1. Equipment Limitations and Challenges in Precision N Management
R.K. Taylor, G. Dilawari, P. Bennur, J.B. Solie, N. Wang, P. Weckler, and W.R. Raun

2. Variable Rate Liquid Applicators
Direct Injection
Complex
Time lag
Fixed orifice nozzles
Flow proportional to square root of pressure
Difficult to achieve range in flow rates
Pulse Width Modulation
Variable orifice nozzles
Pressure/Flow relationship is more complex

3. Objective
To determine the consistency among nozzles and repeatability of individual nozzles with respect to flow rate for commercially available variable orifice nozzles

4. Materials Nozzles: Eight of each type
TurboDrop Nozzles (GreenLeaf technologies): TDVR-02 and TDVR-03
VeriTarget Nozzles (SprayTarget )

5. Test Stand Pump Wet boom equipped with TeeJet 3 nozzle bodies
Pressure relief valve
Throttling valve

6. Methodology
Three nozzles were selected randomly and tested on the three nozzle boom at 20, 30, 40, 50, 60 and 80 psi
8 repetitions for each pressure
Flow was adjusted to the three nozzles to achieve the desired pressure.
Outflow from nozzles was calculated by measuring the volume of water collected from each nozzle over a period of 30 seconds.

7. Data analysis
Analysis of Variance was performed in SAS 9.1 (SAS, Cary, NC) using PROC ANOVA to detect flow differences among nozzles.
Data for each nozzle were analyzed by pressure
Means were separated using the LSD option and at 0.01 level of significance
Pressure-flow curves for each nozzle type were plotted and compared with the manufacturer’s pressure-flow data.

8. Results: TDVR-02 Pressure (psi) Mean (gpm) Min (gpm) Max (gpm)
Range (gpm)
CV (%) 20
0.17
0.15
0.19
0.04
9.56 30
0.20
0.18
0.23
0.05
8.88 40
0.27
0.07
9.44 50
0.33
0.32
0.37
4.68 60
0.44
0.43
0.46
0.03
2.46 80
0.60
0.57
0.63
0.06
2.59

9. Results: TDVR-02

10. Results: TDVR-03 Pressure (psi) Mean (gpm) Min (gpm) Max (gpm)
Range (gpm)
CV (%) 20
0.24
0.22
0.35
0.13
19.35 30
0.31
0.27
0.37
0.10
10.89 40
0.33
0.38
0.07
8.74 50
0.45
0.42
0.47
0.05
3.20 60
0.58
0.56
0.60
0.04
2.04 80
0.78
0.75
0.87
0.12
5.31

11. Results: TDVR-03

12. Results: VeriTarget Pressure (psi) Mean (gpm) Min (gpm) Max (gpm)
Range (gpm)
CV (%) 20
0.17
0.16
0.22
0.06
12.34 30
0.42
0.37
0.48
0.11
7.18 40
0.81
0.76
0.89
0.13
6.65 50
1.00
0.96
1.04
0.08
2.96 60
1.12
1.10
1.16
2.32 80
1.32
1.29
1.35
1.51

13. Results: VeriTarget

14. Conclusions
Inconsistent behavior was observed between the nozzles at different pressures
Repeatability of a nozzle was better at pressures above 40 psi.
Both the TurboDrop nozzles performed according to manufacturer’s specification
CV for VeriTarget nozzles, for most of the nozzles, was around 10% which is acceptable for spraying

15. Sensor v. Map Based VRA
In a map based system, the controller receives a rate change as the applicator crosses into a new zone.
However, with a sensor based system the controller typically receives an updated rate every second and does not have the opportunity to stabilize.

16. Sensor Configurations

17. Accepted Resolution

18. Materials Raven 440 controller Raven Fast Close valve
Data acquisition with flow meter and pressure transducers

19. Test Stand Schematic

20. Model
1st order valve response
Proportional Integral controller

21. Input Data pass Obs Mean Minimum Maximum Std dev Max rate increase
decrease
- L ha-1 - 1
162
168.4
121.4
205.8
19.6
42.8
-50.6 2
162.1
18.2
58.1
-27.5 3
149
179.6
134.5
17.4
50.3
-58.6 4
150
175.7
120.1
44.0
-47.2 5
175
168.2
118.3
24.4
34.9
-44.8 6
183
165.0
22.3
44.8
-36.8 7 88
175.8
19.5
58.6
-83.6 8 85
167.8
102.9
23.8
80.1
-53.3

22. Prescribed Rate

23. Model Output

24. 1 second lag

25. Output Data pass 0 sec lag 1 sec lag r2 slope Mean abs error, L ha-1 1
0.45
0.78
11.6
0.74
1.00
6.0 2
0.76
11.5
0.87
1.04
4.8 3
0.35
0.67
12.8
0.84
1.03
6.1 4
14.7
7.0 5
0.93
1.02
5.1 6
0.62
0.85 7
0.26
0.61
1.11
6.9 8
0.24
0.58
18.6
0.83
1.08
11.2

26. Conclusions
The modeled results showed a mean absolute application error of 12.9 L ha-1.
These results further indicate that the predicted response lagged the prescribed rate by approximately 1 second.
This resulting misapplication could be reduced by half if the controller delay was reduced by 1 second.

27. Addendum

28. Improved System ??

29. Questions
Randy Taylor