Climate change and higher global temperatures are affecting crops in more ways than one. Whilst many growers will be concerned about summer drought, the impact of heavier winter rain can also be significant, particularly in crops that require high volumes of sulfur. Dr. Katharina Koetting,
Director Innovation & Technical Marketing Agriculture at Omya, explains: “Warm air holds more moisture, so as temperatures rise, rainfall will increase. For crop nutrients such as sulfur, which is highly soluble in soil moisture, this will heighten the risk of leaching, reducing the volume of sulfur available to the growing crop in the Spring. Combining this with the reduction in atmospheric levels of sulfur means farmers will have to take steps to make sure their crops are not deficient in this essential nutrient.”
Sulfur is a crucial nutrient for all crops, playing a vital role in many physiological processes including protein formation and chlorophyll production. Trials at leading UK crop research center, Rothamsted Research, have shown that sulfur deficiency impairs plant metabolism, reduces protein synthesis and suppresses nitrate uptake, causing a reduction in nitrogen utilization efficiency. This means that expensive nitrogen fertilizers can be lost through sulfur deficiency. Rothamsted scientists recommend routine sulfur applications to maintain crop yield and quality, with annual applications suggested due to the minimal residual effect of sulfur.
Sulfur levels in agricultural soils are declining globally, and this is having an impact on all crops. Sulfur deficiency can be seen easily in newly emerging leaves during the spring. Pale green or yellow leaves, which are also smaller than usual, often have interveinal striping. Leaf stems may also have a strong purple color.
Dr. Koetting says that after the three primary nutrients of nitrogen, phosphorus and potassium, sulfur is the next most important nutrient required by plants, noting that: “Sulfur is an essential nutrient for all crops but for oilseed rape and sunflowers, it is particularly vital, as it contributes to the synthesis of oil in the seeds. Growers should also remember that sulfur has an impact on the uptake of many other nutrients, especially nitrogen. This is because sulfur and nitrogen are both necessary for protein synthesis so when sulfur is deficient, plants cannot assimilate as much nitrogen, leading to lower nitrogen uptake and efficiency. We recommend a N:S plant tissue ratio of 7-10:1 for balanced nutrient uptake.”
The choice of product is critical too, as plants can only take up sulfur in its sulfate form, so other forms must be mineralized or converted before they can be effective. As Dr. Koetting explains, this is why Omya Sulfoprill is such an effective method of providing sulfur to crops. “Sulfur requirements vary according to crop, soil type, agronomic practices and expected crop yields. When deficiency symptoms start to show, it is almost too late so applying a product with readily available sulfur is essential. Omya Sulfoprill is made from micronized calcium sulfate, so the sulfate ions can be taken up by the crop immediately, making it a very effective way of ensuring crops receive sufficient sulfur.”
Omya’s trials across Europe demonstrated that timing of sulfur applications is critical, with early spring applications essential to support strong plant development. In Germany and Spain, trials in oilseed rape compared Omya Sulfoprill with a standard NPK fertilization program, showing up to a 19% yield increase when applied to oilseed rape.
Similar trials on winter wheat in Germany and Italy compared the efficacy of Omya Sulfoprill with the commonly used ammonium sulfate. Results showed increased chlorophyll content, higher yields and an increased return on investment for the grower.
As Dr. Koetting points out, “The importance of spring applications has been highlighted by our trials, especially those on winter wheat. Spring applications of Omya Sulfoprill led to 5% higher yields than the standard NPK protocol, and also up to 5% higher than the ammonium sulfate treated crops. SPAD testing results from Germany and NDVI analysis from Italy indicated increased chlorophyll levels, which we attribute to improved nitrogen use efficiency in the crop.”
Omya Sulfoprill is a 2 – 6 mm granulated product containing ultra-fine particles of natural calcium sulfate. Dr. Koetting recommends spring applications of between 180 to 350 kg/ha for cereals and double that amount for oilseed rape. “Because Omya Sulfoprill is a granulated product, it can be easily applied with existing farm equipment. The granules dissolve rapidly in soil moisture, dispersing through the rooting zone quickly to provide readily available sulfur and calcium to the growing crop. As we experience more climate variation and wetter winters, managing spring sulfur applications will become key to delivering high yielding, high quality crops.”