Linkages between land management activities and water quality in an intensively farmed catchment in southern New Zealand

Linkages between land management activities and stream water quality are reported for a 2480 ha catchment used for dairy farming, sheep–beef farming and forestry in Southland, New Zealand. Our approach was to reconcile measured loads of nutrients exported from the catchment with those estimated based on characterisation of farming practices within the catchment. The latter was based upon detailed surveys of farm practices and soil quality. Monthly stream monitoring showed that median nutrient (N and P), sediment and faecal bacteria concentrations exceeded guidelines recommended for surface waters. Measured specific yields for suspended sediment (SS), total N (TN) and phosphorus (P) discharged from the catchment were 58, 8.2 and 0.43 kg ha⁻¹ year⁻¹, respectively, for the 2001–2005 monitoring period. In comparison, model estimates of N and P losses in drainage and overland flow from farms in the catchment were 10.1 and 0.59 kg ha⁻¹ year⁻¹, respectively. Field measurements, farm management surveys and farm systems modeling have identified some land management practices that appear to be key sources of many of these pollutants. These sources include subsurface drainage systems (including the preferential flow of irrigated effluent through these soils), overland flow from the heavy soils used for dairy farming in the catchment and the practice of intensively wintering cows on forage crops. Modeling suggests that a significant improvement in catchment water quality could be achieved through the implementation of targeted best management practices (BMPs) on dairy farms in the catchment. These include (i) covered feedpad wintering systems for controlling N losses, (ii) nitrification inhibitor use on milking platforms, (iii) deferred irrigation and low rate application of farm dairy effluent and (iv) limiting soil Olsen P to economically optimum levels. The adoption of these BMPs will, in part, depend on their economic viability. This paper therefore presents a double-bottom-line analysis (i.e. environmental and economic) of some of these BMPs and discusses their potential to cost-effectively deliver improved water quality in the Bog Burn catchment.     

Modelling greenhouse gas emissions from European conventional and organic dairy farms

Agriculture is an important contributor to global emissions of greenhouse gases (GHG), in particular for methane (CH₄) and nitrous oxide (N₂O). Emissions from farms with a stock of ruminant animals are particularly high due to CH₄ emissions from enteric fermentation and manure handling, and due to the intensive nitrogen (N) cycle on such farms leading to direct and indirect N₂O emissions. The whole-farm model, FarmGHG, was designed to quantify the flows of carbon (C) and nitrogen (N) on dairy farms. The aim of the model was to allow quantification of effects of management practices and mitigation options on GHG emissions. The model provides assessments of emissions from both the production unit and the pre-chains. However, the model does not quantify changes in soil C storage.Model dairy farms were defined within five European agro-ecological zones for both organic and conventional systems. The model farms were all defined to have the same utilised agricultural area (50 ha). Cows on conventional and organic model farms were defined to achieve the same milk yield, so the basic difference between conventional and organic farms was expressed in the livestock density. The organic farms were defined to be 100% self-sufficient with respect to feed. The conventional farms, on the other hand, import concentrates as supplementary feed and their livestock density was defined to be 75% higher than the organic farm density. Regional differences between farms were expressed in the milk yield, the crop rotations, and the cow housing system and manure management method most common to each region.The model results showed that the emissions at farm level could be related to either the farm N surplus or the farm N efficiency. The farm N surplus appeared to be a good proxy for GHG emissions per unit of land area. The GHG emissions increased from 3.0 Mg CO₂-eq ha⁻¹ year⁻¹ at a N surplus of 56 kg N ha⁻¹ year⁻¹ to 15.9 Mg CO₂-eq ha⁻¹ year⁻¹ at a N surplus of 319 kg N ha⁻¹ year⁻¹. The farm N surplus can relatively easily be determined on practical farms from the farm records of imports and exports and the composition of the crop rotation. The GHG emissions per product unit (milk or metabolic energy) were quite closely related to the farm N efficiency, and a doubling of the N efficiency from 12.5 to 25% reduced the emissions per product unit by ca. 50%. The farm N efficiency may therefore be used as a proxy for comparing the efficiencies of farms with respect to supplying products with a low GHG emission.     

