Corn in various parts of the state showed varying degrees of coloration as of late last week, reported Bob Nielsen, Purdue University corn specialist. Some fields look perfectly normal. In other fields, some plants are yellowish. And some unexplainable patterns of greenish and then yellowish plants have showed up in field, he says.
While other factors may be involved, such as differences in corn hybrids, it's a safe bet that weather is playing a major role in what corn looks like at this point in the season, he notes. Wet, cool weather for 10 days to two weeks, beginning in early May, took its toll in some areas. Then five or more inches of rain created lakes in some fields, especially in northwestern Indiana. Last week it was central and southern Indiana's turn to get more of the rain from storm systems.
After surveying fields and monitoring the same fields for several days after flooding, Nielsen believes that there will be numerous drown-out spots in fields this year. The water simply stayed on top of plants too long to allow them to survive in many cases. Ironically, these are also the areas where nitrogen loss, if N was applied before planting, is likely to be the highest. N loss won't matter as far as the crop is concerned if there is no crop left there, he notes.
While Nielsen isn't sure exactly what caused the discoloration patterns, and figures most of it is temporary, he believes weather is a major factor. What is puzzling is that some fields develop the condition, yet fields close by don't show symptoms.
One normal culprit for these theories is soil compaction. And while there is no proof that it is causing the discoloration in fields he's seen, there is soil compaction out there, he notes. Soil compaction was evident in southwestern Indiana last week, appearing as yellowish corn everywhere where big tractors with wide tires ran to apply pre-plant anhydrous ammonia. Scott Ebelhor, manager of Beck's Practical Farm Research station, says the tracks are obvious in many fields in the area, not just in some of his plots. He is maintaining 80 acres of plots in the southern Gibson County station this year.
Another theory farmers are bantering about are corn nematodes. Apparently one farmer who had nematodes identified in a field last year is seeing the same symptoms in the same field, planted back into corn, this year. While other agronomists acknowledge that nematodes, allowed to remain near the surface longer than usual due to cool weather until last week, could cause such symptoms, there's still no proof as to exactly why some corn fields have been slow to 'put on the green uniformly' this spring.