Extension Ag Update
May/June 2003
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Optical Sensor Could Revolutionize Application of Granular Fertilizer

Tony Grift; 217-333-2854; grift@uiuc.edu, Writer: Leanne Lucas; 217 244-9085, llucas@uiuc.edu

A new optical sensor that "predicts" the spread pattern of granular fertilizer could dramatically change the way farmers calibrate spreaders and apply granular fertilizer. Traditional calibration is a cumbersome process and dependent on the weather constraints of wind and rain, said Tony Grift, University of Illinois agricultural engineer. It involves driving a spreader over a row of 25 collection trays to collect the fertilizer and weighing each tray’s contents to determine the spread pattern.

By contrast, the optical sensor, installed on a spinner-type spreader, automates this process. It can predict a spread pattern by measuring the velocity and diameter of fertilizer particles as they pass the sensor. To compute velocity, the particles interrupt a double light beam, and the time between the two interruptions is measured. The amount of time a particle blocks either light beam is also measured and combined with velocity to determine diameter.

This information is then used in a mathematical model that predicts where the granules will end up on the ground. Accumulation of a large number of landing spots reveals the shape of the spread pattern. A custom computer program uses this pattern to calculate a simulated pattern for a preset swath width.

Grift and a colleague, Jan Willem Hofstee, began development of the sensor in 1993. Hofstee is an agricultural engineer at Wageningen University in the Netherlands and is currently on sabbatical at the U of I. Grift believes the optical sensor provides the technology necessary for the needs of high-tech farming, also known as precision agriculture. "In precision agriculture," Grift said, "we need to be able to vary the application rate of fertilizer depending on the demands of the crop and soil.

"The spread pattern on a traditional spinner-type spreader is usually very bad, with peaks and valleys," Grift continued. "Peaks mean you are over-applying and there is an economical loss. Valleys mean you are under-applying, and the crop is not going to grow very well." This is the pattern that emerges when the spreader is used at a constant rate. "If you start varying the rate," said Grift, "the pattern gets even worse. So we had to come up with a method that would not only automate the calibration but also allow us to change the application rate in real time."

In his research, Grift uses a single disk, spinner-type spreader, which has a round hopper with two feed holes. He and a grad student are currently working on a design that places three "fingers" within the two feed holes. "When we vary those fingers, we can put the fertilizer wherever we want to," said Grift, "and we can produce a very good spread pattern with a very poorly designed spreader.

"Professional applicators will be able to use this kind of system," Grift noted. "The tractor operator will have a computer screen he watches. He makes one sweep to get an indication of his spread pattern. Then he determines the swath width he needs to get his application rate. When a different application rate is needed, the process is repeated. He has a calibration system that he can take with him on the fly, all the time."

In his current study, Grift uses the sensor to measure particles that pass through the sensor individually. But clusters of particles also pass through the sensor. Grift has taken the development of the optical sensor to the next level, measuring these clusters to determine mass flow. Mass flow is computed by measuring the lengths of the clusters to statistically estimate the number of particles per cluster. "It's a natural progression," said Grift, "going from single particles to mass flow. The concept can be used in higher density mass flows such as the aerial application of fertilizer. In fact, the concept can be used in many industries where mass flow is important. In the end, this might be more important than the original application."

For more information on the optical sensor, log on to the Agricultural and Biological Engineering website at www.age.uiuc.edu. From there, click on the Faculty and Staff button to find Grift's homepage. On the homepage, go from Research Areas to Biosystems Automation to Precision Agriculture to Smart Fertilizer Spreader System.


Establishing Buffer Zone for Genetically Modified Crops Pollen Drift

Dell Rae Moellenberg, 970-491-6009, dellrae.moellenberg@colostate.edu, Colorado State University News

A Colorado State University study takes a step towards finding solutions to pollen drift from genetically modified plants onto organic and traditionally grown crops, a concern raised by some members of the public. The study shows that in Colorado, about 150 feet may be a reasonable buffer zone between genetically modified corn plots and organic and traditional corn plots to prevent significant cross-pollination due to pollen drifting from one field to another.

