harvested from the preplant application. Yields from the side-dress application fell
within the yield goal range while the preplant application treatment was below the range.
Plant and soil samples taken in June indicated a nemotode pressure above the threshold
levels at this demostration site which could have affected the yields. Nitrate
concentrations decreased by 30-50 ppm at all 6 wells during and immediately after this
growing season. Five of the 6 wells went below the drinking water standard by 10/8/91.
The data does not indicate any differences in nitrate concentations from the two
different applications of nitrogen. It does indicate that high nitrates in the groundwater
from the 1990 growing season moved out of the area around the well screen and that the
nitrogen applied in the spring of 1991, stayed in the soil profile and was utilized for plant
growth. This could be from the use of a nitrogen inhibitor as well as fewer large rainfall
events that could leach nitrates to the groundwater.
By 3/25/92, nitrate concentrations increased again to levels above the drinking
water standard in 4 of 6 wells. It's not entirely clear why this happened except manure
and whey (46 lbs/A available N) were applied very early this year before canning peas
were planted on April 8th. Nitrates, from these sources, could have leached to the
groundwater during the period of frost melt and spring recharge. After the pea harvest
on June 17th, 200 lbs/A of bulk urea (138 lbs/A available N) was applied. A short
season corn crop for silage was planted 2 days later. Overall the 1992 growing season
was slightly wetter than normal. A second set of samples taken in 1992, after the
growing season (12/3/92) indicated all 6 wells had nitrate concentrations above the
drinking water standard again, wirh values ranging from 11.9 to 27.7 ppm.