Cotton response to iron sources on calcareous soil

Abstract

Many crops grown on calcareous soils exhibit Fe deficiency symptoms to varying degrees. Cotton (Gossypium hirsutum L.) is generally considered a more efficient utilizer of Fe than plants such as sorghum, and therefore has received less attention in Fe nutrition research. Observed reductions in plant growth and disease association in areas where indicator sorghum crops showed moderate to severe Fe deficiency chlorosis gave impetus to this study.

Cotton was grown on three soils rated slight, moderate, and severe in Fe deficiency. The three soils had histories of producing sorghum with Fe deficiency chlorosis varying from slight to severe. Cotton grown on two of the soils exhibited slight to severe Phymatotrichum root rot disease.

Chelate extractable Fe (DTPA) correlated positively with dry matter and lint production in the greenhouse for the three soils. Although interveinal chlorosis was not evident on cotton grown on the three soils, a slight variation in green color of foliage was observed depending upon the soil level of indigenous Fe.

Cotton plants responded to the Fe sources, Fe‐EDDHA, mine byproduct, and plant complexed residue (Fe‐AR). The extent of the response was tempered by soil Fe levels. Generally, 5 and 10 mg Fe kg^‐1 soil rates of Fe‐EDDHA produced similar growth increases to those receiving 200 mg Fe kg∼l as the inorganic mine byproduct. Data suggested that fertilization with high levels of Fe caused a slight delay in plant death from Phymatotrichum root rot. The largest effect of Fe sources on plant mortality appeared with high rates of a Florida Fe material.

Key words:

• Fe deficiency chlorosis
• Phymatotrichum root rot
• Fe‐EDDHA
• Mining byproduct
• Fe‐enriched Amaranthus
• Gossypium hirsutum L