The ability to spot variation is perhaps the single most important skill in field diagnosis.
Does the field look uniform and healthy? If yes, then everything is probably OK. If no, then determine if the whole field is affected or just parts of the field, then estimate the size of the area affected.
Take observations in a number of locations.
Ensure observations are representative of the field.
- Use the sample field sheet for recording your observations
- Look for variation across the field in terms of color, height, plant damage or groundcover.
- Is there a pattern across the field to the damage? If so, then check typical problem patterns and probable cause for possible causes.
- Estimate the percent of the field affected.
- Are pests apparent? Insects, weeds, rats, birds, other?
- Is field moisture adequate?
In the problem areas
- Note the types of symptoms. Cross check against typical symptoms of common problems.
- Note where the symptoms occur on the plant. Diagnose the probable cause using the identify your problem key.
- Note the growth stage. Check the growth stage and important management factors.
In the field
- If the crop is young, estimate the number of plants per sq m. (For an idea of the preferred number, consult the table on what makes a good crop.)
- Estimate the number of spikes per sq m.
- Estimate ground cover.
- Estimate percent of lodging.