Japanese Journal of Farm Work Research

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Cover crops have been used for maintenance of soil quality in wheat production systems for many years. Examined were biomass accumulation and nitrogen absorption in wheat production of four annual rotational croppings ; spring wheat and bare fallow, hairy vetch, bristle oat, and mixture of hairy vetch and bristle oat, in Hokkaido, with its cool season and snow cover region. The overview of results is as follows. 1) The yields of wheat were increased by cover croppings. It was not influenced by the species of cover crops used. 2) Yield of wheat in 2009 was 55.4% of that in 2008 in the bare fallow plot, while reduction rates of wheat yields from 2008 to 2009 were 36.7% and less in the plots where cover crops were produced. It was suggested that the yield stability of wheat was increased by rotational managements of cover crops. 3) From multiple linear regression analysis with nine explanatory variables ; three candidate nitrogen resources and their C/N ratio, two cover crop species and a tillage method, bristle oat production was found to have a negative effect on the nitrogen absorption of wheat. This result showed the effectiveness of hairy vetch cropping in the rotational production of spring wheat and cover crops. 4) The effect of spring tillage on wheat yield was not detected among cover crops. Nontillage seeding of spring wheat may provide an advantage in saving energy in the field in rotational cropping of spring wheat and cover crops.

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Fruit size enlargement and extension of selling period are assignments to be solved in the kiwifruit cultivar ‘Rainbow Red’. In order to solve these subjects, we investigated the practicability of forchlorfenuron (CPPU) treatments in this cultivar. Treatments by 4.0 ppm or below showed a tendency to increase fruit size, while fruit drop and fruit maturation were promoted. The possibility of hastening the harvesting time was suggested ; if the treatments were to be combined with no-treatments, expansion of harvesting period and selling period are expected. The green color of the pericarp became darker and the fruit apex enlarged by the treatments. Regulations of these undesirable effects are yet to be solved for the cultivation of kiwifruit ‘Rainbow Red’.

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