Tillage and manure application effects on mineral nitrogen leaching from seasonally frozen soils

Land application of manure is a common practice in the Upper Midwest of the United States. Recently, there have been concerns regarding the effect of this practice on water quality, especially when manure is applied during winter over frozen soils. A study undertaken on a Rozetta silt loam (fine-silty, mixed, superactive, mesic Typic Hapludalfs) at Lancaster, WI, evaluated the effects of tillage and timing of manure application on surface and subsurface water quality. The daily scrape and haul liquid dairy manure was applied either in the fall (before snow) or in winter (over snow with frozen soil underneath) to be compared with no manure under two tillage systems (no-till and chisel-plowing). In this paper, we report results on the effects of the above treatments on mineral N leaching. Percolation and mineral N leaching during the nongrowing season were, respectively, 72 and 78% of the annual losses, mainly because of the absence of plant water and N uptake. Percolation was generally higher from no-till compared with chisel-plow but there was no significant effect of tillage on mineral N concentration of the leachate or mineral N losses via leaching. Mineral N leaching was statistically higher from the manure-applied vs. no-manure treatment, but there was no difference between winter-applied manure and no-manure treatments. There were significant tillage by manure interactions with fall manure application followed by chisel-plowing resulting in highest N leaching losses. Averaged over the two years, N leaching rates were 52, 38, and 28 kg N ha(-1) yr(-1) from fall-applied, winter-applied, and no-manure treatments, respectively. These results show that there is substantial N leaching from these soils even when no fertilizer or manure is applied. Furthermore, fall-applied manure followed by fall tillage significantly increases N leaching due to enhanced mineralization of both soil and manure organic N.     

Nitrate leaching under grassland as affected by mineral nitrogen fertilization and cattle urine

An experiment was performed to better understand to what extent nitrogen fertilization rate and date and amount of urine deposition, when acting in combination, influence nitrate leaching under grassland. Leaching was studied during two successive winters using 2-m2 grassed lysimeters under three levels of N fertilization (0, 150, and 300 kg N ha(-1) yr(-1), referred to as 0N, 150N, and 300N, respectively), two levels of 15N-labeled urine (105 and 165 kg N ha(-1), referred to as A2 and A3, respectively), and three dates of urine application (spring, summer, and fall). During the first winter, total N leaching losses varied between 2 and 50 kg N ha(-1). When tested in combination, N applied as urine to grassland resulted in three times the total N loss by leaching that occurred following N fertilization in the first winter (4.3, 20.8, 34.9, 14.2, 17.1, and 28.7 kg NO3- -N ha(-1) for no urine, A2, A3, ON, 150N, and 300N, respectively). Leaching of 15N urine significantly depended on the date of application: 6.6, 17.3, and 29.1 kg for spring, summer, and fall, respectively. A similar pattern was observed for the contribution of 15N urine to total N leaching with 4.3, 12.9, and 21.4%. However, urine application, both in terms of amount and date, showed very little long-term effect on these N losses in Year 2. In our conditions of low winter rainfall and drainage, grazing management (through season, urinary N amounts, and urine N concentration) resulted in a higher impact on water nitrate quality than moderate N fertilization management.     

The localized environmental degradation of protected areas adjacent to bird feeding stations: a case study of the Australian brush-turkey Alectura lathami

This study investigated the potential for wildlife feeding to artificially increase population densities of the Australian brush-turkey, Alectura lathami and assessed the indirect adverse effects that this may have on surrounding forest floor vegetation. Census counts and observations of feeding activity conducted in recreation areas of Australia's Gold Coast hinterland confirmed that brush-turkey population densities were significantly elevated by the provision of food by humans. Brush-turkey densities were high at sites where birds are actively fed, moderate at sites where birds feed opportunistically and low at sites where humans have negligible impact on local food availability. Brush-turkeys caused significant environmental impact at sites where their population densities have been substantially elevated by active feeding. Across all sites, increases in brush-turkey density were accompanied by a significant decline in ground cover, leaf litter weight, seed density and seedling density. Natural environmental variables such as gradient, vegetation type and canopy cover did not explain the observed impacts. The impacts were consistent with those described in trampling studies and suggest that at high density, even small animals can have significant trampling impacts on their local environment. This study demonstrates that wildlife feeding can have detrimental impacts on the integrity of local environments and recommends greater consideration of small animals and their potential indirect impacts when regulating wildlife feeding in National Parks and other nature conservation areas.     

