ARS | Publication request: SIMULATED RAINFALL DURATION AND SOIL SAMPLING DEPTH EFFECTS ON INTERPRETATION OF PHOSPHORUS RUNOFF DATA

Submitted to: American Society of Agronomy Meetings
Publication Type: Abstract Only
Publication Acceptance Date: November 9, 2000
Publication Date: N/A

Technical Abstract: Simulated rainfall is widely used to determine phosphorus (P) loss in surface runoff. We determined runoff sampling time, soil test P, soil sampling depth, and corn management practice effects on dissolved reactive P (DRP) and biologically available P (BAP) concentrations and loads in runoff. Management practices included two tillage systems (chisel plow and no-till) with and without dairy manure. Runoff was collected 30 minutes following runoff initiation (T30) and following 60 minutes of simulated rainfall (T60) applied at 75 mm/hr. Runoff sampling time and soil sampling depth did not influence the interpretation of soil test P effects on P concentrations in runoff; however, concentrations were lower at T60 and had generally higher r-square values for soil P-runoff P relationships at shallower sampling depths. Time affected BAP concentrations and loads, but not DRP in runoff from recently established management practices (established <5 months prior to rainfall simulation). The significant time x management practice interaction on BAP in runoff resulted from greater treatment differences with higher rainfall amounts applied at T60 rather than differences in the amount of time until runoff initiation at T30. These results indicate that the T60 sampling time was a better indicator of the potential effects of recently established management practices on P losses in runoff.