Utsädesbehandling med växtnäring för en snabb uppkomst och förbättrad ogräskonkurrens i vårvete

Enligt EU-direktivet ”Hållbar användning av bekämpningsmedel” måste mängden kemiska bekämpningsmedel minska inom jordbruket. Idag tillämpas integrerat växtskydd (IPM = integrated pest management) som arbetsmetod för att minska användningen av växtskyddsmedel. Detta arbetssätt fokuserar på förebyggande åtgärder mot växtskadegörare och ogräs. Även bevakning, behovsanpassning och uppföljning ingår som centrala delar i integrerat växtskydd. Lantbrukare har idag svårigheter att hantera ogräsproblematiken på ett hållbart sätt. Problem finns både i ekologisk produktion, där en större mängd mekanisk bekämpning behövs och inom konventionell odling som ofta tillämpar kemisk bekämpning istället. En förebyggande åtgärd som har börjat undersökas i Sverige är utsädesbehandling med växtnäring. Metoden har potential att bli en del av integrerat växtskydd i Sverige. Förutom att den har möjlighet att förbättra uppkomsten och den tidiga tillväxten hos grödan skulle metoden kunna användas i förebyggande syfte mot ogräs. Grödans konkurrensförmåga mot ogräs skulle kunna förbättras om uppkomsten och den tidiga tillväxten kan påskyndas. Hushållningssällskapet (HS Konsult AB) har under säsongen 2019 startat ett projekt i samarbete med Yara och NoroTec för att undersöka potentialen med näringsbehandlat utsäde och dess inverkan på grödans konkurrensförmåga mot ogräs. Projektet är finansierat av Landsbygdsprogrammet som ger stöd och ersättningar för nya innovationer inom jordbruket. Sammanlagt har tretton demonstrationsodlingar anlagts i Mellansverige, Östergötland och Skåne. I denna studie har demonstrationsodlingarna med vårvete i Örsundsbro utanför Enköping i Uppland och i Säbylund utanför Kumla i Närke undersökts. Demonstrationsodlingar är uppbyggda som försök med tre olika led (en kontroll och två näringsbetningsprodukter). I båda demonstrationsodlingarna har antalet grödplantor per löpmeter, marktäckningsgrad (gröda och ogräsarter) och ovanjordisk biomassa (gröda och ogräsarter) utvärderats. Vidare har ett kontrollerat lådförsök genomförts vid Sveriges lantbruksuniversitet i Uppsala. Uppkomsttid, uppkomstfrekvens, höjdtillväxtutveckling och ovanjordisk biomassa hos vårvete har jämförts mellan obehandlat och två näringssubstrat, i både ogödslat och gödslat odlingssubstrat. Resultaten från demonstrationsodlingarna visade inga signifikanta skillnader mellan leden med obehandlat och näringsbehandlat utsäde med avseende på antalet plantor per löpmeter, grödans marktäckningsgrad och ovanjordisk biomassa hos gröda och ogräs. Utsädesbehandling med växtnäring påvisade således inga tydliga effekter på grödans konkurrensförmåga mot ogräs. Ogräsens biologi och väderförhållanden verkade ha en större inverkan på ogräsmängden inom fältet där effekten från näringsbehandlingen inte anses vara tillräcklig. Liknande resultat påvisades i lådförsöket där inga signifikanta skillnader hittades i uppkomsttid, uppkomstfrekvens, höjdtillväxt och ovanjordisk biomassa mellan vårveteplantor från obehandlat och näringsbehandlat utsäde, och mellan gödslad och ogödslad odlingssubstrat. Sammanfattningsvis är näringsbehandling ingen självklar metod för att påskynda uppkomst, grödans tidiga tillväxt eller förbättra grödans konkurrensförmåga mot ogräs utifrån resultaten i denna studie. Hela projektet består dock av tretton demonstrationsodlingar 2019 och nio demonstrationsodlingar är planerade under 2020 där det sammanlagda resultatet kan få ett annat utfall. I framtiden behövs mer forskning inom området för att säkerställa näringsbehandlingens effekt

Rattail fescue and squirreltail fescue : biology, distribution and possibilities of control

