Abstract

To optimize the nutrient management of upland rice production on trop-ical ferralsols, a greenhouse experiment was established using the multi-nutrient omission approach. A reciprocal soil origin-rice cultivar transplantexperiment was also conducted to better understand the relative contribu-tions of the soil origin and the rice cultivar in rice nutrient limitation. Wetested the deficiency of seven major and secondary nutrients [nitrogen (N),phosphorus (P), potassium (K), sulfur (S), calcium (Ca), magnesium (Mg),and silicon (Si)] and a solution of six micronutrients (B, Mn, Cu, Co, Na, Mo)likely to limit the growth of two upland rice cultivars, Chhomrong Dan andNerica 4, on two Ferralsols from the highlands of Madagascar. We foundsevere multiple nutrient deficiencies. For both cultivars, P, Ca, N, Mg omis-sion significantly depressed the shoot and root dry biomass and theiramounts in plant tissues. However, the main limiting nutrients were notthe same in both soils. We conclude that the multinutrient deficienciesobserved for rice growth in the Ferralsols are site-specific, even though Plimitation appears to be in common, and requires a holistic considerationof the mineral fertility, including micronutrients.

KEYWORDS : Greenhouse trial; ferralsols; Madagascar; nutrientlimitation; rice cultivars; upland rainfed rice