"One possible source of nitrates is waste from the livestock that are constantly in contact
with the stream and stream banks. Nitrogen fixation by vegetation, both natural and
planted, along the stream bank could also account for a constant supply of nitrates
(Kehew, 2001). Since phosphate concentration varies significantly with
discharge, it is assumed that phosphorus is introduced from outside the stream. The
likely source of phosphorus is synthetic fertilizer applied to the field, which is then
washed into the stream by runoff. Since very little rain fell in the region during the
summer, very few of these fertilizers reached the stream, but instead remained in the
vegetation and the soil. This lack of runoff, along with the fact that phosphorus is the
limiting nutrient in freshwater and any excess would be quickly used for algae and plant
growth, resulted in the low phosphate concentrations during the summer."
Once again, nice try.....