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Developing potato varieties that have enhanced tolerance to soil moisture and high‐temperature stress could improve household food and nutrition security in drought and heat prone areas. A field experiment was conducted at two locations in Ethiopia to evaluate the effectiveness of some stress tolerance indices for the identification of drought and heat tolerant potato genotypes. Treatments consisted of two irrigation regimes and 23 potato genotypes. The experiment was laid out as a split‐plot design in a factorial arrangement with three replications. Irrigation regimes were the main plot factor and genotypes were the sub‐plot factor. Stress tolerance indices were calculated based on the tuber yield under stress (Ys) and non‐stress (Yp) conditions of each genotype. To determine the most desirable stress tolerant genotypes, all indices mean rank (R) and standard deviation of the Rwere computed. Genotypes Cl‐12(CIP‐304371.67), Cl‐13(CIP‐304383.80), Cl‐2(CIP‐302499.30), Cl‐34(CIP‐397079.6), Cl‐15(CIP‐304394.56), and Cl‐14(CIP‐304387.39) were found to have had top mean ranks and higher tuber yield under drought and heat stress. Ranking methods using all indices best determined desirable drought, heat, and combined drought‐heat tolerant genotypes that consistently coincided with the yield rank of genotypes under a given stress condition. This implies that these indices (stress tolerance index, geometric mean productivity, mean productivity, yield stability index, and tolerance index) could be used in combination to differentiate stress tolerances and susceptible potato genotypes. It is recommended that genotypes that exhibited higher drought and/or heat stress tolerance in this study could be further evaluated in drought and heat prone areas for the development of tolerant potato varieties. Different potato genotypes (International Potato Center collections, improved varieties, and local cultivar) were evaluated for drought and heat.Promising genotypes tolerant to drought, heat, or combination of both were identified.Stress tolerance indices were used to identify drought and heat tolerant and susceptible genotypes.Stability of the genotypes under different environments were tested.Stress tolerance indices mean rank standard deviation used to group genotypes to stress tolerant and susceptible.

Low soil moisture content and soil fertility are the major problems constraining productivity of potato (Solanum tuberosumL.) in the eastern highlands of Ethiopia. Therefore, a field experiment was conducted to investigate the effect of drip irrigation regimes and fertilizer rates on tuber yield, as well as nitrogen, phosphorus, and water use efficiencies of potato during the off-season of 2019/2020. The experiment was laid out as a split-plot design with three replications. Three levels of irrigation regimes, viz. 50%, 75% and 100% (full) of ETc were assigned to the main plots. Seven rates of fertilizer [control; 65 kg N + 242 kg NPS ha−1(recommended rate); 50% of the recommended N + 75% of the recommended NPS along with 10 ton FYM ha−1; 75% of the recommended N + 50% of the recommended NPS along with 10 ton FYM ha−1; 75% of the recommended rate of N and NPS along with 5 ton FYM ha−1; 75% of the recommended rate of N and NPS along with 10 ton FYM ha−1and 111 kg N + 92 kg P2O5 ha−1] were assigned to the sub-plots. The results indicated that the optimum total tuber yield (48.38-ton ha−1) and marketable tuber yield (47.80 ton ha−1) were obtained in response to the application of 75% of the recommended rate of N and NPS along with 5 ton FYM ha−1together with 75% ETc. These total and marketable tuber yields exceeded the total and marketable tuber yield obtained in response to 50% ETc together with no fertilizer application by about four-fold. The above-mentioned treatment combination also resulted in the optimum agronomic nitrogen and phosphorus use efficiencies. Water use efficiency was improved by 3 kg m−3in response to the application of 75% of the recommended rates of N and NPS along with 5-ton FYM ha−1together with 50% ETc compared to the same rate of the fertilizer treatment combined with 100% ETc. It is concluded that application of 75% ETc combined with 75% of the recommended rate of N and NPS along with 10 ton FYM ha−1increased potato yield, water productivity and N and P use efficiencies in Haramaya district.

