Marit Jørgensen
Senior Research Scientist
Abstract
Aims Ethiopian soils are severely degraded and nutrient depleted, calling for effective remediation strategies. Enhancing soil biological activity through the cultivation of perennial forages may improve soil nutrient cycling and ameliorate soils. The aim of this study was to evaluate specific forage species as to their ability to improve soil biological functions. Methods We set up a fully factorial greenhouse experiment with Ethiopian soils from two regions differing in mineralogy, soil type and climate and tested the effect of two grass species Urochloa cv. ‘Cayman’, Megathyrsus maximus (Mombassa), and two legumes, Desmodium intortum (Greenleaf), Stylosanthes guianensis (Ubon) grown in single stands and mixtures on soil chemical and microbial variables. After 12 weeks of unfertilized growth, we measured soil mineral nitrogen (N), respiration, exoenzyme activities, microbial biomass N and phosphorus and the symbiotic performance of legumes. Results Soils from lower altitude Sidama region had 24% higher soil microbial activity than those from higher altitude Amhara. Aboveground N yield and shoot:root ratios were good indicators for stimulating effects on soil microbial functions, with S. guianensis having the strongest effect. Mixtures did not perform better than single stands. Legumes induced a 15% increase in acid phosphatase (AP) and 34% increase in N-enzyme activity which improved P-supply in three of the four soils. Conclusions AP-activity was stimulated by legumes in all soils but the overall ameliorative effect of perennial forage species appeared to be highly soil dependent. Plant effects on soil biological functions are more pronounced in less acidic soils with higher extractable P.
Authors
Akhil Reddy Pashapu Sigridur Dalmannsdottir Marit Jørgensen Odd Arne Rognli Mallikarjuna Rao KoviAbstract
The predicted increase in frequency and duration of winter warming episodes (WWEs) at higher northern latitudes is expected to negatively impact the forage production in this region. The formation of non-permeable ice cover due to WWEs creates hypoxic or anoxic conditions for plants, leading to severe winter damage. Knowledge about molecular mechanisms underlying various winter stresses, including ice encasement, is crucial to develop cultivars with better winter survival under changing climatic conditions. To date, very little is known about the molecular stress responses under ice encasement stress. To address this knowledge gap, in this study, we aimed to study ice encasement stress responses at the molecular level in the perennial forage grass timothy (Phleum pratense L.) by RNAseq. Genes encoding ethylene-responsive transcription factors, alcohol dehydrogenase 3, pyruvate decarboxylase 2, pyruvate kinase 1, dehydrins, early response to dehydration 15, glutathione reductase, and superoxide dismutase were highly upregulated under ice encasement conditions. KEGG enrichment analysis identified glycolysis, glutathione metabolism, and fructose and mannose metabolism as highly enriched among upregulated genes, whereas photosynthesis, flavonoid biosynthesis, motor proteins, and glycerolipid metabolism were highly enriched among downregulated genes. As initially hypothesized based on the nature of stress, the results indicate a substantial overlap of ice encasement stress responses with those of hypoxia and freezing stresses. Based on our findings and a comprehensive literature review on freezing and hypoxia stress responses, together with physiological studies of plants under ice encasement, we outline the potential mechanisms behind higher ice encasement tolerance in timothy.
Authors
Ievina Sturite Ellen Elverland Khaled Murad Agha Marit Jørgensen Frøydis Gillund Ragnhild Borchsenius Kauê Feitosa Dias De SousaAbstract
Resultater fra tradisjonelle feltforsøk når ofte ikke ut til bøndene. Et nytt prosjekt vil involvere 200 gårder direkte.
