Sprayer Design for Chemical Conditioning of Alfalfa

Transcription

1 Sprayer Design for Chemical Conditioning of Alfalfa C. A. Rotz, R. J. Davis MEMBER ASAE MECHANIZATION MEMBER ASAE ABSTRACT FIELD drying tests were conducted to determine major design criteria for spray application of a potassium carbonate solution to speed the drying of alfalfa. Drying rate was significantly increased as the carrier (water) application rate was increased, but it was not affected by an increase in concentration of potassium carbonate in the solution. A.8% solution of potassium carbonate in water, applied at L/ha, provided a satisfactory increase in drying. Faster drying was obtained at higher application rates to a maximum recommended rate of about 47 L/ha. Fan, hollow-cone and solid-cone nozzles all provided similar coverage and drying rates of alfalfa. Operating pressure of the spray system had a small effect on plant coverage. Slightly poorer coverage was obtained when fan nozzles were used at a high pressure, but a significant change in drying rate did not occur. INTRODUCTION Large losses of to % of the crop can occur during the field curing process of alfalfa hay harvest. Respiration, microbial activity, leaching by rain and solar bleaching all contribute to losses of dry matter and quality changes. Conditioning treatments speed the drying of alfalfa to reduce field curing time and thus reduce losses. Mechanical conditioning with crimping and crushing rolls is widely used to. Chemical conditioning, a new technology for hay making, has been introduced to the hay grower. This technology involves the use of chemicals to speed the drying of legume crops, particularly alfalfa. Several chemical combinations have been shown to work with the main ingredients being potassium carbonate and sodium carbonate. Application of a potassium carbonate solution to speed the drying of alfalfa was first tested in the field by Tulberg and Minson (9). They found that applying the solution at rates of 9 to 84 L/ha could more than double the drying rate when compared to unconditioned hay. The treatment gave a 4% increase in drying rate over mechanical conditioning. Further testing of chemical treatments was done by Weighart et al. (98). Article was submitted for publication in January, 985; reviewed and approved for publication by the Power and Machinery Div. of ASAE in December, 985. Presented as ASAE Paper No Michigan Agricultural Experiment Station Journal Article Number 44. The authors are: C. A. ROTZ, Agricultural Engineer, USDA-ARS, and R. J. DAVIS, Specialist, U.S. Dairy Forage Research Center, Agricultural Engineering Dept., Michigan State University, East Lansing, MI. They compared a solution of potassium carbonate alone to a combination of potassium carbonate, methyl esters of long-chain fatty acids and an emulsifier. They noted that the three-component solution provided more consistent improvement in drying than did potassium carbonate alone. In a series of field tests, however, the potassium carbonate and water solution performed as well as the three component solution (Rotz and Thomas, 985). Chemical conditioning with potassium carbonate solutions was more extensively field tested by Rotz et al. (984). The treatment was found to work best when used with a roll-type conditioning machine because the mown material was left in a thinner swath and the rolls aided in spreading the chemical over the plant surface. Chemically-treated hay and untreated hay baled at the same moisture content (% wet basis), were shown to maintain similar quality through storage (Johnson et al., 98). Application rate and method appear to be important in applying the chemical conditioning treatment. Very high application rates of 4 to 8 L/ha were used in early research work (Weighart et al., 98; Tulberg and Minson, 9). Lower application rates of 5 to 5 L/ha have been recommended by commercial suppliers of the chemical conditioning treatment in an attempt to remove the need for handling large quantities of water. In a field drying experiment, alfalfa was observed to dry at a faster rate when treated at a higher application rate (Rotz et al., 984). Different types of spray nozzles and operating pressures have been recommended for use in applying the chemical treatment. Both cone and fan nozzles appear to give equally good coverage (Crocker and Lodge, 98), but this has not been shown in a controlled experiment. Liquid pressure may also affect plant coverage and thus, the drying results. s create smaller drops which may improve plant coverage or possibly reduce coverage due to increased drift losses. More complete information on sprayer requirements for chemical conditioning will provide a better basis for recommendations on application of the chemical treatment. OBJECTIVES Field experiments were conducted on alfalfa to determine the effect of major sprayer design parameters on the effectiveness of the chemical conditioning treatment. Specific objectives were:. To measure the drying rate of chemically conditioned alfalfa as influenced by the application rate of the chemical treatment and the level of concentration of the active ingredients in a water solution.. To measure the drying rate and the spray coverage 6 TRANSACTIONS of the ASAE

