Tidsrammen for klargjøring av såbed til vårkorn : laglighet og klimaendringer i Norge

Future increases in winter and spring precipitation in Norway may exacerbate the dilemma of spring fieldwork that farmers have, concerning topsoil compaction versus delayed sowing on autumn-ploughed soil. Both topsoil compaction and delayed sowing increase the loss of yield potential. The overall aim of this PhD project was to explore how seedbed preparation for spring cereals can be adapted to future climate change and how further loss of cereal yield potential can be avoided, on different soil types under contrasting climatic conditions in Norway. To pursue this aim, the thesis starts with presenting the overall agronomical context of northern growing conditions and the theoretical background to seedbed preparation physics. After that, it presents and discusses results from two field experiments and a simulation study. One field experiment focused on timing and traffic intensity in spring tillage operations that minimise soil physical degradation under unfavourably wet conditions. This experiment compared spring fieldwork conducted on different dates (early, medium, late) with different traffic intensity (no wheeling, one, two or three wheelings), with regard to soil physical properties and crop performance. The results show that early spring fieldwork in excessively wet soil gave rise to larger and stronger aggregates, higher penetration resistance and slightly changed pore characteristics, with resulting reduced yields. The increased penetration resistance persisted until autumn. The effect of traffic intensity was less pronounced, probably due to location, soil type and the small range of intensities involved. The proportion of 2-6 mm aggregates and penetration resistance were the most important soil physical factors for both soil quality and cereal yield. This experiment shows that soil physical degradation can be minimised by conducting spring fieldwork at a time when the soil has dried up sufficiently, and that moderate traffic intensity does not interfere with this strategy. The most important aspect of such timing is to avoid unfavourable aggregate size distributions and increases in penetration resistance. The second field experiment explored possibilities, under unfavourably wet conditions, to create a seedbed that can cope with more precipitation by maximising moisture loss after sowing. This experiment compared different implements for seedbed preparation (light, heavy, extra heavy) with regard to the soil physical properties they create, as well as moisture content in the seedbed and crop performance. The results show that, under excess moisture conditions, lighter mechanisation resulted in more favourable seedbed properties, lower moisture content and more uniform crop emergence. In contrast to established seedbed theory, larger aggregates did not reduce the moisture content in the seedbed. From this experiment, it was inferred that heavy modern seed drills with press wheels may cause compaction in the seedbed and limit moisture loss. Larger aggregates did not increase moisture loss after sowing, because the seedbed had become compacted at the same time. The simulation study addressed the question whether projected future climate change, in regions with high soil water content in spring, would aggravate the dilemma that farmers have concerning topsoil compaction versus delayed sowing. Further, it explores how farmers may adjust their long-term farm mechanisation management accordingly. Based on historical and projected future climate for two contrasting cereal-growing regions in Norway, weather data were generated. These data were used in a workability model and a mechanization model for simulations of spring workability, timeliness-limited yield potential, timeliness costs, and mechanization management. Simulations of the two most abundant soil types and different farm mechanisation parameters were included. The results showed that future workability and yield potential in Norway might be either improved or impaired, depending on the region and the soil type. In the future, there will be a general increase in the variability of workability and yield potential, and Central Norway will experience a larger risk of extremely unfavourable years in the least favourable climate scenarios. The study highlighted the importance of soil moisture content in spring as a criterion for sowing dates in simulation studies in general and in impact studies of future climate change in particular. The common thread running through this thesis is that avoidance of compaction seems to be the most important adaptation to climate change in seedbed preparation. Minimum compaction can be realised if spring fieldwork is performed under sufficiently dry conditions and by careful selection of implements, regarding their weight and mode of