Soil samples too old: Fields should be sampled at least every four years. SnapPlus identifies soil samples as being too old if they are four or more years older than the designated crop year.
Too few soil samples: Fields should be sampled with one sample per five acres. SnapPlus identifies how many samples are needed on a field by dividing the field acreage by five and rounding to the nearest whole number (Example: On a 6.8 acre field, one sample is needed because 6.8 acres/5 acres = 1.36, and 1.36 rounds to 1). However, fields that were sampled within the last four years and tested non-responsive (meaning that soil tests are in the Very High or Excessively High ranges) for both P and K get the number of samples required from Table 2.1 in UWEX publication A2809.