Iron Transformation in Loamy Sand Soil of Rajasthan as Influenced by Farmyard Manure and Iron under Graded Levels of Alkalinity

A field experiment was conducted during rabi season of the years 2002–03 and 2003–04 to study the effect of different levels of FYM and iron on iron transformation under graded levels of alkalinity. The experiment comprising 36 treatment combinations replicated four times, was laid out in split plot design with four levels of alkalinity (15, 30, 45 and 60 ESP), three levels of FYM (0, 10 and 20 t FYM ha⁻¹) in main plots, and three levels of iron (0, 5 and 10 kg Fe ha⁻¹) in sub-plots. The content of different fractions of iron in soil decreased significantly with increasing levels of alkalinity and increased with increasing levels of FYM. The highest exchangeable iron (Ex-Fe), adsorbed iron (Ads-Fe), occluded iron (Occ-Fe) and organically bound iron (Om-Fe) recorded under lowest level of alkalinity (15 ESP) and highest level of FYM (20 t ha⁻¹). A perceptible improvement in Ex-Fe, Ads-Fe, Occ-Fe and Om-Fe of soil observed with the increasing application of iron and the maximum value of different iron fractions observed under 10 kg Fe ha⁻¹.