function. In Norwegian cereal production, seedbed preparation is a bottleneck, which is going to gain even more importance in the future, as we expect an increasing incidence of extremely unfavourable spring conditions. The transferability of the agronomical consequences to other countries with northern growing conditions may be possible but remains to be explored.Klimaendringer med mer nedbør om vinteren og våren kan vanskeliggjøre gjennomføringen av våronna i Skandinavia i fremtiden. Gårdbrukeren kan komme til å stå foran valget mellom jordpakking og utsatt såtid. Uansett hva som velges, vil det kunne føre til avlingstap. Formålet med PhD-prosjektet var å studere hvordan klargjøring av såbed til vårkorn kan tilpasses klimaendringene og hvordan man best kan unngå avlingstap på forskjellige jordarter og i kornregioner med ulikt klima. Avhandlingen starter med å presentere den klimatiske, pedologiske og agronomiske konteksten, og den teoretiske bakgrunnen for fysisk såbedskvalitet. Deretter blir resultater fra to feltforsøk og en modelleringsstudie presentert og diskutert. Det ene feltforsøket handlet om hvordan man med valg av såtid og kjøreintensitet under klargjøring av såbedet kan minimere pakkeskader i våt jord. Dette forsøket sammenliknet våronn på forskjellige datoer (tidlig, middels, sein) og med forskjellig kjøreintensitet (ingen, en, to eller tre overkjøringer) med tanke på jordfysiske egenskaper i såbedet og effekten på kornplantene. Resultatene viste at tidlig våronn i for våt jord ga større og sterkere aggregater, høyere penetrasjonsmotstand, delvis endrete egenskaper av porene i jorda og reduserte avlinger. Høyere penetrasjonsmotstand ble også påvist om høsten i samme vekstsesong. Effekten av kjøreintensitet var ikke like tydelig, mest sannsynlig på grunn av lokalisering, jordart og relativt liten forskjell mellom nivåene av denne forsøksfaktoren. Andelen av 2-6 mm store aggregater og penetrasjonsmotstand var de to viktigste jordfysiske egenskapene for jordkvalitet og kornavling. Dette forsøket viser at jordpakking kan minimeres ved å utsette såingen til jorda har tørket opp tilstrekkelig og at moderat kjøreintensitet ikke har så mye å si. Det er spesielt viktig å unngå en uheldig aggregatstørrelsessammensetning og økt penetrasjonsmotstand i såbedet. Det andre feltforsøket undersøkte muligheten for a klargjøre såbedet under for fuktige forhold på en slik måte at det kan tåle vedvarende høy jordfuktighet etter såing ved hjelp av et økt vanntap. Dette forsøket sammenliknet forskjellig mekanisering (lett, tung, ekstra tung) med tanke på jordfysiske egenskaper, vanninnhold i såbedet og effekten på kornplantene. Under for fuktige forhold var det den lette mekaniseringen som resulterte i et bedre såbed med lavere jordfuktighet og jevnere spiring. I motsetning til allment anerkjent såbedsteori, førte ikke større aggregater til lavere jordfuktighet. Ut fra dette forsøket kan man anta at moderne kombisåmaskiner med pakkehjul fører til jordpakking og ikke øker vanntapet, slik det hadde vært ønskelig ved mye nedbør etter såing. Større aggregater økte ikke vanntapet, fordi såbedet samtidig var pakket. Modelleringsstudien undersøkte om klimaendringer vil gjøre våronna vanskeligere i fremtiden på grunn av et høyt vanninnhold i jorda. Dessuten ble det vurdert hvordan gårdbrukere bør tilpasse mekaniseringen til dette. Basert på historisk klima og flere fremtidsscenarier ble det generert værdata. Disse værdata ble brukt i en laglighetsmodell og en mekaniseringsmodell for å simulere jordas laglighet om våren, avlingspotensial, laglighetskostnader og optimal mekanisering. Simuleringene ble gjennomført for de to vanligste jordartene og med forskjellig mekanisering. Resultatene viser at lagligheten og avlingspotensialet enten kan bli forbedret eller forringet i fremtiden i Norge, avhengig av region og jordart. Variabiliteten i laglighet og avlingspotensial kommer generelt til å øke i fremtiden, og Midt-Norge kommer til å oppleve en kraftig økt hyppighet av ekstremt vanskelige år i følge de mest pessimistiske scenariene. Denne studien tydeliggjør viktigheten av vanninnhold i jorda som kriterie for valg av sådato i modelleringsstudier generelt og i studier av effekten av klimaendringer spesielt. Den røde tråden i denne avhandlingen viser at det å unngå pakkeskader er det aller viktigste når våronna skal tilpasses klimaendringer. Man kan minimere pakkeskader ved å utføre våronna i tørr nok jord og ved å velge redskap nøye, med tanke på vekt og arbeidsmåte. Våronna er en flaskehals i kornproduksjonen og kommer til å bli enda mer utfordrende i fremtiden når vi forventer hyppigere år med ekstremt vanskelige forhold. Hvorvidt de agronomiske konsekvensene av dette er overførbare til andre land med liknende agroklimatiske forhold gjenstår å bli undersøkt.Hedmark County, Hamar Municipality and Kverneland Group Operation Norway A

