climatic conditions. Conversion of wetlands for agricultural use is a widespread practice in Ethiopia, particularly in the southwestern part where wetlands cover large areas. Although there are many studies on land cover and land use changes in this region, comprehensive studies on wetlands are still missing. Hence, extent and rate of wetland loss at regional scales is unknown. The objective of this paper is to quantify wetland dynamics and estimate wetland loss in the Choke Mountain range (area covering 17 443 km<sup>2</sup>) in the Upper Blue Nile basin, a key headwater region of the river Nile. Therefore, satellite remote sensing imagery of the period 1986–2005 were considered. To create images of surface reflectance that are radiometrically consistent, a combination of cross-calibration and atmospheric correction (Vogelman-DOS3) methods was used. A hybrid supervised/unsupervised classification approach was used to classify the images. Overall accuracies of 94.1% and 93.5% and Kappa Coefficients of 0.908 and 0.913 for the 1986 and 2005 imageries, respectively were obtained. The results showed that 607 km<sup>2</sup> of seasonal wetland with low moisture and 22.4 km<sup>2</sup> of open water are lost in the study area during the period 1986 to 2005. The current situation in the wetlands of Choke Mountain is characterized by further degradation which calls for wetland conservation and rehabilitation efforts through incorporating wetlands into watershed management plans

Drought resistance in durum wheat

Durum wheat is widely grown as a rainfed crop in the semi-arid tropics. Its production is low and variable from season to season due to frequent drought-stress. Characterization of target environment and employing both analytical and empirical breeding approaches would speed up progress in the development of cultivars with improved adaptation to the prevailing weather conditions.Analysis of historical weather data and a crop growth model were used to predict the growing season and the optimum plant growth cycle in six different ecological regions of Ethiopia. The matching of crop development to the prevailing soil water availability patterns is considered as a major step towards sustainable durum wheat production.High yield and yield stability are equally important breeding objectives under drought conditions. The cause-effect relationships of the duration of vegetative period, the duration of grain-filling period, yield components (number of spikes/m 2, kernels/spike, kernel weight) and grain yield revealed a complex pattern of relationships. Longer grain-filling period, increased number of kernels per spike and limited tillering were found to be associated with drought- resistance.Increasing water use efficiency is the major focus of the dryland cropping system. The different definitions of water use efficiency are explained. Water use efficiency on the basis of grain yield proved the most valuable parameter. The ratios of water used before anthesis and after anthesis by drought-resistant and -susceptible cultivars were different.Relative growth rate (RGR) and its components (leaf area ratio, LAR, and net assimilation rate, NAR) changed with growth stage and moisture availability. Drought-resistant cultivars were characterized by a fast growth rate in the beginning and slow growth later. Deep rooting and a low shoot:root ratio are effective components of drought-resistance.Durum wheat straw is one of the major feed sources. The quality of straw varied among cultivars, but did not correlate with drought-resistance. Drought-stress considerably improved straw quality, due to reduced remobilization of assimilates.The research showed that there is considerable potential to improve the current low and variable durum wheat production in the semi-arid regions

Information, motivation and resources: the missing elements in agricultural pesticide policy implementation in Ethiopia

To promote pesticide governance that protects the environment and human health, Ethiopia has developed a legal framework for pesticide registration and control. However, in Ethiopia, pesticides are still registered, traded and used inappropriately. This research analyses how Ethiopia's pesticide policy is implemented and identifies the barriers for an effective implementation of this policy. With a theoretical framework based on the information, motivations and resources of relevant actors, data are collected from state pesticide experts, traders and end users (farmers) through in-depth interviews. The overall result reveals that major gaps exist between pesticides policy on paper and its implementation in practice. The key policy actors scored low on each of the three characteristics: they have poor information available, have low motivation to implement policies and lack sufficient resources. Involvement of and collaboration with private actors is likely to improve the implementation of pesticide governance, and contribute to sustainability in agricultural and food systems in Ethiopia

Ontogenetic analysis of yield components and yield stability of durum wheat in water-limited environments

