Cosmogenic production rates and recoil loss effects in micrometeorites and interplanetary dust particles

We present a purely physical model to determine cosmogenic production rates for noble gases and radionuclides in micrometeorites (MMs) and interplanetary dust particles (IDPs) by solar cosmic-rays (SCR) and galactic cosmic-rays (GCR) fully considering recoil loss effects. Our model is based on various nuclear model codes to calculate recoil cross sections, recoil ranges, and finally the percentages of the cosmogenic nuclides that are lost as a function of grain size, chemical composition of the grain, and the spectral distribution of the projectiles. The main advantage of our new model compared with earlier approaches is that we consider the entire SCR particle spectrum up to 240 MeV and not only single energy points. Recoil losses for GCR-produced nuclides are assumed to be equal to recoil losses for SCR-produced nuclides. Combining the model predictions with Poynting-Robertson orbital lifetimes, we calculate cosmic-ray exposure ages for recently studied MMs, cosmic spherules, and IDPs. The ages for MMs and the cosmic-spherule are in the range <2.2–233 Ma, which corresponds, according to the Poynting-Robertson drag, to orbital distances in the range 4.0–34 AU. For two IDPs, we determine exposure ages of longer than 900 Ma, which corresponds to orbital distances larger than 150 AU. The orbital distance in the range 4–6 AU for one MM and the cosmic spherule indicate an origin either in the asteroid belt or release from comets coming either from the Kuiper Belt or the Oort Cloud. Three of the studied MMs have orbital distances in the range 23–34 AU, clearly indicating a cometary origin, either from short-period comets from the Kuiper Belt or from the Oort Cloud. The two IDPs have orbital distances of more than 150 AU, indicating an origin from Oort Cloud comets.

Luxembourgish farmers lack information about grain legume cultivation

Grain legume production in Europe has decreased in recent years, while legume demand has rapidly increased due to growth of meat production. Therefore, Europe imports grain legumes, principally soybeans, to meet feed protein requirements. Various investigations have identified problems and benefits of local grain legume cultivation. Nevertheless, grain legume cultivation has still not increased in the last years. Studies investigating why farmers do not cultivate grain legumes are missing. Here, we surveyed the knowledge of farmers about grain legume cultivation, problems and constraints of grain legume cultivation and the barriers faced by and incentives needed by farmers. We sent a questionnaire to 1373 farmers in Luxembourg, with a response rate of 29 %. Results show that only 17 % of all the responding farmers cultivated grain legumes; 88 % of the conventional farmers did not cultivate grain legumes, while 85 % of the organic farmers did. We observed that Luxembourgish farmers feel badly informed about grain legume cultivation; organic farmers generally feel better informed than their conventional colleagues. The main barrier, named by Luxemburgish farmers to not cultivate grain legumes, is not economic issues but a lack of knowledge and extension services for these crops. Main incentives needed to start grain legume cultivation in the future are economic issues. Even though grain legume producers mentioned several negative experiences with grain legume cultivation, they are not discouraged by the poor economic conditions and appreciate the benefits of grain legume cultivation. Overall, our findings show that research results on grain legume should be better disseminated to extension services and farmers.