Sulfur-deficient leaves are often pale green first, later yellowish-green to completely yellow, often with a purple coloration of stems. These characteristics are similar to those observed in nitrogen-deficient plants and can be easily confused. They are first observable in new, upper leaves in the case of sulfur deficiency. In some crops, interveinal yellowing or spotting of the leaf blade may be observed instead (wheat and potato). Leaves usually also grow smaller and narrower and may have necrotic tips. Affected areas in the field can appear pale green or bright yellow from a distance. Stems grow thinner, with inhibited longitudinal growth. If the deficiency starts early in the season, stunted growth of the plant, impaired flowering and delayed maturity of the fruits/grains may ensue. After transplanting, seedlings growing in sulfur-poor soils are likely to have higher mortality rates than normal.
Sulfur deficiency is not particularly common in either nature or agriculture. Sulfur is mobile in the soil and can be easily be leached downwards with water movements. That explains why deficiencies are associated with soils with low organic matter, highly weathered soils, sandy soils or soil with high pH. Most of the sulfur in soil is contained in soil organic matter or is attached to clay minerals. Bacteria in the soil make it available to plants in a process known as mineralization. This process is favored by high temperatures because of the enhanced activity of these microorganisms and their increased number. It is immobile in plants and does not readily translocate from older leaves to young leaves. Therefore, the deficiencies first appear on younger leaves.
A compost mix of animal manure and leaves or plant mulch is ideal to provide plants with organic matter and nutrients such as sulfur and boron. This is a long-term approach to remedy sulfur deficiency.
- Use fertilizers containing sulfur (S). - Example: sulfur 90% WDG for foliar spray. - Consult your agricultural advisor to know the best product and dosage for your soil and crop. Further recommendations: - It is recommended to do a soil test before the start of the cropping season to optimize your crop production. - It is best if sulfur is applied before planting. - Apply citric acid if your soil pH is too high to help your crop uptake sulfur.