Soil C storage as affected by tillage and straw management: An assessment using field measurements and model predictions

Soil tillage and straw management are both known to affect soil organic matter dynamics. However, it is still unclear whether, or how, these two practices interact to affect soil C storage, and data from long term studies are scarce. Soil C models may help to overcome some of these problems. Here we compare direct measurements of soil C contents from a 9 year old tillage experiment to predictions made by RothC and a cohort model. Soil samples were collected from plots in an Irish winter wheat field that were exposed to either conventional (CT) or shallow non-inversion tillage (RT). Crop residue was removed from half of the RT and CT plots after harvest, allowing us to test for interactive effects between tillage practices and straw management. Within the 0–30 cm layer, soil C contents were significantly increased both by straw retention and by RT. Tillage and straw management did not interact to determine the total amount of soil C in this layer. The highest average soil C contents (68.9 ± 2.8 Mg C ha^?1) were found for the combination of RT with straw incorporation, whereas the lowest average soil C contents (57.3 ± 2.3 Mg C ha^?1) were found for CT with straw removal. We found no significant treatment effects on soil C contents at lower depths. Both models suggest that at our site, RT stimulates soil C storage largely by decreasing the decomposition of old soil C. Extrapolating our findings to the rest of Ireland, we estimate that RT will lead to C mitigation ranging from 0.18 to 1.0 Mg C ha^?1 y^?1 relative to CT, with the mitigation rate depending on the initial SOC level. However, on-farm assessments are still needed to determine whether RT management practices can be adopted under Irish conditions without detrimental effects on crop yield.     

Linking spatio-temporal variation of crop response with sediment deposition along paddy rice terraces

In tropical mountainous regions of South East Asia, intensive cultivation of annual crops on steep slopes makes the area prone to erosion resulting in decreasing soil fertility. Sediment deposition in the valleys, however, can enhance soil fertility, depending on the quality of the sediments, and influence crop productivity. The aim of the study was to assess (i) the spatio-temporal variation in grain yield along two rice terrace cascades in the uplands of northern Viet Nam, (ii) possible linkage of sediment deposition with the observed variation in grain yield, and (iii) whether spatial variation in soil water or nitrogen availability influenced the obtained yields masking the effect of inherent soil fertility using carbon isotope (¹³C) discrimination and ¹⁵N natural abundance techniques. In order to evaluate the impact of seasonal conditions, fertilizer use and sediment quality on rice performance, ¹⁵N and ¹³C stable isotope compositions of rice leaves and grains taken after harvest were examined and combined with soil fertility information and rice performance using multivariate statistics. The observed grain yields for the non-fertilized fields, averaged over both cascades, accounted for 4.0 ± 1.4 Mg ha^?1 and 6.6 ± 2.5 Mg ha^?1 in the spring and summer crop, respectively, while for the fertilized fields, grain yields of 6.5 ± 2.1 Mg ha^?1 and 6.9 ± 2.1 Mg ha^?1 were obtained. In general, the spatial variation of rice grain yield was strongly and significantly linked to sediment induced soil fertility and textural changes, such as soil organic carbon (r 0.34/0.77 for Cascades 1 and 2, respectively) and sand fraction (r ?0.88/?0.34). However, the observed seasonal alteration in topsoil quality, due to sediment deposition over two cropping cycles, was not sufficient to fully account for spatial variability in rice productivity. Spatial variability in soil water availability, assessed through ¹³C discrimination, was mainly present in the spring crop and was linearly related to the distance from the irrigation channel, and overshadowed in Cascade 2 the expected yield trends based on sediment deposition. Although δ¹⁵N signatures in plants indicated sufficient N uptake, grain yields were not found to be always significantly influenced by fertilizer application. These results showed the importance of integrating sediment enrichment in paddy fields within soil fertility analysis. Furthermore, where the effect of inherent soil fertility on rice productivity is masked by soil water or nitrogen availability, the use of ¹³C and ¹⁵N stable isotopes and its integration with conventional techniques showed potential to enhance the understanding of the influence of erosion – sedimentation and nutrient fluxes on crop productivity, at toposequence level.     

