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    Research Supporting Nutrient Stewardship (2009)

    The principles of 4R Nutrient Stewardship require scientific support for the choice of practices that deliver the right source of nutrients at the right rate, time and place. The science needs to test these practices for their outcomes in terms of economic, social and environmental sustainability.

    Featured below are interpretive summaries of such research projects supported by the International Plant Nutrition Institute (IPNI) in the Northeast region. More detail can be found at the research database at .


    Impact of Phosphorus and Potassium Fertilization and Crop Rotation on Soil Productivity and Profitability

    Project Leader: Dr. Robert Mullen, The Ohio State University School of Natural Resources

    Project Cooperator: Edwin Lentz

    Growers in the eastern U.S. Corn Belt often fertilize the whole rotation rather than the individual crops. Typically, in the fall prior to corn planting, farmers supply enough phosphorus (P) and potassium (K) to satisfy the nutrient needs of both corn and the following soybean crop. This practice has proved a viable option for corn-soybean rotations on soils with adequate nutrient levels, but questions arise for producers in a three-year rotation of corn-corn-soybean. In 2006, studies assessing P and K fertilization strategies were started in three locations. Two rotations were compared: corn-corn-soybean, and corn-soybean. These rotations were fertilized following soybeans, at P and K rates corresponding to zero, once and twice the crop removal for the rotation. Corn yield was increased at one location by applying both P and K fertilizer. Optimum fertilization boosted yields from the 213 to 215 bushels per acre (bu/A) range to 223 to 225 bu/A. The other two locations did not show consistent yield increases. In 2007, each location had corn in the first rotation and soybeans in the second. Neither crop responded to the P and K treatments, even though the soybean crop produced yields as high as 66 bu/A. Drought reduced corn yields to a range of 122 to 159 bu/A. Changes in soil test levels are being monitored. In 2008, K treatments boosted soybean yields by 7 to 10 bu/A, and the high rate of P increased corn yields by 22 bu/A at the Western Re- search Station, the only location not affected by drought. At the East Badger location, P treatments increased corn yields by 9 percent. At the Northwest Research Station, drought reduced corn and soybean yields to about half of normal, and there were no responses to P or K treatments.

    In 2009, responses to the four years of application of P and K occurred at only one of three sites, and they were small (less than 5 percent). Changes in soil test P are responding to applied P. But soil test K is more puzzling, with no response to applied K in several instances. These mysteries will require further investigation. These current yield response observations provide useful support for extension specialists receiving questions from producers in light of their concerns with fertilizer prices. The experiment is continuing in 2010.


    Optimizing Application of Phosphorus and Potassium to Processing Tomatoes Under Drip Irrigation in Ontario

    Project Leader: Dr. Tiequan Zhang, Research Scientist, Agriculture and Agri-Food Canada, Greenhouse and Processing Crops Research Center, Harrow, Ontario

    Recent research has indicated that processing tomatoes require higher rates of nitrogen (N) when grown with fertigation. The objective of this research is to determine optimum rates of P and K for the higher yields obtained in this production system. Four rates of P, from 0 to 180 pounds phosphorus pentoxide per acre (P2O5/A), were applied in a factorial combination with 640 pounds potassium oxide per acre (K2O/A) in a drip-irrigated system fertilized with N at 240 lbs/A. Soil test levels for P and K varied from year to year, but were generally high, representative of those of typical producer fields.

    From 2006 to 2009, marketable yield responded to P and K, each in two of the four years. Yields were boosted by 5 percent and 11 percent  P at soil test P levels of 37 to 65 parts per million (ppm). Potassium increased soluble solids content and also raised marketable yields by 10 percent and 12 percent at soil test K levels of 160 to 233 ppm. Vitamin C was increased one year in three by P, but not by K. Neither P nor K influenced lycopene concentrations in any of the four years. The positive yield and quality impacts measured at these relatively high soil test levels support current nutrient use practices of progressive growers, but opportunity to improve fertilizer uptake efficiency remains, particularly for P. The field research was completed in the 2009 growing season, with the project completion planned for early 2010.

    Long-Term Optimum Nitrogen Rates for Corn Yield and Soil Organic Matter in Ontario

    Project Leader: Dr. Bill Deen, University of Guelph, Dept. of Plant Agriculture, 5 Stone Road, Guelph, ON N1G 2W1 Canada 

    Project Cooperators: John Lauzon and Greg Stewart

    Decisions on optimum N rates are often made on the basis of single-year responses. Data are limited on the long-term impact on productivity and soil organic matter of rates higher or lower than these short-term optima. This controlled experiment was designed as a base for testing the application of dynamic soil-crop-atmosphere models as predictors of N rates for corn that optimize sustainability. The specific objectives include the following: one, assessment of short and long-term effects of N on productivity, environmental impact, profitability and cropping system sustainability; and two, validation of crop models, such as Hybrid-Maize, for simulating yield potential, seasonal growth and yield, and fertilizer N management requirements.