The first round study was conducted in Morgan County in eastern Colorado, the state’s corn belt – and also a windy area in the region, and at a second location on a plot in Boulder County. Results showed that less than one1 percent of corn farther than 150 feet from test plots is cross-pollinated by pollen from the test corn. That means that very little of the pollen from the test corn fields drifted more than 150 feet. “We realize that one year’s data is not sufficient for this type of study,” said Patrick Byrne, Colorado State University crop sciences professor and researcher. “Given the year-to-year variability in weather conditions, we will repeat the research again during the 2003 growing season.”

The study tracked drift of blue kernel corn pollen at one site in Boulder County and the drift of Roundup Ready corn, a genetically modified crop, at the Morgan County site. The corn was planted adjacent to corn varieties without those traits. When the corn was harvested, samples were collected from various distances away from the test plots. These samples were tested for traits from the test plots, which indicate the amount of cross-pollination. The farthest sample was collected 305 meters – about 915 feet -- away from the edge of the test plots.

Cross-pollination was highest at the closest sampling sites -- up to 46 percent at three-quarters of a meter south of the blue corn plot in Boulder County. However, cross-pollination dropped off in a short distance, with only 0.5 percent cross-pollinated kernels near the blue corn plot at 150 feet. At that same distance in the Morgan County plot, 0.75 percent of the corn showed cross-pollination with the Roundup Ready test plot. The farthest distance at which any cross-pollination was detected was 600 feet in Boulder County and 270 feet in Morgan County.

“The growth in U.S. acreage planted with genetically modified crops has been paralleled by growth in the demand for organically produced foods,” said Byrne. “It can be argued that both genetically modified and organic agriculture are approaches to improving conventional farming methods, but the two forms of agriculture are in conflict because of U.S. organic standards that prohibit the use of genetically modified products and pollen drift from genetically modified crops to nearby organic fields. Given the growing importance of both the biotechnology and organic sectors of food production, co-existence between the two becomes a critical issue. We hope that this study will eventually help to establish protocols for co-existence of these two types of food production.”

This study came out of discussions in Boulder County, where Byrne served on a committee to study the concerns of that county’s residents, particularly those who raise organic crops, with allowing the farming of genetically modified crops on county-owned open space land. The study was used to establish genetically modified crop protocols on county open space cropland.


Similar Swine Diets May Actually Be Different

David Elstein, 301-504-1654, delstein@ars.usda.gov, ARS News Service, USDA

Swine that are fed the same diet in different locations don't always get the same level of nutrients. That's the conclusion of Agricultural Research Service scientists who participated in a collaborative study, with 24 universities from north-central and southern regions of the United States, to evaluate the consistency of feed mixtures fed to swine.

The ARS Roman L. Hruska U.S. Meat Animal Research Center in Clay Center, Neb., along with university researchers, prepared the same corn-soybean meal diet, fortified with vitamins and minerals, at each location. Samples of each station's feed mixture were later analyzed for crude protein, calcium, phosphorus and zinc concentrations. Laboratory analysis showed that although the diets were mixed uniformly, there was considerable variation in the nutrient concentrations at the 25 test locations. In other words, the diets mixed at some locations had higher levels of crude protein, calcium, phosphorus and zinc than those mixed at others.

Part of the variation in crude protein came from the corn and/or soybean meal that each location used. Differences in calcium and phosphorus contents could have been caused by various sources of supplemental dicalcium phosphate. Variation in zinc concentration was probably due to erroneous amounts of trace mineral premix added to the diet. Another reason for different results in calcium, phosphorus and zinc concentrations may have been that some laboratories do not routinely conduct mineral assays.

As a result of this study, published in the Journal of Animal Science, scientists and technicians should be careful when mixing test diets and should guard against drawing incorrect conclusions regarding dietary treatment effects. Accuracy in diet mixing is important when conducting animal nutrition research at multiple locations.


Organic vs. Conventional Corn and Soybean Yields

Paul Porter, Univ. of Minnesota, pporter@umn.edu., published in the Agronomy Journal, March-April 2003

A conventional two-year corn-soybean rotation that relies on synthetic fertilizers and pesticides was compared with an extended four-year certified organic rotation incorporating oats and alfalfa. Corn and soybean yields slightly decreased in the organic system, according to a 10-year study in Minnesota. When production costs (though without taking organic price premiums into account) were calculated the net returns of the organic compared to conventional systems were equivalent. These results suggest that organic production systems can be competitive with conventional production systems.