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Chilcote, David O.

Youngberg, Harold Wayne, 1929-

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AGRONOMIC CROP SCIENCE REPORT Research Extension l>ti,• PROPANE FLAMER BURNING OF GRASS EED FI ELD STUBBLE lJ · :( .· . , 0. O. Chilcote and H. W. Younqberg 2/ APR . . .. Introduction Alternatives to open burning of grass seed fields after harvest include the possibility of the use of other heat sources, such as propane or diesel, to provide the thermal sanitation so beneficial to seed production. Propane flamers are presently used in mint fields for control of disease pests, how-ever, in this case, removal of residue is not the issue but rather destruc-tion of the pathogens within the plant tissue. Obviously, such a treatment could only be considered where a large portion of the straw would be mechan-ically removed prior to use of the flamer for burning remaining residue. The flamer (burning propane) ignites the stubble remaining after removal of the straw, so that residue burning is facilitated over a wider ranqe of en-vironment conditions and provides the thermal treatment normally achieved in an open burn. Hith most of the residue removed, the potential for emis-sion of pollutants from burning is greatly reduced. To ascertain the possi-ble use of such an alternate heat source for thermal sanitation of grass fields, studies were undertaken comparing propane flamer burning with open burning. Most of the residue down to a 2-inch stubble height was removed by flail-chopping prior to flamer treatment. An estimated 3/4 ton of residue remained on the fields. Time of season and grass species, as well as speed of operation, were variables in these investigations. Of course, variation in residue load would affect fire spread, as well as soil surface temperature. Results The use of a propane flamer to burn grass seed field stubble is a high cost operation requiring the removal of residue to leave as little fuel as pos-sible on the soil surface. The operation can also be hazardous because of risk of fire spread, depending on humidity and wind speed. Environmental conditions were found to influence the effectiveness of the treatment. 1/ Progress Report EXT/ACS 8, Agricultural Experiment Station, O.S.U. 3/75 y Professor of Crop Physiology and Extension Agronomist, respectively, De-partment of Agronomic Crop Science. 2 Season of Treatment. Early propane burning is more beneficial than late burning, probably because of the presence of a lesser amount of green re-growth with higher moisture content and the higher moisture content of straw which is likely to occur later in the season (Table 1). Early propane flam-ing treatments resulted tn seed yield response which compared favorably with open burn treatments (see Table 2). In almost every case, the seed yield with propane flaming was equal to or better than conventional open burning. Table 1. Seed yields in four grass species when propane flaming l/ was used early (August} versus late (October}, 1967-68. Seed Yield (lbs/A} Species Early Late Chewings Fescue 809 288 Perennial ryegrass 1221 763 Orchardgrass 1049 1149 Merion bluegrass 1200 967 Temperature and Speed. The results from studies on temperatures produced versus speed of operation indicate that the faster the operation the lower the temperature (Figure l) perceived at soil surface and the shorter the duration of the temperature. A low temperature for a short period would be a concern in terms of effective sanitation. The temperature exposure from propane flaming may not be sufficient to destroy disease organisms and an increase in disease infestation might occur. No effort was made to evaluate disease control in this study since the fields were quite gree of disease from previous burning history. Open field burning shows quite a different temperature exposure pattern compared to flaming (Figure 2). Although tem-peratures may not be any higher, they are maintained for a longer period of time. The demonstration of survival of organisms (weed seed) on the soil surface lends further credance to the possibility that disease control would be inferior to open burning. Smoke Emission. The technique of propane flamer burning of grass seed field stubble may contribute copious amounts of smoke because of the incomplete combustion of residue and smoldering after passage of the flame front. 4/ In addition, the smoke is retained at a low level in the atmosphere. Tne fate of this smoke and its effect remain to be assessed. Total emissions should be reduced because only a portion of the total residue is burned. 3/ Straw and stubble were chopped and removed prior to flaming and burning remaining residue. 4/ The amount of smoke produced would depend on the condition of the straw, regrowth, and the climatic condition, all of which influence the combus-tion process. 3 Table 2. Seed yields for five grass species when propane flaming was used, 5/ expressed as a percent of early open burn yields. -Species Percent of earl.l'.': open 6urning Chewings fescue 100 Creeping red fescue 90 0rchardgrass 101 Merion bluegrass 102 Highland bentgrass 108 Mean 100 Annual Versus Perennial Grass Crops. At present, burning of the residue after harvest is a primary method of weed control in annual ryegrass. Burning de-stroys the viability of seed on the surface of the soil. Studies with annual ryegrass showed that the temperature level and duration for propane flaming (approx. 2 1/2 mph} were not sufficient to destroy many of the weed seeds left in the fields after harvest and therefore a concomitant increase in weed infestation was noted. In fact, some promotion in the germination rate of weed seed was observed. In perennial crops where herbicides are used extensively for weed control, propane flaming may be a more feasible alternative since it does remove the remaining residue after flail-chopping and removal of the straw, and appears to maintain seed yields. Where disease control may be less critical and for varieties or species sensitive to open burning, propane flamer burning may be a viable management practice for maintaining high seed yield. The technique might be particularly adaptable to the 11close-clip 11 system of resi-due removal to provide an added measure of sanitation. Conclusions A propane flamer can be used to burn the residue remaining in seed fields after mechanical removal of straw and stubble. It seems most feasible in perennial grass crops, particularly those sensitive to burning, but has a high dollar and energy cost as compared to open burning. Early season treat-ment is most effective. Slower operating speeds provide the most effective thermal exposure. 5/ Straw and stubble were chopped and removed prior to flaming and burning remaining residue. 4 Propane flaming at rates above 2 mph in annual ryegrass failed to destroy weed seeds. This apparent limitation in thermal treatment also casts doubt on the ability of the flamer to destroy disease organisms, important in grass seed producti-0n. If the speed of travel is slow enough, satisfactory sani-tation might be obtained. Smoke emission, although reduced, is still a prob-lem and it is confined to lower levels of the atmosphere. 900 800 700 400 300 200 1 MPH 2 MPH 3 MPH 0 60 120 0 60 120 0 TIME IN SECONDS FIGURE 1. COMPARISON F TEMPERATURE PROFILE AT l/2H ABOVE GROUND SURFACE FOR PROPANE FLAMER AT VARIOUS SPEEDS OF OPERATION, 60 0 u. w a:: 1250 1000 ~ 750 c( a:: w Q.. ~ w t-50 25 flGURE 2, OPEN FIELD BURN TEMPERATURE PROFILES (0RCHARDGRASS), 1968 t, TEMP.ATGROUND I '( I ' I I I I TEMP. 6 1 ABOVE I GROUND I I I I I .. __ STRAW MOISTURE "4.73 ¼ STUBBLE -11- 44.63 •;. SOIL - 11- 25.17 ¾ 0 L-----+-----+-----+----t------11-----+-----+-----+---' 0 60 120 l80 240 300 360 420 480 54C TIME IN SECONDS 01 

Propane flamer burning of grass seed field stubble

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Propane flamer burning of grass seed field stubble

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