Evaluation of white clover and rye grown in rotation with no-tilled rice

White clover and rye were grown during the winter and spring (November-May) for two seasons from 1999 to 2001 in Ehime, Japan in order to evaluate biomass production, N states and weed growth in following paddy rice. Our goal was to develop external low-input, sustainable agriculture (ELISA). Five no-till, direct-sown, winter rice crop (Oryza sativa L.) plots and a conventional transplanted rice control were evaluated in 2000. The conventional control was deleted in 2001 and transplanting and fertilization sub-treatments added to the original no-till, direct-sown plots. Rice yielded 0.5-3.58 t/ha in 2000 and 0.05-6.36 t/ha in 2001. Shoot N of rice contained 1.23-9.77 g/m(2) in 2000 and 0.39-18.1 g/m(2) in 2001. White clover residues contained about 14 g/m(2) before submergence, therefore the release of N from residues was potentially sufficient to supply the rice crop demand. Total weed dry weight ranged from 93 to 482 and 66 to 505 g/m(2) in 2000 and 2001, respectively, when sampled at rice ripening. At rice harvesting in 2000, weed nitrogen content ranged from 1.06 g/m(2) in the fertilized rye-rice plot to 6.32 g/m(2) in the control. Due to their shoot N content, Echinochloa crus-galli and Polygonum hydropiper posed the greatest competition to rice growth. Our results show that the white clover in rotation with rice was the best ELISA option, producing good rice yield and minimizing weed infestation. The rye-white clover treatments also reduced weeds, but without fertilizer and transplanting did not yield as well as white clover alone, and they were difficult to manage. (C) 2003 Elsevier Science B.V. All rights reserved.