    The 2009 growing season was the first in which treatments were applied. Economically optimum rates of N were 15 percent higher than recommended for the preplant application and 32 percent higher than recommended for the side-dress application, possibly because of a relatively cool, wet and long growing season. Corn grain N concentration was 0.60 to 0.66 lbs/bu at rates of N sufficient for maximum economic yield. Residual soil nitrate increased sharply when N rates exceeded the economic optimum, and they were higher for side-dress than for preplant N applications. This project also received support from the Ontario Agri Business Association for sampling soil residual nitrate and soil organic carbon. The project implementation so far forms an excellent basis for achieving the long-term objectives.


    Evaluation of Ammonium Sulfate Nitrate in Virginia Snap Bean Production

    Project Leader: Dr. Mark Reiter, Virginia Tech, Eastern Shore Agricultural Research and Extension Center

    Fresh-market snap beans occupy 5,500 acres in Virginia. Producers wanted to explore sources and rates to improve N use efficiency. This trial compared five N sources (urea with dicyandiamide, ammonium nitrate, calcium nitrate, ammonium sulfate-nitrate and urea-ammonium nitrate) at three rates.

    For spring-grown beans, urea with dicyandiamide increased yield by 25 percent over the control, while the other sources did not. For fall-grown beans, all N sources increased yield by 56 percent over the control, with an optimum N rate of 80 lbs/A, and reduced symptoms of common rust (Uromyces appendiculatus).

    These first-year findings support N management decisions that optimize food yields while minimizing risk of water contamination by N on the sandy loam soils of the Chesapeake Bay watershed.

    Evaluation of Ammonium Sulfate Nitrate in Virginia Sweet Corn Production

    Project Leader: Dr. Mark Reiter, Virginia Tech, Eastern Shore Agricultural Research and Extension Center

    Virginia farmers grow over 3,000 acres of fresh market sweet corn. They wanted to explore sources and rates to improve N use efficiency. This trial compared three N sources (urea-ammonium nitrate, ammonium nitrate and ammonium sulfate-nitrate) at three rates. The first two N sources were compared with and without sulfur (S), applied as gypsum, at a rate designed to supply the equivalent amount of S provided by ammonium sulfate-nitrate (65 lbs/A).

    The N sources increased marketable yields by 16 to 50 percent using optimum N rates ranging from 110 to 125 lbs/A. Agronomic efficiency ranged from 11 to 35 pounds of marketable yield increase per pound of N applied. Sulfur added as gypsum didn’t increase yields, but ammonium sulfate-nitrate produced higher yields than the other two N sources.

    These first-year findings support N management decisions that optimize food yields while minimizing risk of water contamination by N on the sandy loam soils of the Chesapeake Bay watershed. VA-23F


    Building a Maximum Yield Cropping System for Corn, Wheat and Double-Cropped Soybeans in Maryland

    F. Ronald Mulford, University of Maryland, Poplar Hill Research Center

    The goal of this study was to develop a management program that increases crop yield, input efficiency and profit potential in a predominantly no-till cropping system. This cropping system consisted of four crops planted over three years, including no-till soybeans in corn stubble, followed by minimum-till wheat double-cropped with no-till soybeans, and then no-till corn.

    In research conducted on the Eastern Shore of Maryland, N use efficiency in corn and wheat improved when ammonium sulfate (AS) was blended with either urea or ammonium nitrate (AN). Research in 2009 again confirmed that blends containing an amount of AS sufficient to supply 30 pounds S per acre produced corn yields higher than those achieved with granular urea applied preplant. Despite a drought year, these blends produced corn yields of around 120 bu/A with a total application of 120 pounds N per acre. Blends of ammonium nitrate with ammonium sulfate and urea produced yields as high as those with ammonium sulfate and urea in no-till and higher than those with ammonium sulfate and urea in strip-till.

    Ammonium Sulfate and Ammonium Sulfate Nitrate Application on White Potatoes

    Project Leader: F. Ronald Mulford, University of Maryland, Poplar Hill Research Center

    Project Cooperator: David Armentrout

    Managing plant nutrition for potatoes can be challenging since the crop’s nutrient demands are high, and so is its potential for impact on soil and water quality. This experiment examines the effects of N sources for potatoes grown in rotation with wheat, soybeans and corn within strip-till and no-till management systems.

    In 2009, urea and ammonium sulfate applied preplant proved equally effective for increasing potato yield. Highest potato yields were obtained when urea and ammonium sulfate were applied preplant, followed by side-dressing with urea and ammonium sulfate nitrate. MD-14F 

    Source: International Plant Nutrition Institute (IPNI).