Biodegradable coating improves crop yields.

Improving crop yields has been a primary goal of the agriculture industry for decades, as population growth has increased at a dramatic rate. Today, the issue is even more critical as the demand for increased production of ethanol derived from corn is placing a greater strain on the food supply. Any products that can improve crop yields without negatively impacting the soil quality or the environment are significantly important.

Specialty Fertilizer Products (SFP) of Belton, MO, has developed one such product. Its AVAIL[R] technology is based on a new polymer coating for increasing the efficiency of phosphorus use while reducing its environmental impact. By controlling the microenvironment around the fertilizer, AVAIL blocks the elements that fix phosphorus in the soil, making more nutrients available to plants' root systems throughout the growing season.

In typical phosphorous-based fertilizers, only 5-25% of the phosphorus is actually available for use by the plant root system. The remainder is fixed in the soil by positively charged cations that react with the negatively charged phosphorus in the fertilizer.

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SFP was established in 1998 to develop and commercialize new technologies serving the plant-nutrient industry. Its AVAIL technology relies on the use of a highly charged polymer that inhibits fixation and improves phosphate fertilizer performance. "The poor availability of phosphorus is an age-old problem," says Dr. Larry Sanders, CEO and co-founder of SFP. "Anywhere from 75-95% of the phosphorus in traditional fertilizers is fixed in the soil and can ultimately become an environmental hazard, particularly in run off that goes into waterways and causes toxic algae blooms that deplete oxygen for aquatic life."

At the heart of the new AVAIL technology is a range of itaconic acid/maleic acid copolymers with molecular weights in the range of 3000-4000. These water-soluble copolymers provide two types of barriers for the fertilizer. In the first case, the coating provides a physical barrier, reducing dust issues during handling of the dry fertilizer before it is applied. Once the fertilizer comes in contact with moisture in the soil, the dicarboxylic, anionic copolymer expands and forms a negatively charged barrier around the phosphorus.

Because the charge of the polymer (~1800 meq) is much larger than that of the phosphorus, their cation-exchange capacity is very high, and the cations in the soil (calcium, iron, magnesium, and aluminum) are attracted to the polymer, leaving a much greater percentage of phosphorus available to serve as a nutrient. As a result, more of the applied phosphorus accumulates in crop biomass, crop yields increase, farm profits improve, and adverse environmental effects are lessened.

There are additional benefits of the AVAIL technology copolymers. First, they can be applied directly to granular phosphorous fertilizers as a coating or impregnated onto the fertilizer through mixing with the liquid at the commercial seller. Second, it takes only a small amount of the polymer--just a half gallon per ton of fertilizer--to get a very good coating. Third, the copolymer is biodegradable and, according to Sanders, studies have shown that the coating is destroyed during the 12- to 15-month period between field crops, with no residual effect on subsequent crops. Plus, the itaconic acid used to produce the copolymer is a renewable resource.

SFP has commercialized its AVAIL line of phosphorous fertilizer enhancers, which includes AVAIL[R] for Granular Phosphate, AVAIL SD[R] (Side-Dress) for Liquid Phosphate, and AVAIL OS[R] (On-Seed) for Liquid Phosphate.

Numerous research studies have been conducted in the United States on the effects of this technology on key crops, including potatoes, wheat, corn, soybeans, rice, onions, cotton, and sugar beets. University and private research plots demonstrate a 10-15% increase in phosphate uptake in AVAIL-treated plants, resulting in higher yields and improved plant quality. Other crops for which the phosphorous fertilizer enhancers are being used include alfalfa, cole crops, and tomatoes. Because phosphorus availability is a soil phenomenon and not a plant phenomenon, AVAIL is effective on all crops and in any soil environment.

The numbers speak for themselves, according to Sanders. "Four-year data from Kansas State on wheat indicate an average per-acre return of approximately $6.00 to $22.00 per $1.00 invested." In the case of corn, the crop most recently in the news because of its use for ethanol production, using SFP's AVAIL technology can increase production by 10-20 bushels per acre. "This improvement can make a huge impact on our ability to meet the demand for corn in the coming years," Sanders stresses.

SFP recommends that the AVAIL phosphorous fertilizer enhancer be used at the normal application rates rather than reducing them. Utilizing the recommended phosphorus rates plus the new polymer technology can lead to even higher yields, reduced production costs per bushel, and higher crop profits. It is important to note that the cost of AVAIL will vary depending on the rate of phosphorus applied and the type of crop and soil.

SFP has also explored other applications for the technology, both within and outside of the plant-nutrient field. A variation of the copolymer used in the AVAIL products has been developed for coating nitrogen fertilizers. In this instance, the coating prevents the volatilization of the nitrogen, which results in increased crop yields and reduced environmental issues.

Seed coatings have been developed by SFP using the same family of copolymers. The coating provides two benefits: more nutrients are supplied to the seed early in the growth stage, and the seed is protected from disease as a result of the barrier provided.

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"SFP is a very research-intensive organization," asserts Sanders. "We lead the agriculture industry in designing products that manage the fertilizer environment with visible results measured in increased crop yields." The company has patented two families of copolymers and is working to commercialize these chemistries and develop new applications for them. SFP also has several new chemistries under investigation that Sanders hopes will be patented in the near future. "As a company, our goal is to develop polymer technologies for the plantnutrient industry and then ultimately find a broad array of applications that go well beyond the initial use for which they were created."

Even out in the crop fields, coatings technology plays an important role.