Soil-profile organic carbon and total nitrogen during 12 years of pasture management in the Southern Piedmont USA

Soil organic C (SOC) and total soil N (TSN) sequestration estimates are needed to improve our understanding of management influences on soil fertility and terrestrial C cycling related to greenhouse gas emission. We evaluated the factorial combination of nutrient source (inorganic, mixed inorganic and organic, and organic as broiler litter) and forage utilization (unharvested, low and high cattle grazing pressure, and hayed monthly) on soil-profile distribution (0–150 cm) of SOC and TSN during 12 years of pasture management on a Typic Kanhapludult (Acrisol) in Georgia, USA. Nutrient source rarely affected SOC and TSN in the soil profile, despite addition of 73.6 Mg ha^?1 (dry weight) of broiler litter during 12 years of treatment. At the end of 12 years, contents of SOC and TSN at a depth of 0–90 cm under haying were only 82 ± 5% (mean ± S.D. among treatments) of those under grazed management. Within grazed pastures, contents of SOC and TSN at a depth of 0–90 cm were greatest within 5 m of shade and water sources and only 83 ± 7% of maximum at a distance of 30 m and 92 ± 14% of maximum at a distance of 80 m, suggesting a zone of enrichment within pastures due to animal behavior. During 12 years, the annual rate of change in SOC (0–90 cm) followed the order: low grazing pressure (1.17 Mg C ha^?1 year^?1) > unharvested (0.64 Mg C ha^?1 year^?1) = high grazing pressure (0.51 Mg C ha^?1 year^?1) > hayed (?0.22 Mg C ha^?1 year^?1). This study demonstrated that surface accumulation of SOC and TSN occurred, but that increased variability and loss of SOC with depth reduced the significance of surface effects.     

Disaggregated greenhouse gas emission inventories from agriculture via a coupled economic-ecosystem model

Estimates of regional greenhouse gas emissions from agricultural systems are needed to evaluate possible mitigation strategies with respect to environmental effectiveness and economic feasibility. Therefore, in this study, we used the GIS-coupled economic-ecosystem model EFEM–DNDC to assess disaggregated regional greenhouse gas (GHG) emissions from typical livestock and crop production systems in the federal state of Baden-Württemberg, Southwest Germany. EFEM is an economic farm production model based on linear programming of typical agricultural production systems and simulates all relevant farm management processes and GHG emissions. DNDC is a process-oriented ecosystem model that describes the complete biogeochemical C and N cycle of agricultural soils, including all trace gases.Direct soil emissions were mainly related to N₂O, whereas CH₄ uptake had marginal influence (net soil C uptake or release was not considered). The simulated N₂O emissions appeared to be highly correlated to N fertilizer application (R² = 0.79). The emission factor for Baden-Württemberg was 0.97% of the applied N after excluding background emissions.Analysis of the production systems showed that total GHG emissions from crop based production systems were considerably lower (2.6–3.4 Mg CO₂ eq ha⁻¹) than from livestock based systems (5.2–5.3 Mg CO₂ eq ha⁻¹). Average production system GHG emissions for Baden-Württemberg were 4.5 Mg CO₂ eq ha⁻¹. Of the total 38% were derived from N₂O (direct and indirect soil emissions, and manure storage), 40% were from CH₄ (enteric fermentation and manure storage), and 22% were from CO₂ (mainly fertilizer production, gasoline, heating, and additional feed). The stocking rate was highly correlated (R² = 0.85) to the total production system GHG emissions and appears to be a useful indicator of regional emission levels.     

Nutrient flows in small-scale peri-urban vegetable farming systems in Southeast Asia—A case study in Hanoi

