Season-specific varietal management as an option to increase rainfed lowland rice production in East African high altitude cropping systems

Due to land expansion and an increase in productivity, rice production in sub-Saharan Africa has been growing at a rate of 6% in the past decade. Rainfed rice production systems have accounted for a large share of this expansion. In these systems, the potential growing period not only depends on the length of the rainy season and thus water availability, but is often, especially in the highlands of East Africa, bordered by the onset of the cool period of the year, when low minimum temperatures compromise rice yields. The objective of this study was to investigate the yield potential of 30 rice varieties contrasting in crop duration and cold tolerance in the highlands of East Africa, with its limited length of growing period. A field trial was conducted in the cropping seasons in 2016 and 2017 at the Fogera rice research station, Ethiopia. As a function of the onset of rains, rice was sown mid-July in 2016 and early July in 2017. Early sowing in 2017 led to an extended crop duration and significantly lower yields of the short-duration varieties, and to a shortened duration and significantly higher yields of the medium- and long-duration varieties, when compared to late sowing in 2016. Late sowing compromised yield of the medium- and long-duration varieties because of low temperatures during booting stage, which led to high spikelet sterility. Early sowing resulted in low yields of the short-duration varieties, probably due to low solar radiation during the cloudy rainy season, which coincided with the vegetative stage. Therefore, choice of variety should be a function of the variable onset of the rainy season and related sowing date. However, crop models precisely calibrated for potential varieties and the respective environmental conditions could fully support the selection of a suitable variety, depending on the date of sowing, for example with the help of online tools or smartphone applications.     

Effects of land management practices and land cover types on soil loss and crop productivity in Ethiopia: A review

Identifying land management practices (LMPs) that enhance on-site sediment management and crop productivity is crucial for the prevention, reduction, and restoration of land degradation and contributing to achieving land degradation neutrality (LDN). We reviewed studies in Ethiopia to assess the effects of LMPs on soil loss (84 studies) and crop productivity (34 studies) relative to control practice. Yield variability on conserved lands was assessed using 12,796 fixed plot data. Effects of LMP on soil loss were 0.5–55 t ha⁻¹y⁻¹ compared to control practices yielding 50 to 140 t ha⁻¹y⁻¹. More than 55% of soil loss records revealed soil loss less than the tolerable rate (10 t ha⁻¹). Area closure, perennial vegetation cover, agronomic practices, mechanical erosion control practices, annual cropland cover, and drainage groups of practices led to 74.0 ± 18.3%, 69.0 ± 24.6%, 66.2 ± 30.5%, 66.1 ± 18.0%, 63.5 ± 20.0%, and 40 ± 11,1% soil loss reduction, respectively. A yield increase of 25.2 ± 15.0%, 37.5 ± 28.0%, and 75.4 ± 85.0% was found from drainage, agronomy, and mechanical erosion control practices, respectively. The average yield loss by erosion on fields without appropriate land management practice and on conserved fields was 26.5 ± 26.0% and 25 ± 3.7%, respectively. The findings suggest that practices that entail a continuous presence of soil cover during the rainy season, perennial vegetation, retention of moisture, and barriers for sediment transport were most effective at decreasing soil loss and increasing productivity. This review provides evidence to identify the best LMP practices for wider adoption and inform decision-making on LMP investments towards achieving sustainable solutions to reverse land degradation.     

Body Size and Testicular Traits of Tropically–adapted Bucks Raised Under Extensive Husbandry in Ethiopia

