Biological Control of Weeds in Great Plains Rangelands

Chemical control of weeds has increased agricultural productivity, but complete reliance on chemicals has serious drawbacks. These include high cost per acre, decreasing effectiveness, negative effects on plant community diversity, and increased opportunities for environmental contamination. One alternative is biocontrol, the use of biological factors that naturally limit weed populations. Long-term research goals focus on improving our knowledge of the processes that control and limit potential plant pests naturally and to use that knowledge to develop predictable, sustainable, low-cost, biologically-based weed management strategies. This paper reviews the ecological underpinnings of classical biological control of weeds, including basic research on the interaction of natural enemies with native thistles in Nebraska. The fundamentals for developing a biological weed control program are summarized and research in the central and northern Great Plains on applying biological controls to limit introduced noxious rangeland weeds is reviewed. This is followed by a discussion of one of the problems associated with biological control, the potential secondary effects of biocontrol agents on non-target plant species. The evidence suggests that biological control is an ecologically sound, sustainable and economical option for limiting introduced rangeland weeds. Biological control represents an attractive technique for limiting the negative impacts of high weed densities, while not eradicating the introduced weed. Expanding interest in sustainable agricultural systems and more environmentally- friendly pest control and the prohibitive costs of chemical control suggest that biological weed control is likely to become an increasingly important part of rangeland management

Remnant and Restored Prairie Response to Fire, Fertilization, and Atrazine

The effect of spring burning, fertilization, and atrazine on herbage yield of warm- and cool-season grasses, flowering stalk density, and seed yield of selected warm-season grasses was determined on a remnant prairie and a restored prairie located near Lincoln and Center, Nebraska, respectively. Sites were burned in mid-April 1987 and followed by application of fertilizer (112 kg N/ha at the remnant prairie and 112-22 kg N-P/ha at the restored prairie) and atrazine (2.2 kg active ingredient/ha). Herbage yield of warm-season grasses increased more than 100% following burning in combination with fertilization at both sites and atrazine application alone at the restored prairie. Warm-season grass flowering stalk density increased more than 3 and 2 times following burning combined with fertilization and fertilization only at the remnant and restored prairies, respectively. Germinable seed numbers increased over 600% following a combination of burning, fertilization, and atrazine application at the remnant prairie and more than doubled following atrazine application at the restored prairie. Evidence provided by this research indicates that spring burning, fertilization, and atrazine can be used to renovate and improve productivity of tallgrass prairie in Nebraska

Gaseous-Hydrogen Pressurant Requirements for the Discharge of Liquid Hydrogen from a 3.96 Meter /13 ft/ Diameter Spherical Tank

Hydrogen gas pressure requirements during pressurization and transfer of liquid hydrogen from spherical tank

Evaluation of Four Intermediate Wheatgrass Populations under Grazing

The grazing season in the central and northern Great Plains could be extended by use of adapted cool-season grass pastures for spring and fall grazing to augment the native warm-season range. A grazing trial was conducted to evaluate the forage quality of four intermediate wheatgrass [Thinopyrum intermedium (Host) Barkw. & D.R. Dewey] populations for use in forage-livestock systems. The cultivars Slate and Oahe and two populations selected for improved IVDMD, ‘Manska’ and NE TI 1, were evaluated. Each population was seeded in the fall of 1987 in three replicated 0.4-ha pastures arranged in a randomized complete block design. Pastures were stocked with three beef yearlings for 28 d in spring 1989 and 42 d in spring 1990 to provide a stocking rate of 7.5 steers ha-’. Duration of grazing was shorter in 1989 because of inadequate soil moisture. Average daily gain (ADG) and gain per hectare were higher (P 5 0.10) in 1989 than 1990, despite the lower (P 5 0.10) forage availability and lesser number of grazing days in 1989. Steers grazing Manska in 1989 gained 1.59 kg d-’, compared with 1.42,1.27, and 1.43 for Oahe, Slate, and NE TI 1, respectively. There were no differences (P \u3e 0.10) in ADG or gain per hectare among populations in 1990. The improvement in ADG resulted in 30 to 65 kg more gain per hectare from Manska compared with the other populations in l989. These results demonstrate the excellent quality of intermediate wheatgrass for grazing livestock and the impact that modest improvements in forage quality can have on animal performance

Fitting Age-Period-Cohort Models Using the Intrinsic Estimator: Assumptions and Misapplications

We thank Demography’s editorial office for the opportunity to respond to te Grotenhuis et al.’s commentary regarding the methods used and the results presented in our earlier paper (Masters et al. 2014). In this response, we briefly reply to three general themes raised in the commentary: (1) the presentation and discussion of APC results, (2) the fitting of full APC models to data for which a simpler model holds, and (3) the variation in the estimated age, period, and cohort coefficients produced by the intrinsic estimator (IE) (i.e., the “non-uniqueness property” of the IE, as referred to by Pelzer et al. (2015))

Evaluation of Four Intermediate Wheatgrass Populations under Grazing

The grazing season in the central and northern Great Plains could be extended by use of adapted cool-season grass pastures for spring and fall grazing to augment the native warm-season range. A grazing trial was conducted to evaluate the forage quality of four intermediate wheatgrass [Thinopyrum intermedium (Host) Barkw. & D.R. Dewey] populations for use in forage-livestock systems. The cultivars Slate and Oahe and two populations selected for improved IVDMD, ‘Manska’ and NE TI 1, were evaluated. Each population was seeded in the fall of 1987 in three replicated 0.4-ha pastures arranged in a randomized complete block design. Pastures were stocked with three beef yearlings for 28 d in spring 1989 and 42 d in spring 1990 to provide a stocking rate of 7.5 steers ha-’. Duration of grazing was shorter in 1989 because of inadequate soil moisture. Average daily gain (ADG) and gain per hectare were higher (P 5 0.10) in 1989 than 1990, despite the lower (P 5 0.10) forage availability and lesser number of grazing days in 1989. Steers grazing Manska in 1989 gained 1.59 kg d-’, compared with 1.42,1.27, and 1.43 for Oahe, Slate, and NE TI 1, respectively. There were no differences (P \u3e 0.10) in ADG or gain per hectare among populations in 1990. The improvement in ADG resulted in 30 to 65 kg more gain per hectare from Manska compared with the other populations in l989. These results demonstrate the excellent quality of intermediate wheatgrass for grazing livestock and the impact that modest improvements in forage quality can have on animal performance