Iron and Calcium Availability to Groundnut Plants as Affected by Calcium Carbonate and Water Levels in Calcareous Soil

ABSTRACT

To assess possible causes of soil and plant iron deficiency and chlorosis in groundnut (Arachis hypogaea L.) on calcareous clay loam soils of Karnataka, India, a pot experiment was conducted to evaluate the availability of iron and calcium at varying levels of CaCO₃ and soil water and their influence on pod yield. The CaCO₃ levels of the soil achieved by liming were: 5% (C₁), 7% (C₂), 10% (C₃), 15% (C₄), and 20% (C₅) (on mass basis). Three soil water levels, i.e., 75% (M₁), 150% (M₂), and 200% (M₃) of field capacity, were imposed for one week each at flowering and pegging stages. Amorphous iron oxide-occluded iron, free iron oxide, and water-soluble calcium increased significantly with increasing levels of soil water. The diethyl triamine pentaacetic acid salt (DTPA)-extractable Fe, however, decreased at higher levels of CaCO₃ and soil moisture. Conversely, the concentration of bicarbonate ions increased at higher levels of CaCO₃ and soil water. The pod yield of groundnut, which was highest under M₂C₂, decreased at higher levels of CaCO₃. This decrease in groundnut yield at higher levels of CaCO₃ was attributed to deficiency of available Fe, DTPA-Fe, as caused by the increased concentration of bicarbonate ions.

KEYWORDS:

• Calcareous soil
• water-soluble calcium
• bicarbonate
• DTPA-Fe
• water-soluble iron
• iron deficiency
• iron oxides
• pod yield of groundnut

Notes

Sarkar, R. 2000. Solution Chemistry and Availability of Iron to Groundnut (Arachaes hypogaea L.) Crop in Calcareous Soils. Master of Science (Soil Science and Agricultural Chemistry) Thesis, University of Agricultural Sciences, Dharwad, Karnataka, India.