Farm level evaluation of drainage technology for mungbeans grown prior to lowland rice

There is substantial potential to expand the area planted to pre-rice upland crops on rainfed lowland ricelands if practical surface drainage methods can be used to reduce waterlogging during the early rains. Previous agronomic research Found substantial yield advantages in pre-rice mungbean performance with simple ridging technology. We conducted studies in cooperation with farmers from 1987 to 1990 to evaluate these tractor-ridging and animal-ridging methods on a field scale. Heavy rainfall caused natural surface flooding on 7 to 25 days in broadcast-seeded plots. Tractor-ridging elevated the upper root zone 11 cm above the soil surface, and maintained free-water levels below the ridge surface. The ridge height with animal ridging was half that obtained with tractor-ridging, and protection from surface flooding was intermediate. Grain yields were significantly higher across farms (n=7) with tractor ridging compared to broadcast-seeding (360 kg/ha vs 166 kg/ha). Comparativenet returns with ridging were 215O/ha vsrn49/ha. In a season without waterlogging. Yields among planting systems were comparable (672 kg/ha vs 602 kg/ha). The greatest advantages of ridging were exhibited in fields subject to moderate waterlogging stress. Simple surface drainage techniques tend to stabilize yields, and enable expanded pre-rice mungbean production on waterlog-prone ricelands.

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