Runoff under natural rainfall from small tall fescue catchments in the Georgia Piedmont, United States

Abstract

The environmental outcomes from tall fescue (Lolium arundinaceum [Schreb.] Darbysh.) pastures managed with different levels of endophyte (Neotyphodium coenophialum) infection and choices of harvest and fertilization methods are not well known. We monitored runoff from 14 tall fescue paddocks, 0.9 to 1.1 ha (2.2 to 2.7 ac) each, from April of 2002 to April of 2010 near Watkinsville in the Georgia Piedmont. Three grazed Jesup tall fescue-endpohyte associations (endophyte infected high alkaloid—Wild, endophyte infected low alkaloid—MaxQ, and endophyte free—Free), and two sources of fertilization (inorganic and broiler litter), were replicated twice in a randomized block design. A replicated hayed treatment was planted to Jesup MaxQ with inorganic fertilization as a grazing control. Drought reduced the maximum number of runoff events to 77. A Standardized Precipitation Index analysis showed that the degree of drought was dependent on the time scale considered. The near normal period peaked at a 1-month (74%) scale and was least at a 9-month time scale (32%). Considering a 1-month time scale, there were on average 4 times as many runoff events per month during the near normal, and 16 times as many during the wet and wetter period, as those in the dry and drier period. Fertilizer and fertilizer by fescue interactions in grazed paddocks had significant effect on runoff, whereas main effects of fescue type and harvest methods (graze versus hay) did not. Inorganically fertilized paddocks had 30% greater runoff than those with broiler litter fertilization. The largest runoff amount occurred with inorganic fertilizer and endophyte-free fescue, suggesting a combined impact of reduced persistence of the endophyte-free fescue, with low organic matter input from the inorganic fertilizer. Grazing of Piedmont pastures with MaxQ-endophyte association of tall fescue, and fertilized with broiler litter, does not appear to pose additional risk for runoff, compared to tall fescue pastures under the common wild-type-endophyte association that are hayed or grazed, and fertilized inorganically or with broiler litter. These results further support a previous recommendation for increased adoption of MaxQ with broiler litter fertilization in the southeastern United States, because of excellent average daily gain by cattle and stand persistence of MaxQ.