One main reason for the slow improvement of durum wheat in water-limited environments is the lack of clear understanding of the interrelationships among yield components and their compensatory changes under low and erratic moisture availability. Five cultivars, varying in many physiological attributes, were tested under different drought-stress conditions in field and greenhouse experiments. The cause-effect relationships of duration of vegetative period, duration of grain-filling period, number of spikes per m2, kernels per spike, kernel weight and grain yield per m2 were assessed. Furthermore, yield stability was evaluated. Yield reduction was largest under mid-season stress (58%), followed by terminal stress (30%) and early stress (22%). Cultivar Po was very sensitive to terminal stress. Path-coefficient analysis revealed a complex pattern of relationships among the six variables. An increase in vegetative period reduced the grain-filling period under all conditions. It increased number of kernels per spike under non-stress conditions. The direct effect of spikes per m2 on grain yield was significantly positive. However, more spikes per m2 resulted in fewer kernels per spike and a low kernel weight and, as a result, a negative relationship with grain yield under early stress. Grain-filling period had a strong influence on grain yield via kernel weight. Kernels per spike had the largest direct effect on grain yield. However, it was negatively correlated with kernel weight, especially under terminal stress. Grain yield heavily depended on kernels per spike under early stress and grain-filling period and kernels per spike under terminal stress. Variation in drought susceptibility index among cultivars was significant under early and terminal stress conditions, but not under mid-stress conditions. Yield potential and stability were not correlated for the different drought-stress conditions. Longer grain-filling period, increased number of kernels per spike and limited spike number per m2 can be used as selection criteria for sustainable yield in water-limited environment

Agroclimatic analysis: a tool for planning sustainable durum wheat (Triticum turgidum var. durum) production in Ethiopia

Long-term weather data for six locations representing different eco-regions of Ethiopia were analyzed to generate information for appropriate management practices and research priorities of durum wheat (Triticum turgidum var. durum) in Ethiopia. Among the weather elements examined, rainfall was variable and seasonal. The annual rainfall showed a random year-to-year variation both in space and time. Rainfall distribution during the growing period was much more variable than the seasonal total, resulting in a limited growing period. Dependable rainfall is much lower than the mean, particularly for the low-rainfall regions (Asmara, Metahara and Melkasa). A close relationship between the amount of rainfall and the length of the growing season was observed. The beginning of the rainy season (planting time) ranged from early June to mid-July and the end of growing season varied from early September to November. The growing season (moisture-available period) ranged from 60 days (Metahara) to 140 days (Debre Markos). The results suggest that crop improvement strategies and cropping systems for sustainable durum wheat production should be designed for the different climatic-soil zones based on a realistic assessment of prevailing weather conditions

Application of a crop growth model (SUCROS-87) to assess the effect of moisture stress on yield potential of durum wheat in Ethiopia

A spring wheat growth model (SUCROS-87) was used to identify moisture stress periods during the growing seasons and simulate yield potentials of durum wheat (Triticum turgidum var. durum) in six durum wheat growing regions of Ethiopia. The start of the rainy season and distribution of rainfall were erratic, particularly in the low-altitude regions. As a result, simulated dates of emergence varied from June to August. Moisture stresses of various intensities, at different growth stages of the plant, were limiting to durum wheat production in all the regions except Debre Markos. Terminal moisture stress was simulated in 7 out of 10 years in all locations except Debre Markos, whereas intermittent stress. was simulated in three locations in 2 out of 10 years. In Metahara rain-fed durum wheat production is not feasible without irrigation. Water use efficiency decreased with decreasing rainfall but the transpiration coefficient increased. The average simulated potential grain yields at all the locations were high (6600 kg ha−1) compared with the actual national average. Development of versatile and region-specific improvement strategies are emphasized to improve durum wheat production in the country

Differences in developmental plasticity and growth rate among drought-resistant and susceptible cultivars of durum wheat (Triticum turgidum L. var. durum)

Understanding how growth and development of durum wheat cultivars respond to drought could provide a basis to develop crop improvement programmes in drought-affected tropical and subtropical countries. A greenhouse experiment was conducted to study the responses of five durum wheat cultivars to moisture stress at different developmental phases. Phenology, total dry matter (TDM), relative growth rate (RGR), leaf area ratio (LAR), net assimilation rate (NAR), leaf weight ratio (LWR), specific leaf area (SLA) and shoot:root ratio were compared. Pre-anthesis moisture stress delayed phenological development, whereas post-anthesis moisture stress accelerated it. TDM accumulation rate was different between drought-resistant and susceptible cultivars. RGR and its components changed with age and moisture availability. Drought-resistant cultivars had a high RGR in favourable periods of the growing season and a low RGR during moisture stress. In contrast, the drought-susceptible cultivar (Po) showed an opposite trend. LAR explained the differences in RGR (r=0.788) best, whereas the relationship between NAR and RGR was not significant. Even though both LWR and SLA were important factors determining the potential growth rate, LWR was of major importance to describe cultivar differences in LAR, and consequently in RGR. The drought-resistant cultivars Omrabi-5 and Boohai showed vigorous root development and/or a low shoot:root ratio. It is concluded that biomass allocation is the major factor explaining variation in RGR among the investigated durum wheat cultivars