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1.Evaluation of Productive Sustainability in the Legume Mulch and No-Tillage Rice Cultivation Method for Low-Input Sustainable Farming from the Viewpoints of Weed Occurrence and Nutrient Supply

Kazumasa Hidaka, Hideto Ueno, Takuya Mineta(College Research Farm, College of Agriculture, Ehime University)

An experimental rice cultivation with legume living mulch and no-tillage, as an example of energy low-input sustainable farming systems, were conducted under no usage of synthetic chemicals and no weeding. Three kind of legumes, the Chinese milky vetch, white clover and hairy vetch, and abundant treatment as a control plot with two replications have been designed systematically since 1995 in collage research farm of Ehime University. Although yields of rice grain until 1997 was around the level of 500kg/10a in any legumes in the exception of less than 300kg/10a in control plot, in the 4th years of 1998 its markedly declined to the levels of 14-28% of 1997. Yield in hairy legumes living mulching in 1998 was relatively higher than 1997, and nitrogen supply was keeping enough to grow rice plant as same level as in 1997. Weed occurrence in 1998 increased much more abundant than in 1997, 15-23 folds in winter weed and 4.5 ?9.5 folds in summer weed of previous years. NH4-N and potassium density of soil at some levels of layer decreased rapidly after tillering stage of rice plant. Therefore tremendous weed increase in the 4th years of 1998 under this cultivation methods without weeding, caused marked yield decline through much more severe competition of rice plant and weed in absorption of soil nutrients than until previous years. Weeding practices against harmful weed species must be necessary in this energy low-input sustainable rice production systems since initial years of continuous cropping.

Keywords: living mulch, leguminous plant manure, no-tillage, weed management, soil fertility, low-input sustainable rice cultivation