Groundnut (Arachis hypogaeaL.) is a high economic value oil crop commonly grown in low-land semi-arid areas of Ethiopia. The crop production is constrained by low soil fertility; however, the nutrient management practice has been given low attention. This study was therefore conducted during the main cropping season of 2015/2016 ​at Babile and Fedis sites of East Hararghe, Ethiopia to evaluate the growth, nodulation, and yield response of groundnut varieties to the application of combined mineral nitrogen, phosphorus, and vermicompost fertilizers, and zinc. Treatments consisted of a factorial combination of three varieties (Ba-ha-Gudo, Ba-ha-Jidu, and Roba); three fertilizers combinations (0: 0 ​kg ​N: P2O5ha−1with no VC, 46: 46 ​kg ​N: P2O5ha−1with no VC, and 46: 46 ​kg ​N: P2O5ha−1with 2.5 ​t VC ha−1); and three rates of Zn (0, 5, and 10 ​kg Zn ha−1) in a randomized complete block design at both sites. The growth, nodulation, yield components, and yield data were subjected to analysis by SAS. The result revealed that plant height was significantly affected by variety and fertilizers combination, the number of branches plant−1affected by the interaction of variety and fertilizers combination while canopy spread and nodulation parameters were affected by the interaction of variety, fertilizers combination, and Zn rate. Pod plant−1and hundred seed weight, dry biomass, pod and seed yields, and seed oil content were significantly affected by the interaction of variety, fertilizers combination, and Zn rate. The highest dry biomass (7.26 ​t ​ha−1), pod (3.13 ​t ​ha−1), seed (2.16 ​t ​ha−1) yields and seed oil content (51.3%), net benefit ($1704.2 ​ha-1) with a marginal rate of return of 242% were obtained from variety Ba-ha Gudo received the combined application of 46: 46 ​kg ​N: P2O5ha−1and 2.5 ​t VC ha−1with 5 ​kg Zn ha−1. Therefore, it can be concluded that the Ba-ha Gudo variety is preferably produced using the combined application of 46: 46 ​kg ​N: P2O5ha−1and 2.5 ​t VC ha−1with 5 ​kg Zn ha−1for high productivity in the study sites and similar agro-ecologies.

Soil acidity is a serious problem constraining faba bean (Vicia fabaL.) production in southern Ethiopia. Therefore, we conducted experiments in 2016 and 2017 to investigate the response of the crop to seed inoculation with Rhizobium bacteria and phosphorus application. The treatments consisted of inoculating seed of faba bean with three rhizobium isolates (FB-1018, FB-1035 and FB-Murdoch) plus one uninoculated and five rates of phosphorus fertilizer (0, 10, 20, 30, and 40 kg P ha−1). The experiments were laid out as a randomized complete block design in a factorial arrangement with three replications. We first tested the soil for selected physical and chemical properties. We then collected plant data on nodulation, yield components, and yield. The soil is strongly acidic (pH 5.1) and very low in contents of available phosphorus. The results revealed that the main effects of inoculation and phosphorus application significantly (P ≤ 0.01) influenced nodulation and yield. Inoculating faba bean seed with FB-1035 rhizobium isolate resulted in the highest grain yield of 3137 kg ha−1. Similarly, applying 30 kg P ha−1resulted in the optimum grain yield of 3105 kg ha−1. We concluded that both seed inoculation and application of phosphorus fertilizer equally increased the yield of the crop, exceeding the yields of the respective control treatments by about 39% and 68%. The results imply that inoculating faba bean seed with Rhizobium bacteria is a valuable approach to enhance the yield of the crop for enhancing food and nutrition security with environmental sustainability.

Climate change poses challenges to maize production and productivity in eastern Ethiopia. Impact assessment using climate predictions is the prime step to design adaptation strategies. Crop Environment Resource Synthesis (CERES)-Maize model in DSSAT (Decision Support System for Agrotechnology Transfer) was calibrated using GenCalc software. The model was used to simulate change in maize yield in the baseline (1988–2017) and future climate periods (2030s and 2050s) under (Representative Concentration Pathways) RCP4.5 and RCP8.5 scenarios using 17 CMIP5 (Coupled Model Inter-comparison Project Phase Five) GCMs (Global Circulation Models). During calibration and evaluation of the model excellent agreement of measured and simulated anthesis, and days to physiological maturity for all the cultivars with normalized root mean square error (nRMSE) of less than 10% and R2value of 0.99 was obtained. The seasonal leaf area index (LAI) and top weight progressions were also predicted well by the model with d-index of 0.96 and 0.99, respectively. Excellent (nRMSE < 10) to good (nRMSE 10–20) predictions were also obtained for grain yield and tops weight. The average annual temperature would increase by (1.90 ± 0.36) oC, (2.45 ± 0.53) oC and rainfall would increase (8 ± 5) %, (12 ± 8) % under RCP 4.5 in 2030s and 2050s, respectively across GCMs compared to baseline in the study area. As a result in 2030s yield reduction,  – 10.6% to  – 15.4% and  – 7.4% to  – 9.3% in 2050s of maize cultivar was projected across GCMs. In 2030s and 2050s under RCP4.5 and RCP8.5 long maturing cultivars (BH661) on 15th May planting with 130.5 kg N ha–1application predicted the highest maize grain yield.

