Greg Roth
Associate Professor
Penn State
January, 2003

Background

     This field was planted on May 9 and we evaluated the stand twenty days later on May 29. The field had experienced heavy rain following planting followed by cool conditions. The soil surface showed little evidence of soil structure. This was likely because the soil aggregates were not stable and disintegrated during the rainfall events. This resulted in a soil surface that became sealed and crusted. The stand was less than desired averaging about 16,000 plants per acre. In addition, some of the plants (about 2000 plants per acre) that were emerging were stunted and deformed. Based on this we assumed the final stand to be 14,000 healthy plants per acre. (Click on the image to the right for a larger view)

Diagnosis

     We carefully dug up row sections where plants had not emerged and found that the plants were leafing out underground. We diagnosed the problem as soil crusting. (Click on the image to the right for a larger view)

     We assessed the yield potential of the new stand using our replant chart located in the Penn State Agronomy Guide. This showed that the yield potential of a 14,000 plant per acre stand planted on May 9 was about 83% of a full (25,000 plants per acre) stand. Using the same table, we estimated that replanting on May 31 and achieving a stand of 25,000 plants would have resulted in a yield potential of 87% of a full stand, or 4% higher than not replanting. Given the yield potential of the field was about 120 bushels per acre and the corn price was about $3.00/bushel, then the added gross income from replanting would be about $15.00 per acre. Since it is unlikely that we could have replanted the field for less than $15.00 per acre, we decided not to replant the field. This was difficult since the field was ragged and not easy to look at.

     Other factors can complicate this analysis. Sometimes leafing out is associated with herbicide injury. This may translate into a lower yield potential for the original stand than is estimated with the replant charts. There is also a risk that the replanted corn will not yield as well in this seedbed.

     In the long term, soil management practices should be altered to help rebuild the soil structure in the field to enhance the structural stability of the soil. Crop rotation with forage crops, manure applications and reduced tillage could all help to avoid this problem in the future. Avoiding excessive tillage operations would also help maintain the soil structure.