As asparagus plants are grown for a long period after transplanting, it is not possible to plow the field for soil improvement. Recently, because of global warming, establishment of new cropping system with carbon sequestration in soil has been expected. Cover crops provide a large amount of organic matter into the soil in many cropping. The effects of living mulch of cover crops on weed control and carbon storage were evaluated in the asparagus field planted for more than 16 years at the Experimental Farm of Hokkaido University, Sapporo, Japan. Wheat 'Hokushin' and 'Mulchi-mugi', barley 'Temairazu' and rye 'Kita-midori' were used as living mulch and were sown from early April to middle in May. Cropping with living mulch was repeated from 2006 to 2008. Wheat and barley continued vegetative growth because of no meeting of low temperature when they were sown in late April and May. However they were planted in early April, heading was observed in some plants. Weeds in interrow space were controlled by the emerged leaves of living mulch. Weed control ability of barley was high because of broad leaves emerged. Weed dry weight in summer reduced to 5% in barley living mulch compared with bare field when barley was planted at seeding density of 10 kg/10 a, in 2008. It reduced to 25% in wheat 'Mulch-mugi' which has tolerance to hot temperature. Heading was observed in rye even if rye was sown in May. Carbon content in the top soil with barley and rye increased 0.26-0.28% in average compared with bare field (no living mulch), however, there was no significant difference in soil carbon content among observed fields with or without cover crops. Spear yield was measured in 'Gijnlim' field, 8 years old, treated with living mulch in 2008 and significant difference was not recognized between rows with and without wheat living mulch in spring 2009.
