Hark E. Berge - Graduate Assistant
Jon Walter - Research Assistant
Agricultural Engineering, North Dakota State University
With the rising costs and increasing use of agricultural chemicals, it is of great interest to all to increase the efficiency of chemical application. The objective of this project is to test and evaluate several band spraying configurations in the laboratory. It is hoped that these laboratory tests will give information that will be useful under field conditions. Configurations that will give the best coverage on the plant using the least amount of spray will be the most desirable. This information will be applicable to fungicides and pesticides. The same apparatus may be used in testing coverage around the plant for herbicide application.
The first part of this project was finding a means of determining the amount of spray on a leaf. After trying several methods it was decided to use a Hunter Lab D-25 colorimeter and a black dye solution as the spray source. The Hunter Lab colorimeter is a device that reads the amount of light reflected off of an object. It gives a reading of 100 for pure white (100' reflected light) and a reading of 0 for pure black (0, reflected light). The colorimeter reading was related to the amount of dye on the leaf by preparing a large sample of leaves with known quantities of dye on them and pi-acing them in the colorimeter for a reading. The weights of the spray and their corresponding colorimeter readings were then used to develop an equation that related the weight of spray on the leaf to the reading from the colorimeter. This equation was used to determine the weight of spray on the leaves later in the experiment.
A single row band sprayer mounted on a moving boom apparatus was used to apply the spray to three rows of plastic plants. The boom moved at a constant speed of 5 miles per hour and operated at a constant pressure of 40 pounds per square inch. These factors will be varied later in the project to determine their effects on spray deposition. In the middle row there were three target leaves on every other plant for a total of 36 paper leaves. White 100% cotton 20 weight bond paper leaves were used as the target surface. Two repetitions were done with each sprayer set up, thus giving a total of 72 paper leaves sprayed for each configuration. The three nozzle configurations used were: 1) three nozzles, with one directly over the row and one to each side; 2) two nozzles,with one to each side of the row; and 3) one nozzle, directly over the row. The two types of nozzles that have been tested to this date are 80 degree flat fan nozzles and 80 degree even flow nozzles. The nozzle sizes were selected so that all three configurations would be putting out the same total gallons per minute. In this case Tee Jet nozzles were used, SS8001 s and 8001E's for the three nozzle set-up, SS80015's and 80015E's for the 2 nozzle set-up, and SS8003's and 8003E's for the single nozzle set-up. The even flow nozzles are supposed to have an even distribution of spray across their fan as opposed to the flat fans which have a heavier concentration of spray at the middle of the fan.
Both sides of the leaf were read with the colorimeter to determine which configuration gave the best coverage of the top and bottom leaf surface. The colorimeter readings were then entered into NDSU's computer with the corresponding information telling under what conditions the samples were produced. This information consisted of the nozzle configuration, the nozzle type, and the repetition of the run. An analysis of variance (ANOV) was then done on the data to determine if there was a significant difference in any of the independent variables. The Duncan's Multiple Range Test was used to identity which independent variables were significantly better.
The analysis of variance program showed that there was no significant difference at the 5% level between the repetitions in any of the six configurations. This shows that the experiment is repeatable, therefore any reference made to a certain configuration will apply to both repetitions. The results from the Duncan's Range Test are summarized in Table 1.
Concentration of spray was measured on both sides of the simulated leaves separately. All of the nozzle configurations were significantly different at the 5% level. The single nozzle was the worst as far as spray deposition on the bottom surface of the leaf. The two nozzle set up gave the best results as far as the bottom surface was concerned, with the three nozzle configuration in the middle. The reason for the difference between the two and three nozzle setup is a result of the nozzle adzes. The nozzles were initially chosen so that the total output of the system would be the same for the one, two, and three nozzle set ups. Therefore with the side nozzles being the main contributors to the deposition of spray on the bottom leaf surfaces, the two nozzle configuration would put out more spray than the side two nozzles of the three nozzle system as far as the top surface is concerned, the single nozzle configuration proved to be the best for the same reason. The top single nozzle seems to be the major source of spray on the top surface of the leaves. Since the single nozzle act up has the largest nozzle it puts most of the spray on the top lea, surfaces. No significant differences were noted on spray concentrations between the two and three nozzle configurations on the top leaf surface.
Nozzle type was not significant in the bottom surface of the leaf. This indicates that the factors that control the disposition of spray on the back of the leaf are more dependent on nozzle position than nozzle type, at least as far as these two nozzle types are concerned. Nozzle type had a significant effect on the top surface of the leaf, with the flat fan being the best. The probable reason for this is that the regular flat fad nozzle tends to have a heavier spray distribution towards the canter of its fan than it does at the outer edges thus the center region of the top nozzle should concentrate more of its spray on the central part of the plants than on the outer edges.
Since the statistics support that this is a viable means of collecting data for this project, it is appropriate to discuss the future plans of using a colorimeter to evaluate band spraying systems. The final study will consist of comparisons between two, or three different ground speeds, at least three pressures, several more nozzle, types, and possibly a few more nozzle configurations. there are also possibilities,or the addition and evaluation of wind effects to the experiment. It is also possible that several of the newer spray systems will be tested in this study. There have been quite a few new systems developed in recent years, such as electrostatic spray systems, and a few air blast systems. It is hoped that this study will answer some questions about the relative efficiencies of some commonly used band spraying set-ups and some of the new spray systems.
1983 Sugarbeet Research and Extension Reports. Volume 21, pages 86-88.
