Some of the questions that came up again and again at the show this week; “how do I calibrate my sprayer?” or “how do I know what spay tip to use?” or the very direct “how do I know I am applying the right amount of material?”

While some farmers have opted to purchase expensive electronic equipment to regulate their sprayers, the average farmer can determine their application rate very easily, it just requires a little simple math (you remember math right? school rooms, teachers with yard sticks, etc). First you must determine some basic input information, remember that these equations are set up for either U.S., Metric or Imperial measurements; don’t mix and match!

1. Material Output – this is the total volume of liquid after dilution you wish to spray per a specific parcel of land expressed as either litres per hectre (metric) or gallons (U.S. or Imperial) per acre.
2. Velocity – the speed of the tractor expressed as either kilometers or miles per hour, sometimes this is easier said than done for folks who own older tractors with no speed gauge and no charts to determine speed from gear ratio/RPM. A good trick is to borrow a handheld GPS unit that has a velocity readout. If that isn’t available to you, remember that an average walking pace is about 3.5 miles per hour,  and an average jogging pace is about 5.5 miles per hour.
3. Spacing – for conventional and tower air delivery systems, this is the distance between the rows. for field sprayers this is the effective distance sprayed by the booms.  Measured in either metres (metric) or feet (U.S. and Imperial)
4. Number of nozzles – the total number of nozzles being used on the sprayer.

Now that we have our required information we can plug it into the proper formulas:

Imperial/U.S. Units:

Output = Required Quantity (gal/acre) x Speed (mph) x Spacing (feet)
500

Metric Units:

Output = Required Quantity (liter/hectare) x Speed (km/h) x Spacing (meter)
600

The number derived from this formula will give you the total output required to distribute the volume you require, now you must divide this by the number of nozzles you wish to use to determine the output per nozzle.

So for example, if you wanted to spray 700 litres of material per hectare through 10 nozzles and you were diving at 5 kilometers per hour through your 2.5 metre rows then:

700x5x2.5
600

Leaves 14.58 litres per minute total output divided over 10 nozzles equals 1.46 litres per minute per nozzle.

Okay, so we now know how much material per nozzle we want to spray, now what? the amount of material put out by a nozzle depends on how big the orifice is and how much pressure is being put behind it. Nozzle manufacturers almost always produce info sheets along with their products that outline how much material they will put out at various pressures. Munckhof sprayers are fitted with high quality aluminum oxide nozzles, that feature easy to use color codes for their various sizes, the info sheets for these nozzles look like this:

 

Flow Rate Per Nozzle In English Gallons Per Minute

Flow rates per nozzle in ENGLISH GALLONS per minute.  Quantite d’eau voulue a GALLONS ANGLAIS/minute/plaquette.
Pressure  Pression		Colour/number nozzle  Couleur/nombre plaquette
BAR	PSI	208  Lilac Lilas	210  Brown Brun	212  Yellow Jaune	215  Orange Orange	220  Red Rouge	223  Green Vert	230  Blue Blue
2.0	29.00	0.051	0.066	0.103	0.136	0.193	0.249	0.343
2.5	36.25	0.057	0.075	0.115	0.154	0.220	0.277	0.385
3.0	43.50	0.064	0.081	0.127	0.167	0.237	0.304	0.420
3.5	50.75	0.068	0.088	0.138	0.180	0.257	0.330	0.455
4.0	58.00	0.073	0.095	0.147	0.193	0.275	0.352	0.486
4.5	65.25	0.077	0.101	0.156	0.204	0.292	0.374	0.514
5.0	72.50	0.081	0.105	0.165	0.215	0.307	0.394	0.543
5.5	79.75	0.086	0.110	0.174	0.226	0.323	0.414	0.569
6.0	87.00	0.088	0.116	0.180	0.237	0.336	0.431	0.596
7.0	101.50	0.097	0.125	0.196	0.255	0.363	0.466	0.642
8.0	116.00	0.103	0.134	0.209	0.273	0.389	0.497	0.686
9.0	130.50	0.108	0.141	0.220	0.290	0.411	0.528	0.727
10.0	145.00	0.114	0.149	0.233	0.305	0.435	0.557	0.767
11.0	159.50	0.121	0.156	0.244	0.325	0.455	0.583	0.804
12.0	174.00	0.125	0.163	0.255	0.334	0.475	0.609	0.842
13.0	188.50	0.130	0.169	0.266	0.349	0.495	0.636	0.875
14.0	203.00	0.136	0.176	0.275	0.363	0.514	0.660	0.908
16.0	232.00	0.145	0.189	0.295	0.387	0.549	0.704	0.971
18.0	261.00	0.154	0.200	0.312	0.411	0.582	0.748	1.011
20.0	290.00	0.163	0.211	0.330	0.433	0.615	0.788	1.086
Prefer red figures / Use de preference les chiffres rouge

 

