Clean-out of Combines for Identity-Preserved Grain Production

Emerging identity-preserved grain markets depend on avoidance of commingling grain at harvest. Knowledge of where grain resides in a combine, cleaning labor requirements, and resulting purity levels would assist producers. Measurements were made of grain and other material residing in different areas of rotaryand cylinder-type combines in replicated cleanouts during corn and soybean harvest and also in preliminary clean-outs during oat harvest. Concentration of the prior (i.e. commingled) grain was measured in the first grain harvested of the subsequent crop. Total material remaining in the combine ranged from 95 to 153 lb, 59% of which was whole grain. The greatest amounts of corn and soybean material (17 to 55 lb) were found in the grain tank and rock trap. Intermediate amounts were found in the head or feederhouse, elevators, and at times the cylinder/rotor (soybeans), the unloading auger (soybeans, oats), and rear axle/ chopper area. The least amounts were found in the cleaning shoe and straw walkers (cylindertype machine). Time spent to clean the combine varied from about two hours to seven hours. Cleaning the head, grain tank, threshing rotor, and cleaning shoe required more time than other areas. Immediately after cleaning, small amounts of prior (commingled) grain and foreign material, 0.2 to 2.5 lb, were found in the first bushel of subsequent grain harvested. Following clean-outs, commingled grain levels dropped below 0.1% after 20 bu were harvested. Over 14 lb of wheat were found during the first clean-out of a combine following 50 ac of oat harvest (no physical clean-out prior to oat harvest). Introduction Differentiated, identity-preserved grain and oilseed market opportunities are developing for U.S. farmers. An important factor in further development is customers' confidence in the farmer's ability to deliver consistent products of high purity levels. To deliver a consistent product of high purity, farmers will need to be knowledgeable of where residual grain and oilseeds are most likely to be harbored in their most complex piece of machinery, the combine, and what the most effective clean-out techniques are. Few measurements of the amount of grain remaining in a combine after field emptying have been reported. In a study on management techniques to control insect infestation in wheat Quick (1977) found 92 lb of wheat and crop residue in an Australian pull-type combine. Greenlees and Shouse (2000) found 59 lb of corn residue during a 1.5 person-hour clean-out in a relatively small-capacity john Deere 4420 combine. After a limited clean-out, the percentage of an earlier-harvested grain variety entering the grain tank dropped to about 2% in the first 30 2005 Integrated Crop Management Conference Iowa State University minute of harvesting a second crop. Sampling during the next 200 bushels harvested indicated the percentage of the earlier-harvested variety dropped below 1%, but was still present in a low concentration that fluctuated randomly Impure grain exiting the combine at random intervals suggests continued low-level contamination as grain is randomly scoured from numerous locations during subsequent harvest. With purity objectives of 99.5% or greater (and in many cases, a stated 0% tolerance for impurity), growers and processors are at great risk of having loads rejected. The presence of even small amounts of a food allergen or toxin can cause immediate chaos in markets, destroying years of market development and brand trust. Estimates of potential grain in various parts of the combine and labor required would allow farmers to better evaluate costs for various purity requirements. Future growth of these emerging, value-added markets for farmers will greatly depend on the producer's ability to use improved field production techniques to reliably deliver high purity products. Field measurements were taken during harvest with the following objectives: 1. To determine the amount of corn or soybeans and other foreign material remaining in various regions of a combine (e .g. grain tank, head, feederhouse , rock trap, cleaning shoe, etc.) after operating the grain tank auger "empty" for one minute. 2 . To determine the concentration of impure grain in the next grain harvested after cleaning. 