Biofuels and crop nutrients
By Dr. Paul Tracy

Pay attention to crop nutrient removal and the challenges of nutrient application as biofuels shape the market.

Over the past five years, I have constantly received questions about how biofuels will affect our industry. I have been (and still am) hesitant to prognosticate concerning this topic. It is simply too fluid and politically charged to make accurate predictions. However, I think it is safe to say that corn grain ethanol and soy diesel will dominate the local short-term biofuel industry. Bioenergy is bound to influence many components of the agricultural community. For the purpose of this article, I’ll concentrate on how I believe ethanol production will influence crop nutrient management in our region.

Latest USDA estimates are that 92.8 million acres of corn were planted in the United States in 2007. This is a 14.6 million acre increase compared to 2006. During this time, soybean acres dropped 11.4 million acres. Obviously, ethanol has been the force driving these acreage numbers.

As we convert energy production feedstocks from petroleum to bio-based sources, more pressure will be put on our agricultural resources. That either means that we put more acres into crop production, or increase average yields produced per acre. Both of these scenarios require increased crop nutrients.

It is reasonably safe to assume that until alternative fuel crops or cellulosic ethanol procedures become mainstream, corn acres will stabilize or continue to increase. I have estimated nutrient balances that occur among major crops in our region (see table). Every acre of soybeans converted to corn will require a minimum additional 135 pounds of nitrogen, 31 pounds of phosphate and 32 pounds less potash. The fertilizer costs for these additional nutrients would be about $55 for corn compared to soybeans, $29 for corn compared to wheat and $32 for corn compared to cotton acreages. Nationally, a 5-million-acre conversion from soybeans to corn will require 675 million pounds (734,000 tons of urea) more nitrogen, 155 million pounds (168,000 tons of triple super phosphate) more phosphate and 160 million pounds (129,000 tons muriate of potash) less potash.

Urban sprawl, combined with recreational and environmental land purchases and the reluctance to put conservation acres back into production lead me to believe that we will not increase total crop production acres in the near future. Therefore, increased production on a per acre basis is necessary to sustain both the biofuel and grain industries. Current grain/biomass research and production industries, combined with our outstanding farming operations are keeping up with the increased demand placed upon our agronomic resources.

Cellulosic solutions
Many folks are looking toward cellulosic ethanol production as a viable alternative to high nutrient requirements associated with corn production. They see ethanol production from cellulosic sources such as switchgrass, corn stalks/cobs, poplar trees, kenaf, industrial hemp, potatoes, sawdust, waste materials or other sources as requiring lower plant nutrient inputs. Nothing could be further from the truth. Biomass crops remove the entire above ground plant, not just the grain. The non-grain crop residue contains large amounts of nitrogen, phosphorus, potassium, sulfur and carbon (which has received lots of attention in the global warming debate). Waste materials could and probably will provide some “low-input” cellulose, but current supply chains and infrastructures are not in place for the volumes required to meet our ethanol energy demands.

Follow the nutrient removal numbers in the table. Corn silage requires 31 pounds more nitrogen, 7 pounds less phosphate and 114 pounds more potash fertilizer compared to corn grown for grain. Switchgrass removes 3 pounds less nitrogen, 26 pounds less phosphate and 224 pounds more potash compared to corn grain. Society needs to be aware of these numbers before hopping on the “lower-input” cellulosic ethanol bandwagon.

What does all this mean in agronomic terms? We need to do a better job increasing nutrient use efficiencies. Increased corn acreages require moving more nutrients through an already overloaded manufacturing, transportation, inventory capacity and field application management system.

For phosphorus and potassium, we will continue to preach keeping soil test levels in the optimum ranges and choosing application timings based upon convenience. I cannot overemphasize the importance of getting phosphorus and potassium out of the way in the fall or winter (only on non-frozen ground).

With more nitrogen required in an already stressed, very narrow application timing window, ethanol will put additional logistic stresses upon this nutrient. I am already receiving many questions concerning fall nitrogen application to help reduce this stress. As always, fall nitrogen can be a risky business, especially south of Interstate 70. We do not want to exacerbate an already stressed system with poor agronomic management practices.

Volatile nitrogen prices and a constricted optimum nitrogen application timing window have created a potential market for fertilizer additives, specialty products and non-traditional nitrogen sources.

Many products like N-Serve, ESN, and Agrotain are proven to improve nitrogen use efficiencies under many cropping environments. Many other products are unproven and in many cases are being marketed improperly. Do not let nitrogen fertilizer prices or logistics influence your decision to use enhancement products.

Like always, I recommend products that have been tested by unbiased individuals, especially university researchers. Also insist on obtaining local verification before going full bore into any new product.

In my opinion, the most efficient nitrogen management system for corn is split applications and the use of in-season nutrient monitoring. As nutrients become more valuable, these systems will become more important.

Can we use the dried distillers grains (DDG) as fertilizers to apply nutrients back to the farmland that was used to provide the biofuel feedstuff? Even though DDG do contain crop nutrients, their use as a fertilizer is inconsistent, uneconomical and inferior to commercial fertilizers. They may provide an option to organic growers, but I see little fit for mainstream crop producers.

The full effect that ethanol will have on crop nutrition programs has yet to be determined. It is placing additional stress on some of our current systems, but that burden has yet to become too restrictive. We will respond to the nutrient needs for ethanol feedstuff production in an efficient manner. To date, the benefits of a permanent biofuel industry far outweigh the growing pains that many in our industry are facing.

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