Flow Rate Per Nozzle In American Gallons Per Minute

Flow rates per nozzle in AMERICAN GALLONS per minute.  Quantite d’eau voulue a GALLONS AMERICAIN/minute/plaquette.
Pressure  Pression		Colour/number nozzle  Couleur/nombre plaquette
BAR	PSI	208  Lilac Lilas	210  Brown Brun	212  Yellow Jaune	215  Orange Orange	220  Red Rouge	223  Green Vert	230  Blue Blue
2.0	29.00	0.061	0.079	0.124	0.164	0.233	0.299	0.413
2.5	36.25	0.069	0.090	0.140	0.185	0.264	0.334	0.463
3.0	43.50	0.077	0.098	0.153	0.201	0.286	0.366	0.505
3.5	50.75	0.082	0.106	0.167	0.217	0.310	0.397	0.548
4.0	58.00	0.087	0.114	0.177	0.233	0.331	0.424	0.585
4.5	65.25	0.093	0.122	0.188	0.246	0.352	0.450	0.619
5.0	72.50	0.098	0.127	0.198	0.259	0.370	0.474	0.653
5.5	79.75	0.103	0.132	0.210	0.272	0.389	0.498	0.6.85
6.0	87.00	0.106	0.140	0.217	0.286	0.405	0.519	0.717
7.0	101.50	0.116	0.151	0.235	0.307	0.437	0.562	0.772
8.0	116.00	0.124	0.161	0.251	0.328	0.468	0.599	0.825
9.0	130.50	0.129	0.169	0.265	0.349	0.495	0.636	0.876
10.0	145.00	0.138	0.180	0.280	0.368	0.524	0.670	0.923
11.0	159.50	0.146	0.188	.0294	0.392	0.548	0.702.	0.968
12.0	174.00	0.151	0.196	0.307	0.402	0.571	0.734	1.013
13.0	188.50	0.156	0.204	0.320	0.421	0.595	0.763	1.053
14.0	203.00	0.164	0.212	0.331	0.437	0.619	0.795	1.093
16.0	232.00	0.175	0.228	0.354	0.466	0.661	0.848	1.169
18.0	261.00	0.185	0.241	0.376	0.495	0.701	0.901	1.217
20.0	290.00	0.196	0.254	0.397	0.521	0.741	0.949	1.307
Prefer red figures / Use de preference les chiffres rouge

 

Flow Rate Per Nozzle In Liters Per Minute

Flow rates per nozzle in LITERS per minute.  Quantite d’eau voulue a LITRES/minute/plaquette.
Pressure  Pression		Colour/number nozzle  Couleur/nombre plaquette
BAR	PSI	208  Lilac Lilas	210  Brown Brun	212  Yellow Jaune	215  Orange Orange	220  Red Rouge	223  Green Vert	230  Blue Blue
2.0	29.00	0.23	0.30	0.47	0.62	0.88	1.13	1.56
2.5	36.25	0.26	0.34	0.53	0.70	1.00	1.26	1.75
3.0	43.50	0.29	0.37	0.58	0.76	1.08	1.38	1.91
3.5	50.75	0.31	0.40	0.63	0.82	1.17	1.50	2.07
4.0	58.00	0.30	0.43	0.67	0.88	1.25	1.60	2.21
4.5	65.25	0.35	0.46	0.71	0.93	1.33	1.70	2.34
5.0	72.50	0.37	0.48	0.75	0.98	1.40	1.79	2.47
5.5	79.75	0.39	0.50	0.79	1.03	1.47	1.88	2.59
6.0	87.00	0.40	0.53	0.82	1.08	1.53	1.96	2.71
7.0	101.50	0.44	0.57	0.89	1.16	1.65	2.12	2.92
8.0	116.00	0.47	0.61	0.95	1.24	1.77	2.26	3.12
9.0	130.50	0.49	0.64	1.00	1.32	1.87	2.40	3.31
10.0	145.00	0.52	0.68	1.06	1.39	1.98	2.53	3.49
11.0	159.50	0.55	0.71	1.11	1.48	2.07	2.65	3.66
12.0	174.00	0.57	0.74	1.16	1.52	2.16	2.77	3.88
13.0	188.50	0.59	0.77	1.21	1.59	2.25	2.88	3.98
14.0	203.00	0.62	0.80	1.25	1.65	2.34	3.00	4.13
16.0	232.00	0.66	0.86	1.34	1.76	2.50	3.20	4.42
18.0	261.00	0.70	0.91	1.42	1.87	2.65	3.40	4.60
20.0	290.00	0.74	0.96	1.50	1.97	2.80	3.58	4.94
Prefer red figures / Use de preference les chiffres rouge

 

Its important to note the red sections of the charts, at these pressures the nozzles produce their optimal atomization. This the the best droplet size to get the most complete coverage.

So returning to our sample problem from earlier, if you wanted to spray 1.46 litres per nozzle the best combination would be to spray with ORANGE nozzles at 158 PSI from referring to the metric information sheet.

A caveat for users of towers and conventional air delivery systems. In the early season when there is limited plant growth, you will be turning off nozzles in the areas that do not yet have leafy growth, this does not mean you have to recalculate the output of the sprayer, chemical manufactures give their recommended application rates based on full canopy growth, if you are only spraying 50% of a canopy then you only require 1/2 the nozzles to place the correct amount of material. Simply set the sprayer up for recommended application rates at full canopy, and then set nozzles as required.