In many peri-urban areas of Southeast Asia, land use has been transformed from rice-based to more profitable vegetable-based systems in order to meet the increasing market demand. The major management related flows of nitrogen (N), phosphorus (P), potassium (K), copper (Cu) and zinc (Zn) were quantified over a 1-year period for intensive small-scale aquatic and terrestrial vegetable systems situated in two peri-urban areas of Hanoi City, Vietnam. The two areas have different sources of irrigation water; wastewater from Hanoi City and water from the Red River upstream of Hanoi. The first nutrient balances for this region and farming systems are presented. The main sources of individual elements were quantified and the nutrient use efficiency estimated. The environmental risks for losses and/or soil accumulation were also assessed and discussed in relation to long-term sustainability and health aspects.The primary source of nutrient input involved a combination of chemical fertilisers, manure (chicken) and irrigation water. A variable composition and availability of the latter two sources greatly influenced the relative magnitude of the final total loads for individual elements. Despite relatively good nutrient use efficiencies being demonstrated for N (46–86%) and K (66–94%), and to some extent also for P (19–46%), high inputs still resulted in substantial annual surpluses causing risks for losses to surface and ground waters. The surplus for N ranged from 85 to 882 kg ha⁻¹ year⁻¹, compared to P and K which were 109–196 and 20–306 kg ha⁻¹ year⁻¹, respectively. Those for Cu and Zn varied from 0.2 to 2.7 and from 0.6 to 7.7 kg ha⁻¹ year⁻¹, respectively, indicating high risk for soil accumulation and associated transfers through the food chain.Wastewater irrigation contributed to high inputs, and excess use of organic and chemical fertilisers represent a major threat to the soil and water environment. Management options that improve nutrient use efficiency represent an important objective that will help reduce annual surpluses. A sustainable reuse of wastewater for irrigation in peri-urban farming systems can contribute significantly to the nutrient supply (assuming low concentrations of potential toxic or hazardous substances in the water). Nutrient inputs need to be better related to the crop need, e.g. through better knowledge about the nutrient concentrations in the wastewater and improved management of the amount of irrigation water being applied.     

Evidence of rich microbial communities in the subsoil of a boreal acid sulphate soil conducive to greenhouse gas emissions

The largest areas of acid sulphate (AS) soils in Europe are located in Finland, where 67,000–130,000 ha of AS soils are in agricultural use. In addition to their acidifying effects on waters, AS soils might be a significant source of greenhouse gases. In this pilot research, carbon and nitrogen content and microbial activity were studied in an AS and a non-AS soil. Large carbon and nitrogen stocks (110 Mg C_org ha^?1 and 15 Mg N_tot ha^?1) as well as high substrate induced respiration (33 μg CO₂–C g^?1h^?1) were found in the C horizons of the AS soil but not in the non-AS soil. High microbial activity in these horizons of the AS soil was further confirmed by the measurement of dehydrogenase activity, basal respiration, the numbers of culturable bacterial cells, and the ratio of culturable to total numbers of cells. Still, the denitrifying enzyme activity was very low in the anaerobic horizons of the AS soil, indicating the prevalence of microbes other than denitrifiers. We suspect that the microbial community originated with the genesis of AS soil and has been supported by the large stocks of accumulated carbon and mineral nitrogen in the C horizons. If these permanently water-saturated subsoils are exposed to oxygen and their microbial activity consequently increases, large carbon and nitrogen stocks are likely to be mobilised, resulting in increased emission of greenhouse gases. Additional studies of boreal AS soils are needed to assess their potential contribution to increases in greenhouse gas fluxes at the local, regional, and global scales.     

Biodiversity,carbon stocks and sequestration potential in aboveground biomass in smallholder farming systems of western Kenya

While Carbon (C) sequestration on farmlands may contribute to mitigate CO₂ concentrations in the atmosphere, greater agro-biodiversity may ensure longer term stability of C storage in fluctuating environments. This study was conducted in the highlands of western Kenya, a region with high potential for agroforestry, with the objectives of assessing current biodiversity and aboveground C stocks in perennial vegetation growing on farmland, and estimating C sequestration potential in aboveground C pools. Allometric models were developed to estimate aboveground biomass of trees and hedgerows, and an inventory of perennial vegetation was conducted in 35 farms in Vihiga and Siaya districts. Values of the Shannon index (H), used to evaluate biodiversity, ranged from 0.01 in woodlots through 0.4–0.6 in food crop plots, to 1.3–1.6 in homegardens. Eucalyptus saligna was the most frequent tree species found as individual trees (20%), in windrows (47%), and in woodlots (99%) in Vihiga and the most frequent in woodlots (96%) in Siaya. Trees represented the most important C pool in aboveground biomass of perennial plants growing on-farm, contributing to 81 and 55% of total aboveground farm C in Vihiga and Siaya, respectively, followed by hedgerows (13 and 39%, respectively) and permanent crop stands (5 and 6%, respectively). Most of the tree C was located in woodlots in Vihiga (61%) and in individual trees growing in or around food crop plots in Siaya (57%). The homegardens represented the second C pool in importance, with 25 and 33% of C stocks in Vihiga and Siaya, respectively. Considering the mean total aboveground C stocks observed, and taking the average farm sizes of Vihiga (0.6 ha) and Siaya (1.4 ha), an average farm would store 6.5 ± 0.1 Mg C farm^?1 in Vihiga and 12.4 ± 0.1 Mg C farm^?1 in Siaya. At both sites, the C sequestration potential in perennial aboveground biomass was estimated at ca. 16 Mg C ha^?1. With the current market price for carbon, the implementation of Clean Development Mechanism Afforestation/Reforestation (CDM A/R) projects seems unfeasible, due to the large number of small farms (between 140 and 300) necessary to achieve a critical land area able to compensate the concomitant minimum transaction costs. Higher financial compensation for C sequestration projects that encourage biodiversity would allow clearer win–win scenarios for smallholder farmers. Thus, a better valuation of ecosystem services should encourage C sequestration together with on-farm biodiversity when promoting CDM A/R projects.     

