It is mainly visible in the new leaves, and the affected areas in the field can appear pale green or bright yellow from the distance. These leaves are usually smaller and they turn chlorotic yellow, with necrotic tips. In some rice varieties, rows of brown spots develop along the veins starting from the tip. If the deficiency starts early in the season, stunted growth and delayed maturity ensue. Symptoms may also be exacerbated. Plants become more susceptible to diseases affecting the stem and the panicles (e. g. stem rot), resulting in yield loss. Sulfur deficiency can be confused with nitrogen deficiency. The difference is that sulfur deficiency affects the upper leaves while the lack of nitrogen is first visible on older leaves.
Sulfur deficiency is not particularly common in irrigated rice. It is usually seen in patches or on areas of fields. It is associated with soils with low organic matter, highly weathered soils and sandy soils. 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. This process is favored by high temperatures because of the enhanced activity of these microorganisms and their increased number. Sulfur is mobile in the soil and can be easily be leached downwards with water movements. In this case, the shallow rice roots cannot access it anymore and the deficiency occurs. Volcanoes and fossil-fuel burning power plants are also sources of sulfur.
A compost mix of animal manure and leaves 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.
Sulfur can be applied before planting to promote rice tillering and early closure of the canopy. This is by far the most efficient method in relation to yield potential. Sulfur treatments before flooding the field or after the flooding are less effective and provide 90% and 50% percent of the yield potential of pre-plant treatments respectively. The latter amendments do not result in earlier canopy closure.