Timeliness and traffic intensity in spring fieldwork in Norway: Importance of soil physical properties, persistence of soil degradation, and consequences for cereal yield

Future increase in precipitation in Scandinavia may exacerbate the dilemma of spring fieldwork that farmers have, concerning topsoil compaction versus delayed sowing on autumn ploughed soil. The former may lead to soil physical degradation, while the latter may lead to a shorter growing season, both with consequential loss of cereal yield potential. In order to enable farmers to adapt their spring fieldwork to climate change, research needs to include seedbed preparation at higher soil moisture conditions. A split-plot experiment in southeastern Norway in 2014–2017 explored the effects of timing (early, medium, late) and traffic intensity (zero, one, two or three additional wheelings) of spring fieldwork on soil physics and yield. Early spring fieldwork in the unfavourably wet conditions of 2016 gave rise to larger and stronger aggregates, higher penetration resistance, changed pore characteristics and reduced yields. Increased penetration resistance persisted until autumn. The small effect of traffic intensity was explained by location, soil type and intensity range involved. In this context of spring fieldwork timeliness, the proportion of 2–6 mm aggregates and penetration resistance were the properties most strongly correlated with other soil physical properties and cereal yield

Arktisk klimaregnskap - Forprosjekt for kartlegging av behov for lokalt tilpasset klimaregnskap og nye muligheter for bruk av arealdata

NLR Nord Norge opplever at målkonflikten mellom å opprettholde matproduksjon i hele landet og klimatiltak stiller den nordnorske bonden overfor tilsynelatende uforenelige krav. Ved hjelp av litteraturstudie og bruk av arealdata og kart undersøkes behov og muligheter for bedre lokalt tilpasset datagrunnlag til klimaarbeidet på kommune- og gårdsnivå. Litteraturstudiet viser at metodikken i kommunalt klimaregnskap og Landbrukets klimakalkulator i liten grad tar hensyn til de nordlige driftsforholdene, og at sammenlikning av eget klimaavtrykk med andres har begrensninger. Det er viktig å se klimaarbeidet i sammenheng med bærkraftig arealforvaltning i jordbruket. Uttesting i Vestvågøy kommune og på fem testbruk viser at data og kart fra jordkartlegging og vegetasjonskartlegging kan være nyttige supplement i klimaarbeidet på kommune- og gårdsnivå. Rapporten sammenstiller forslag til forbedringer og oppfølgingsprosjekter.Arktisk klimaregnskap - Forprosjekt for kartlegging av behov for lokalt tilpasset klimaregnskap og nye muligheter for bruk av arealdatapublishedVersio

Relationship between rhizome fragmentation, mowing and competition in control of common couch grass (Elymus repens)

The perennial Elymus repens is considered to be one of the most important weeds on arable land in the Nordic countries. The 1st part of this thesis is principally a literature review on the species` biology and physiology related to control methods and its regrowth capacity, with emphasis on (storage) carbohydrates in plants. Elymus repens’ high tolerance to control measures and its great regeneration ability makes it necessary to combine all possible control methods, direct and preventive, cultural and mechanical. Especially in reduced tillage all available measures might be practiced for optimal control of E. repens: use of competitive crops, mowing and potentially rhizome fragmentation. The 2nd part of the thesis is an independent scientific paper arisen from the experimental part of the master project where the relationship between (i) a simulated innovative belowground (BG) control method of rhizome fragmentation and the common aboveground (AG) control methods, (ii) mowing and (iii) competition (white clover), was investigated in a factorial pot experiment. Elymus repens` response to weed control was recorded in number of early and final shoots, AG and BG biomass and concentrations of simple sugars and fructan. Fragmentation showed a significant effect on some of the responses, but there was no clear linear relationship. Competition from white clover had a significant reducing effect on all responses. Decreasing stubble height had a decreasing effect on BG biomass and fructan concentration in BG plant material. Increasing cutting frequency had a decreasing effect on BG biomass, concentration of simple sugars in AG and of fructan in AG and BG plant material, but stimulated formation of new aerial shoots. The latter might be exploited in a starvation strategy combined with other control treatments. In comparison with reference pots, cutting seemed to be more important than stubble height or the developmental stage at cutting. The study reports several interactions between the different treatment factors and their levels, with essentially synergistic effect or potential to be exploited in a starvation strategy. Among those a new discovery was that high cutting frequency stimulated formation of new aerial shoots. The relative importance of the different factors in this study were competition, stage when cut, stubble height and fragmentation, ranking from high to low importance. In practical use the ranking might be different if different levels of competition are considered. Although the pot experiment may indicate that the innovative method of belowground fragmentation of E. repens has restricted control effect, this method might be more important if its effect is related to an undisturbed system lacking fragmentation totally