Fine tuning water quality regulations in agriculture to soil differences

Groundwater quality has been defined in terms of threshold values for nitrate (50 mg l⁻¹) and pesticides (0.1 μg l⁻¹ active substance). Variability in space and time, and cost and safety considerations have made it unattractive to verify water quality by repeated measurements. Proxy values have, therefore, been defined to characterise water quality. For nitrate, maximum allowable fertilisation rates have been specified and farmers have to apply the MINAS book-keeping system to keep track of their N-flows. For pesticides, listing of allowed pesticides functions as another proxy quality measure. Field tests and simulations on a Dutch farm demonstrated that water quality assessment using these proxy values does not correspond with direct assessment based on measurements and a comparison with the threshold values, which represent the true standard. A second problem is the generic character of the proxy methods, which do not reflect quite different nitrate and pesticide dynamics in different types of soil. These problems make the proxy approach quite problematic. We, therefore, propose the systematic introduction of information technology to be used for deriving soil-specific management practices that do not lead to an increase of the thresholds. Existing techniques for precision agriculture can be used, and the current registration of all parcels in The Netherlands in a geographical information system, including occurrence of different soil types, will be quite helpful. Such an information system on internet will allow better control than the current generic proxy systems and is likely to be quite motivating to farmers.     

Long-term impact of a gliricidia-maize intercropping system on carbon sequestration in southern Malawi

Tree/crop systems under agroforestry practice are capable of sequestering carbon (C) in the standing biomass and soil. Although studies have been conducted to understand soil organic C increases in some agroforestry technologies, little is known about C sequestered in simultaneous tree/crop intercropping systems. The main objective of this study was to determine the effect of agroforestry practice on C sequestration and CO₂-C efflux in a gliricidia-maize intercropping system. The experiment was conducted at an experimental site located at the Makoka Agricultural Research Station, in Malawi. The studies involved two field plots, 7-year (MZ21) and 10-year (MZ12), two production systems (sole-maize and gliricidia-maize simultaneous intercropping systems). A 7-year-old grass fallow (Grass-F) was also included. Gliricidia prunings were incorporated at each time of tree pruning in the gliricidia-maize. The amount of organic C recycled varied from 0.8 to 4.8 Mg C ha⁻¹ in gliricidia-maize and from 0.4 to 1.0 Mg C ha⁻¹ in sole-maize. In sole-maize, net decreases of soil carbon of 6 Mg C ha⁻¹ at MZ12 and 7 Mg C ha⁻¹ at MZ21 in the topsoil (0–20 cm) relative to the initial soil C were observed. After 10 years of continuous application of tree prunings C was sequestered in the topsoil (0–20 cm) in gliricidia-maize was 1.6 times more than in sole-maize. A total of 123–149 Mg C ha⁻¹ were sequestered in the soil (0–200 cm depth), through root turnover and pruning application in the gliricidia-maize system. Carbon dioxide evolution varied from 10 to 28 kg ha⁻¹ day⁻¹ in sole-maize and 23 to 83 kg ha⁻¹ day⁻¹ in gliricidia-maize. We concluded that gliricidia-maize intercropping system could sequester more C in the soil than sole-maize.     