2 TABLE. INITIAL CROP CONDITIONS AND WEATHER CONDITIONS DURING THE FIRST TWO DAYS OF EACH DRYING TEST Test date 9/7/8 9/8/8 9/9/8 9/9/8 9//8 6/7/8 6/8/8 6/9/8 6//8 6//8 7/9/8 7//8 7//8 7/5/8 7/6/8 8/4/8 8/5/8 8/6/8 8//8 9//8 9/7/8 9/8/8 7//84 7//84 7/6/84 7/7/84 7/9/84 7//84 8/6/84 8/7/84 8//84 8//84 8//84 8//84 Experiment Alfalfa Conditions Cutting Maturity (% bloom) 8t) Initial moisture content, % Yield, t/ha Temperature, C Daytime Weather Conditions Relative humidity, % Solar insolation, W/m Wind, m/s Rainfall, cm. of alfalfa with the chemical treatment applied by fan, hollow-cone and solid-cone nozzles at two levels of liquid pressure at the nozzle and a constant application rate. EQUIPMENT AND PROCEDURE Field drying experiments were conducted at East Lansing during the 98, 98 and 984 hay seasons to monitor alfalfa drying following chemical conditioning with various spray equipment. Alfalfa was cut with a.7 m mower-conditioner which used a cutterbar for mowing and intermeshing rubber rolls for conditioning. Alfalfa was field dried in full-width swaths with treatments located adjacent to one another to reduce any variance due to crop and field variations. Each field experiment consisted of six or eight replications of the same test under different crop and weather conditions (Table ). Weather data was obtained from a portable weather station located in the alfalfa field. Alfalfa drying rate was monitored using a procedure described by Rotz and Sprott (984). Three samples of each treatment were immediately cut from a freshlymown swath and placed in trays. Sample mass was measured every h during time drying until the alfalfa reached % moisture (wet basis). All samples were then oven-dried to obtain final dry mass. In experiments where nozzle types and pressures were compared, spray coverage was used as a measure of effectiveness along with drying rate. Coverage was measured by attaching strips of water sensitive paper to standing alfalfa. Two strips were stapled to the top and two strips were stapled to the bottom of plants. One of the strips faced toward the oncoming spray device and the other faced away. Three replications were made across the swath width for each treatment of each test. The alfalfa was mowed and conditioned with a given treatment. Following the treatment, the paper strips were retrieved from the freshly-mown swath. Portions of the paper exposed to the chemical (moisture) changed color. The paper strips were then rated by three people by comparing the coverage on individual strips to that on a preset scale. Each strip was given a rating between and with being complete coverage. Most chemical treatments were applied with a tractormounted sprayer described by Rotz et al. (984). The sprayer traveled ahead of the mower-conditioner so that mowing and mechanical conditioning occurred immediately after spraying. A push-bar located just ahead of the spray nozzles laid the alfalfa over to allow the spray to penetrate the leaf canopy. One of two spray booms, mounted 8. cm behind the push-bar, was used to apply the chemical. One boom had six fan nozzles with a 45.7 cm spacing. This boom was located. cm above the push bar which was. cm above the level of the ground. Hollow and solid-cone nozzles were used with the other boom where 8 nozzles were mounted with a 5. cm spacing. This boom was 6.7 cm above the push bar. For a portion of the application rate experiment conducted on first cutting alfalfa, the sprayer boom was mounted between the reel and conditioning rolls of the mower-conditioner to spray the mat of cut material just ahead of the rolls. The two spray systems were previously shown to provide similar drying performance (Rotz et al., 984). EXPERIMENTAL DESIGN AND ANALYSIS Three major experiments were conducted to study the effects of: (a) application rate and concentration; (b) nozzle type with varied line pressure; and (c) nozzle type. Vol. 9(l):January-February, 986 7