Relationship between rhizome fragmentation, mowing and competition in control of common couch grass (Elymus repens)

The perennial Elymus repens is considered to be one of the most important weeds on arable land in the Nordic countries. The 1st part of this thesis is principally a literature review on the species` biology and physiology related to control methods and its regrowth capacity, with emphasis on (storage) carbohydrates in plants. Elymus repens’ high tolerance to control measures and its great regeneration ability makes it necessary to combine all possible control methods, direct and preventive, cultural and mechanical. Especially in reduced tillage all available measures might be practiced for optimal control of E. repens: use of competitive crops, mowing and potentially rhizome fragmentation. The 2nd part of the thesis is an independent scientific paper arisen from the experimental part of the master project where the relationship between (i) a simulated innovative belowground (BG) control method of rhizome fragmentation and the common aboveground (AG) control methods, (ii) mowing and (iii) competition (white clover), was investigated in a factorial pot experiment. Elymus repens` response to weed control was recorded in number of early and final shoots, AG and BG biomass and concentrations of simple sugars and fructan. Fragmentation showed a significant effect on some of the responses, but there was no clear linear relationship. Competition from white clover had a significant reducing effect on all responses. Decreasing stubble height had a decreasing effect on BG biomass and fructan concentration in BG plant material. Increasing cutting frequency had a decreasing effect on BG biomass, concentration of simple sugars in AG and of fructan in AG and BG plant material, but stimulated formation of new aerial shoots. The latter might be exploited in a starvation strategy combined with other control treatments. In comparison with reference pots, cutting seemed to be more important than stubble height or the developmental stage at cutting. The study reports several interactions between the different treatment factors and their levels, with essentially synergistic effect or potential to be exploited in a starvation strategy. Among those a new discovery was that high cutting frequency stimulated formation of new aerial shoots. The relative importance of the different factors in this study were competition, stage when cut, stubble height and fragmentation, ranking from high to low importance. In practical use the ranking might be different if different levels of competition are considered. Although the pot experiment may indicate that the innovative method of belowground fragmentation of E. repens has restricted control effect, this method might be more important if its effect is related to an undisturbed system lacking fragmentation totally.This master project was facilitated by experimental and secretarial services at the Norwegian Institute for Agricultural and Environmental Research (Bioforsk) and the Department for Ecology and Natural Resource Management at the Norwegian University of Live Sciences. Thanks to Yara Norge AS for providing partial financial support.2017-01-01M-P

Relationship between rhizome fragmentation, mowing and competition in control of common couch grass (Elymus repens)

