The proud story of Rainbow Plant Food began in Montgomery, Alabama, with a company known as International Agriculture Corporation (IAC). At the time – around 1925 – the company was heavy into pulverized materials, and began marketing “Rainbow for Cotton,” a premium plant food mixture designed to maximize lint and profit out of each acre in a field. The product was among the first of new fertilizers that intermingled acid phosphate and anhydrous ammonia, and sparked a revolution in the fertilizer business that incorporated more chemistry than ever before. Though the product disappeared briefly from the market during World War II to support the war effort, the process by which it was made remained unchanged until the 1950s, when researchers discovered that they could revolutionize the process yet again – this time for good. When this second revolution began, IAC was growing by leaps and bounds, and was looking for a new product to take the agribusiness world by storm. That product came in the form of granulated fertilizer manufactured into small pellets by introducing Sulfuric acid and revolving the material in a cooler, then screening it to size.
Today, historians have a hard time tracing the innovation to one or two specific people, but admit that the process made mixed fertilizers a thing of the past. Because these new “granules” contained nitrogen, potassium, and phosphorus – all of the nutrients necessary for maximum crop yields– the product took off virtually overnight. Like a true star, Rainbow Premium Fertilizer was born. Later that decade, the company hired Dr. R.P. Thomas, Ph.D., a renowned soil scientist, to come in and evaluate how to better tailor the Rainbow product to the marketplace as a whole. Dr. Thomas spent weeks reviewing the company’s formulations, and recommended three levels of granulated products: International (basic), Rainbow (better), and Super Rainbow (best). Thomas boldly suggested that the top-level Plant Food be manufactured as the best product money could buy, and introduced a process through which manufacturers would eventually integrate micro nutrients such as manganese, boron, zinc and copper into the product. The company, at the time known as International Minerals and Chemical Corporation (IMC), was the first company in the Southeast U.S. to incorporate nutrients of this kind; within years, every other major fertilizer company followed suit.
Over the next few decades, the company continued to grow. As the company refined its business approach, so too did it refine the granular Rainbow Plant Food products, adapting nutrient formulations as crop cycles and farming techniques changed. In 2006, Agrium acquired Royster-Clark. In 2018 Agrium and Potash Corporation completed a merger of equals to become Nutrien Ltd., which continues to manage both of the remaining granulation plants in the U.S.