3 The application rate experiment consisted of six treatments which included a control (no chemical treatment) and three application rates at two levels of concentration. Six tests were completed with three on each of first and third cutting alfalfa yielding 4.8 and.8 t/ha respectively. Fan type nozzles were used for all application rates. Nozzle types used to deliver the three application rates of 47, and 5 L/ha were TJ 88, TJ 86 (Spraying Systems Co., Wheaton, IL)* and LF.8 (Delavan, West Des Moines, IA), respectively. Application rates were maintained by regulating the liquid pressure between 5 and kpa. At the rates of and 5 L/ha, treatments were also included where the concentration of active ingredients was increased to give the same active ingredient per unit of plant material as that obtained with a 47 L/ha application rate. The chemical solution used in the application rate experiment consisted of three components: potassium carbonate, methyl esters and an emulsifier (X77, Chevron Chemical Co., San Francisco, CA). The normal concentration of the three ingredients in a water solution were.8,. and.%, respectively. In the second experiment, the effects and interaction of nozzle type and pressure were measured. A series of eight field drying tests were conducted on second and third cutting alfalfa. Field drying tests consisted of six treatments including a control (untreated swath) and fan and solid-cone nozzles used at low and high pressures. Nozzle tips were selected so that all types and pressures gave the same application rate of 8 L/ha. The nozzle tips used and their respective operating pressures were: (a) fan at kpa, TJ 86; (b) fan at 69 kpa, LF.8; (c) solid-cone at 9 kpa, D- and (d) solid-cone at 5 kpa, Dl-. In the third experiment, a more complete study of the nozzle type was done. Fan, hollow-cone and solid-cone nozzles were compared at similar operating pressures and application rates. Nozzle tips used were TJ 86, D-5 and Dl.5-, respectively. Three field tests were completed on each of second and third cuttings, 984. *Trade names are used in the paper solely to provide specific information. Mention of a trade name does not constitute a warranty of the product by the United States Department of Agriculture or Michigan State University nor an endorsement of the product to the exclusion of other products not mentioned. In the second and third experiments, the primary chemical used was a mixture of.8% potassium carbonate in water. This solution was shown to provide similar drying results in field experiments as the three component solution of experiment (Rotz and Thomas, 985). A commercial solution provided by Domain, Inc. (New Richmond, WI) was also used for half of the second experiment which had a chemical make-up similar to the three component solution. Alfalfa drying rates were analyzed by calculating a mean drying constant for each treatment. The drying "curve" over a given time interval was assumed to fit an exponential model and the drying constant was the natural logarithm of the moisture ratio divided by the length of the time interval (Rotz and Sprott, 984). A drying constant was determined for each time interval between consecutive moisture measurements using the following equation: - M k = In. t M where: k t M = M n = [] drying constant, h - length of time interval, h sample moisture content (dry basis) at end of time interval sample moisture content (dry basis) at beginning of time interval. Drying constants during time drying were averaged to give an overall drying constant for each sample for each. Drying constants for intervals between initial and % moisture (wet basis) were averaged to obtain the overall constant or mean drying rate. Analysis of variance was used to determine the significant main effects and interactions between treatments for both drying rate and spray coverage. Treatment means were compared using Duncan's Multiple Range Test at p = 5 significance to determine treatment differences. RESULTS AND DISCUSSION Application Rate and Concentration Alfalfa drying rates were significantly influenced by the application rate of water used as a carrier for the chemical treatment with the highest drying rates TABLE. FIELD DRYING RATE* OF ALFALFA WHEN TREATED WITH A SOLUTION OF POTASSIUM CARBONATE, METHYL ESTER AND EMULSIFIER AT FOUR RATES OF APPLICATION AND FOUR LEVELS OF CONCENTRATION (EXPERIMENT ) Application rate K C (g/kg)t Solutic >n, L/ha Cut Cut First First cutting, 98 After first a.5 ab.6 ab.9 bc.49 c.47 c First Third cutting, 98 After first a.86 b.89 b.5 b. b.5 c over both cuttings.7 a.56 b.57 b.7 b.76 b. c abcdg U p erscr ipt letters indicate treatment means which are a statistically homogeneous group as determined by the Duncan's Multiple Range Test (p = 5). * Drying rate determined as the average drying constant (h - ) over the drying period. fgrams of potassium carbonate per kg of dry matter with an average dry matter yield of 4.8 t/ha on first cutting and.8 t/ha on third cutting alfalfa. 8 TRANSACTIONS of the ASAE

