Two field sites on a loam soil were established to monitor N20 concentration in the soil atmosphere and rate of emission from the soil surface. The sites were cropped to maize (Zea mays L.) and managed at two high-N levels (181 or 237 kg N ha-~). Both sites received 168 kg N ha -~ as feedlot cattle (Bos taurus) manure (preplant-incorporated) and 13 kg N ha -~ as NH4NO~ fertilizer in the row at planting. One site (Site B) received additional soil-incorporated N (56 kg N -~) asure a. Fluctuations in N20 emissions from the two sites were temporally similar, and differed only in magnitude with Site A (no additional fertilizer), emitting about 3.6 kg N20-N ha-' yr -~ and Site B about 5.2 kg N20-N ha-' yr -1, or about 2% of the N applied. Most of the N~O was emitted between mid-June and the end of July when the soil was warm and NH~-N was present, and at spring thaw (late March the following year) when soils were cold and near water-saturated. High N~O emissions during the growing season occurred following precipitation events, and hence were associated with high soil water and probably with the initiation of soil drying. Nitrous oxide production was continuous during winter months, presumably a result of denitrification. The N20 concentration in the profile of the frozen soil increased to high levels (nearly 2000 #L L -~ N~O at Site B) before spring thaw. At thaw, nearly 330 d after application of the N amendments, an apparent physical release period occurred and N~O flux was far higher (about 50 g N20-N ha -d -~) than at most times during the growing season. Additional index words: Zea mays L., Nitrification, Denitrification, Cold soils, Soil atmospheres, Profile nitrous oxide, Ozone layer. Cates, R.L., Jr., and D.R. Keeney. 1987. Nitrous oxide production throughout the year from fertilized and manured maize fields. J. Environ. Qual. 16:443-447.

Multifunctional agricultural landscapes and the ecosystem services they provide are gaining more attention. One example of this is the reintroduction of native species to cool-season grassland agroecosystems managed for livestock production. While such projects have potential ecological and agronomic benefits, there is little information on how restoration management affects pasture production and quality. The objective of this study was to determine how management to establish native warm-season grasses into temperate pastures affects forage production and quality. We tested this over three years (2004 through 2006) using a field experiment with combinations of disturbance (burning and grazing), soil amendments (ambient, nitrogen, and carbon), and native grass seeding times (fall and spring). We measured aboveground net primary production (ANPP), belowground net primary production (BNPP), and two forage quality parameters-neutral detergent fiber and in vitro neutral detergent fiber digestibility. For ANPP, there was a significant disturbance ´ soil amendment interaction effect in each year, but the nature of the interaction varied by year. In 2005, plots where nitrogen was applied had 513 lower BNPP than carbon and ambient plots. In 2006, burned plots had greater BNPP than grazed plots. For each level of disturbance, over 50% of the variability in the forage quality parameters was attributed to non-management variables, such as season. Our results showed no consistent effect of restoration management on pasture production or quality. They highlight the complexity of grassland agroecosystems and demonstrate the importance of evaluating the variability of treatment effects over time.

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We combined burning and rotational grazing in an effort to promote persistence of recently established native grasses. The experiment took place on a farm in south-central Wisconsin on a cool-season grass pasture that was drill seeded with native warm-season grasses: big bluestem (Andropogon gerardii), Indiangrass (Sorghastrum nutans), and switchgrass (Panicum virgatum). We used a split-plot experimental design to assess native grass persistence under varying disturbance treatments (burned, burned-grazed, and grazed). We used a paired t-test to determine if the difference between 2006 and 2007 native grass density was significantly different from zero. Native grass tiller density increased under the burned (202%) and grazed (186%) treatments, but not the burned-grazed (29%) treatment. However, the actual native grass tiller numbers in 2007 were much higher in the burned-only than the grazed-only treatment (80 ± 10 tillers/m 2 and 2 ± 1 tillers/m 2 , respectively). We found no loss to native grass tiller density when rotational grazing was applied to plots in the first year after two years of grazing exclusion with burning. In addition, we found that native grass cover was greatest in the burned treatment but not significantly different in the burned-grazed and grazed treatments. Our results suggest that the combined use of burning and grazing as a management tool for native grass persistence in pastures may be possible with deferred grazing during the establishment phase, but alternative timing, intensity, and types of grazing animals should be tested.