Publications
NIBIOs employees contribute to several hundred scientific articles and research reports every year. You can browse or search in our collection which contains references and links to these publications as well as other research and dissemination activities. The collection is continously updated with new and historical material.
2026
Abstract
No abstract has been registered
Authors
Akhil Reddy Pashapu Sigridur Dalmannsdottir Marit Jørgensen Mallikarjuna Rao Kovi Odd Arne RognliAbstract
Timothy is the most important perennial forage grass species in northern Norway, a region that is predicted to experience variable winter weather conditions due to climate change. Knowledge about how timothy cultivars respond to a changing climate is crucial for safeguarding forage production at higher latitudes. In the current study, we investigated changes in gene expression under freezing and ice encasement stresses and SNP allele frequencies between temporal populations (seed generations) of the two northern-adapted timothy cultivars Engmo and Noreng. In general, there was a decrease in freezing tolerance (defined as LT 50 , the temperature lethal to 50% of the population) and an increase in ice encasement tolerance (defined as LD 50 , the duration lethal to 50% of the population) over time. Comparative transcriptome analyses identified several genes known to be involved in stress responses, such as ethylene-responsive transcription factors, dehydration-responsive element binding transcription factors, reversion to ethylene sensitivity 1, and abscisic acid repressor 1, as differentially expressed between the temporal populations of Noreng under freezing stress. Several loci with large allele frequency changes were observed to be in close proximity to the genes displaying patterns resembling shifts over time in Noreng. Very few gene expression differences between populations of both cultivars under ice encasement stress could be due to weak selection pressure during seed multiplication. There was a gradual decline in genetic diversity in populations of both cultivars over time. The results indicate that phytohormone-mediated transcriptional regulation might be one of the key mechanisms for adaptation to changing winter weather conditions at higher latitudes. These findings underscore the importance of monitoring genetic shifts during seed multiplication to maintain cultivar stability and suggest that the identified stress-responsive genes could serve as valuable targets for breeding climate-resilient forage crops.
Abstract
No abstract has been registered
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.
Abstract
This study quantified field-scale nitrogen (N) and phosphorus (P) removal by crop harvests, balances, and use efficiencies in 14 grass fields in the Timebekken catchment. Measurements of grass yields, nutrient concentrations, manure composition, and soil properties across multiple fields and farms were combined with survey data. Results showed large variation across farms and fields in day matter yield, nutrient inputs, removals, balances, and use efficiencies. Annual dry matter yield ranged 6,830–12,800 kg ha-1 (mean 9,010 kg ha-1) in 2024 and 7,480–12,130 kg ha⁻¹ (mean 9,800 kg ha⁻¹) in 2025. In 2024, nutrient inputs as mineral fertilizers and manure ranged 169–362 kg N ha⁻¹ (mean 240 kg ha⁻¹) and 23–57 kg P ha⁻¹ (mean 40 kg ha⁻¹). Corresponding nutrient removal ranged 150–303 kg N ha⁻¹ (mean 220 kg ha⁻¹) and 22–40 kg P ha⁻¹ (mean 29 kg ha⁻¹). Nutrient balances ranged from −111 to +182 kg ha⁻¹ (+14 kg ha⁻¹) for N and from −14 to +35 kg ha⁻¹ (12 kg ha⁻¹) for P. Nutrient use efficiency (input∕removal) ranged 50%–166% (mean 100%) for N and 38%–160% (mean 80%) for P. Overall, results indicate consistent management within farms but clear differences between farms, and therefore substantial potential for improving fertilizer and manure precision while maintaining yields. Phosphorus yield exceeded 27 kg ha-1 in several fields, in some 35 kg ha-1, which are the maximal allowed fertilizer limits from 2033. This substantiates farmers’ concerns about these limits being too low, yet average P inputs still exceeded crop demand. Despite lower topsoil P-AL in 2023 than in 2005, soil P status remained high, likely sustaining yields under stricter P limits. Elevated subsoil P highlights long-term loss risks and the need for targeted mitigation measures in hotspot areas. The study also calls for more monitoring of manure nutrients, yields, and soil P properties.
