Infrared Interpretation Sheet

The Area covered by your Infrared Photograph is one square mile, unless a quarter section has been ordered. Infrared false colour film is designed to show subtle differences in vegetation growth. It will also penetrate haze, allowing clear, sharp photos from over one mile high.

Colour Code:

Crop Stress

Any area of your field with less vigorous growth will not have as strong a reflection of infrared energy. Consequently, the overall colour on the photograph will not be as rich a red. Severely stressed areas may have a pink appearance. Mildly stressed areas show a slightly darkish appearance of the red signature. Try to relate these areas of your fields to known trouble spots such as excess moisture, insufficient moisture, thin topsoil, chemical carryover, and areas of lower fertility.

Crop Yields

Look for a uniform colour and texture across a field. A darker, more solid red colour indicates more vigorous growth. Check carefully to see if any soil (green) is showing between the plants. Compare the actual yield to the response on your photograph. With a little practice, you will soon be able to estimate crop yield very well. Caution: You must consider the seeding date, i.e. a cereal crop in head or beginning to ripen will have less response than a lighter crop in the shortblade stage.

Fertilizer Response

Uneven distribution of fertilizer is vividly illustrated. Heavier application stands out in repeated red lines around the field. N.B. One millimeter on a 10" x 10" print of one section equals 25 ft. If these red lines are due to fertilizer application problems, and they occur every two mm. On the print, then the application must have a 50 ft. swath.

Check the fertilizer response when you double apply your product on the headland or if you deliberately leave a check-strip with no fertilizer. Many researchers use infrared photographs to illustrate differences in fertilizer response in test plots.

Drainage Problems

Moist soil appears dark green when there is no vegetation coverage. Drown-out spots are clearly documented as green spots within the "red" growth. Often the natural drainage runs or streambeds are evident throughout the fields illustrated as a darker red pattern.

Many farmers use the infrared photo as a working plan to improve their drainage system. Where previous drainage tile or pipeline has been buried, the pattern is evident as a much lighter green colour.

Field History

Often a uniform rectangular shape appears in a larger field which supports a heavier or lighter growth. A stronger red colour of a square patch may be due to recently cleared land recently brought into production. One client noticed a healthier patch in the field that he traced to an alfalfa field seven years before!

Weak uniform squares within a larger field can be traced back to historically smaller fields, some which may be "farmed out" or have had topsoil depletion during the "dustbowl" years. It can be very profitable to separate soild test areaas and selectively apply additional nutrients to bring the production in line with the rest of the field.

Forage

A vigorous crop of alfalfa has the strongest possible red reflection. At the peak of alfalfa blossom, there is a slight orange cast to the red signature. Uneven plant stands of forage are clearly illustrated where bare soil (green) shows through.

Note: Within less than 24 hours after alfalfa is cut, the forage in the swath losses its red appearance. The resulting "stubble" shows a light green due to the dead plant matter and the visibility of bare soil.

Any cured hay or straw appears white on the photograph. Different crop vigor is noted in different age of alfalfa. Infrared photos can help to determine when a crop should be worked down and resown.

Germination Patterns

Any green patches within a red field are the result of spaces in the crop canopy. Thin areas of low plant population will result in a combination of red and green appearing on the colour photograph. Caution: Some slightly green areas often have a considerable amount of plant growth. One should always combine first-hand knowledge of the land with the information on the photograph.

The stage of crop development is also very important. A young, immature crop, especially flax, will have a lot of soil exposed when viewed vertically, resulting in a predominately green colour. Watch for different seeding rates, different planting depths and areas of your field that tend to "bake" under wet conditions.

Irrigation Patterns

Pivot systems reveal much valuable information of water patterns. "Spoking" effect is caused if the system hesitates in forward motion yet continues pumping water. Uneven nozzle performance is illustrated with concentric rings. Even more information is yielded with a fertigation program with a strong red response where more water and fertilizer have been applied.

Excess water application in poorly drained areas show up first as stressed crop, then as green patches where the crop has died off. The photo enables the manager to closely check on problem areas as they arise, consequently causing the monitoring system to be more effective.

Lodging

Watch for abrupt pink spots with a strong red field. This is caused by the infrared light waves reflecting off the undersurface of the plants causing a different signature.

Many growers use the photos as a map when applying fertilizer the following season. By withholding all fertilizer in those areas for a year or two, the lodging soon disappears.

Insects

The damage from grasshoppers, aphids and flea beetles has often been clearly illustrated on infrared crop photos. Watch for a jagged deterioration of crop growth along headlands or drainage ditches. Serious aphid problems may show up as pink stress areas within a field.

