Tolerance to high aluminium (Al) and low phosphorus (P) concentration by plant species and varieties grown in tropical soils
High Al and low P are one of the biggest constraints for crop growth in highly weathered and low fertility tropical soils. Plant species and varieties vary greatly in their tolerance to high Al concentration and some species and varieties have also shown acquisition of P from low P soils through morphological changes in their root system. The International Institute of Soil Biology and Fertility of Soils (CIAT) in Colombia, with whom we have had very close cooperation for the last 10 years, have initiated a program to assess the potential of various species (grasses, beans etc) and their varieties in acquiring P from low P soils. The proposed study will be connected to this program and will be carried out at this centre. The study will involve both field or greenhouse and laboratory work.
In cooperation with International Institute CIAT in Colombia)
Kontaktperson: Bal Ram Singh
Bioenergi: Utnyttelse av biprodukter fra biogassprosessen til gjødsel i planteproduksjon.
Knyttet til temaet fornybar energi og utnyttelse av biomasse til energiproduksjon, ønsker en her å utnytte biprodukter fra gassprosessen til ny biomasseproduksjon. Biproduktene fra en gassprosess med biomasse som råstoff inneholder bl.a. plantenæringsstoffer som en ønsker å resirkulere i produksjon av planter.
Metode: Karforsøk i klimaregulert vekstrom. Jord tilført biprodukt som vekstmedium for planter.
Det kan fokuseres på måling av makro- og mikronæringstoffer, event. på skadestoffer.
Kontaktpersoner: Trine Sogn
Susanne Eich-Greatorex
Bioenergi: Beregne effekter av økt biomasseuttak fra skog (uttak av GROT) på karbonlagring/CO2
I samarbeidsprosjekt med Institutt for Skog og landskap studeres effekter av økt biomasseuttak (utnyttelse av GRener Og Topper, GROT til bioenergiproduksjon) på
-utslipp og skogens langsiktige næringstilgang v.hj.a. mekanistisk, prosessorientert modellering
46
skogøkosystemets bærekraft. Nye data sammenstilles med data samlet inn over lengre tid i skogovervåkningsprogram, og ved hjelp av modellering beregnes mulige effekter av høyt biomasseuttak på skogens næringsstatus.
Metode: Databehandling, statistisk analyse, samt mekanistisk modellering.
Kontaktpersoner: Trine Sogn
Susanne Eich Greatorex
Silje Skår
Roots or shoots: what contributes most to CO2
This study is part of a research project with Bioforsk on the emission of soil borne green house gases from agriculture. Main hypothesis: roots contributes more than shoot residues to the formation of soil organic matter. This is of importance also for soil fertility. Advanced dynamic modelling of soil processes can be used for the interpretation of the data, depending on the student’s interest.
sequestration and building of soil organic
matter? Several alternative thesis, 30 or 60 ECTS (PV, MINA, Agroecology) . There is scope for cooperation between students working on different thesis.
Carbon sequestration in soil organic matter as a means of reducing atmospheric CO2 is a hot international topic. This is also the case for bioenergy production, but removing plant residues for production of bioenergy may result in loss of soil organic matter and no overall positive effect on CO2
emissions. Much depends on how quickly plant residues are decomposed after incorporation to the soil and to their contribution to the formation of “stable” soil organic matter. In a previous master thesis Torleif Bakke (Master in Agroecology) has labelled shoots and roots using 13C labelled CO2
We know already that shoots decompose much faster than roots, but we do not know a) what is their relative final contribution to “stable” humus, and b)how laboratory results compare with
decomposition under field conditions. A partly unexpected challenge is a tremendous increase in the mineralization of the organic matter already present in the soil, when plant residues are added. How long does it last? We follow this and the formation of (partially) stable organic carbon-soil aggregates using the
. The so labelled shoots and roots are now incubated under natural conditions in the field, as well as under controlled conditions in the lab.
13C/12C signature of the initial plant residue, of respired CO2
Kontaktperson: Marina A. Bleken
and of the organic carbon in different soil fractions. Laboratory and/or field study.
Effect of low temperatures on decomposition of plant residues and soil organic. Several thesis 30 or 60 ECTS (PV, MINA, Agroecology).
This study is part of a research project in collaboration with Bioforsk and the University of Århus (Denmark) for improved efficiency of nitrogen in organic
47
farming The focus is on the mineralization of plant residues and soil organic matter during the winter.
