Prediction model for the initial seed clearing angles of a precision seed meter based on vector fields

Seed clearing is a critical stage during precision seed metering process to ensure high seed singulation.However,there is a lack of understanding of the dynamics in the seed clearing process.In this study,a model was developed to predict initial seed clearing angle,in the seed clearing process using vector fields.The model was applied to an existing high-speed metering device and soybean seeds,and the model was evaluated with bench testing results.Results showed that dynamic changes in forces and constraints of seeds during the seed clearing process could be abstracted as vectors,and the changes of vector directions could be described by their phase angles.The phase angles were functions of the rotational angle of the seed meter.The phase angle of the constraint boundary linearly increases with the increase of the rotational angle.The phase angle of the force fluctuates,as the rotational angle changes.Initial seed clearing angle obtained from the phase angles varies from 8°to 59°,depending on the seeder travel speed.When comparing the values of the initial seed clearing angles predicted by the model with those from the bench tests,the root mean square error(RMSE)were from 2.73 to 3.14,and the correlation(r)between predict and observer were all higher than 0.98,indicating that the model had reasonably good accuracy.

Deciphering the effects of disperser assemblages and seed mass on patterns of seed dispersal in a rodent community

The sizes of both seed dispersers and seeds are traits that are likely to interact to influence seed fate in many synzoochoric plant species.Here,we examined whether members of a granivorous rodent community consist­ing of species of different body size vary in their effectiveness as seed dispersers,and how this relationship may be altered by seed size.We marked northern red oak(Quercus rubra)acorns with plastic tags and placed them in size-selective rodent exclosures.The exclosures allowed differential access of rodent groups based on dif­ferent body size:(i)small(e.g.Peromyscus spp.);(ii)small and medium(e.g.Tamias striatus);and(iii)small,medium and large(e.g.Sciurus carolinensis)species of rodents.Acorn removal did not differ among exclosure types,but more seeds were missing when removed by small rodents,probably because of larderhoarding.The treatments did not influence the relative frequency of acorn consumption.However,small rodents cached con­siderably fewer and partially ate more acorns than the other 2 groups.The mean dispersal distance was the lon­gest for cages with medium openings,intermediate for cages with large openings and the shortest for cages with small openings.Acorn mass positively affected the probability of caching and this relationship was unaffected by exclosure type.In conclusion,granivorous rodents of different body sizes strongly differed in their interac­tions with acorns,with small rodents acting primarily as acorn predators and medium and large species contrib­uting significantly more to dispersal of red oaks.