Contents Five tropically adapted buck breeds extensively managed in Ethiopia were studied to determine possible effects of breed and age on body size and testicular traits. In all, 177 bucks were selected following stratified random sampling, and evaluated in three age groups: <14 months (young), 14–19.5 months (intermediate) and 19.6–24 months (old). The breeds studied were Arsi-Bale (AB; N = 35), Central Highlands (CH; N = 33), Afar (N = 35), Boran (N = 36) and Woito-Guji (WG; N = 38). In all the three age groups, Boran and CH bucks were the heaviest (p < 0.05), Afar were the lightest, and AB and WG were in between. The highest body weight (BW) was achieved in the intermediate age group for Afar, but in the oldest age group for the other breeds. In the youngest age group, scrotal circumference (SC) was the widest (p < 0.05) for Boran and CH and the narrowest for Afar, AB and WG, while in the intermediate and the oldest age groups, Boran showed the widest SC. Boran, WG and CH had higher (p < 0.05) testicular weight (TW) than Afar and AB in the youngest age group. Boran retained the highest (p < 0.05) TW in the intermediate and the oldest age groups, while in the oldest age group WG and AB medium TW and Afar had the lowest TW. However, Afar had the highest TW expressed as percentage of BW. SC was well correlated with TW (p < 0.001; r  = 0.74) and BW (p < 0.001; r  = 0.61), indicating a linear, positive association between BW and TW (p < 0.001; r  = 0.51). In conclusion, body size and testicular traits of Ethiopian bucks under an extensive management system are influenced differently by breed and age group.     

Status of bovine tuberculosis and its zoonotic implications in Borana zone,Southern Ethiopia

A cross-sectional study was carried out from April 2015 to June 2016 to estimate the status of bovine tuberculosis (BTB), assessment of community’s current knowledge, and zoonotic importance on this disease in Borana zone, southern Ethiopia. In this study, comparative intradermal tuberculin (CIDT) test, structured questionnaires, and retrospective data were used, while the result indicated 3.8% prevalence at individual animal level with 5.6% (31/554) of doubtful reactors. Among related risk factors included, old animals were significantly infected by BTB than young one (χ ²?=?32.005, P?=?0.001). Parity number again showed significant difference (χ ²?=?29.163, P?=?0.001) where animals with many parity were more reactive to conducted test than few parity numbers. Animals born in the breeding center managed under semi-intensive production system were more infected (χ ²?=?10.795, P?=?0.029) than those brought from outside of the center. Questionnaire survey in this study indicated that out of 130 interviewed respondents, only 30% pastoralists knew what BTB mean; whereas the level of individual knowledge from interviewed showed about 72.3% of respondents had poor understanding of BTB and only about 11.5% of them knew its zoonotic importance. Meat eating habit of communities in the area were culturally inhabited to eat cooked meat and only 12.3% (16/130) of respondents gave response on habit of eating both raw and cooked meat. Milk drinking habit of pastoralist in the area showed about 79.2% drunk raw milk and the rest 20.8% used both raw and boiled milk. A retrospective data from Yabello Hospital indicated that current prevalence of human TB as 38.79% and showing the disease was highly increasing from year to year in the study area. This implies a great importance of human tuberculosis and its future concern in Borana zone. From this, there should be detail awareness of communities on BTB, its zoonotic importance, and the need of further investigation to develop control and prevention strategies according to the pastoral settings.     

Climatic determinants of lowland rice development

Accurate modelling of plant development is the basis for any assessment of climate change impact on crop yields. Most rice models simulate development (phenology) based on temperature and photoperiod, but often the reliability of these models is reduced beyond the environment they were calibrated for. In our study, we tested the effects of relative air humidity and solar radiation on leaf appearance rate in greenhouse experiments and analysed data sets from field studies conducted in two extremely different rice-growing environments in Nepal and Senegal. We also analysed environmental effects on duration to flowering of one popular IRRI material (IR64) for eight different sites covering the entire temperature range where rice is widely cultivated. Both low relative air humidity and low solar radiation significantly decreased leaf appearance rate. Mean air temperature explained 81% of the variation in duration to flowering across sites, which was furthermore significantly influenced by relative air humidity. Across all sites, a simple linear regression approach including mean air temperature and mean relative humidity in the calculation of duration to flowering led to a root mean square error (RMSE) of 10 days, which was slightly lower than the RMSE of 11 days achieved with an automated calibration tool for parameter optimization of cardinal temperatures and photoperiod sensitivity. Parameter optimization for individual sites led to a much smaller prediction error, but also to large differences in cardinal temperatures between sites, mainly lower optimum temperatures for the cooler sites. To increase the predictive power of phenological models outside their calibration range and especially in climate change scenarios, a more mechanistic modelling approach is needed. A starting point could be including relative air humidity and radiation in the simulation procedure of crop development, and presumably, a closer link between growth and development procedures could help to increase the robustness of phenological models.     

