Professor of Biosphere Resource Science and Technology Program, Faculty of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan

Biograph
Professor Hisayoshi HAYASHI got his PhD in 1986 at University of Tsukuba in crop science. He had job experiences as an extension officer and a researcher in local governmental level for seven years, then moved to University of Tsukuba. He belongs to Biosphere Resource Science and Technology Program, Faculty of Life and Environmental Sciences, University of Tsukuba and majored in crop production systems. His research group focused on the following researches: The effects of crop production systems on environmental loads for example greenhouse gases (CO2, CH4, N2O), chemical fertilizers and agro-chemicals, and carbon sequestration; Development of sustainable agricultural production systems with less environmental loads, and stable and high yield of crops; Production systems of buckwheat (Fagopyrum esculentum Moench.) and its usage for rural development in Japan and in the world; Food culture (Syokuiku) activities using millets and evaluate their effects on school children.

Speech Title: Paddy rice production using living mulch

Abstract: There are many crop production systems for achieving low input and sustainable agriculture. Crop production system using living mulch is one of the popular one in upland crops but not applied in paddy rice. So, we tried to use aquatic plants as a living mulch in paddy field for achieving sustainable rice production system. Spirodela polyrhiza, common aquatic plants from tropical to temperate zone were used as inoculated plant in transplanted paddy rice field. Rice yield was increased around 10% compared to un-inoculated control when S. polyrhiza was inoculated during 50 to 75% coverage of the water surface at 7 days after transplanting (DAT) of rice. We couldn’t find out clear differences on rice yield when S. polyrhiza was inoculated during 0 to 21 DAT of rice. Polyculturing systems using 75% coverage at 7 DAT of S. polyrhiza had a benefit to increase rice yield by reducing weed number. Living mulch had advantages on the costs and labor compared to hand weeding and paper mulch cultivation. The total biomass of rice plant was increased after inoculation of living mulch. Although the light competition was not existed between rice and living mulch but the cumulative solar radiation (CSR) on the soil surface during rice growing period was reduced 18% in S. polyrhiza plot compared to no-inoculated control. There was a positive correlation between CSR and number of weeds at maturity, but correlation coefficient was the highest during 0-4 WAT. It was reduced when the cumulative period was elongated. Number of weeds was reduced directly by sunlight-blocking on the floating mat of living mulch during the growing season. Thus, polyculturing system using living mulch will be an ecofriendly and labor saving sustainable production systems in paddy rice production.

Keywords: light interception, polyculturing system, Spirodela polyrhiza, weed supression