Robert A. Masters

Response of Central Plains tallgrass prairies to fire, fertilizer, and atrazine.

Tallgrass prairies are an important forage resource in the eastern Central Great Plains. The effect of spring burning, fertilization, and atrazine [6-chloro-N-ethyl-N-(1-methylethyl)-1,3,5-triazine2,4-diamine] on standing crop of selected herbaceous species and categories of vegetation was determined in 6 tallgrass prairie environments located near Lincoln and Virginia, Neb., from 1987 through 1989 and 1 site near Bloomfield, Neb., in 1987. The grasslands were in good to excellent condition at the time these studies were conducted. Portions of each site were burned in mid-to late spring, atrazine was applied at a rate of 2.2 kg a.i. ha 1 in late April to early May, and fertilizer was applied in mid-May. Despite below-normal precipitation at 6 of the 7 sites, burning combined with fertilization improved warm-season grass standing crop by 50 to 127% in 5 of the 7 grassland environments studied. This reflected the positive response of the dominant warm-season grasses, big bluestem (Andropogon gerardii Vitman var. gerardii Vitman) and indiangrass [Sorghastrum nutans (L.) Nash], to burning or fertilization. Atrazine increased warm-season grass standing crop at only the site near Bloomfield. Kentucky bluegrass (Poa pratensis L.) and annual bromes (Bromus spp.) were more susceptible to atrazine than smooth brome (Bromus inermis Leyss.). Forb standing crop was significantly reduced by atrazine alone or by burning followed by atrazine application in 4 of the 7 prairie environments. Burning combined with fertilizer application improved warm-season grass standing crop in good to excellent condition grasslands and obviated the need to use atrazine.

Technical Note: A rotary seed processor for removing pubescence from seed of prairie grasses

Many of the perennial prairie grasses that are used in restoration plantings in the central Great Plains have seed appendages such as awns and pubescence that make seed now through planters difficult. We have developed a rotary seed processor that efficiently processes small breeder or experimental lots of seed that can then be easily planted with small plot cone planters or conventional planters. The processor consists of a metal cylinder that is lined with corrugated rubber and a rotating center shaft with rubber paddles. Processing can be controlled by varying shaft rotation speed and processing time. A top-opening, full length trap door allows for easy loading and the cylinder can be inverted to dump out processed seed. The processor has been used successfully for several years on big bluestem [Andropogon gerardii Vitman], indiangrass [Sorghastrum nutans (L) Nash], little bluestem [Schizachyrium scoparium (Michaux) Nash], prairie sand reed [Calamovilfa longifolia (Rook.) Scribner] , and blue grama [Bouteloua gracilis (Willd. ex Kunth) Lagascaex Griffiths] seed. By removing seed appendages and pubescence, seed bulk is reduced and seed density and flow ability are improved. The processing operation is relatively gentle and seed germination per unit weight of seed is improved.

Tebuthiuron Use in Restoring Degraded Tallgrass Prairies and Warm-season Grass Pastures

Abstract Tallgrass prairies pastures are desirable grazing resources and preferred habitat for some wildlife species. Invasion of cool-season grass into these warm-season dominated grasslands is a common problem, and selectively removing cool-season grasses can be a challenge. In four trials conducted in southeastern Nebraska, we evaluated the effectiveness of the herbicide tebuthiuron, applied at rates between 0.7 and 2.7 kg ai ha−1, on selectively controlling cool-season grasses in tallgrass prairie pastures. We included glyphosate (1.3 kg ae ha−1) and imazapic + glyphosate (0.21 + 0.4 kg ae ha−1) in two of the trials for comparison. In three of the four trials, tebuthiuron at 0.9 kg ha−1 or greater reduced cool-season grass yields by over 60% and increased warm-season grass yields by 50 to 300%. Glyphosate and imazapic + glyphosate reduced cool-season grass yields but had no effect on warm-season grass or forb yields.

A Research Plot Herbicide Application System1

A tractor-mounted, air-pressurized, herbicide application system was designed and constructed for use in weed management research on cropland, pastures, and rangeland. The spray system was designed to minimize wind-induced spray pattern distortion, to enable accurate application of multiple treatments, to withstand the stresses of use on uneven and rough terrain, to apply herbicide treatments reliably, to be easy to transport, to be constructed with readily available spray system components, and to enable quick diagnosis and resolution of operational problems. The spray system has a total shield frame length of 5.2 m. The shielded frame comprises three sections. The two outside sections are connected to the center section by hinges so that they can be folded up and over the center section for transport or storage. Four spray booms are mounted inside the shield with a 50-cm distance between nozzles. Herbicides are usually applied with the bottom of the shield placed 20 cm above the soil or plant surface. This height provides 100% overlap of the spray pattern between adjacent nozzle tips. The spray system has been a durable and reliable tool that accurately and quickly applies herbicide treatments. Additional index words: Application technology, cropland, pasture, rangeland, weed control. Abbreviations: ID, inside diameter; PVC, polyvinylchloride.