Application of limestone would be justified if soil pH is lower than 6. Zinc Soybeans are usually not sensitive to low soil zinc levels and grow well at zinc test levels much lower than sensitive crops like dry beans and corn. A recent North Dakota study with 10 locations and nine varieties with and without zinc revealed no significant differences even at soil test levels as low as 0.2 ppm. Although rare zinc deficiencies have been observed in North Dakota, it is not a problem most producers need consider. Iron Soybeans are susceptible to low soil iron availability.
Iron deficiency is expressed as yellowing in between veins on younger leaves.
Iron chlorosis is not seen until the first trifoliar leaf emerges, since prior to this stage iron from the seed is translocated to new growth. At emergence of the first true leaves, iron becomes an immobile nutrient and the plant must rely on soil availability to supply iron needs. Figure 4 . Iron chlorosis in this region is different than chlorosis reported in the central US soybean growing belt. High soil carbonates, increased solubility of bicarbonate caused by soil wetness, and the presence of elevated levels of soluble salts have been shown to influence the presence and severity of iron chlorosis in soybeans in North Dakota and northwestern Minnesota.