N.B. Obviously a photo taken once during the growing season does not provide an effective monitoring system for insect management.

Manure Spreading

Areas which have had manure application will show a more vigorous growth resulting in a stronger red colour. Historically, there have been repeated applications of manure near old farmstead sites. The carry-over soil benefits have been illustrated on the infrared photos as much as 20 years after the farm no longer owned livestock!

Many growers use the photographs to delineate weaker areas of the fields which will benefit more from the application of manure.

Machinery Problems

Frequently, repetitive lines occur throughout the fields. This is often due to overlapping, spacing or improperly adjusted equipment. By carefully measuring the space between the lines and noting the direction of the field operation, the faulty equipment can be quickly isolate. Remember: 1 mm on a 10" print equals approximately 25 ft. 1/16" equals approximately 33 ft.

Salinity

Naturally occurring salinity areas are starkly illustrated. There is often a very pronounced switch from a healthy red colour to a strong green reflection of saline areas. Check carefully around potholes, roadsides and poorly drained areas for problem spots.

Village sewage lagoons and irrigation ditches very often illustrate the same problem. A historical sequence of photos will help one to conclude if the saline area is getting larger or receding.

Soil Differences

Exposed subsoil is clearly illustrated by a whitish reflection compared to a dark green colour of topsoil with organic content. Soil transition zones are often clearly illustrated by studying the crop which they support. E.g. If the sold abruptly changes from a deep loam to sandy or shallow topsoil, the current crop canopy will often have a weaker red reflection.

This is especially true during the hot days of June when poorer soils have run out of moisture. It is best to attempt an overview of the section and to trace the general trend across the entire photo. There is no question that these photos provide a good indication of the relative productivity of any quarter section of land.

Grazing Land

In early June most grazing land will produce a moderate light red reflection, but never as strong as a cultivated cereal crop. Eroded hilltops and drained slopes will produce less of a red colour.

Fertilizer or manure applications show a dramatic positive response. Overgrazed areas become lightish green to white. As pastures "burn off" during the summer months, the red vegetation reflection quickly diminishes.

Wind Erosion

Wind erosion with depletion of topsoil is clearly illustrated. If the soil is bare, the eroded areas are relatively lighter.

One senior farmer picked out a quarter section which he recalled had drifted worse than any other during the 30's. The preventative benefit of shelterbelts is clearly illustrated in may infrared photographs.

Summer Fallow

All bare soil reflects some form of green coloration. Shallow topsoil, land leveling and pipeline installation, usually have a much lighter reflection. Freshly tilled summerfallow always is darker in colour due to the freshly exposed moisture.

Sprayer Patterns

As with other machinery patterns, misses show very clearly. For example, wild mustard in cereal crops shows as a white strip. Lack of wild oat control occasionally shows as a darker strip.

Spray Drift

On some occasions the damage due to severe chemical drift can be illustrated on infrared photos. Look for uneven colouration along the border of the damaged field with the effects gradually diminishing across the field. The stressed crop will illustrate a distinct loss of healthy red colour where it is severely effected.

In cases of sever spray drift creating liability, the photograph should be used only as one source of data and not the sole evidence.

Rent, Buy or Sell

The abundant information of infrared photos provides an excellent indication of the productivity of a specific location of land. An up-to-date copy photographed during the growing season becomes invaluable in determining the resale value of the land.

Real estate members make wide-spread use of this photo information. When a farmer rents an new piece of land, the photograph is useful in making cropping and management decisions as well as accurate acreage assessment.

Acreage Measurement

acreage grids are available for both 8" and 10" size photos. Field sizes can be determined exactly to enable accurate yield calculations. It is vital to know the exact size of fields when buying expensive seed and herbicide.

Tillage practice

The crop response in any field is the net result of all inputs including tillage practice. Often an area of a field is substandard due to improper tillage practice.

Farmers have isolated areas in a photo where land was worked too early in the spring causing compaction and poor germination. Improper planting depth is often illustrated in some of the small seed crops.

Weeds

Recall that all healthy vegetation has a red reflection. However, each type of crop has a slightly different shad of red. Canada thistle is easy to identify in a cereal crop, showing up as dark red spot. Weeds in canola fields show very clearly.

These subtle differences combined with your first-hand knowledge of the crop provide remarkably accurate data.

Water

Clean water appears to be black in the photograph. If water has suspended clay or soil particles, it appears to be blue-green. Moist soil is a very dark green.

Conclusion

The above ideas are meant to be guidelines only. The best interpretation is a combination of the knowledge of your land with the information on the infrared photographs. In a very short time you will discover a great number of valuable uses for this practical management tool.