Exploring stress-tolerant plant growth-promoting rhizobacteria from groundnut rhizosphere soil in semi-arid regions of Ethiopia.

The potential of rhizobacteria with plant growth promoting (PGP) traits in alleviating abiotic stresses, especially drought, is significant. However, their exploitation in the semi-arid regions of Ethiopian soils remains largely unexplored. This research aimed to isolate and evaluate the PGP potential of bacterial isolates collected from groundnut cultivation areas in Ethiopia. Multiple traits were assessed, including phosphate solubilization, indole-3-acetic acid (IAA) production, ammonia production, salt and heavy metal tolerance, drought tolerance, enzyme activities, hydrogen cyanide production, antibiotic resistance, and antagonistic activity against fungal pathogens. The identification of potent isolates was carried out using MALDI-TOF MS. Out of the 82 isolates, 63 were gram-negative and 19 were gram-positive. Among them, 19 isolates exhibited phosphate solubilization, with AAURB 34 demonstrating the highest efficiency, followed by AURB 12. Fifty-six isolates produce IAA in varying amounts and all isolates produce ammonia with AAURB12, AAURB19, and AAURB34 displaying strong production. Most isolates demonstrated tolerance to temperatures up to 40°C and salt concentrations up to 3%. Notably, AAURB12 and AAURB34 exhibited remarkable drought tolerance at an osmotic potential of -2.70 Mpa. When subjected to levels above 40%, the tested isolates moderately produced lytic enzymes and hydrogen cyanide. The isolates displayed resistance to antibiotics, except gentamicin, and all isolates demonstrated resistance to zinc, with 81-91% showing resistance to other heavy metals. AAURB34 and AAURB12 exhibited suppression against fungal pathogens, with percent inhibition of 38% and 46%, respectively. Using MALDI-TOF MS, the promising PGP isolates were identified as Bacillus megaterium, Bacillus pumilus, and Enterobacter asburiae. This study provides valuable insights into the potential of rhizobacteria as PGP agents for mitigating abiotic stresses and contribute to the understanding of sustainable agricultural practices in Ethiopia and similar regions facing comparable challenges.

The nitrogen fertilizer replacement values of incorporated legumes residue to wheat on vertisols of the Ethiopian highlands.

Soil fertility depletion and continuous cereal cropping are reducing crop production in Ethiopia. Integrated Soil Fertility Management (ISFM) is a good approach for resource-poor farmers because ISFM can help reduce the need for inorganic fertilizer by increasing nitrogen (N) availability in the soil. The study aimed to investigate the effect of preceding crops, legume residue management practices, and N levels on wheat planted. The experiment was set up using a split plot in a randomized complete block design with three replications. The N fertilizer replacement value method was used to estimate the N contribution of legumes to a succeeding wheat crop. The results showed that grain yield and N uptake of wheat crops varied in response to N fertilizer, legume residue management treatments, and tillage practices. Legume residue incorporation positively influenced the agronomic parameters of wheat compared to teff and fallow wheat rotations. The average N fertilizer replacement value from legume rotation was 18-46 kg ha-1. This study showed that a one-year legume-in-biannual wheat rotation is preferable to lying bare fallow during the cropping season. Nevertheless, drainage during legume and wheat cropping is a condition for providing full positive impacts.

Method for conducting systematic literature review and meta-analysis for environmental science research.

This paper presents a method to conduct a systematic literature review (SLR) and meta-analysis studies on environmental science. SLR is a process that allowed to collect relevant evidence on the given topic that fits the pre-specified eligibility criteria and to have an answer for the formulated research questions. Meta-analysis needs the use of statistical methods that can be descriptive and/or inferential to summarizing data from several studies on the specific topic of interest. The techniques help to generate knowledge from multiple studies both in qualitative and quantitative ways. The usual method has four basic steps: search (define searching string and types of databases), appraisal (pre-defined literature inclusion and exclusion, and quality assessment criteria), synthesis (extract and categorized the data), and analysis (narrate the result and finally reach into conclusion) (SALSA). However, this work added two steps which are research protocol (define the research scope) and reporting results (stating the procedure followed and communicating the result to the public) at the initial and last step, respectively. As a result, the new method has six basic steps which are abbreviated as PSALSAR. Therefore, this method is applicable to assess the existing knowledge, trends, and gaps in ecosystem services. In sum, this literature review method presents: •The PSALSAR method is an explicit, transferable and reproducible procedure to conduct systematic review work.•It helps to assess both quantitative and qualitative content analysis of the literature review.•The procedure listed here added two basic steps (protocol and reporting result) on a commonly known SALSA framework.

Ecosystem services research in mountainous regions: A systematic literature review on current knowledge and research gaps.

Mountain ecosystem services (MES) can provide a wide range of benefits for human well-being, including provisioning, regulating, supporting and cultural services. This systematic review work analyzed existed knowledge and research gaps on MES at the global level. The study used databases of science direct, Scopus and google scholar using searching, appraisal, synthesis, and analysis (SALSA) framework. Using specific keywords for the searching engine, the number of publications linked with MES were about 1252 which published between 1992 and June 2019. But, only 74 publications fulfilled the inclusion criteria. The analysis highlighted the existence of gaps in the literature including case studies from a limited geographical areas, focus on regulating and provisioning services, and lack of studies that explore the kinds of interlink between ecosystem services, and occurrence of limitation linked with data and methodology. From the 74 publications used for analysis, only seven of them were addressed mainly trade-offs and synergies, but most of them focus on quantification, qualification and economic valuation of the services. From the total case studies, the services addressed were summed up to 317 services, and the services such as climate regulation, food and fodder, fresh water, recreation and ecotourism, and erosion regulation studied more. On the contrary, photosynthesis, ornamental resources, net primary production, disease regulation, genetic resources, water purification and waste treatments were the least studied. Therefore, future research works should focus on mountainous areas of no and least studied of its ecosystem services. Critical studies are also required that indicate the link between a human being with MES, the trade-offs and synergies between MES and the influence of human beings on the quality and accessibility of ecosystem services. Besides, priority should be given by researches for methodological development and proposing management option for the mountain ecosystem and resource.