Main hypothesis: The effect of temperature on the mineralization of organic residues depends on their quality. Methods used are incubation of soil with and without addition of plant material ( labelled with 13C) at temperatures between 0 and 15 ⁰C. Advanced dynamic modelling of soil processes can be used for the interpretation of the data, depending on the student’s interest.
Decomposition of plant residues during the winter, when plants’ uptake is low, yields mineral nitrogen that is easily leached out of the soil and thus constitutes an environmental problem as well as a loss of a fundamental plant nutrient. An increase in winter temperature will shorten the period when the soil is frozen and thus increase the problem. In order to predict the consequences of climate changes and suggest improved crop management it is necessary to know better the relationship between temperature and decomposition of organic matter. An important aspect is the ratio between mineralized carbon and mineralized nitrogen. It is commonly assumed that it is unaffected by
temperature, but there are evidences that challenge this assumption. The net mineralization of nitrogen is the result of two opposite processes, one the decomposition of organic matter by microorganism in order to get energy, the other is the assimilation of nitrogen in microbial biomass. If low temperature reduces microbial growth more than respiration, the ratio of the mineralized C/N will decrease, implying that the risk of nitrogen leaching during winter is larger than presently recognized.
Kontaktperson: Marina A. Bleken
Effect of low temperatures on decomposition of digestate from biogas production . 30 ECTS (PV, MINA, Agroecology)
This study is complementary to the one above, and related to the search for improved strategies for a better management of crop residues and green manure management .
Kontaktperson: Marina A. Bleken
Selected rock-powder for improved plant nutrition and sustainability of organic farming:
30 or 60 ECTS (PV, MINA, Agroecology)
This study is in collaboration Michael Heim (Geology), Elin Lovise Gjengedal (environmental chemistry) and Tore Krogstad (soil chemistry). support by representatives of the mineral industry and NGU (Norges Geologiske Undersøkelser). This study will be part of a EU project, if granted.
Long-term fertility of organically managed soils is challenged by repeated removal of plant nutrients through cash crops. We are investigating the potential of
selected rock-powder to maintain and improve soil fertility under organic farming conditions. The use of rock-powder is in agreement with the principles of organic farming, and research about it provides fundamental knowledge on rock weathering and plant nutrition, which is of great relevance also for conventional farming. There have been already a few master studies on this topic showing very promising results.
48
The photo above is from a previous master thesis (Koen 2007). The white clover was grown on an extremely poor sandy soil often used to demonstrate nutrient deficiency, without any addition of soluble fertilizer except for the fertilised controls. Nitrogen was provided exclusively by symbiotic bacteria growing in nodules inside the clover roots. All the tested rock powders (4th to 9th row from left) improved growth and yield compared to the untreated control (3rd row from left), although none
of them could compete with the treatments fertilized with conventional soluble fertilizer (1st and 2nd row from left).
A rock is often made up by a mixture of
minerals.The picture to the left shows crystals of variety of minerals which are characteristic of a rock considered in this study. The crystals have been separated by natural weathering.
Illustration by Michel Heim
Kontaktperson: Marina A. Bleken
Modelling the nitrogen (N) efficiency and carbon balance of organic cereal production based on green manure. 60 ECTS (PV, MINA, Agroecology)
Green manure is a crop used to increase soil fertility. This study considers a N-fixing clover-grass mixture, with the herbage left on the field for incorporation in the soil, or removed for biogas production. It utilizes existing results of 4 field experiments in the Byggro project, in collaboration with Randi Berland at Bioforsk Organic. The main research question is which management of green manure gives the best results in terms of improved N utilization by the cereal crops and reduced N loss from the production system as a whole. This is basically a modelling study, using the SPN (Soil Plant Nitrogen) model to estimate N losses (leaching and denitrification) which could not be measured directly on the field. The basis assumption is that if the model manages to reproduce satisfactorily the observed N uptake by the plants and the observed mineral N content in the soil, then the model gives also the best estimates of N losses from the cropping systems( in absence of direct measurements). Strength and
weaknesses in this approach will be explored by alternative modelling exercises.
A topic will also be a critical analysis of organic cereal production separated from animal production in terms of nitrogen use efficiency.
Kontaktperson: Marina A. Bleken
49