To improve the grain self-sufficiency ratio in Japan, application of the rice - winter barley - soybean triple-cropping two-year system to clayey paddy fields is required in a Hokuriku region with heavy snowfall in win-ter. The clayey soils are hardly drained because of the low hydraulic conductivity; besides, the soils have limited amount of available water. The FOEAS (Farm-oriented en-hancing aquatic system) water table management system was developed to overcome these problems. We inves-tigated the discharge of water, nitrogen, hosphorus and suspended matter from FOEAS fields with the crop rota-tion system. We also evaluated effect of the groundwater level control on the discharge of water, nutrients and sus-pended matter. Rice was cultivated by the V-furrow no-till direct seeding method. The amount of nitrogen, phospho-rus, and suspended matter ischarge in the V-furrow no-till direct seeding rice period were same or smaller than in fields planted with the conventional methods includ-ing puddling and transplantation. During the crop rotation period, 94 % of water was discharged to the subsurface drains in the free drainage plot (FD). In the groundwater level control plot (GC), 32 % of water was discharged via surface runoff, demonstrating insufficient development of shrinkage cracks in the subsoil, which act as a pathway for the water. During the winter barley period, the concentra-tions of total nitrogen and nitrate in the discharge tended to be high, particularly in the pre-snow period, the concen-trations and the amount of discharge of nitrogen and sus-pended matter were the lower in GC than in FD, suggest-ing that denitrification was encouraged, and nitrification and shrinkage crack formation were suppressed in GC. In contrast, in the case of phosphorus, the concentration and the amount of discharge from GC was higher than FD, sug-gesting reduction condition in the subsurface. During the winter barley period, 70 % - 94 % of total water, nitrogen, phosphorus, and suspended matter discharge occurred in the crop rotation system.
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