The source of the velvetleaf spreading its distribution rapidly and causing serious problems in forage fields all over Japan since the mid 1980s was thought to be a new accidental introduction of seeds from velvetleaf mingled in some imported grains from the USA and Australia. However, velvetleaf used to be cultivated as a fiber crop until the 1880s. We examined the intraspecies variations, such as morphological characteristics and growth habits, using accessions previously collected and obtained from imported grains. Using principal component analysis (PCA), the accessions were classified into crop type and weed type. The crop type capsule was mostly an ivory color, and the weed type was mostly an ebony color. The crop type showed characteristics of a fiber crop, such as an erect form, uniform flowering and a low seed dormancy rate. Conversely, the imported grains were classified into the weed type which showed a strong weedy nature, such as branched form, long flowering period, high reproductive ability and a high dormancy rate. These results suggest that the new introduction is different from the indigenous fiber crop, and may possibly be the source of the present invasive velvetleaf because of its strong weedy nature. However, further studies comparing the new introduction directly with the present velvetleaf are necessary.
This paper describes the effect of the oxygen absorbed in the free volume of polyethylene on electr~ cal treeing phenomena. The ac tree initiation and growth were investigated at room temperature using virgin samples and also samples degassed by a vacuum pump. The tree starting voltage of the degassed samples is much higher than that of virgin samples. The exper~ mental results show this improvement can be attributed to the removal of oxygen from PE. We also observed in detail the processes of tree initiation and growth in the degassed samples. The observations with other results led us to conclude that the charge carriers injected from the point electrode playa dominant role in the tree initiation.
Round bale silage is a widely used forage production system in Japan. In recent years, several suspected instances of damage to bales of round bale silage by sika deer were reported on a dairy farm in central Japan. We sought to confirm whether this damage was indeed caused by sika deer, and if so, when and how they caused the damage. We also analyzed the effects of possible covariates on seasonal and spatial variances in the incidence of the observed damage. Continuous monitoring using camera traps revealed that sika deer were responsible for the damage to the bales of round bale silage. The sika deer were observed to nibble at the surface of the bales of round bale silage after puncturing the plastic film used to promote anaerobic digestion of the silage. Several sika deer were responsible for damaging the bales of round bale silage, and the incidence of damage to the bales increased as snow cover increased in winter. Further, the incidence of damage to the bales of round bale silage was greatest farthest away from the center of the farm facilities, and farthest inside the wildlife protection area, which covered a large proportion of the farm. The findings clarified the extent of damage caused by sika deer to bales of round bale silage, and illustrated the need to prevent such damage throughout the country.
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