ABSTRACT: In the southern Great Plains pastures of nativegrass mixtures have been shown to provide early season forage and contain grasses that vary in seasonal forage distribution providing higher quality forage further into the growing season than monocultures such as switchgrass (Panicum virgatum). Compared to improved pastures of bermudagrass (Cynodon dactylon), nativegrass mixtures increase wildlife habitat, lower maintenance cost, and can improve land value. These benefits have increased interest in conversion of improved pasture land areas to nativegrass pastures. Because of its herbicide tolerance, ability to propagate from stolons, rhizomes, and seed, bermudagrass is difficult to control making conversion challenging. To be successful, conversion methods need to be acquired. A two-year, two location conversion study was developed to determine efficacy and economics of twelve conversion systems for bermudagrass control and establishment of a nativegrass mixture of little bluestem (Schizachyrium acoparium ‘Cimarron’), big bluestem (Andropogon gerardii ‘Kaw’), indiangrass (Sorghastrum nutans ‘common’), switchgrass (‘Alamo’), and green sprangletop (Leptochloa dubia ‘common’). Conversion systems consisted of combinations of preparation time (7, 11, 19 months from treatment initiation to planting), cover crops (0, 1, 2, 3), glyphosate application (6, 8, 10 qts/ac) (13.8, 18.4, 23 L ha-1) and tillage (conventional till, no-till). Nativegrass planting date for all conversion systems was April. Tillage systems were more effective than no-tillage. Mean yields across locations and years for no-till were 858 lb/ac and 2868 lb/ac compared to tillage yields of 2243 lb/ac and 6637 lb/ac for nativegrass and switchgrass respectively. Tillage systems with cover crops (2 or 3) and preparation time (11 or 19 months) were more successful in establishing nativegrass but had little effect on switchgrass establishment. For the base-case threshold measure of success (>=70% of total stand), the clean till system with three cover crops was most economical at the Burneyville, Oklahoma, location, realizing a $208 net return per acre. At the Ardmore, Oklahoma, location, systems established with clean-till and no-till methods with both 2 and 3 cover crops were equally more profitable than systems that utilized chemical fallow methods. Systems that utilized chemical fallow methods did not realize positive net returns, but did meet the minimum threshold of success requirement of at least 70% of total NG stand. Relative net returns between systems were most sensitive to prices of rye and sorghum-sudan hay.


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