Influence of soil moisture regimes on subsequent soil manganese availability and toxicity in two cotton genotypes.
Weil R.R. | Foy C.D. | Coradetti C.A.
Differential plant tolerance to high levels of Mn and effects of changing soil aeration on Mn availability and are major factors in the problem of Mn toxicity in acid soils. A pot study was conducted to evaluate the effects of temporary flooding or drying on Mn forms and toxicity during subsequent cotton/Gossypium hirsutum L.) growth. Two acid, high-Mn Hapludalfs were incubated for 16 d in flooded, air-dry, or moist conditions, then restored to field moisture content and planted with two cotton genotypes: C-310,73-307 (307, Mn-tolerant) and C-Sg1,70-517 (517, Mn-sensitive). After the incubation period, levels of exchangeable Mn in the Jackland soil (pH 4.8) were 9.0, 2.6, and 0.3 mmol kg-1, respectively, for flooded, air-dry, and moist pretreatments. Corresponding values for the Myersville soil (pH 5.2) were only 4.4, 0.6, and 0.1 mmol kg-1. Three days after seedling emergence in the flooded pretreatment, exchangeable Mn declined to 4.4 mmol Mn kg-1 in the Jackland soil and 0.2 mmol Mn kg-1 in the Myersville soil. Manganese toxicity symptoms (crinkle leaf) for both cotton genotypes developed only on the Jackland soil, with severity of symptoms following the order: flood > air dry > moist. With both soils, flooding pretreatment decreased dry matter production; generally more for 517 than for 307. Tissue Mn concentrations were 20 to 50 times higher in leaves from Jackland soil compared to those from Myersville soil. Where flooding caused toxicity symptoms in both genotypes, lower exchangeable Mn was measured in pots growing Mn-tolerant cotton. Differential Mn tolerance of cotton genotypes was not associated with differential Mn uptake or tissue concentration.
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