4 ^ o a: Q - First Cutting (4.8 t/ha) Application Rate (% of dry matter) Fig. The increase in drying rate obtained through chemical conditioning of alfalfa over a range of application rates at two levels of yield. Each point is the average of three tests with three replications per test. occurring at the highest carrier application rate. As the carrier application rate was reduced, the drying rate of the treated alfalfa decreased nearly in direct proportion (Table ). Larger differences in drying rates between treatments occurred in the third cutting tests than those in the first cutting. The chemical has been found to be less effective on first cutting in previous tests (Rotz et al., 984). In the third cutting tests, the 47 L/ha application rate provided significantly faster drying than all other treatments. The and 5 L/ha rates did not provide significantly different results, even though the higher rate did dry faster. In the first cutting tests, little difference in drying was found between the 47 and L/ha rates. The 5 L/ha rate produced poor results which were not significantly better than untreated alfalfa. High alfalfa yields greatly reduce the effectiveness of the chemical treatment. This is only partly explained by the difference in the amount of chemical applied per unit 8 TABLE. RELATIVE COVERAGE OF WATER SENSITIVE PAPER ATTACHED TO ALFALFA FOLLOWING MECHANICAL AND CHEMICAL CONDITIONING USING SELECTED NOZZLES AND PRESSURES (EXPERIMENT ) Spray device Control (no treatment) Fan nozzle Solid cone nozzle Bottom of plant Front 4.6* Back Top of plant Front Back a 8. C 7. b 7.6 bc 7.9 C abc Superscript letters indicate treatment means which are a statistically homogeneous group as determined by the Duncan's Multiple Range Test (p = 5). * Relative coverage with being complete coverage and being no coverage. of plant material. A plot of the increase in drying rate as a function of the application rate per unit of plant material (Fig. ) shows the chemical performance on third cutting to be double that of first cutting. A major cause for the difference is still yield. With a higher yield, more alfalfa is in the swath creating a more dense swath. The amount of material in the swath has been shown to reduce the affect of the chemical (Rotz et al., 984). A dense swath inhibits moisture removal which restricts the benefit obtained with the chemical. Other factors which may contribute to the difference between the first and third cutting include soil moisture, temperature and possibly plant structure. Increasing the concentration of the active ingredients in the carrier beyond the base.8% mixture had no effect upon the drying rate of treated alfalfa. In no case was the drying rate at a set application rate significantly improved when the concentration of active ingredients was increased. Therefore, the amount of potassium carbonate, or other active ingredient applied, is not as important as the application rate of the carrier. Large amounts of water are required to provide adequate coverage of the plant. A decrease in carrier application rate will decrease the effectiveness of the treatment while an increase in concentration of the active ingredient will not improve the effectiveness of the treatment. TABLE 4. DRYING RATEf OF ALFALFA FOLLOWING CHEMICAL CONDITIONING WITH TWO TYPES OF CHEMICALS AND SELECTED NOZZLES AND PRESSURES (EXPERIMENT ) Spray device Cut Solution I Cut Avg. Cut Solution II Cut Avg. Control Flat fan nozzle Solid cone nozzle.54* a.8 c.96 bc.95 bc.7 ab b.95 b.9 b.5 b.49 a.5 b.96 b.9 b.99 b Superscript letters indicate treatment means which are a statistically homogeneous group as determined by the Duncan's Multiple Range Test (p = 5). *Four field tests using Solution I (potassium carbonate and water) were begun on 7/5, 7/5, 8/ and 9/7/8 and four field tests using Solution II (Domain, Inc.) were begun on 7/9, 7/, 8/4 and 8/5/8 (Table ). tdrying rate determined as the average drying constant (h"l) over the drying period. Vol. 9(l):January-February, 986 9

