Spraying a dense crop canopy often results in most of the product landing on the tops of plants, allowing the diseases and insects that live below to escape.A device developed by Haken Pettersson of Sweden and tested at two American locations has proven effective at applying the product all the way to ground level if necessary.Originally called the Slapduk, the application enhancement device was renamed Crop Surfer when the first unit arrived in North America for field testing. The rigid poly wing surfs across the top few inches of standing crop like a surfboard.The Crop Surfer travels through the crop ahead of the boom, bending the plants. The spray is directed into the opening as the poly wing presses the plants forward, allowing the droplets to penetrate the entire plant canopy.The surfboard can be mounted slightly below and in front of any type of boom. The plastic is mounted to a network of parallelograms made of springy stainless steel and spaced 33 centimetres apart.The lead top corner of each parallelogram mounts to the boom while the nozzle mounts to the rear top corner. The nozzles automatically follow the motion as pressure from the crop moves the poly wing and the parallelograms up and down, allowing the nozzles to continue aiming at the target area.The device also has other benefits, mainly linked to the close proximity of the nozzle to the plant. Drift reduction is the main factor.In conventional spray systems, the boom and nozzles run above the crop and are susceptible to even slight breezes. Crop Surfer puts the nozzles down into the crop where the spray is not blown around. This allows spraying in higher winds than with a conventional system. Placing the boom in the crop also reduces boom bounce and improves nozzle height control.Research conducted by the Swedish University of Agricultural Sciences concluded that the rearward-spraying angle resulted in significant improvements in chemical performance. Angling the nozzles rearward also reduced the amount of product landing on the soil, a problem often associated with air-assist spraying systems.The study also found that better chemical efficiency reduces the volume of product to eight gallons of liquid per acre, resulting in more spraying time between refills or lighter loads in the field.Agronomist Phil Needham of Needham Ag Technologies in Kentucky saw enough merit in the concept to visit Sweden four years ago to see the device in action.One of the farms he visited was using the Slapduk to spray fungicide on a winter wheat field. What he saw convinced him that the device was doing what it’s supposed to do, and he bought one to bring back to Kentucky.“A lot of times, your insect, weed and disease problems are hiding down in the crop where you can’t get the spray on them,” Needham said.“When I saw the Slapduk in action for myself, I could see how well it opened the canopy so they got better coverage on the whole plant.“The shape of the wing works almost like an airplane wing. It forces the product down into the canopy, even if it’s too windy for conventional sprayers.”Needham installed his Crop Surfer on one of his customer’s Apache high clearance sprayers and used it in soybeans and wheat. He found that it worked better in soybeans than in wheat.Needham also conducted replicated trials with a smaller Crop Surfer mounted on a four-wheel all-terrain vehicle. Using liquid sensitive paper, he documented how the spray covered the plants all the way to ground level.Needham does not have a price for the Crop Surfer because the machines are not exported to North America. The unit he brought over was a development and demonstration machine.Ohio State University researchers who studied the Slapduk three years ago already knew that fungicides applied by a conventional sprayer place only 25 percent of the product on the lower portions of soybean plants. The problem was that rust causes all of its damage in the lower part of the plant.The Slapduk seemed a strong candidate as they searched for a better application method. The full report of their research was published in a November 2008 on-line publication of the American Society of Agricultural and Biological Engineers’ power and machinery division.In that paper, the scientists report that 95 percent drift reduction is possible using the Slapduk.However, they also found that the wing can damage plants if it bends the crop over too far. As well, the spray won’t achieve maximum penetration if the nozzle is not positioned the correct distance from the rear edge of the wing.In short, everything needs to be perfect if the anticipated results are to be realized. It’s not as simple as just mounting a plastic wing in front of the boom.The project, which was headed by Heping Zhu, examined the relationship between the position of the poly wing and the nozzle. To find the best nozzle location and angle, he measured the speed at which the plant rebounds and the time it takes for the droplet to travel from the nozzle tip to the surface of the moving plant.He used a Canon digital video camera, sample soybean plants and a complex mathematical formula to test different nozzles, plant heights and nozzle locations.Two sample conclusions indicate how critical it is to properly fine tune the Slapduk assembly.Using an XR8002 nozzle at 276 kPa, the droplet took 0.027 seconds to travel 0.33 metres to reach the plant.Using an XR8004 nozzle also at 276 kPa, the droplet took 0.023 seconds to reach 0.33 metres.Armed with this data as well as data about plant rebound, the Ohio engineers were able to make definite statements about the placement of the poly wing and nozzles.For example, if a 1.06-metre-high soybean plant was sprayed with an XR8002 nozzle, the wing should run no deeper than 0.18 metres below the top of the crop canopy. The nozzle should be placed no further than 0.54 metres behind the leading edge of the poly wing.If producers were spraying the same 1.06-metre-high plant with an XR8004 nozzle, the wing should run no deeper than 0.14 metres below the top of the crop and the nozzle should be no further than 0.47 metres behind the leading edge of the wing.Resistance is the main drawback of the Crop Surfer.Even the best of today’s North American spray booms are designed to operate above the crop and not within the crop.Resistance from the crop is enormous when the Crop Surfer wing drops down into the crop, which limits the ground speed.Needham said European farmers spray at six to 10 m.p.h. and don’t go higher than 60 to 90 foot booms because of their concern for a quality spray job.“Here in North America we’re in a hurry. We spray at 15 to 20 m.p.h. You can’t do that with a Crop Surfer or with a 120 foot boom,” Needham said.“I hope guys don’t buy these and put them on their sprayers and then go out and spray at 20 m.p.h. It just won’t work. You’ll have excessive crop damage and boom damage.“These devices are designed for prudent, high quality spraying operations. The attitude in Europe is that they concentrate on performance in the spraying operation, not just acres per day.”He said the Crop Surfer in North America is probably better suited to high value crops such as potatoes, beans and sugar beets rather than cereal crops.Another drawback is that the Crop Surfer does not do a good job applying fungicides to fusarium head blight in wheat because it only covers half the head.However, Needham said it excels at foliar applications for diseases such as leaf rust and septoria where the chemical needs to cover the entire plant.For more information, contact Phil Needham at 270-785-0999 or visit www.needhamag.com.The Slapduk/Crop Surfer is sold in Sweden by CNH dealer Viby Teknik, which can be found at www.vibytenik.se.The full text of Heping Zhu’s Ohio research is available at ddr.nal.usda.gov/bitstream/10113/26983/1/IND44164827.pdf.
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