Five million "Non-Planted" acres in 1999 will provide many challenges this next crop year. One challenge will be nitrogen management. While there was no crop produced on these acres in 1999, there was heavy weed growth on many fields. As the fields dried out, many growers used herbicides and tillage to control the weeds. This weed growth used a large amount of nitrogen from the soil profile. In some situations, the weed growth appeared to have used as much nitrogen as a good crop. In other areas, growers were able to till their fields several times, starting in late June. This variability in weed growth, along with excessive rainfall through July in some areas has resulted in quite variable nitrogen levels in the non-planted fields.

AGVISE Laboratories began an education project July 1 to track the soil nitrate levels in four fields that did not get planted. An area was staked off in each field to prevent any tillage, (75' by 75'). One soil sample was collected in the non-tilled area and one sample was collected just outside the staked area. The rest of the field was treated with whatever herbicide and tillage practices the grower used. All of the fields were small grain the year before and no fall nitrogen was applied. Soil samples were collected periodically from inside and outside the marked area in each field. The soil test data from two of the fields is shown in the figures. The nitrogen levels in field #1 remained relatively low all through the season with little difference between the tilled and non-tilled areas. This field has a loamy sand texture, a low organic matter (2.3%) and was tilled only once in mid August. In this field the tillage was done so late that there was little time for nitrogen to accumulate through the summer. Field #4 shows a large difference in nitrogen level between the tilled area and the non-tilled area by the end of the season. This field has a clay loam texture, an organic matter of 4.1% and was tilled twice during the season (July 15 & August 15). This field started with a higher nitrogen level and was able to accumulate a substantial amount of nitrate-nitrogen where the weeds were controlled by tillage.

As you can see, there are large differences in nitrogen levels in fields that did not get planted last year. Some factors affecting the nitrogen level in each field include the extent of weed growth, when tillage or herbicide burndown was done, how much nitrogen was in the soil initially and how much nitrogen fertilizer had been applied.

Soil testing is the only management tool that can tell growers how much nitrogen they need for next years crop. If you soil tested most or all of your growers non-planted acres this fall, congratulations on a job well done for your growers. If your growers didn't soil test their non-planted acres, you need to talk with them about soil testing before next planting season! Many thanks to Don Uglem for letting us use his fields and equipment for this project.

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