Reconnecting crop and cattle farming to reduce nitrogen losses to river water of an intensive agricultural catchment (Seine basin,France): past,present and future

Nitrate and pesticide contamination of surface and groundwater has become a major problem in intensive farming regions in Europe, with nitrate concentrations reaching values above the standard defined in 2000 by the European Water Framework Directive. In the Seine basin, a major issue is the closure and abandonment of drinking-water wells, which force water managers and drinking-water producers to explore solutions for water resource protection. Organic farming has appeared as a credible alternative to conventional farming, and this study explores the potential of organic farming to reconcile agricultural production and water quality. On the basis of agricultural statistics, survey questionnaires and experimental data, the nitrogen soil surface balance (N-SSB) has been established at the scale of a small 104-km² catchment (The Orgeval sub-basin), representative of the intensive cash crop farming in the Seine basin. The N-surplus for arable land in specialized organic cash crop systems has been found to be half that of current conventional systems (15 kg N ha⁻¹ yr⁻¹ versus 30 kg N ha⁻¹ yr⁻¹, respectively). The N-yield in organic systems is 21% lower than in conventional systems, but total fertilization (mostly symbiotic N fixation) is also 26% lower. Whereas 2–3 years of forage legume (e.g., alfalfa) as a starter crop of the typical 7- to 10-year diversified rotation builds up N soil fertility and helps prevent weeds without pesticides, the existence of an outlet for this fodder production is a limiting factor for the economic sustainability and the environmental benefits of these farming systems. Therefore, we explored the possibility of a reconnection of livestock and crop farming systems in the Orgeval catchment, a traditional dairy farming and Brie cheese production region. We calculated the N-SSB for this type of a reconnected livestock and cropping system and found a value very close to the specialized organic cash crop system with full utilization of fodder production, leading to profitable animal production, essentially as milk in this farm design. This reconnected system is compared with the estimated situation in 1955 before separation of plant and livestock production. Furthermore, the N-SSB values were converted into infiltrating sub-root concentrations and used as a boundary condition to a biogeochemical model. Organic cropping and organic reconnected livestock cropping systems result in a 50% reduction of surface water nitrate concentrations, a surface water quality 20% better than that reconstructed for 1955, with an overall higher protein production.     

Dairy farm CH4 and N2O emissions,from one square metre to the full farm scale

The greenhouse gas emissions from agricultural systems contribute significantly to the national budgets for most countries in Europe. Measurement techniques that can identify and quantify emissions are essential in order to improve the selection process of emission reduction options and to enable quantification of the effect of such options. Fast box emission measurements and mobile plume measurements were used to evaluate greenhouse gas emissions from farm sites. The box measurement technique was used to evaluate emissions from farmyard manure and several other potential source areas within the farm. Significant (up to 250 g CH₄ m⁻² day⁻¹and 0.4 g N₂O m⁻² day⁻¹) emissions from ditches close to stables on the farm site were found.Plume emission measurements from individual manure storages were performed at three sites. For a manure storage with 1200 m³ dairy slurry in Wageningen emission factors of 11 ± 5 g CH₄ m⁻³ manure day⁻¹ and 14 ± 8 mg N₂O m⁻³ manure day⁻¹ were obtained in February 2002.Mobile plume measurements were carried out during 4 days at distances between 30 and 300 m downwind of 20 different farms. Total farm emissions levels ranged from 14 to 95 kg CH₄ day⁻¹ for these sites. Expressed as emission per animal the levels were 0.7 ± 0.4 kg CH₄ animal⁻¹ day⁻¹ for conventional farms. For three farms that used straw bedding for the animals1.4 ± 0.2 kg CH₄ animal⁻¹ day⁻¹ was obtained. These factors include both respired methane and emission from manure in the stable and the outside storages.For a subset of these farms the CH₄ emission was compared with monthly averaged model emission calculations using FarmGHG. This model calculates imports, exports and flows of all products through the internal chains on the farm using daily time steps. The fit of modelled versus measured data has a slope of 0.97 but r² = 0.27. Measurements and model emission estimates agree well on average, for large farms within 30%. For small farms the differences can be up to a factor of 3. CH₄ emissions during winter seem to be underestimated.     