Quality and Quantity of Suspended Particles in Rivers: Continent-Scale Patterns in the United States

Suspended solids or sediments can be pollutants in rivers, but they are also an important component of lotic food webs. Suspended sediment data for rivers were obtained from a United States–wide water quality database for 622 stations. Data for particulate nitrogen, suspended carbon, discharge, watershed area, land use, and population were also used. Stations were classified by United States Environmental Protection Agency ecoregions to assess relationships between terrestrial habitats and the quality and quantity of total suspended solids (TSS). Results indicate that nephelometric determinations of mean turbidity can be used to estimate mean suspended sediment values to within an order of magnitude (r² = 0.89). Water quality is often considered impaired above 80 mg TSS L^–1, and 35% of the stations examined during this study had mean values exceeding this level. Forested systems had substantially lower TSS and somewhat higher carbon-to-nitrogen ratios of suspended materials. The correlation between TSS and discharge was moderately well described by an exponential relationship, with the power of the exponent indicating potential acute sediment events in rivers. Mean sediment values and power of the exponent varied significantly with ecoregion, but TSS values were also influenced by land use practices and geomorphological characteristics. Results confirm that, based on current water quality standards, excessive suspended solids impair numerous rivers in the United States.     

Transport and degradation of toluene and o-xylene in an unsaturated soil with dipping sedimentary layers

A lysimeter trench was established at the Gardermoen delta (50 km north of Oslo, Norway) to study the flow of water and transport and degradation of aromatic jet fuel components (toluene and o-xylene) in the undisturbed unsaturated zone. Site investigations with ground-penetrating radar revealed the presence of dipping sedimentary layers within the foreset unit. This study has shown that the foreset bed of the Gardermoen delta structure provided a preferential flow path for the transport of the solute plumes, but did not have dramatic effects on the degradation potential under the current conditions. The degradation potential for toluene and o-xylene in the unsaturated zone at Gardermoen was very high and almost all of the injected hydrocarbons were biodegraded before reaching the saturated zone. However, the horizontal displacement of the plume showed that knowledge about sedimentary structures in the unsaturated zone is important for a sufficient monitoring of contaminant transport and for remediation purposes. Carbon dioxide and O2 were measured in situ simultaneously with extraction of water samples, and indicated aerobic biodegradation of toluene and o-xylene. Overall, first-order degradation coefficients were calculated to be in the range of 0.19 to 0.21 d(-1) and 0.10 to 0.11 d(-1) for toluene and o-xylene, respectively.     

Relationships between stream size,suspended particles,and filter-feeding macroinvertebrates in a great plains drainage network

Suspended fine particles (seston) are an important component of energy and nutrient cycling in streams, but they can also be pollutants. We examined seston dynamics and filter-feeding macroinvertebrate communities in sites representing headwaters to large rivers in the Kansas River drainage, northeastern KS. Seston samples were collected at least seasonally during low to moderate flows for one year beginning in the summer of 1999, and quality was assessed by determining organic content and C to N ratio. A rapid bioassessment approach was used to examine filter-feeders. Relationships between stream size and seston concentrations were markedly influenced by anthropogenic activities. There was no relationship between total seston concentration and stream size across all sites (r = 0.14, p > 0.05), but a significant, positive relationship was evident when impounded and suburban sites were excluded (r = 0.73, p < 0.01); this same trend was evident for organic and inorganic components. Seasonal patterns of C to N ratio were evident, with generally lower values during winter and highest values in summer. However, seasonal patterns were dampened in suburban sites and virtually absent below impoundments. Filter-feeder richness was correlated with average organic seston concentrations (r = 0.8, p < 0.01), but this relationship was also obscured by impoundments and suburban development. In particular, impoundments had a dramatic, negative effect on richness. Abundance of most hydropsychid caddisfly taxa was positively correlated with organic seston concentration. Results indicate there are significant patterns regarding seston, filter-feeders, and stream size in this Great Plains river system, but patterns are strongly influenced by human activities. These relationships are relevant to management issues regarding suspended particles and the potential development of bioassessment techniques.     