3. To establish statistical confidence levels on the level of purity achieved following combine clean-out procedures. Materials and Methods Combines Both cylinderand rotary-type threshing combines were used in replicated clean-out tests. During 2003 harvest, a cylinder combine, John Deere 9500 (Moline, IL), with 204-bu grain tank and 14-ft unloading auger was cleaned. It was powered by a 215 hp engine and had 1,3 78 separator hours. Headers used with this combine were a 30-ft grain platform for soybean harvest Qohn Deere model930) and six-row 30-in. corn head Qohn Deere model 643). Also during 2003 harvest, a rotary combine, John Deere 9660 STS, with 250 bu grain tank and 21.5ft unloading auger was cleaned. It used a 305 hp engine and was a new machine with just 10 separator hours. Headers used with this machine were a 30-ft grain platform Qohn Deere 630) and eight-row 30-in. corn head Qohn Deere 893). During 2004 harvest, clean-outs were done on two rotary combines, Case 2388 (Racine, WI) and John Deere 9750 STS. The Case 2388 had a 305-bu (with extensions) grain tank, 18-ft unloading auger, and 280-hp engine with 680 separator hours. Headers used were a 25-ft grain platform (Case 1020) and eight-row 30-in. corn head (Case 1083). The John Deere 9750 STS had a 180-bu grain tank, 20-ft unloading auger, and 325-hp engine. Separator hours shown on instrumentation were 619, but because the machine was an early prototype, actual hours were likely greater. Headers used were a 30-ft grain platform Qohn Deere 930) and eight-row 30-in. corn head Qohn Deere 893). Clean-out procedures In the field prior to actual cleaning, the unloading auger was operated for one to two minutes 20051ntegrated Crop Management Conference -Iowa State University 31 after the grain tank appeared empty. Chaffer and sieve screens in the cleaning shoe were opened and fan speed increased to maximum. Concave clearance around the rotor or cylinder was maximized. The head was lowered to cutting height and the separator and feederhouse drives were alternately engaged and disengaged at least twice, usually while driving across rows to dislodge grain. At the clean-out location the head was removed and the combine was cleaned top-to-bottom and front-to-back using compressed air and pry bars to dislodge grain for collection either on tarps or a concrete surface, or a shop vacuum was used to collect material (particularly in the grain tank or interior cavities). Virtually all visible grain (except as noted later in the bottom of the unloading auger) was collected from the combine during the following procedures. The roof of the operator's cab was vacuumed and vacuuming was used extensively inside the grain tank starting at the top and including ledges, steps, lights, sensors, wiring, and around a window to the cab. Tank extensions were opened and closed if hinged rather than fixed . Grain was vacuumed from around and inside the bubble-up intake auger (able to be opened on the 9750 and 9660 STS). At the bottom of the tank grain was vacuumed from floor cross-augers. As a final step in the tank area grain was cleaned from the sump. This was facilitated by opening access (clean-out) doors below the sump and using compressed air to dislodge grain before finishing vacuuming of the sump. After cleaning the grain tank sump, approximately 2.5 ft3 of wood chips (pine, 0 to 0.5 in. long) were put into the sump to flush residual grain from the turret unloading auger. If a spring-loaded check was present to prevent grain spillage at the end of the auger it was either clamped open or springs were removed and the auger operated for one minute. If access panels were present on the unloading auger (typically one or two) they were removed for localized cleaning and/or to improve flushing. Remaining wood chips and grain were vacuumed from the sump and grain tank cross-augers as well as the exit of the unloading auger. The feederhouse was cleaned by first lowering it to the ground and using compressed air to blow off the exterior. Exterior panels were removed and access doors above and below the feeder were opened. Grain was removed from all joints, crevices, and power transmission components such as pulleys, belts, and driveshafts. Material was blown and vacuumed from inside the feederhouse and the feeder chain was shaken to dislodge grain. If a feed accelerator was present, it was cleaned and combined with feederhouse material. After cleaning the feederhouse it was raised and the hydraulic cylinder stop engaged to gain entry to the rock trap area. The rock trap door was opened and after initial prying to dislodge crop, compressed air and vacuum were used to remove material. Clean-out steps in the threshing area differed somewhat depending on whether the combine was a rotor or cylinder machine. On rotary combines, all access doors present on one or both sides of the combine (depending on make/model) were removed to expose the concave and rotor. The concave screen was cleaned with compressed air and mechanical prying as necessary. After material was dislodged the concave and rotor were vacuumed first making sure the top of the rotor was cleaned and then working toward the bottom of the area including concave, ledges, wiring, beater, pre-cleaner, auger pans, and accessible sieves. If reasonably accessible, concave sections were occasionally removed to gain further access to the rotor. On the cylinder combine, 32 2005 Integrated Crop Management ConferenceIowa State University access doors were opened on both sides of the combine and a door beneath the rock trap to expose the clean-grain augers. Material was dislodged with a combination of compressed and vacuum airflow as well