Effects of atmospheric ammonia (NH3) on terrestrial vegetation: a review.

Summary Biodiversity is responsible for the provision of many ecosystem services; human well-being is based on these services, and consequently on biodiversity. In soil, earthworms represent the largest component of the animal biomass and are commonly termed ‘ecosystem engineers’. This review considers the contribution of earthworms to ecosystem services through pedogenesis, development of soil structure, water regulation, nutrient cycling, primary production, climate regulation, pollution remediation and cultural services. Although there has been much research into the role of earthworms in soil ecology, this review demonstrates substantial gaps in our knowledge related in particular to difficulties in identifying the effects of species, land use and climate. The review aims to assist people involved in all aspects of land management, including conservation, agriculture, mining or other industries, to obtain a broad knowledge of earthworms and ecosystem services.

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A review of earthworm impact on soil function and ecosystem services

Gaseous ammonia (NH3) is the most abundant alkaline gas in the atmosphere. In addition, it is a major component of total reactive nitrogen. The largest source of NH3 emissions is agriculture, including animal husbandry and NH3-based fertilizer applications. Other sources of NH3 include industrial processes, vehicular emissions and volatilization from soils and oceans. Recent studies have indicated that NH3 emissions have been increasing over the last few decades on a global scale. This is a concern because NH3 plays a significant role in the formation of atmospheric particulate matter, visibility degradation and atmospheric deposition of nitrogen to sensitive ecosystems. Thus, the increase in NH3 emissions negatively influences environmental and public health as well as climate change. For these reasons, it is important to have a clear understanding of the sources, deposition and atmospheric behaviour of NH3. Over the last two decades, a number of research papers have addressed pertinent issues related to NH3 emissions into the atmosphere at global, regional and local scales. This review article integrates the knowledge available on atmospheric NH3 from the literature in a systematic manner, describes the environmental implications of unabated NH3 emissions and provides a scientific basis for developing effective control strategies for NH3.

Ammonia in the atmosphere: a review on emission sources, atmospheric chemistry and deposition on terrestrial bodies.

The original review of macropores and water flow in soils by Beven and Germann is now 30 years old and has become one of the most highly cited papers in hydrology. This paper attempts to review the progress in observations and theoretical reasoning about preferential soil water flows over the intervening period. It is suggested that the topic has still not received the attention that its importance deserves, in part because of the ready availability of software packages rooted firmly in the Richards domain, albeit that there is convincing evidence that this may be predicated on the wrong experimental method for natural conditions. There is still not an adequate physical theory linking all types of flow, and there are still not adequate observational techniques to support the scale dependent parameterizations that will be required at practical field and hillslope scales of application. Some thoughts on future needs to develop a more comprehensive representation of soil water flows are offered.

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Macropores and water flow in soils revisited

Review on materials & methods to produce controlled release coated urea fertilizer.

soils, problems associated with poor drainage are still not satisfactorily resolved. This is because the landscape This study quantified the effects of tillage (moldboard plowing is relatively flat (,2% slope) and has many small de[MP], ridge tillage [RT]) and nutrient source (manure and commercial fertilizer [urea and triple superphosphate]) on sediment, NH41‐N, pressions (pot holes) where water stands after snowmelt NO 2 3‐N, total P, particulate P, and soluble P losses in surface runoff and heavy rainfall. Standing water hinders the timeliness and subsurface tile drainage from a clay loam soil. Treatment effects of farm operations and is also deleterious to planted were evaluated using simulated rainfall immediately after corn (Zea crops. To overcome these problems, farmers have inmays L.) planting, the most vulnerable period for soil erosion and stalled surface tile inlets that drain water from these water quality degradation. Sediment, total P, soluble P, and NH 1 4‐N depressions to subsurface tile drains. These tile inlets losses mainly occurred in surface runoff. The NO2 3‐N losses primarily allow transport of sediment and surface-applied chemioccurred in subsurface tile drainage. In combined (surface and subsur- cals to subsurface tiles, which ultimately flow to surface) flow, the MP treatment resulted in nearly two times greater face waters. sediment loss than RT (P , 0.01). Ridge tillage with urea lost at least In addition to being wet, the soils in the upper Mid11 times more NH 1 4‐N than any other treatment (P , 0.01). Ridge

Tillage and Nutrient Source Effects on Surface and Subsurface Water Quality at Corn Planting