ABSTRACTThe potato (Solanum tuberosumL.) is an important cash and food security crop in the eastern highlands of Ethiopia. However, the yield of the crop is constrained by low soil fertility and poor agronomic practices. Therefore, the field experiment was conducted at the main campus of Haramaya University and at Hirna Research substation during the 2015 main cropping season. The objective of the experiments was to elucidate the effect of seed tuber planting depth and nitrogen fertiliser rate on yield-related traits and yield of the crop. The treatments consisted of four seed tuber planting depths (5, 10, 15 and 20 cm) and five rates of nitrogen (0, 46, 92, 138 and 184 kg N ha−1). The experiment was laid out as a randomised complete block design with three replications. The results of the experiment at both locations revealed that the main effect of nitrogen application rate influenced total dry weight, unmarketable tuber yield, the percentage of small-sized and medium-sized tubers. Nitrogen rate and seed tuber planting depth also interacted to influence unmarketable tuber yield, the percentage of medium and large-sized tubers produced, and tuber starch content. The main effects of seed tuber planting depth significantly influenced total dry biomass, unmarketable tuber yield, total tuber yield, marketable tuber yield, the percentage of small-sized tubers produced and tuber starch content. Increasing seed tuber planting depth generally enhanced the aforementioned parameters. However, for most parameters, the highest values were obtained already at the seed tuber planting depth of 10 cm. The optimum total and marketable tuber yields of 26.93 t ha−1and 26 t ha−1for Haramaya and 34.57 t ha−1and 32.65 t ha−1for Hirna were obtained in response to planting seed tubers at the depth of 10 cm.

A previous study demonstrated that cabbage was P efficient compared to carrot and potato. However, calculating plant P uptake by a mechanistic simulation model based on P transport by diffusion and mass flow, P uptake of roots according to the Michaelis-Menten kinetics, and morphological root characteristics including root hairs, revealed that these parameters could explain only 2/5 of the total P uptake of cabbage, but 4/5 of that of carrot and potato (Dechassa et al., 2003). Therefore, it was hypothesized that a higher root exudation of organic anions may enhance P mobilization and hence P uptake of cabbage. The objective of this research was to determine root exudation of organic anions by the three species, and to investigate the influence of plant age and dark/light period on organic-anion exudation by cabbage. Experiments were conducted in a growth chamber in nutrient solution with or without P. Organic anions were determined in root exudates and in root tissue. With cabbage and potato, P deficiency induced exudation of citrate and succinate, respectively. Citrate-exudation rate of P-deficient cabbage plants was correlated with accumulation of citrate in root tissue. In contrast, high succinate-exudation rates in potato were not correlated with an increased concentration in root tissue. For carrot, no change was observed in the exudation of any of the organic anions in response to P deficiency. The results also showed that succinate- and citrate-exudation rates of cabbage roots increased with increased plant age. There was also a significant increase in exudation rates of organic anions of cabbage roots during the light period of the day. It was concluded that cabbage had the ability to exude large amounts of citrate in response to P deficiency by which it can additionally enhance its P-uptake efficiency, whereas carrot and potato showed little evidence of possessing such a mechanism.

Background: Current theories on biodiversity-carbon sequestration relationship describe biodiversity as an important factor influencing carbon storage, either through complementarity effect or by mass ratio effect. So far, the expected form of biodiversity-carbon relationships in tropical ecosystems has not been known with certainty. Therefore, we explored the relationship between aboveground carbon stock and different biodiversity measurement indices (i.e., species richness, species diversity, species evenness, and functional diversity) in different land cover types of Eastern Ethiopia. A total of 48 plots were established using stratified random sampling. Vegetation parameters such as diameter at breast height, diameter at stump height, tree height, and species type were recorded. Results: We found that the average aboveground carbon stock of the study area is 147.6 ± 17.2 t ha−1(mean, SE) across land cover types. Species richness, Shannon index, and functional diversity together explained 73.5%, 61.4%, 58.9%, and 52.0% of the variation in aboveground carbon storage in woodland, riparian forest, bushland, and farmland, respectively. Functional diversity was a significant predictor explaining the total aboveground carbon stocks (26.7%) across the land cover types. The effects of biodiversity on aboveground carbon storage were mediated by functional diversity and presence and dominance of species. This shows that both the selection effects and the niche complementarity are important for carbon storage. However, the impact of functional diversity effects (niche complementarity) was higher than that of functional dominance effects (selection effects). Conclusions: Implementation of protected area-based ecosystem conservation practices in the country seems feasible to mitigate climate change and Reducing Emissions from Deforestation and Forest Degradation (REDD+) programme should emphasize on biodiversity conservation.