Some North American Great Plains tallgrass prairie grasses have potential for restoration of abandoned agricultural land. Investigations from1949 through 1952 were undertaken to assess the effects of burning, cutting and competition from non-native grasses on establishment of seeded native grasses on two infertile, run-down fields on the University West Hill Farm and University Arboretum at Madison in Wisconsin (north-central USA).
On one field, Sudan grass Sorghum bicolor was grown in the year prior to the experiment. The second was vegetated with non-native Canada bluegrass Poa compressa, Kentucky bluegrass P.pratensis and quackgrass Agropyron repens, and herbs. The fields were ploughed, disked and harrowed to create a seedbed.
In spring 1949, a seed mix of 10 native grasses (big bluestem Andropogon gerardi, little bluestem A.scoparius, sideoats grama Bouteloua curtipendula, Canada wildrye Elymus canadensis, Virginia wildrye E.virginicus, switchgrass Panicum virgatum and Indiangrass Sorghastrum nutans,feather bunchgrass Stipa viridula, sand dropseed Sporobolus cryptandrus andsand lovegrass Eragrostis trichodes) was broadcast with an oat companion crop within 3 x 12 m plots. In July, oats and weeds were topped and removed.
Four replications of each treatment were applied in 1950 and 1951:
1) burning in late spring (before initiation of warm-season grass growth);
2) harvesting at the ‘pasture stage’ i.e. commencing the third week of June, cut four times at 28-day intervals;
3) cut at the ‘hay stage’ i.e. mown (clippings not removed) in mid-August (bluestems, Indiangrass and switchgrass in bloom);
4) plots untreated (controls).
In autumn, plant species density and vigour in each plot was determined within 25 cm² sample quadrats.
Feather bunchgrass, lovegrass and dropseed did not establish or were present in very small numbers. Establishment of the other grasses regardless of treatment was less in 1950 and 1951 (differences leveling out by 1952) on the field previously vegetated with non-native grasses (despite better soil and higher moisture), competition from these and other weeds being detrimental to establishment and vigour.
Burning reduced Canada and Virginia wildrye (growth commencing early spring), and bluestems and sideoats grama on eroded areas. Switchgrass, little bluestem, Indiangrass increased, and big bluestem also in plots where burning reduced otherwise severe competition.
Cutting at the hay stage adversely affected big bluestem, Indiangrass and switchgrass. Canada wildrye and little bluestem increased, whilst Virginia wildrye and sideoats grama exhibited little effect, compared with the controls.
Cutting at the pasture stage reduced big bluestem, switchgrass and Virginia wildrye vigour and density. Indiangrass and little bluestem were little effected, sideoats grama increased greatly.