Comparison of Genotype and Cultural Practices to Control Iron Deficiency Chlorosis in Soybean

Abstract

Iron deficiency chlorosis is a common problem for soybean [Glycine max (L.) Merr.] grown on calcareous soils. Iron is essential for chlorophyll biosynthesis and any deficiencies may hinder photosynthetic capabilities of the plant that may result in yield loss. Proper management and/or cultivar selection may reduce this problem. The objective of this study was to determine the most effective treatment efficacy of several common fertilizer treatments and several different cultivars for controlling iron deficiency chlorosis in soybean in Kansas. Field evaluations at three locations were conducted for two seasons. In the first season, treatments consisted of: four rates (11.2, 22.4, 44.8, and 89.6 kg ha⁻¹) of 28% granular iron sulfate fertilizer placed with the seed, or 5 cm away from the seed, at planting; two applications of an iron foliar spray; an iron chelate seed treatment; and an untreated control. The following season, the 44.8 kg ha⁻¹ rate was placed with the seed, the iron chelate seed treatment, and the untreated control were re‐tested, along with 44.8 kg ha⁻¹ of 20% granular iron sulfate fertilizer, increased seeding rates of 40 and 52 seeds m⁻¹, two plant residue treatments of 3.6 and 8.4 kg ha⁻¹ with 44.8 kg ha⁻¹ iron fertilizer incorporated into the soil before planting; a resistant genotype; a moderately resistant genotype; and a moderately resistant genotype with 44.8 kg ha⁻¹ iron fertilizer added. Entries were analyzed in a repeated measures design for chlorosis visual scores and a randomized complete block design for agronomic characteristics. The plants were visually evaluated for chlorosis every two weeks until the plants outgrew the chlorosis or reached maturity. In the second year, plants were also evaluated for maturity date, lodging, height, stand, seed weight, and yield. In 1999, no yield data was taken due to severe stand reduction and overall poor growth in all of the plots. In 1999, no treatment was consistently better at reducing iron chlorosis symptoms than the control; however, placing 44.8 kg ha⁻¹ iron sulfate with the seed significantly reduced chlorosis scores compared to the control at one location. In 2000, the resistant genotype had significantly lower chlorosis scores than all other treatments for the first few weeks of growth. In two of the three locations, the resistant genotype had the lowest yield. The iron fertilizer, seeding rate, plant residue, and iron chelate treatments did not significantly reduce chlorosis scores compared to the control. Increasing the seeding rate did significantly increase seed yield at some sites. Iron deficiency chlorosis was not adequately controlled by any of the evaluated commercial fertilizer products. Using resistant genotypes may be the most effective treatment if yield potential for these cultivars can be improved. Increasing seeding rate may represent a viable option to minimize moderate iron deficiency symptoms.

Keywords:

• Iron chlorosis
• soybean
• calcareous soil