Publikasjoner
NIBIOs ansatte publiserer flere hundre vitenskapelige artikler og forskningsrapporter hvert år. Her finner du referanser og lenker til publikasjoner og andre forsknings- og formidlingsaktiviteter. Samlingen oppdateres løpende med både nytt og historisk materiale. For mer informasjon om NIBIOs publikasjoner, besøk NIBIOs bibliotek.
2006
Authors
Svein Øivind Solberg Steinar DraglandAbstract
Varius plastic mulch, fiber mulch and paper mulch were examined in four perennial herb crops in a field experiment during a three-year period in Norway. Over-wintering, total yield, herbs nutrient content, soil temperatur, and soil nitrogen were examined.
Authors
Ingvild WartiainenAbstract
Gjennomgang av hva man i dag vet om hvordan forurensingen fra smelteverkene i Nikel og Pechenga påvirker natur og mennesker i nærområdene i Norge og Russland.
Authors
R. M. Bajracharya S. Sharma B. M. Dahal B. K. Sitaula Alhaji JengAbstract
The concept of soil quality, first proposed in the 1970"s, involves a soil"s capacity to function within an ecosystem to sustain plant and animal productivity, maintain and enhance air and water quality, and to support human health and habitation. It is a useful tool for assessing the overall soil condition and response to management, or resilience towards natural and human degradative forces. Soil quality may be inferred from various soiul indices, such as, chemical or biological attributes that reflect its condition and response. While physical and chemical attributes are well established, they are usually costly to determine and require specialized equipmentto measure. Biological indices, like abundance, biomass, and diversity of micro-, meso-, amd macro-fauna, can be determined relatively rapidly and at minimal cost. It has the added advantage of being integrative over a long timeframe and holistically considers overall quality or status of the soil as influenced by multiple stressors. Thus, this preliminary study attempted to evaluate soil quality both by physiochemical parameters and using biological (soil meso- and macro-fauna) indices, and correlate as well as compare the outcomes using both methods, for different land uses in a mid-hill watershed of central Nepal.
Abstract
Chemical recalcitrance of specific molecules is one of the factors governing organic matter stabilization in soils. Little is known about the relationship between the chemical nature and the dynamics of soil organic matter at the long-term scale. Lignin molecules are abundant in plant tissues and are generally considered as slowly biodegradable in soils. In a previous study, using compound specific isotopic tracer techniques applied to agricultural lands converted from C3 to C4 cropping, we showed that lignin turnover was faster than that of total organic carbon. Lignin dynamics was well described by a two-pool model, distinguishing lignins in fresh plant residues and those more closely associated to the soil matrix. These two pools may be transformed into non-lignin products, which includes CO2, microbial biomass and chemical substances, which are no longer recognized as lignin derivatives. The aim of the present work was to study the nature and dynamics of these non lignin products formed during lignin degradation in a laboratory incubation of 13C-labelled lignin with soil. Maize plants were grown for 1 month under 13C enriched CO2. The lignins of leaves and stems were isolated after treatment with cellulolytic enzymes and solubilization in dioxane:water (1:9). The Milled Maize Lignin (MML) obtained had a 13C abundance of 1.4 %. Solid-state 13C NMR spectroscopy of MML before analysis showed that the isolation method produces a lignin-cellulose complex, as indicated by the presence of some polysaccharides (the 60-115 ppm region represented about 40 % of total C of isolated lignins). Lignins were incubated with soil (1 mg lignin/g soil) at 20°C in sealed glass jars and analyzed after 1, 2, 4, 8, 16, 32 and 48 weeks. A control sample was incubated without lignin. We monitored the mineralization, solubilization and incorporation in the microbial biomass of lignin C by measuring 13C enrichments in respired CO2, water-soluble fractions, and fumigated biomass, respectively. Lignins remaining in incubated soils were quantified by CuO oxidation and the 13C contents of vanillyl, syringyl and cinnamyl units (VSC) were measured. After 4 months, 3% of the 13C of the labelled lignin was mineralized. This mineralization rate was less than that found by Martin and Haider (1979) for DHP lignins but more than the 5% per year found in situ by Dignac et al. (2005). Less than 0.5% of incubated lignin C was water soluble and 0.5 % was incorporated into the soil microbial biomass. The main part (96%) of incubated MML remained in soil. We used compound-specific isotopic analysis of the CuO oxidation products and pyrolysis analysis to estimate the proportion of intact lignins remaining in the soil.
Abstract
Lignin is a major plant litter compound. Due to its aromatic structure it is not easily decomposable by the soil microbial biomass and has for a long-time been considered to accumulate in soil. A recent study, however, indicated that lignin has a faster turnover than the bulk soil organic matter, suggesting that there is no long-term storage of the pristine lignin molecule in soil. Using a modelling approach we were able to show that more than 90 % of lignin deposited on the soil surface is transformed into non-lignin products. The aim of this study was to elucidate the forms of lignin derived carbon during a longterm laboratory incubation of 13C labelled lignin in soil. The conceptual approach included the extraction of lignin from a 13C labelled maize plant and its incubation under ideal conditions for 11 months. Our results show that the non-lignin products are mostly CO2, with few incorporation of lignin-derived carbon into the soil microbial biomass. We were able to detect a priming effect of soil organic matter induced by lignin addition. Analysis of the mineralisation kinetics suggested that the 13C labelled isolated lignin consisted of two compartments with different decomposition rates. One of the two compartments might be related to the presence of cellulose within the isolated lignin, which has been detected using 13C CPMAS NMR spectroscopy. Molecular analysis of lignin using chemolytical methods showed that lignin becomes more accessible to chemical attack in the course of incubation. Higher yields of lignin monomers were obtained after 4 month using cupric oxide oxidation as well as thioacidolysis. These results indicate that lignin degradation in soil can hardly be separated from cellulose decomposition
Authors
B. M. Dahal B. K. Sitaula R. M. Bajracharya K. Atreya Alhaji JengAbstract
Soil and nutrient losses are a major threat to farmland productivity in Nepal. Thus, soil and nutrient losses were monitored and analyzed from two and three crop patterns per year in Ansikhola watershed. Erosion was monitored from multi-terraced garicultural plots consisting of 2 to 3 terraces. The agricultural soil of the watershed was generally rich in terms of organic matter and nutrients (N, P, K). The nitrogen content of soil in leve lowland farm plots was higher in the 2 cropping plots compared to the 3 cropping plots. The soil pH ranged from 4.4 to 5.2 in both intensive and less intensive areas. Soil and nutrient losses were comparitively higher from intensively cropped areas; however, overall losses were less than average losses in other similar watersheds in Nepal.
Authors
Trond MæhlumAbstract
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Authors
Ove BergersenAbstract
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