Authors
Niklas Jan WickanderAbstract
Ethiopia suffers from severe soil degradation resulting from poor agricultural management practices, deforestation, cultivation on slopes, and heavy, erratic rainfall patterns. This degradation places substantial pressure on smallholder farmers through the loss of topsoil, which reduces soil fertility and diminishes the area of arable land available for cultivation. Smallholder farmers typically practice mixed crop-livestock system, in which animals are often kept on small plots of land during the dry season and fed crop residues, while being allowed to graze on communal lands during the rainy season. Livestock is important to Ethiopian livelihoods, with a large proportion of the population dependent on it. However, the high density of animals, combined with low forage production, exacerbates soil degradation through overgrazing on communal land and increased reliance on crop residues for feed, thereby reducing the return of organic matter to the soils. To address these issues, inclusion of perennial forage mixtures as leys has been proposed as a strategy to both improve livestock feed production and restore degraded soils while preventing further degradation. Plant mixtures, particularly of grasses and legumes, have well-documented benefits to enhance soil organic C (SOC) and nutrient content, reduce the risk of erosion by stabilizing soil structure, and increase forage yields and feed quality. Improved soil nutrient status due to plant inputs also stimulates soil microbial communities, increasing microbial activity and exoenzyme synthesis. This has positive ramifications for soil nutrient cycling and may help remediate degraded Ethiopian soils in low-input agricultural systems. However, the effects of different plant species mixtures in soils with varying chemical and mineralogical composition remain unclear and require further investigations to identify optimal plant mixtures for different soil types. This thesis aims to elucidate the effects of four forage plant species on selected soil parameters in degraded soils from two distinct Ethiopian regions, with a particular focus on soil microbial functions. The thesis comprises three papers, each with focus on different aspects of plant-soil-plant feedbacks in various settings: (I) the effects of plant diversity and biomass on microbial activity and nutrient cycling in a field experiment, (II) the effects of specific plant species inputs on soil microbial nutrient stoichiometry and nutrient cycling under controlled greenhouse conditions, (III) microbial carbon use efficiency (mCUE) in weathered soils under cultivation of perennial forage species in a greenhouse experiment. The thesis is based on three separate experiments: a field experiment in the Amhara and Sidama regions of Ethiopia, and both large- and small-scale factorial experiments in greenhouse using soils sampled from these regions. Two grasses (Urochloa hybrid cv. Cayman and Megathyrsus maximus) and two legumes (Desmodium intortum and Stylosanthes guianensis) were grown in the experiments described in Papers I and II, whereas only U. cv. Cayman and D. intortum were grown in the experiment described in Paper III. Soil chemical and physical characteristics were determined prior to the experimentation for all soils. Microbial nutrient status and its responses to plant input were assessed via analysis of exoenzyme activity (EEA), while specific microbial functions such as nitrification and denitrification were also measured. The plant effect on microbial C-turnover and growth was determined by using the 18O-H2O stable isotope probing (SIP) method, determining mCUE and microbial growth rate. Overall, plant inputs had generally positive effects on soil microbial functions, although responses varied considerably depending on initial soil properties. The strongest effects were typically observed in the more fertile Sidama soils, compared to the less fertile Amhara soils. The magnitude and nature of plant input effects also differed across the three studies. Plant species diversity and biomass had minor effects on soil microbial functions, while U. cv Cayman showed some positive effects on belowground functions in Hawassa soil (Paper I). Legumes, particularly S. guianensis, enhanced EEA which contributed positively to the soil microbial nutrient cycle (Paper II). Plant inputs affected mCUE only in the Sidama soils, with a positive effect of increased plant biomass on mCUE and a negative effect of the U. cv. Cayman × D. intortum mixture on mCUE (Paper III). In summary, the implementation of perennial forage mixtures had positive effects on soil microbial nutrient cycling, with potential long-term effects for soil health. However, these effects were soil-specific, with stronger responses and higher microbial activity in the more fertile, phosphorus (P) rich soils of the Sidama region. The low responsiveness of soil microbes to plant inputs in the Amhara region may be attributed to inherently low P availability. Alleviating P limitation may therefore be necessary before realizing the beneficial effects of perennial forage mixtures in P-limited soils. In addition, site-specific selection of plant species mixtures that can successfully establish and co-exist is recommended to achieve optimal plant performance and effective soil remediation.
Abstract
This conference proceedings paper investigates how forage species and seasonal cuts affect mass balance, dry matter distribution and crude protein recovery in green biorefinery. The study compares timothy, red clover and a grass–clover mixture across seasonal cuts, with focus on pulp, green protein concentrate and brown juice fractions.
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.
Abstract
No abstract has been registered
Abstract
Abstract Background and Aims Efficient phosphorus (P) and management is essential for sustainable arable systems. Cover crops (CCs) are promising, but their performance is uncertain in high-latitudes. This three-year study evaluated CCs’ effects on P dynamics in a P-rich soil undersown in barley in Mid-Norway (63.9°N)—one of the northernmost trials of its kind. Methods A randomized complete block design included three CC treatments: ryegrass (CC1), a ryegrass–clover mix (CC2), and a four species mix including grass, legumes and herbs (CC3), and controls without CC (with/without NPK fertilizer). Soil and plant analyses included total and available P, total N, potentially mineralizable N (PMN), pH, permanganate-oxidizable carbon, root biomass, plant P concentrations, and microbial abundance via qPCR. Statistical analysis was based on Linear Mixed Models (LMMs). Results Cover crops successfully established (average biomass: 1525 kg ha⁻ 1 ), accumulated ~ 7 kg P ha⁻ 1 , and did not reduce barley yields. LMMs showed significant effects of CC treatment on root biomass, total P, and bacteria. Pairwise comparisons also revealed that fungal abundances in CC1 and CC3 were significantly higher than in the unfertilized control. Pairwise regression revealed that soil total P was strongly predicted by root biomass (β = 1.37, P < 0.001). Available P was negatively controlled by microbial pools (Bacteria: β = -9.22, P < 0.001) and residue quality (C:P ratio: β = -0.36, P < 0.001). Conclusions CCs can be used at 63°N without yield penalty. The primary P mechanism is mass-driven sequestration (root biomass) into the stable total P pool. However, P availability is temporally constrained by residue quality and microbial competition. Graphical Abstract