The perennial Elymus repens is considered to be one of the most important weeds on arable land in the Nordic countries. The 1st part of this thesis is principally a literature review on the species` biology and physiology related to control methods and its regrowth capacity, with emphasis on (storage) carbohydrates in plants. Elymus repens’ high tolerance to control measures and its great regeneration ability makes it necessary to combine all possible control methods, direct and preventive, cultural and mechanical. Especially in reduced tillage all available measures might be practiced for optimal control of E. repens: use of competitive crops, mowing and potentially rhizome fragmentation. The 2nd part of the thesis is an independent scientific paper arisen from the experimental part of the master project where the relationship between (i) a simulated innovative belowground (BG) control method of rhizome fragmentation and the common aboveground (AG) control methods, (ii) mowing and (iii) competition (white clover), was investigated in a factorial pot experiment. Elymus repens` response to weed control was recorded in number of early and final shoots, AG and BG biomass and concentrations of simple sugars and fructan. Fragmentation showed a significant effect on some of the responses, but there was no clear linear relationship. Competition from white clover had a significant reducing effect on all responses. Decreasing stubble height had a decreasing effect on BG biomass and fructan concentration in BG plant material. Increasing cutting frequency had a decreasing effect on BG biomass, concentration of simple sugars in AG and of fructan in AG and BG plant material, but stimulated formation of new aerial shoots. The latter might be exploited in a starvation strategy combined with other control treatments. In comparison with reference pots, cutting seemed to be more important than stubble height or the developmental stage at cutting. The study reports several interactions between the different treatment factors and their levels, with essentially synergistic effect or potential to be exploited in a starvation strategy. Among those a new discovery was that high cutting frequency stimulated formation of new aerial shoots. The relative importance of the different factors in this study were competition, stage when cut, stubble height and fragmentation, ranking from high to low importance. In practical use the ranking might be different if different levels of competition are considered. Although the pot experiment may indicate that the innovative method of belowground fragmentation of E. repens has restricted control effect, this method might be more important if its effect is related to an undisturbed system lacking fragmentation totally.This master project was facilitated by experimental and secretarial services at the Norwegian Institute for Agricultural and Environmental Research (Bioforsk) and the Department for Ecology and Natural Resource Management at the Norwegian University of Live Sciences. Thanks to Yara Norge AS for providing partial financial support.2017-01-01M-P

Adaptation of seedbed preparation for spring cereals to unfavourably high soil moisture conditions in loam soil

In the future, increased precipitation in spring may force Scandinavian farmers to prepare their cereal seedbeds under conditions with excessive soil moisture, and thereby risk soil compaction, oxygen deficiency and yield loss. To adapt to climate change and avoid yield loss, a possible strategy may be to increase moisture loss from the seedbed, in contrast to earlier seedbed research, which has focused on minimising moisture loss. In this study, we compared light and heavy mechanisation alternatives for secondary tillage in an experiment with relatively dry and excess moisture conditions. The mechanisation alternatives’ suitability for excess moisture conditions was assessed in terms of resultant aggregate size distribution, penetration resistance, bulk density, air-filled porosity, air permeability, soil moisture content and cereal emergence. In general, lighter mechanisation created more favourable seedbed characteristics and seemed to be more suitable under excess soil moisture conditions. Larger aggregates after heavier mechanisation did not result in lower soil moisture content, probably because of compaction in the seedbed. We conclude that, under Norwegian conditions, the most important adaptation to climate change in seedbed preparation for spring cereals is the avoidance of compaction. Implement management for seedbed preparation should be more differentiated

Jordsmonnet vi lever av. Forslag til system for dokumentasjon og rapportering av jordsmonnets tilstand og endring

Denne rapporten beskriver et forslag til et jordovervåkingssystem for dokumentasjon og rapportering av jordsmonnets tilstand og endring. Rapporten inneholder en behovsanalyse for et jordovervåkingssystem og redegjør for utvalgte eksisterende overvåkingssystemer i jord. I det anbefalte jordovervåkingssystemet inngår indikatorer, rapporteringsmuligheter, datafangst, dataforvaltning, utvalgssystem, organisering av overvåkingssystemet og kostnadsestimat. Systemet er avgrenset til jordsmonn på jordbruksareal, men kan utvides til å omfatte andre arealer ved behov.publishedVersio

Jordsmonnet vi lever av. Forslag til system for okumentasjon og rapportering av jordsmonnets tilstand og endring

Denne rapporten beskriver et forslag til et jordovervåkingssystem for dokumentasjon og rapportering av jordsmonnets tilstand og endring. Rapporten inneholder en behovsanalyse for et jordovervåkingssystem og redegjør for utvalgte eksisterende overvåkingssystemer i jord. I det anbefalte jordovervåkingssystemet inngår indikatorer, rapporteringsmuligheter, datafangst, dataforvaltning, utvalgssystem, organisering av overvåkingssystemet og kostnadsestimat. Systemet er avgrenset til jordsmonn på jordbruksareal, men kan utvides til å omfatte andre arealer ved behov