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Fluid Journal : Fall 2010
Variable rate application has come a long way since its inception. With improved technology and information, it will be desirable to apply variable rates of P and K to the soil to obtain very high and profitable yields with reduced risk of insufficient P or K. Time and labor are substantial issues facing farmers and fertilizer suppliers, especially as farm operations get larger and the territory served by fertilizer dealers expands. Fertilizer applications that require more time, management and specific placement equipment often are passed over in favor of broadcast application as a farmer's acreage grows. With increased emphasis on early and timely planting, larger farm operations often pass on application methods that slow or delay planting. Storage space also becomes an issue for the dealer if non-traditional nitrogen (N) and P products are desired. Some of these products may have increased efficiency attributes desired by the grower, but extra storage needs for these products can be a negative issue for the dealer. Regardless, timing and fertilizer placement choices are influenced by the dealer's and grower's needs, and they Summary: Challenges undoubtedly face the fertilizer and nutrient management industry as crop yields and potential demand escalate. Are today's nutrient recommendations appropriate for the future? Will they enable these ever- increasing yields to be realized or will they become yield-limiting? Do we have the research in place to develop nutrient best management guidelines for these very high yields? If not, where do we start and what are the nutrient/ crop priorities? What are the economic and environmental consequences of this extraordinary high-yield production system? Will time of application and placement method guidelines need to be reevaluated? How will the logistics and capabilities of the farmer and the dealer fit into these "new" nutrient management guidelines? Corn being a primary responder, yield goals in the next 20 years are targeted at 250 to 300 bu/A by some in the seed industry. Are Current Fertilizer Recommendations Adequate? Current status Aging recommendations. Many of the current recommendations are based on research conducted in the '70s and '80s, and even earlier. Back then U.S. average yields ranged from 80 to 120 bu/A, and it is likely that yield in many of the calibration research trials seldom exceeded 175 bu/A. Yield response probabilities and critical levels are currently based on these calibration studies. In some states, little phosphorus (P) and potassium (K) calibration research has been conducted since. In other states, notably Iowa, some perceptive scientists began long- term P and K response trials that have been most helpful for updating nutrient rate recommendations. Recently, the University of Nebraska changed its longtime soil test P (STP) critical level from 15 ppm to 25 ppm for corn after corn, based on current high-yield data. Logistical concerns. Soil testing is critical to the implementation of sound nutrient rate recommendations. But, soil testing has its share of uncertainties and a vigorous research and extension effort is needed to complement new fertilizer recommendations. The Fluid Journal • Ofﬁcial Journal of the Fluid Fertilizer Foundation • Fall 2010 • Vol. 18, No. 4, Issue #70 Dr. Gyles Randall Fall 2010 The Fluid Journal 04 require consideration by the nutrient research community as research is developed and prioritized. Risk of yield loss is a concern that faces both dealers and farmers. The possibility that yield is left in the field due to inadequate nutrient availability or supply is unthinkable for growers attempting to maximize return on their fertilizer dollar. As farmers work with their dealers and/or agricultural advisors to arrive at a nutrient application game plan, risk plays a key role in arriving at the final decision. Researchers, working to provide adequate nutrient supply for high and very high yield conditions, need to keep economic and environmental risks in mind. Land tenure. Whether the land to be fertilized is owned or is rented can and perhaps should play an important role in decisions on fertilizer rate and placement. To date, this factor has not been included in fertilizer guidelines provided by most universities. Kansas State University has led the way in developing P recommendations based in part on land tenure. Farmers who own land to be fertilized generally have a long-term vision for that land that
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