Effect of Soil Water and Aeration on Fe and Mn Utilization by Flax

Flax (Linum usitatissimum) plants usually become chlorotic when grown on wet or waterlogged Manitoba soils. Chlorosis has been associated with Fe and Mn concentrations in plants. Reports on levels of Fe and Mn in chlorotic flax plants or factors affecting the utilization of these nutrients by flax were not found in the literature. Thus, experiments were conducted to determine the effects of soil water and aeration on yield and Fe and Mn concentrations in the plant. Plants were grown at 100 and 150% of field capacity. Flax plants became chlorotic on four of six soils when grown at 150% of field capacity. Chlorotic plants had lower yields, contained lower concentrations of iron and higher concentrations of Mn than did non-chlorotic plants. The ratio of Mn to Fe in chlorotic plants was four or greater. Yields of flax, measured after 35 days of growth decreased with increase in Mn concentration and Mn:Fe ratio of plants. The r values for the relation between yield and Mn concentration and yield and Mn:Fe ratio were −0.73 and −0.76, respectively. Yield of flax increased with increases in the Fe concentration of the plants (r = 0.57). The effect of soil water (100, 120 or 150% of field capacity) and aeration (soil at 100 or 150% of field capacity with N₂, air or no N₂ or air passed through the soil) on the Fe and Mn concentrations of flax tops and roots were also investigated. Irrespective of treatment exceedingly large amounts of Fe and only small amounts of Mn accumulated in flax roots. Fe concentration or uptake was not directly related to aeration or oxygen supply in the soil. The ratio of the concentration of Fe in the roots to tops of flax grown on a soil showing chlorosis was lower at field capacity than at 150%. of field capacity. Thus, the reduction in translocation of Fe from roots to tops contributed to chlorosis when soil water content was increased.