Sulfur in Soil and Plants

sulfur in plants and soil

Despite the fact that it has been known for over 70 years that sulfur, in combination with other elements is necessary for plant nutrition, the question of sulfur content in plants seems to have gotten very little attention in the broad spectrum of plant health.  Why is sulfur so necessary to plants?  Sulfur is vital for all living cells, but humans and animals are only able to get their supply from plants.  That means that all living animals in the world rely on the sulfur supply that is found in plants.  Sulfur is essential in the nitrogen fixing process in legumes.  It is also necessary in the production of chlorophyll, a pigment that gives plants green appearance.  Plants also utilize sulfur when making proteins, amino acids, enzymes and even vitamins.  These just some of the functions that a plant depends upon a sufficient level of sulfur for growth.  When sulfur levels are adequate in plants and in soil, plants are also more resistant to disease, grow better and also form seeds more efficiently.

While sulfur is not needed in very high quantities in order for a plant to grow well, plants actually need almost as much sulfur as they do phosphorus.  Despite this fact, sulfur is still considered a macronutrient. The other macronutrients include calcium, silicon, potassium, nitrogen and magnesium.  All seven of these nutrients are needed in high quantities in order for a plant to reach its full growing potential.

In its pure elemental form, sulfur actually forms a very bright yellow crystal that makes for quite an attractive stone.  In addition to the elemental form, sulfur is also found as sulfides and sulfates.  Sulfate is the form of sulfur that is most typically found in soil solutions that is readily taken up for plant growth through the roots.  However, because there is a process of converting the sulfur into a form which is ready for plant use, it is considered a slow-release fertilizer, which is oxidized for use throughout the growing season.  One compound that is absorbed quickly is Epsom salts (magnesium sulfate), a compound which adds both magnesium and sulfur to your soil solution.

Plants are able to gather their sulfur from three different sources.  Those three sources include particles in the air, breaking down of minerals in surrounding soil, and microbial activity.  But, as mentioned earlier, sulfur plays a vital role in a number of different functions throughout the entire plant.  In addition to those named earlier, plants which have sufficient sulfur through fertilization have also been shown to increase the seed-oil content of crops like soy beans and flax, for example.

Just how much sulfur is necessary to optimize growth of your plants?  Plant and animal scientists have shown that plant tissue should contain one part sulfur for roughly each 15 to 20 parts nitrogen.  If your ratio in your garden is much higher than 15 to 1, then sulfur fertilization should provide significant benefits to your plant yields.

Similar to nitrogen, sulfur is a mobile nutrient that is able to move quickly throughout the soil and plant.  This can sometimes make it more difficult to diagnose if there is a deficiency.  Though your plant might have the appearance of sulfur deficiency, there could potentially be sulfur available below the soil layer which you tested.  If you are attempting to perform a soil sample to test for sulfur levels, you should take a 6-to-12 inch or even 12-to-24 inch sample for more accurate results and diagnoses.

Prior to taking a soil sample, however, there are a few signs and symptoms that you can look for to better tell if your plants need some additional sulfur to reach their full health and maximize yield.  Generally, if your plants are small and spindly with shorter, slender stalks, it could be a sign that your plants are experiencing a sulfur deficiency.  If the growth rate for your plants is slowed or full maturity is set back, these are also potential symptoms to look for.  Also, check your plants for light green or yellowish leaves with veins that are even lighter colored.  This one is a little bit tricky as it can be easily confused with a nitrogen deficiency.  On legumes, there is significantly less nodulation and fruits typically are not able to mature completely.  There can also be some spotting on the leaves on your fruits.

Keep a close eye on the plants in your garden for these signs and symptoms of a sulfur deficiency so that you can help them grow healthy and strong to their full potential.  A maximum yield in the garden is the goal of every gardener.  You are now armed and ready with the information that you need to help your plants obtain the right level of sulfur in the soil and in the plants themselves.  Maximizing the sulfur levels in the soil and plants means maximizing the yield in your crop or garden.  All Dyna-Gro complete nutrients contain adequate levels of sulfur.  For an extra boost, Mag-Pro® can be applied to provide a big boost in sulfur as well as magnesium and phosphorus.