Stream Invertebrate Communities, Water Quality, and Land-Use Patterns in an Agricultural Drainage Basin of Northeastern Nebraska, USA

We used invertebrate bioassessment, habitat analysis, geographic information system analysis of land use, and water chemistry monitoring to evaluate tributaries of a degraded northeast Nebraska, USA, reservoir. Bimonthly invertebrate collections and monthly water chemistry samples were collected for two years on six stream reaches to identify sources contributing to reservoir degradation and test suitability of standard rapid bioassessment methods in this region. A composite biotic index composed of seven commonly used metrics was effective for distinguishing between differentially impacted sites and responded to a variety of disturbances. Individual metrics varied greatly in precision and ability to discriminate between relatively impacted and unimpacted stream reaches. A modified Hilsenhoff index showed the highest precision (reference site CV = 0.08) but was least effective at discriminating among sites. Percent dominance and the EPT (number of Ephemeroptera, Plecoptera, and Trichoptera taxa) metrics were most effective at discriminating between sites and exhibited intermediate precision. A trend of higher biotic integrity during summer was evident, indicating seasonal corrections should differ from other regions. Poor correlations were evident between water chemistry variables and bioassessment results. However, land-use factors, particularly within 18-m riparian zones, were correlated with bioassessment scores. For example, there was a strong negative correlation between percentage of rangeland in 18-m riparian zones and percentage of dominance in streams (r ² = 0.90, P < 0.01). Results demonstrate that standard rapid bioassessment methods, with some modifications, are effective for use in this agricultural region of the Great Plains and that riparian land use may be the best predictor of stream biotic integrity.     

Transfrontier conservation areas: Integrating biodiversity and poverty alleviation in Southern Africa

Sub‐Saharan Africa continues to face the daunting challenge of alleviating poverty due to slow economic growth. In southern Africa, most countries are adopting policies that promote the integration of biodiversity conservation and rural development to contribute to rural poverty alleviation. Numerous approaches have been undertaken in this endeavour, including Transfrontier Parks (TFPs) and Transfrontier Conservation Areas (TFCAs). This paper discusses some of the limitations of the TFPs. In conclusion I posit that unlike TFPs, which are state controlled and managed, TFCAs, which promote multi‐land use and multi‐stakeholder participation are attainable and have a higher probability of sustaining biodiversity conservation and contributing to the alleviation of rural poverty, if: (i) areas of high biodiversity conservation within communal areas can be identified, zoned and leveraged to biodiversity conservation and managed in partnership between the communities and the private sector; (ii) local communities can secure legal rights to their customary land being devoted to biodiversity conservation and use such pieces of land as collateral in negotiating partnerships with the private sector in developing conservation‐based enterprises; (iii) functional community natural resource governance institutions can be established and empowered to represent their constituencies in securing fair equity from profits made from sustainable use of the conserved biodiversity assets and tourism businesses; (iv) concerted effort can be invested in developing and implementing family planning and fertility reduction strategies that would slow down human population growth to levels that can be sustained by the available natural resources; and (v) if sustainable financing mechanisms can be developed, and the governance of protected areas occurring in the TFCAs can be broadened to include other stakeholders.