Råttsvingel (Vulpia myuros) och ekorrsvingel (Vulpia bromoides) har blivit allt vanligare problem i norra Europa. I Danmark finns stor förekomst av främst råttsvingel i gräsfröodlingar men även i höstveteodlingar. I odlingar av rödsvingel och ängsgröe har framförallt råttsvingel blivit en etablerad art i södra delen av Sverige. Råttsvingel anses vara det vanligaste ogräset av de två arterna medan ekorrsvingel antas vara relativt sällsynt i Sverige. Med en större mängd höstveteodlingar och ökad användning av reducerad bearbetning är risken stor att råttsvingel blir ett betydligt vanligare ogräs också i höstvetefält. Råttsvingel följer ofta gräsfröodlingarnas utbredning och med ett gynnsammare klimat ökar risken att arten sprids längre norrut. Råttsvingel producerar många frön och har en snabb omsättning av fröbanken som gör att bekämpningsstrategier måste fokusera på att förhindra fröspridning. Kemisk bekämpning är idag mycket svår att utföra mot råttsvingel. Det finns inga herbicider som ger en fullständig kontroll i rödsvingel, selektiviteten är oftast dålig och med en utbredd naturlig tolerans mot framförallt ACCase-hämmande herbicider måste en bekämpningsstrategi främst fokusera på förebyggande åtgärder. Idag är de främsta förebyggande åtgärderna en varierad växtföljd med många vårgrödor, våretablering av gräsfröodlingar, rengöring av maskiner, väletablerad gröda och bortplockning av enstaka plantor. För att genomföra en hållbar bekämpningsstrategi är också mekaniska åtgärder viktiga. De metoder som främst tillämpas mot råttsvingel är användning av falsk såbädd och plöjning. För att lantbrukaren ska bli lyckosam med sin bekämpning mot råttsvingel är det viktigt att varje odlingsåtgärd utförs noggrant och beslut av insatser avvägs omsorgsfullt. Avslutningsvis kommer framförallt råttsvingel vara ett ökade problem i framtiden för Sverige och det är viktigt att redan idag försöka minimera spridningen av arten för att undvika stora ekonomiska förluster längre fram.Rattail fescue (Vulpia myuros) and squirreltail fescue (Vulpia bromoides)have become increasing problems in Northern Europe. In Denmark there is a large frequency of rattail fescue in grass seed production, as in winter wheat. Among crops of Red-fescue and meadow grass in southern Sweden,rattail fescue has especially become an established weed. Rattail fescue considered to be the most common weed of the two species, while the squirreltail fescue is considered to be relatively rare in Sweden. With a larger amount of winter wheat crops and increased use of reduced tillage, the probability increases for rattail fescue to become a much more common weed in the winter wheat fields as well. Rattail fescue often follows the spreading of the grass seed production and, with a more favourable climate, the risk increases that the weed is spreading further up-north. Rattail fescue produces many seeds and has a rapid turnover of its seedbank, which means that control strategies must focus on avoiding seed spreading. Chemical control is today very difficult to accomplish. There are no herbicides that provides complete control against rattail fescue, selectivity is poor and with widespread natural tolerance to, especially, ACCase inhibitory herbicides, a control strategy must focus on preventive measures. Today, the main preventive measures are a diverse crop rotation with many spring crops, spring establishment of grass seed production, machine cleaning, well-established cropping and picking up of single plants. Mechanical methods are also important in order to implement a sustainable control strategy. The methods that are mainly applied to rattail fescue are the use of stale seedbeds and ploughing. For a farmer to be successful against rattail fescue, it is important that every cultivation practice is carried out carefully and that decisions of efforts are carefully weighed. In conclusion, especially rattail fescue will become an increasing problem in the future in Sweden, and it is important to try to minimize the spread of the weed already now to avoid major economic losses later on

Algorithms for Wavefront Reconstruction

Knowing the solution to Helmholtz equation in a narrow band, with a width of order wave length around a scatterer, we investigate the possibility to construct the wave fronts predicted by the asymptotic methods Geometrical Optics (GO) and Geometrical Theory of Diffraction (GTD). More specifically we show how to build a polynomial approximation of the asymptotic solution on a circle around the scatterer and hence, in a second step, be able to propagate this solution by wavefront construction methods or standard ray-tracing