Effect of organic residue amendments and soil moisture on N mineralization,maize (Zea maysL.) dry biomass and nutrient concentration

Greenhouse pot experiments using four tropical soils were conducted to measure the effect of crop residues on nitrogen mineralization/immobilization and the growth of maize plants under two soil moisture regimes (pF2.5 and pF3.5). Nitrogen-rich residues of pigeon pea [PP, Cajanus cajan (L.) Millps, C/N, 18.8] enhanced plant growth and increased the assimilation of mineral elements (N, P and K) at both moisture regimes. Less nitrogen-rich residues of haricot beans [HB, Phaseolus vulgaris (L.), C/N, 28.9] had a slightly negative effect on plant growth and the assimilation of mineral elements, and a stronger negative effect was recorded for the most N-poor plant residue, maize [M, Zea mays (L.), C/N, 33.6]. For PP, we estimated the recovery of residue-nutrients in maize plants (net increase in N, P and K assimilation due to PP incorporation) as 19% for N, 88% for P and 86% for K in the high-moisture regime (pF2.5). The equivalent values for the drought-stress regime (pF3.5) were 10, 34 and 38%, respectively. The results demonstrate the immediate enhancement of plant growth by plant residues with a low C/N ratio, even under drought-stress conditions.     

Carbon and nitrogen mineralization dynamics in different soils of the tropics amended with legume residues and contrasting soil moisture contents

Seasonal drought in tropical agroecosystems may affect C and N mineralization of organic residues. To understand this effect, C and N mineralization dynamics in three tropical soils (Af, An₁, and An₂) amended with haricot bean (HB; Phaseolus vulgaris L.) and pigeon pea (PP; Cajanus cajan L.) residues (each at 5 mg g⁻¹ dry soil) at two contrasting soil moisture contents (pF2.5 and pF3.9) were investigated under laboratory incubation for 100–135 days. The legume residues markedly enhanced the net cumulative CO₂–C flux and its rate throughout the incubation period. The cumulative CO₂–C fluxes and their rates were lower at pF3.9 than at pF2.5 with control soils and also relatively lower with HB-treated than PP-treated soil samples. After 100 days of incubation, 32–42% of the amended C of residues was recovered as CO₂–C. In one of the three soils (An₁), the results revealed that the decomposition of the recalcitrant fraction was more inhibited by drought stress than easily degradable fraction, suggesting further studies of moisture stress and litter quality interactions. Significantly (p < 0.05) greater NH₄⁺–N and NO₃⁻–N were produced with PP-treated (C/N ratio, 20.4) than HB-treated (C/N ratio, 40.6) soil samples. Greater net N mineralization or lower immobilization was displayed at pF2.5 than at pF3.9 with all soil samples. Strikingly, N was immobilized equivocally in both NH₄⁺–N and NO₃⁻–N forms, challenging the paradigm that ammonium is the preferred N source for microorganisms. The results strongly exhibited altered C/N stoichiometry due to drought stress substantially affecting the active microbial functional groups, fungi being dominant over bacteria. Interestingly, the results showed that legume residues can be potential fertilizer sources for nutrient-depleted tropical soils. In addition, application of plant residue can help to counter the N loss caused by leaching. It can also synchronize crop N uptake and N release from soil by utilizing microbes as an ephemeral nutrient pool during the early crop growth period.     

Major causes of mastitis and associated risk factors in smallholder dairy farms in and around Hawassa, Southern Ethiopia

