Testing Disturbance, Seeding Time, and Soil Amendments for Establishing Native Warm‐Season Grasses in Non‐Native Cool‐Season Pasture

Abstract

Incorporating native C4 grasses into pastures dominated by C3 grasses can augment tallgrass prairie restoration efforts while improving pasture production. We examined grazing and burning disturbances to promote the establishment of native C4 grasses sown in fall and spring into existing C3 pastures. A second objective was to test the role of resource availability on C4 grass establishment by manipulating inorganic nitrogen (N) availability within each seeding time and management treatment combination. We drill seeded three C4 native prairie grasses (Andropogon gerardii Vitman [big bluestem], Panicum virgatum L. [switchgrass], and Sorghastrum nutans (L.) Nash [Indiangrass]) into an existing C3 grass pasture and applied combinations of disturbance (grazed or burned) and soil amendments (carbon [+C], ambient [N0], nitrogen [+N]) treatments. We monitored native grass recruitment within these treatments over a 3‐year period (2005 through 2007). Whereas native grasses established under rotational grazing, higher recruitment was observed with annual burning. There were periods of N immobilization with C addition, but we observed no benefit to native grass recruitment. Native grasses did not establish under N addition, irrespective of disturbance and seeding, and were not affected by seeding time. Regression tree analyses showed that the best predictor of native grass density in 2006 and 2007 was belowground net primary production in 2006, which was greater under burned plots in 2006 but did not differ between C addition and ambient soil N treatments. This research demonstrates that burning facilitates and nutrient enrichment inhibits native warm‐season grass reintroduction and establishment into non‐native cool‐season grass dominated pastures.