Dynamics of Iron Oxides in Two Benchmark Inland Valley Soils and Rice Grain Yields in Nigeria

Abstract

An investigation was conducted on two contrasting inland valley soils (Fluvauents and Tropaquents) over two cropping seasons (1993, 1994, and 1995) in two benchmark wetlands in Nigeria, and the contents and dynamics of iron (Fe) forms (active and organic) were examined when two different rice (Oryza sativa L) cultivars (‘ITA 212’ and ‘Suakoko 8’) were planted. Results showed that active Fe ranged between 0.96 and 3.16% on Fluvaquents and between 1.57 and 4.73% on Tropaquents; organic Fe, on the other hand, ranged between 0.05 and 2.84% (Fluvaquent) and between 0.60 and 2.38% (Tropaquents). Dynamics of the two Fe forms did not follow any clear pattern in the two cropping seasons on both soil types. On Fluvaquents, grain yields (GY) ranged between 2.40 and 3.46 t/ha (‘ITA 212’) and between 2.35 and 3.15t/ha (‘Suakoko 8’). Similarly, on Tropaquents, the GY ranged between 0.68 and 2.13 t/ha (‘ITA 212’) and between 0.61 and 2.11 t/ha (‘Suakoko 8’). Generally, the GY on Fluvaquents was higher than on Tropaquents and declined in the second cropping seasons. Results further showed that active Fe is significantly negatively correlated with GYs of rice. Critical active Fe and organic Fe contents for lowland rice on these soils were 2.90 and 1.80%, respectively.

Keywords:

• Inland valley soils
• iron
• rice
• wetlands