A cross-sectional study was carried out from October 2008 to May 2009 in smallholder dairy farms in and around Hawassa to estimate the prevalence of mastitis, to isolate and characterize major bacterial pathogens, and to identify possible associated factors. The study involved a total of 201 milking cows randomly drawn from smallholder farms. The prevalence of clinical and subclinical mastitis was determined through clinical examination of the udder and using mastitis indicator paper (Bovivet indicator paper, Kruuse, Denmark). The prevalence of mastitis at cow and quarter level was 30.3 (61/201) and 10.3 (79/766), respectively. Subclinical mastitis was 25.4% and 5.0% was clinical. Stage of lactation significantly affected (P < 0.05) the prevalence of mastitis, with the highest prevalence observed in the late stage of lactation (41.3%) as compared to early (25.0%) and mid (22.1%) stages of lactation. Floor type and bedding had association (P < 0.05) with mastitis prevalence. Cows housed in concrete-floored houses had lower prevalence (19.0%) of mastitis compared to cows kept in soil-floored houses (47.6%). Mastitis prevalence was low in farms which do not use bedding (23.5%) as compared to farms using hay/straw bedding (37.4%). However, age, parity, and history of mastitis had no association (P > 0.05) on the prevalence of mastitis. The pathogens isolated from mastitic cows were Staphylococcus aureus (48.6%), other staphylococci species (15.7%), Streptococcus agalactiae (11.4%), other streptococci (17.1%), Bacillus species (2.9%), and coliforms (Escherichia coli and Klebsiella species) (4.3%). Strict hygienic measure of housing and bedding should be considered, in reducing the prevalence of mastitis.     

Inoculation with indigenous rhizobial isolates enhanced nodulation,growth, yield and protein content of soybean (Glycine max L.) at different agro-climatic regions in Ethiopia

Abstract

Soybean cultivation in Ethiopia is dominated by smallholder farmers who use little or no inputs, often resulting in low yields. The use of effective rhizobia strains was considered as an ecologically and environmentally sound approach for soybean production. Field experiments were conducted during 2015/16 cropping seasons at two different agro-climatic regions in Ethiopia to investigate the effectiveness of local soybean isolates for improving nodulation, growth, yield and quality of soybean. Ten treatments comprising of seven indigenous rhizobia isolates, one exotic strain, nitrogen fertilized treatment and uninoculated control were arranged in randomized complete block design in three replications. Results of the experiment revealed that nodule number and nodule dry weight significantly increased from nil in the uninoculated control to 14–34 and 110–521?mg plant^?1, respectively due to inoculation with different isolates. Furthermore, inoculation significantly increased shoot dry weight by 24–46%, shoot nitrogen concentration by 20–30%, shoot N content by 29–49%, plant height by 14–41%, pods per plant by 12–38%, seeds per pod by 7–19%, thousand seed weight by 15–24%, grain yield by 22–115% and protein content by 7–39% compared with the uninoculated control. Generally, isolates Jm-1-Bo, As-5-Aw, Bk-3-Aw, Cw-6-Aw and MAR 1495 performed better than the others in most yield parameters at both locations of which Jm-1-Bo and As-5-Aw were the local isolates performing best irrespective of location, and were superior to the effective exotic standard strain. Therefore, isolates Jm-1-Bo, As-5-Aw and Bk-3-Aw could be utilized as candidates for inoculant production at large scale in areas with similar agroecology.     

Impact Assessment of a Community-based Animal Health Project in Dollo Ado and Dollo Bay Districts,Southern Ethiopia

Participatory methods were used to assess the impact of a community-based animal health worker (CAHW) project in two remote pastoralist districts of Ethiopia. The CAHW project had been operating for 3 years at the time of the assessment. Participatory methods were standardized and repeated with 10 groups of informants in the project area. The assessment showed significant reductions in disease impact for diseases handled by CAHWs compared with diseases not handled by CAHWs. In camels, there was significant reduction (p < 0.001) in the impact of mange, trypanosomosis, helminthosis, anthrax and non-specific respiratory disease. In cattle there was a signficant reduction (p < 0.001) in the impact of blackleg, anthrax and helminthosis. In sheep and goats there was a sign reduction (p < 0.001) in the impact of mange, helminthosis, contagious caprine pleuropneumonia, orf and non-specific diarrhoea. In order of importance, these reductions in disease impact were attributed to (1) increased use of modern veterinary services provided by CAHWs, (2) vaccination campaigns involving CAHWs, (3) good rainfall and availability of grazing and (4) decreased herd mobility. Decreased herd mobility was also associated with negative impact of tick infestation. Community-based animal health workers were considered to be highly accessible, available, affordable and trustworthy relative to other service providers. They were also perceived to be suppliers of a good quality service. Specific types of positive impact attributed to CAHW activities were increases in milk, meat, income and draught power.