Good agronomic strategies are needed to improve the stability and resilience of Norwegian cereal production. Diversifying crop rotations with spring oilseed Brassica (SB) can be an important strategy to lower disease levels in cereals and can have a positive effect on soil structure and nutrient supply. Despite these advantages, national oilseed production remains low due to issues with poor establishment, inadequate plant nutrition and losses from insects and diseases. The project "Improving the profitability of spring oilseed Brassica production - a key to improving quality and yield of cereal crops in Norway" (BRAKORN) started in 2015, and has provided a better understanding of these challenges for spring oilseed production in Norway.
The goals included 1) produce knowledge regarding factors affecting germination and establishment, including seedling vigour and soil tillage regimes, 2) develop fertilization strategies for hybrid spring rapeseed, 3) develop IPM strategies, and 4) document the rotation effects of SB crops on the quality and yield of cereal crops.
Early seeding of SB is necessary due to the growing degree requirements of this crop. Early seeding can imply cool temperatures, and shallow seeding, no deeper than 2 cm, is recommended. Rolling prior to seeding can be recommended to achieve more precise seeding depth. Soil crusting and structure issues can be detrimental for the establishment of SB, and it is especially important to avoid deep seeding depths in silt and clay soils. Increasing the amount of straw on the soil surface reduces the risk of soil crusting. SB compensate their development when plant density is low. Approximately 90 rapeseed plants/m2 allows for optimal yield and quality, and corresponds to a seeding rate of 150 seeds/m2 (0,7 kg/daa).
Seed of good quality, with a high germination rate, is fundamental to successful emergence. However, field observations have shown that some seed lots germinate more poorly in the field than one would except based on standard germination results. This may be due to poor seedling vigour. We have therefore tested a new standardized method (Radical Emergence test) to assess seed vigour, and results indicate that seeding vigour is a better indicator of emergence in the field than a regular germination test for some seed lots.
Spring rapeseed has a higher yield potential than spring turnip rapeseed, and a yield of 300 kg/daa is possible with a good stand of hybrid rapeseed. Achieving high yields requires adequate supply of N, P and K. Results show that the optimal fertilization rate for hybid rapeseed is approximately 15 kg N/daa. The majority of nitrogen (10-12 kg/daa) should be applied at seeding, but up to 5 kg/daa can be delayed until late formation of side shoots or just as elongation begins. This strategy can reduce the risk of N leaching or gas losses. Fullgjødsel® 22-3-10 supplies sufficient amounts of P, K and S for spring rapeseed. A fertilizer product containing sulfur can be chosen if split fertilizing. Foliar applications with micronutrients have not resulted in yield increases in our experiments.
Sclerotinia stem rot is the most economically damaging disease of SB crops in Norway. SB crops are most susceptible in the flowering period, however new results show that infection can occur both prior to and after flowering. Research has shown that moisture conditions in the canopy have a large influence on infection rates. Under controlled conditions, we have observed that spores can survive for over three weeks under low moisture condition and then infect petals and stems when moisture levels increase. This disease has many host plants, and host plants are a potential source of infection. Our studies have shown that the disease can develop in SB in fields where only non-susceptable crops have been grown for the last 10 years. This knowledge is important for the improvement of guidelines for the control of sclerotinia that is available as an IPM tool on VIPS (www.vips-landbruk.no).
SB crops are a target for many pest insects, however differences exist between species and varieties of SB and to what degree pests favour them. Flea beetles and pollen beetles are the most important pest insects in SB in Norway, and many species exist. Beetles use visual and olfactory cues to locate their host plants at particular phenological plant stages. An early flowering, turnip rape cultivar as a trap crop combined with kairomone traps placed in the trap crop can enable a reduction of insecticide use in SB.
Crop rotation, the practice of growing different crops in succession, is an important soil and fertility improvement strategy as well as disease management tool in cereal production. The results from this project show that spring rapeseed as a pre-crop to wheat increased wheat yield with 58 kg/daa (11 % increase) and improved grain quality (hectoliter weight and thousand grain weight), compared to wheat as a pre-crop to wheat.
Prosjektet har levert nyttige resultater for optimalisert dyrking av våroljevekster i Norden. Ny såmengdeanbefaling for vårraps er ca. 0,7 kg/daa. Redusert jordarbeiding med halm i overflata anbefales på skorpeutsatt jord. Grunn såing er viktig når det er lav temperatur ved såing. Spirekraftanalyse er et nyttig supplement til vanlig spireanalyse. Analysen etableres hos Kimen Såvarelaboratoriet. Rapsen krever mye næring om våren for å utnytte avlingspotensialet. Ca. 5 kg N/daa av tildelinga kan utsettes, og gis ved stor rosett/tidlig strekningsfase. Bladgjødsling med mikronæring gav ingen meravling.Storknolla råtesopp kan angripe raps i lengre periode enn før antatt. Nedbør er ikke et krav, høy luftfuktighet kan være tilstrekkelig for å gi angrep. Bruk av fangstplanter kan være en strategi for kontroll av glansbiller, og kan i enkelte tilfeller gjøre kjemisk bekjempelse overflødig. Vårraps som forgrøde til hvete ga en meravling på 11 % og bedre kvalitet i forhold til hvete etter hvete.
Norwegian cereal production faces serious challenges, including soil compaction, implementation of Integrated Pest Management (IPM), yield stagnation, quality problems, poor profitability and sinking production acreages. Sound agronomic approaches, such as a diverse crop rotation, are necessary to improve the stability of cereal production. Crop rotations with spring oilseed Brassica (SB) crops can lower disease levels in cereals and can have a positive effect on soil structure. Limited SB cultivation in Norway is due to poor yields and low profitability as a result of poor establishment and losses from insects and diseases. Establishment problems may be due to sub-optimal sowing date, uneven seed bed, poor seed quality and damage from diseases and insects during germination and emergence. Turnip rapeseed was the most common SB crop prior to 2000, but rapeseed represents now approx.70% of SB acreage. Optimal fertilization strategies which take advantage of the higher yield potential of rapeseed have never been developed for Norwegian conditions. A number of pests can reduce the yield of SB crops significantly, and resistance development and ban of seed treatments create challenges for insect control. Accurate prediction models are necessary for more effective disease control. The rotational benefits of SB crops on wheat yield, quality, disease levels and risk of mycotoxins and impact on soil structure are poorly documented and communicated. This project will 1) produce knowledge regarding factors affecting germination and establishment under different tillage regimes and soil types, 2) develop fertilization strategies and IPM strategies that are suited to the yield potential of SB crops, plus 3) document the rotation effects of SB crops on the quality and yield of cereal crops. Dissemination of knowledge will focus on improving the profitability of SB production, and the spin-off benefits for cereal production.