Irrigation and N management are perhaps the most important aspects of successful potato (Solanum tuberosum L.) production in central Minnesota. With rising concern about current irrigation and N management practices and ground water quality, a two-year study was undertaken to evaluate the impact of alternative irrigation and N management practices on potato yield, tuber quality, and N uptake. The treatments were different irrigation schemes (sprinkler and drip), irrigation triggers (70 and 40% of available water [AW] remaining), drip tape placements (surface or buried at 25 cm), N sources (urea, turkey manure, sulfur-coated urea [SCU]), and timings of inorganic N fertilizer application. Rainfall in the area was less in 1994 (260 mm) than in 1995 (380 mm). As a result, irrigation applications in 1994 were greater than in 1995. Drip irrigation amounts were less than half of that applied by sprinkler irrigation treatments in both years. Except for the buried drip with fertigation (43.0 and 27.8 Mg ha -1 in 1994 and 1995) and the control (36.5 and 13.3 Mg ha -1 in 1994 and 1995), total tuber yields were similar regardless of irrigation and N source treatment. The turkey manure treatments in 1994 had significantly higher marketable tuber yields than the control, averaging 48.3 Mg ha -1 for both years. Total N uptake in 1994 was nearly 100% of that applied, while in 1995 it accounted for only 60% of the application. Lower N uptake was observed for the control (85.3 and 30.2 kg N ha -1 in 1994 and 1995, respectively), SCU (165.2 and 111.3 kg N ha -1 in 1994 and 1995), and BDF (157.2 and 80.1 kg N ha -1 in 1994 and 1995) treatments. The results showed that the use of unconventional N sources such as turkey manure and SCU are viable alternatives for potato production, provided they are managed properly.

Irrigation and Nitrogen Management Effects on Potato Yield, Tuber Quality, and Nitrogen Uptake

Water and solute movement in soil as influenced by macropore characteristics: 2. Macropore tortuosity

In cold climates, snowmelt runoff often exceeds rainfall runoff during the year Conservation tillage practices may be effective in reducing runoff during the cropping season but not during the snowmelt period A plot study was conducted on a cropped hillslope to assess how tillage practices affect snowmelt runoff and the associated losses of sediment, phosphorus (P), and chemical oxygen demand (COD) Tillage systems were fall moldboard and chisel plowing with spring disking, and a ridge till system utilizing only the tillage associated with summer row cultivation Tillage and planting were done up and down the slope Ridge tilled plots had higher fall residue cover, retained more snow, had less surface roughness, and consequently produced more runoff than the moldboard plow treatment The amount of runoff from chisel plowed plots was similar to runoff from ridge tilled plots despite a relatively rough surface and moderate amount of residue cover Phosphorus losses in runoff were higher for the ridge till and chisel plow systems than for the moldboard plow system For all tillage systems, soluble P represented a major portion (75%) of the total P loss in snowmelt runoff Although erosive losses in snowmelt were low, the P losses were substantial and merit consideration in studies evaluating management systems impact on surface water quality in regions where snowmelt runoff is important

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Snowmelt runoff, sediment, and phosphorus losses under three different tillage systems

Controlled release fertilizers, especially polymer-coated urea (PCU), have been shown to reduce nitrate (NO 3 ) leaching while maintaining potato (Solanum tuberosum L.) yields, but cost has been prohibitive. A new type of PCU (Environmentally Smart Nitrogen, Agrium, Inc., Calgary, AB) is less costly than previous PCUs, but its effectiveness on potato production has not been extensively studied. A 2-yr field study was conducted on loamy sand to evaluate the effect of this PCU on Russet Burbank tuber yield and to determine if it is economically comparable to soluble N sources. Several N rates of PCU applied at emergence were compared with two split applications of soluble N at equivalent rates. Additional treatments examined N application timing of PCU and a fertigation simulation with urea/ammonium nitrate. Petioles and midseason soil samples were collected to determine N status during the season. Overall, PCU and soluble N at equivalent N rates were found to have similar total and grade A yields and net monetary returns. The optimal N rate that resulted in maximum net returns was 251 and 236 kg N ha ―1 as soluble N and PCU, respectively. Petiole NO 3 concentrations were typically higher with soluble N early in the season and higher with PCU later in the season. Soil NO 3 determined in samples collected in late June was found to be a better predictor of yield and potential N need than those collected in mid- to late July. Overall, PCU may reduce or eliminate the need for split applications of N on coarse-textured soils.

J. F. Moncrief

Papers

Tillage and Nutrient Source Effects on Surface and Subsurface Water Quality at Corn Planting

Irrigation and Nitrogen Management Effects on Potato Yield, Tuber Quality, and Nitrogen Uptake

Water and solute movement in soil as influenced by macropore characteristics: 2. Macropore tortuosity

Snowmelt runoff, sediment, and phosphorus losses under three different tillage systems

Potato Response to a Polymer-Coated Urea on an Irrigated, Coarse-Textured Soil