Effectiveness of buffer strips in removing pollutants in runoff from a cultivated field in North-East Italy

Buffer strips are an efficient and economical way to reduce agricultural nonpoint source pollution. Local researches are necessary to gain information on buffer performance, with particular emphasis on narrow buffers. The effect of a 6 m buffer strip (BS) in reducing runoff, suspended solids and nutrients from a field growing maize, winter wheat and soybean was assessed in a field experiment conducted in North-East Italy during 1998–2001. The BS was composed of two rows of regularly alternating trees (Platanus hybrida Brot.) and shrubs (Viburnum opulus L.), with grass (Festuca arundinacea L.) in the inter-rows.The BS reduced total runoff by 78% compared to no-BS, in which cumulative runoff depth was 231 mm over 4 years. With no-BS runoff appeared to be influenced mostly by total rainfall, while with BS maximum rainfall intensity was more important. The filtering effect of the BS reduced total suspended solids (TSS), particularly after the second year, when the median yearly concentrations ranged from 0.28 to 0.99 mg L⁻¹ and were smaller than 0.14 mg L⁻¹, with no-BS and with BS respectively. The combination of lower concentrations and runoff volumes significantly reduced TSS losses from 6.9 to 0.4 t ha⁻¹ over the entire period.A tendency to increased concentrations of all forms of N (total, nitrate and ammonium) while passing through the BS was observed, but total N losses were reduced from 17.3 to 4.5 kg ha⁻¹ in terms of mass balance. On the contrary, P concentrations were unmodified (soluble P), or lowered (total P) by the BS, reducing total losses by about 80%. The effect on total P, composed mainly of sediment-bound forms, was related to particulate settling when passing through the BS.A numerical index (Eutrophic Load Index), integrating water quality and runoff volumes, was created to evaluate the eutrophication risk of runoff with or without the BS. It showed that the BS effect was mostly due to a reduction of runoff volumes rather than improving the overall water quality.     

Comparing carbon fluxes between different stages of secondary succession of a karst grassland

Abandonment of marginal agricultural areas with subsequent secondary succession is a widespread type of land use change in Mediterranean and mountain areas of Europe, leading to important environmental consequences such as change in the water balance, carbon cycling, and regional climate. Paired eddy flux measurement design with grassland site and tree/shrub encroached site has been set-up in the Slovenian Karst (submediterranean climate region) to investigate the effects of secondary succession on ecosystem carbon cycling. The invasion of woody plant species was found to significantly change carbon balance shifting annual NEE from source to an evident sink. According to one year of data succession site stored ?126 ± 14 g C m^?2 y^?1 while grassland site emitted 353 ± 72 g C m^?2 y^?1. In addition, the seasonal course of CO₂ exchange differed between both succession stages, which can be related to differences in phenology, i.e. activity of prevailing plant species, and modified environmental conditions within forest fragments of the invaded site. Negligible effect of instrument heating was observed which proves the Burba correction in our ecosystems unnecessary. Unexpectedly high CO₂ emissions and large disagreement with soil respiration especially on the grassland site in late autumn indicate additional sources of carbon which cannot be biologically processes, such as degassing of soil pores and caves after rain events.     

Linkages between land management activities and stream water quality in a border dyke-irrigated pastoral catchment

This paper describes key linkages between land management activities and stream water quality for a 5230 ha catchment used for intensive pastoral agriculture in southern New Zealand. Due to low annual rainfall and the wide coverage of soils with low available water-holding capacities, flood irrigation of the 2400 ha of flat land within the catchment is an important feature impacting on farm business profitability and stream health. Water quality variables and nutrient and sediment yield estimates are reported for a four-year period. This monitoring shows that some improvement in farm environmental performances would generally be desirable, with stream concentrations of nutrients (N and P), sediment and faecal bacteria regularly exceeding guidelines recommended for surface waters. Field measurements, farm management surveys and farm systems modelling have identified some land management practices that appear to be key sources of many of these pollutants. Border dyke irrigation runoff has a potentially large effect on a range of water quality parameters, due to both the excessive stream flows generated by over-watering and the entrainment of P, N and faecal bacteria in this flow as it passes from land to stream. Stock access to some of the remaining un-fenced lengths of the stream was also recognised as an important land management practice that needed to be addressed if some of the key catchment values identified by stakeholders, such as maintaining a healthy trout fishery and a stream suitable for recreational use, were to be protected. Assessments of the effectiveness and cost-effectiveness of a number of potential mitigation practices identified that managements which targeted reducing irrigation runoff (e.g. by installing bunds or using appropriate watering times) and fencing and planting riparian margins showed the greatest potential to meet these key values with least cost to farm businesses. Other farm practices were also identified that incurred nil or minimal cost while also delivering small or moderate benefits to stream water quality.     