5 TABLE 5. RELATIVE COVERAGE AND DRYING RATE OF ALFALFA FOLLOWING MECHANICAL AND CHEMICAL CONDITIONING USING MAJOR TYPES OF NOZZLES (EXPERIMENT ) Spray coverage Drying constant (h"l) Treatment Top of plant Bottom of plant Cut Cut Control (no spray) Fan nozzle Hollow-cone nozzle Solid-cone nozzle a 5. b 5.8 C 5.8 C.4 a.45 b.6 b.8 b.5 a.57 b.7 b.8 b.47 a.5 b.7 b.5 b abc Superscript letters indicate treatment means which are a statistically homogeneous group as determined by the Duncan's Multiple Range Test (p = 5). Relative coverage of plant with spray material as measured with water sensitive paper where is complete coverage and is no coverage. Nozzle Type and Pressure The two experiments performed to compare nozzle types and operating pressures did not show large or consistent differences. In the 98 experiment, fan and solid-cone nozzles provided similar coverage and drying rates of the alfalfa crop when the spray systems were operated at a low pressure of about kpa (Tables and 4). In 984, a similar experiment was repeated where fan, hollow-cone and solid-cone type nozzles were compared at the same pressure. Although the fan provided a small but significant reduction in coverage, a significant difference in drying performance was not found. In four of the six individual field tests, the fastest drying alfalfa was that treated with a hollow-cone nozzle. Overall, the drying rate with the hollow-cone nozzle averaged a little higher than the other nozzles, but the difference again, was not significant. Spray coverage of the plant was always best on the side of the plant facing the spray. Normally the top of the plant was covered better than the bottom (Table ). Differences in coverage across the plant would likely be greater without the mechanical conditioning treatment. Since the alfalfa was pressed by the conditioning rolls immediately after being sprayed, the rolls helped wipe the chemical across the plant. This was observed by the pattern left on water sensitive paper. The mechanical conditioning treatment may also nullify any difference in coverage due to the type of nozzle. If one type of nozzle did provide better coverage of the plant, the rolls would again spread the chemical, removing any difference due to nozzle type. Differences may occur if the chemical is applied without a roll-type conditioning treatment. The operating pressure of the spray system showed some small and inconsistent effects. Plant coverage was significantly reduced when the fan nozzle was used at the higher pressure (Table ). The higher pressure caused smaller droplets which may have increased drift causing a decrease in application. The smaller droplets also may have been less visible on the water sensitive paper which caused a lower rating. In either case, when application rate was held constant, different operating pressures on the fan nozzle did not have a significant effect on alfalfa drying. An interaction occurred between the chemical mixture and the spray device. With the potassium carbonate solution, poorer drying results were obtained with a highpressure, solid-cone nozzle; however, this nozzle produced the fastest drying alfalfa with the commercial solution (Table 4). Since the commercial solution contained methyl esters, perhaps the fine atomization from this nozzle created better wetting than was possible without this form of surfactant. This interaction is probably due to experimental error, however, since the same phenomenon was not observed with the fan nozzle. When averaged over all tests, the pressure did not have a significant effect on drying. CONCLUSIONS. As application rate of the water carrier was increased, the effectiveness of the treatment increased in proportion. Increasing the concentration of active ingredients in the solution did not improve the drying results obtained with the treatment. A high carrier application rate is required in chemical conditioning of alfalfa to provide adequate plant coverage.. At a fixed application rate, nozzle type and nozzle operating pressure did not have a significant effect on alfalfa drying. Although a fan nozzle often showed a reduction in chemical coverage of the plant, the drying of alfalfa treated using this nozzle was not significantly different from that treated using hollow or solid-cone nozzles when chemical and mechanical conditioning were used together. References. Crocker, G. J. and G. M. Lodge. 98. Potassium carbonate speeds up lucerne haymaking. Agric. Gazette of N.S.W. June, pp Johnson, T. R., J. W, Thomas, and C. A. Rotz. 98. Quality of alfalfa hay chemically treated at cutting to hasten field drying. J. Dairy Sci. 66: Rotz, C. A. and J. W. Thomas Chemicals which speed the drying of alfalfa. Proceedings of the 985 Forage and Grassland Conference, American Forage and Grassland Council, Lexington, KY. 4. Rotz, C. A. and D. J. Sprott Drying rates losses and fuel requirements for mowing and conditioning alfalfa. TRANSACTIONS of the ASAE 7(): Rotz, C. A., D. J. Sprott and J. W. Thomas Interaction of mechanical and chemical conditioning of alfalfa. TRANSACTIONS of the ASAE 7(4): Tulberg, J. N. and D. J. Minson. 9. The effect of potassium carbonate solution on the drying of lucerne: field studies. J. Agric. Sci. 9: Weighart, M., J. W. Thomas, M. B. Tesar, and C. M. Hansen. 98. Acceleration of alfalfa drying in the field by chemical application at cutting. Crop Sci. :5-9. TRANSACTIONS of the ASAE