We have all seen the Clint Eastwood (Dirty Harry) movie when he asks the punk if he feels lucky (while staring down the barrel of a 357 Magnum). This is the same feeling growers should get if they wonder whether they should soil test each field or not this year (Do you feel lucky?)
Soil testing went at a record pace this fall. As the fall season progressed, it became obvious that soil nitrate levels were extremely variable from field to field. The best way to show people this variability is to use the soil test data to tell the story. AGVISE Laboratories in Northwood ND has tested over 160,000 soil samples this fall from all over the region. The test results from these samples show that there is more variability than we have seen for many years. This includes cropped fields and fields that were not seeded this year (about 6 million acres in ND alone). Everyone knows the reasons why fields have different levels of soil nitrate in the fall (even fields within a mile or two). The list includes, different crop yields, different N fertilizer rates, more or less N lost to leaching or denitrification, more or less N gained from soil OM mineralization, differences in weed control, differences in tillage, differences in previous crop, manure applications etc. etc. The list of reasons is very long. Each region experienced different environmental conditions, so the data is broken down by zip code or postal code area. The data in the table is from areas that had the highest amount of unseeded acres in 2011. The first table reflects the nitrogen soil test data from over 30,000 wheat fields tested this fall. The second table reflects the nitrogen soil test data from over 8000 fields which were not seeded in 2011 (fallow/unseeded). In the “fallow” table, it is obvious that the soil N test levels vary a lot from field to field this fall. There is also a large percentage of fields testing higher than 60 lb/a, which reflects nitrogen that has accumulated in the soil profile due to fallow practices such as controlling weed growth through the season, and nitrogen released from the soil following summer tillage. The value in each column is the percentage of fields testing in each range of soil nitrogen (Example: 18% of wheat fields tested from 0-20 lb/a for the 582 zip code area). If you have any questions on the data in these tables, please give us a call.