Quasi-free (p,pN) scattering of light neutron-rich nuclei around N = 14

Background: For many years, quasifree scattering reactions in direct kinematics have been extensively used to study the structure of stable nuclei, demonstrating the potential of this approach. The RB3 collaboration has performed a pilot experiment to study quasifree scattering reactions in inverse kinematics for a stable C12 beam. The results from that experiment constitute the first quasifree scattering results in inverse and complete kinematics. This technique has lately been extended to exotic beams to investigate the evolution of shell structure, which has attracted much interest due to changes in shell structure if the number of protons or neutrons is varied. Purpose: In this work we investigate for the first time the quasifree scattering reactions (p,pn) and (p,2p) simultaneously for the same projectile in inverse and complete kinematics for radioactive beams with the aim to study the evolution of single-particle properties from N=14 to N=15. Method: The structure of the projectiles O23, O22, and N21 has been studied simultaneously via (p,pn) and (p,2p) quasifree knockout reactions in complete inverse kinematics, allowing the investigation of proton and neutron structure at the same time. The experimental data were collected at the R3B-LAND setup at GSI at beam energies of around 400 MeV/u. Two key observables have been studied to shed light on the structure of those nuclei: the inclusive cross sections and the corresponding momentum distributions. Conclusions: The knockout reactions (p,pn) and (p,2p) with radioactive beams in inverse kinematics have provided important and complementary information for the study of shell evolution and structure. For the (p,pn) channels, indications of a change in the structure of these nuclei moving from N=14 to N=15 have been observed, i.e., from the 0d5/2 shell to the 1s1/2. This supports previous observations of a subshell closure at N=14 for neutron-rich oxygen isotopes and its weakening for the nitrogen isotopes

Strong neutron pairing in core+4n nuclei

The emission of neutron pairs from the neutron-rich N=12 isotones C18 and O20 has been studied by high-energy nucleon knockout from N19 and O21 secondary beams, populating unbound states of the two isotones up to 15 MeV above their two-neutron emission thresholds. The analysis of triple fragment-n-n correlations shows that the decay N19(-1p)C18∗→C16+n+n is clearly dominated by direct pair emission. The two-neutron correlation strength, the largest ever observed, suggests the predominance of a C14 core surrounded by four valence neutrons arranged in strongly correlated pairs. On the other hand, a significant competition of a sequential branch is found in the decay O21(-1n)O20∗→O18+n+n, attributed to its formation through the knockout of a deeply bound neutron that breaks the O16 core and reduces the number of pairs

Coulomb dissociation of <SUP>20,21</SUP>N

Neutron-rich light nuclei and their reactions play an important role in the creation of chemical elements. Here, data from a Coulomb dissociation experiment on N20,21 are reported. Relativistic N20,21 ions impinged on a lead target and the Coulomb dissociation cross section was determined in a kinematically complete experiment. Using the detailed balance theorem, the N19(n,γ)N20 and N20(n,γ)N21 excitation functions and thermonuclear reaction rates have been determined. The N19(n,γ)N20 rate is up to a factor of 5 higher at T<1GK with respect to previous theoretical calculations, leading to a 10% decrease in the predicted fluorine abundance

Quasifree (p, 2p) Reactions on Oxygen Isotopes: Observation of Isospin Independence of the Reduced Single-Particle Strength

Quasifree one-proton knockout reactions have been employed in inverse kinematics for a systematic study of the structure of stable and exotic oxygen isotopes at the R3B/LAND setup with incident beam energies in the range of 300-450 MeV/u. The oxygen isotopic chain offers a large variation of separation energies that allows for a quantitative understanding of single-particle strength with changing isospin asymmetry. Quasifree knockout reactions provide a complementary approach to intermediate-energy one-nucleon removal reactions. Inclusive cross sections for quasifree knockout reactions of the type OA(p,2p)NA-1 have been determined and compared to calculations based on the eikonal reaction theory. The reduction factors for the single-particle strength with respect to the independent-particle model were obtained and compared to state-of-the-art ab initio predictions. The results do not show any significant dependence on proton-neutron asymmetry

