AGRONOMIC NEWS ITEMS
From Agronomists of the
Potash & Phosphate Institute
655 Engineering Drive, Suite 110
Norcross, Georgia 30092-2837
Phone (770) 447-0335
Summer 1997, No. 4
As farm sizes have increased, time to spend walking fields has been more difficult to find. So we resort to windshield surveys and other more general observations as a first pass at identifying problems. Regardless of the farm size, there is really no substitute for a good scouting program to find nutrient deficiencies. The money and other resources invested in a growing crop should be sufficient incentive for spending time looking for profit-robbing nutrient deficiencies. It is just a habit that needs to be cultivated.
New tools can help focus scouting efforts and make the time spent in the field more efficient in identifying problems. Yield monitors show areas of depressed yields, indicating potential nutrient problems. Remote sensing can help determine the extent of a nutrient deficiency problem that is identified from field scouting "ground truth". It may also help identify areas in other fields that should be scouted for potentially having the same problem.
Learn the common deficiency symptoms of nutrients that are sometimes inadequate in your area. Review pictures of these symptoms and learn what can be done to correct the deficiencies. Take detailed notes and photographs of the problem. Digital cameras, or standard photographs that are later digitized, can be used to add visual records to computer database files for future reference. Some farmers use a video camera to get a broader documentation of the problem area. If possible, determine the exact location in the field of the symptoms identified, using global positioning system (GPS) data if available. Information about the deficiency can then be added to your geographic information system (GIS) for a permanent record.
Once a potential deficiency area is found, other new tools can help identify the cause. In-field plant tissue and soil analysis can be done with hand-held electronic testers, using ion-specific electrodes. For confirmation and potential identification of interacting deficiencies, collect samples from the deficient area for laboratory analysis. Collect additional samples from normal-looking areas of the field for comparison analysis.
Using tissue and soil testing as a routine part of a regular scouting program will help identify deficiencies before visual symptoms are present. This "hidden hunger" deficiency has been shown to cause significant losses in yields and profits, even though the crop may look healthy. Hand-held chlorophyll meters may also provide useful comparative measurements of relative health of plants in different parts of a field, and possibly help identify developing nutrient deficiencies.
Identifying the nutrient deficiency is an important step, but does not complete the scouting process. Nutrient deficiencies may indicate a true shortage of essential plant nutrient supplies, but they may be a secondary symptom of another problem. Many physical, climatic, or pest problems may be manifested in visual nutrient deficiency symptoms. Phosphorus deficiency symptoms in early stages of corn growth, for example, may actually be a side-effect of slow root growth under cool, dry soil conditions. Nitrogen deficiency later in the season may be a result of dry soil restricting availability of nutrients to the roots. Injury from insects and diseases may restrict root growth and trigger nutrient deficiencies, even though soil nutrient supplies are in the normally adequate range.
Be a good crop scout...and become a better manager.