Residual value of ferrous sulfate for clover production on humic sandy podsols

Abstract

The residual value of ferrous sulfate, as an iron fertiliser, was measured in 3 field experiments using yield of dry herbage of clover (Trifolium subterraneanum L.). The clover was grown on limed acid peaty sandy soils and the iron fertiliser was spread over the soil surface. In 1995, the effectiveness of freshly applied iron was compared with that of iron applied 1–5 years previously. Additions of iron increased clover herbage (DM) yield by about 0.80 t/ha in October. The longer the period since iron was applied, the less effective was the fertiliser. Iron applied 1 year previously was about 60% as effective as current iron while iron applied 5 years previously was about one-third as effective as current iron for herbage production. About 15–20 kg of freshly applied iron/ha was required for maximum DM yield of clover. The critical concentration of iron in the whole shoot of clover plants for 90% of maximum DM yield was about 70 mg/kg.