Plants may grow without adequate sulfur in the soil, but they won’t be healthy. That’s important because sulfur is required for plants to create the amino acid methionine.
Why do we care about this amino acid? Humans can’t make methionine and must get it from what we eat. If plants don’t make much, then we are malnourished. This is happening all over the world. You don’t have to be hungry to be nutrient-deficient.
Even if you didn’t care about the health of your neighbors (but we know you do), the health and resilience of your crops are at stake with less than optimal sulfur.
Sulfur and Plant Growth and Development
Sulfur (S) is the fourth most important nutrient for plant growth after nitrogen, phosphorus, and potassium. It is closely related to crop yield and crop quality.
The widespread shortage of sulfur in the soil is the result of intensified industrial agriculture, the use of nutrient-demanding, high-yielding crop varieties, increased use of low-S, high-analysis synthetic fertilizers, and the decreased use of S-based fungicides.
It can take decades for a S deficiency in your soil to show up. Recent studies have shown most arable soils around the world have been S-deficient for over three decades. (1)
Sulfur is rapidly becoming a limiting element in crop productivity, quality, and yield.
The Function of Sulfur in Plant Development
Sulfur compounds inhibit microbial growth, add plant resistance to insects and herbivores, and are key nutrients in plant adaptation to abiotic stress.
Sulfur compounds are dominant players in a plant’s defense mechanism against disease. They often have a peculiar aroma that wards off insects and herbivores. Think cooked cabbage.
The ways plants use S are complex. Many metabolites are developed along the pathway of S metabolism by plants. One of these metabolites is glutathione. It protects plants from oxidative stress, heavy metals, and xenobiotic materials such as microplastics or pesticides.
Methionine is produced along the plant-soil-S-pathway. It’s an amino acid responsible for the primary and secondary metabolism in plants. The color and fragrance of flowers, the taste and aroma of foodstuffs, and the crop yield and quality depend on sulfur and the influence it has on other nutrients.
The Sulfur-Nitrogen Interaction
Historically, we’ve thought the main nutrient responsible for yield has been nitrogen. But we’re learning that plants won’t effectively use nitrogen if other nutrients, especially sulfur, aren’t available. A deficiency in S reduces the N use efficiency, so more fertilizer is needed for the same result. In other words, an S deficiency is bad for agricultural economics.
Not only yield but plant health are dependent on the correct ratio of sulfur and nitrogen. When these two macronutrients are out of balance, the plant is unable to take up the nitrogen. Crops across the board depend on S and N being in balance. In plants, S and N play a synergistically central role in the creation of proteins, and the supplies of these nutrients in plants are highly interrelated.
Seed production, especially the protein content, is improved with adequate sulfur in the soil. This makes a dramatic difference in the quality of the seed crop. For example, the sulfur (S) level in wheat affects gluten quality, baking quality, and protein. The quality of a crop is compromised without adequate S, and the crop is worth less on the market.
Plant Health, Animal Health, and Human Health
Humans are unable to create many amino acids, and we need to get almost all the essential amino acids for a healthy life from what we eat. But it’s not just humans who can’t make essential amino acids. Most mammals, including livestock, can’t synthesize all the amino acids needed for life. That means humans and all mammals rely on a dietary intake of amino acid and protein-rich foods.
As a producer, you’re interested in healthy livestock. That can’t happen if your pasture doesn’t have a balance between sulfur and nitrogen. Cattle diets deficient in sulfur can lead to decreased microbial populations in the rumen. This leads to an inability to properly ferment food so much of the nutritional content is lost.
The quality of sheep wool is impacted by insufficient sulfur. A balanced nutritional diet is necessary for developing protein both in the wool and meat.
Our diets depend on those amino acids and protein-rich foods. Whether we’re vegetarians, vegans, or omnivores, our health is tied to foods that supply us with the essential amino acids. Sulfur impacts food quality much more than we usually consider. It affects breadmaking and malting, the strength of our muscles, hormones, and neurotransmissions in our brains.
Our livestock and humanity depend on balanced nutrients in our food to lead healthy lives. In our next blog, we’ll look at how you can diagnose sulfur deficiencies and their solutions.
To learn more about soil nutrients, visit our blog. We’re here to help you succeed. When soil speaks, we listen.