Biosolids and mineral fertilizers (MF) can provide nutrient recycling and nutrients for hay production,
but excessive or inappropriate applications can also contribute to water quality degradation when sediment,
nutrients, and bacteria are included in surface runoff. Rainfall simulation studies were completed
in a hayfield typical of the Ozark mountain region to compare sediment and nutrient content, and bacteria
concentration in surface runoff from plots receiving biosolids or MF with or without pre-irrigation
that simulated small (no runoff) rainfall events. No differences among treatments were detected for
total suspended solids. According to an LSD test, fecal coliform colony-forming unit (CFU) levels in
runoff in all biosolids treatments and the pre-irrigated MF treatment were similar to the unamended
control; however, pre-planned orthogonal contrasts indicated more CFUs were included in runoff from
pre-irrigated plots. Pre-irrigating treatments decreased certain forms of nitrogen and phosphorus losses
found in surface runoff when compared to treatments that did not receive irrigation before a runoff event.
Total Kjeldahl nitrogen, dissolved total Kjeldahl nitrogen, ammoniacal-nitrogen, dissolved ammoniacalnitrogen,
total phosphorus (TP), and dissolved phosphorus (DP) losses from the MF treatment that
received a runoff producing rainfall immediately after application were greater than any other treatment
(P ≤ 0.05). Similarly, an orthogonal contrast of all MF treatments (with and without pre-irrigation)
againstthe low rate of biosolids treatments (withand withoutpre-irrigation) revealed thatMFhad greater
runoff losses of TP (P ≤ 0.0001) and DP (P ≤ 0.0002). Results suggest that MF applications have the potential
to deliver higher nutrient pollutant loads through surface runoff than biosolids applications when a
runoff producing rainfall event occurs soon after amendments are applied. This results in increased risk
of nutrient loading to surface waters in states or areas where buffer areas are not required to protect
them from MF runoff. In addition, nutrient losses in runoff may decrease when application is made such
that small rainfall events occur prior to a runoff producing event