Requirement of Micronutrients by Lowland Rice

Abstract

Lowland or flooded rice is mainly responsible for about 76% of total rice production at global level, yet information on micronutrient requirements for this crop is limited. Six greenhouse experiments were conducted at the National Rice and Bean Research Center of EMBRAPA, Santo Antônio de Goiás, Brazil, to determine requirements of zinc (Zn), copper (Cu), boron (B), molybdenum (Mo), manganese (Mn), and iron (Fe) for lowland rice grown on a Brazilian Inceptisol. The levels of micronutrients used were Zn (0, 10 20, 40, and 80 mg kg−1), Cu (0, 5, 10, 20, and 40 mg kg−1), B (0, 5, 10, 20, and 40 mg kg−1), Mo (0, 2, 4, 8, and 16 mg kg−1), Mn (0, 50, 100, 300, and 600 mg kg−1), and Fe (0, 250, 500, 1000, and 2000 mg kg−1). Grain yield was significantly increased in a quadratic fashion with the addition of Zn, Cu, B, Mo, Mn, and Fe. The adequate rates of micronutrients for maximum grain yield were Zn 33 mg kg−1, Cu 25 mg kg−1, B 26 mg kg−1, Mo 10 mg kg−1, Mn 250 mg kg−1, and Fe 1269 mg kg−1. In addition to grain yield, plant height, straw yield, panicle density, and root growth of lowland rice were also improved with the addition of most of these micronutrients. Improvement in root growth has special significance in improving nutrient-use efficiency under nutrient-stress conditions. Micronutrient-use efficiency (grain yield per unit nutrient applied) was in the order of Cu > Zn > Mn > Fe > Mo > B.