Systematic investigation of projectile fragmentation using beams of unstable B and C isotopes

Background: Models describing nuclear fragmentation and fragmentation fission deliver important input for planning nuclear physics experiments and future radioactive ion beam facilities. These models are usually benchmarked against data from stable beam experiments. In the future, two-step fragmentation reactions with exotic nuclei as stepping stones are a promising tool for reaching the most neutron-rich nuclei, creating a need for models to describe also these reactions. Purpose: We want to extend the presently available data on fragmentation reactions towards the light exotic region on the nuclear chart. Furthermore, we want to improve the understanding of projectile fragmentation especially for unstable isotopes. Method: We have measured projectile fragments from C10,12-18 and B10-15 isotopes colliding with a carbon target. These measurements were all performed within one experiment, which gives rise to a very consistent data set. We compare our data to model calculations. Results: One-proton removal cross sections with different final neutron numbers (1pxn) for relativistic C10,12-18 and B10-15 isotopes impinging on a carbon target. Comparing model calculations to the data, we find that the epax code is not able to describe the data satisfactorily. Using abrabla07 on the other hand, we find that the average excitation energy per abraded nucleon needs to be decreased from 27 MeV to 8.1 MeV. With that decrease abrabla07 describes the data surprisingly well. Conclusions: Extending the available data towards light unstable nuclei with a consistent set of new data has allowed a systematic investigation of the role of the excitation energy induced in projectile fragmentation. Most striking is the apparent mass dependence of the average excitation energy per abraded nucleon. Nevertheless, this parameter, which has been related to final-state interactions, requires further study

Effective proton-neutron interaction near the drip line from unbound states in 25,26 F

Background: Odd-odd nuclei, around doubly closed shells, have been extensively used to study proton-neutron interactions. However, the evolution of these interactions as a function of the binding energy, ultimately when nuclei become unbound, is poorly known. The F26 nucleus, composed of a deeply bound π0d5/2 proton and an unbound ν0d3/2 neutron on top of an O24 core, is particularly adapted for this purpose. The coupling of this proton and neutron results in a Jπ=11+-41+ multiplet, whose energies must be determined to study the influence of the proximity of the continuum on the corresponding proton-neutron interaction. The Jπ=11+,21+,41+ bound states have been determined, and only a clear identification of the Jπ=31+ is missing. Purpose: We wish to complete the study of the Jπ=11+-41+ multiplet in F26, by studying the energy and width of the Jπ=31+ unbound state. The method was first validated by the study of unbound states in F25, for which resonances were already observed in a previous experiment. Method: Radioactive beams of Ne26 and Ne27, produced at about 440AMeV by the fragment separator at the GSI facility were used to populate unbound states in F25 and F26 via one-proton knockout reactions on a CH2 target, located at the object focal point of the R3B/LAND setup. The detection of emitted γ rays and neutrons, added to the reconstruction of the momentum vector of the A-1 nuclei, allowed the determination of the energy of three unbound states in F25 and two in F26. Results: Based on its width and decay properties, the first unbound state in F25, at the relative energy of 49(9) keV, is proposed to be a Jπ=1/2- arising from a p1/2 proton-hole state. In F26, the first resonance at 323(33) keV is proposed to be the Jπ=31+ member of the Jπ=11+-41+ multiplet. Energies of observed states in F25,26 have been compared to calculations using the independent-particle shell model, a phenomenological shell model, and the ab initio valence-space in-medium similarity renormalization group method. Conclusions: The deduced effective proton-neutron interaction is weakened by about 30-40% in comparison to the models, pointing to the need for implementing the role of the continuum in theoretical descriptions or to a wrong determination of the atomic mass of F26

"Salting-out" chromatography: Empirical equations relating RF values to atomic refraction constants

Peptides, [alpha]-amino acids and miscellaneous organic compounds were chromatographed on filter paper using saturated ammonium sulfate solution as the developing solvent. Equations relating RF values to molecular refraction constants were derived empirically. Applications of such equations in predicting RF values and obtaining information concerning molecular structure are discussed briefly.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/32497/1/0000584.pd