Comparing intensive,extensified and organic grassland farming in southern Germany by process life cycle assessment

To reduce the environmental burden of agriculture, suitable methods to comprehend and assess the impact on natural resources are needed. One of the methods considered is the life cycle assessment (LCA) method, which was used to assess the environmental impacts of 18 grassland farms in three different farming intensities — intensive, extensified, and organic — in the Allgäu region in southern Germany. Extensified and organic compared with intensive farms could reduce negative effects in the abiotic impact categories of energy use, global warming potential (GWP) and ground water mainly by renouncing mineral nitrogen fertilizer. Energy consumption of intensive farms was 19.1 GJ ha⁻¹ and 2.7 GJ t⁻¹ milk, of extensified and organic farms 8.7 and 5.9 GJ ha⁻¹ along with 1.3 and 1.2 GJ t⁻¹ milk, respectively. Global warming potential was 9.4, 7.0 and 6.3 CO₂-equivalents ha⁻¹ and 1.3, 1.0 and 1.3 CO₂-equivalents t⁻¹ milk for the intensive, extensified and organic farms, respectively. Acidification calculated in SO₂-equivalents was high, but the extensified (119 kg SO₂ ha⁻¹) and the organic farms (107 kg SO₂ ha⁻¹) emit a lower amount compared with the intensive farms (136 kg SO₂ ha⁻¹). Eutrophication potential computed in PO₄-equivalents was higher for intensive (54.2 kg PO₄ ha⁻¹) compared with extensified (31.2 kg PO₄ ha⁻¹) and organic farms (13.5 kg PO₄ ha⁻¹). Farmgate balances for N (80.1, 31.4 and 31.1 kg ha⁻¹) and P (5.3, 4.5 and −2.3 kg ha⁻¹) for intensive, extensified and organic farms, respectively, indicate the different impacts on ground and surface water quality. Analysing the impact categories biodiversity, landscape image and animal husbandry, organic farms had clear advantages in the indicators number of grassland species, grazing cattle, layout of farmstead and herd management, but indices in these categories showed a wide range and are partly independent of the farming system.     

Monitoring of diffuse pollution from agriculture to support implementation of the WFD and the Nitrate Directive in Estonia

This paper discusses the monitoring network for diffuse pollution from agriculture in Estonia in the context of implementation of the EU Water Framework Directive (WFD) and the Nitrate Directive (ND). Seven surface water monitoring stations in agricultural catchments represent two out of three river basin districts designated in Estonia according to the WFD criteria. The national monitoring programme of ground water quality involves 516 stations of which about half were monitored in 2005. The monitoring sites cover all main ground water bodies in Estonia but are largely concentrated in the Nitrate Vulnerable Zone (NVZ). Analyses did not reveal any significant trends in total nitrogen (TN) and total phosphorus (TP) concentrations in studied rivers during the last 15 years except in one site. The ground water quality stabilised after decrease of nitrate concentrations in the early 1990s, especially in the south part of the NVZ, but even in 2005 the nitrate concentration exceeded 50 mg l⁻¹ in 42 out of 145 ground water samples in this region. The existing surface water quality monitoring network provides only restricted information to select between different management options when implementing action programmes for the NVZ and the river basin management plans (RBMP) under the WFD.     

Emissions of N2O and NH3, and nitrogen leaching from direct seeded rice under different tillage practices in central China

Tillage practices affect the fate of fertilizer nitrogen (N) through influencing transformations of N, but few studies have examined N₂O and NH₃ emissions, and N leaching from different rice tillage systems. Thus the objective of this study was to assess N₂O emission, NH₃ volatilization and N leaching from direct seeded rice in conventional tillage (CT) and no-tillage (NT) production systems in the subtropical region of China during the 2008 and 2009 rice growing seasons. Treatments were established following a split-plot design of a randomized complete block with tillage practices as the main plot and N fertilizer level as the sub-plot treatment, and there were four treatments: NT + no fertilizer (NT0), CT + no fertilizer (CT0), NT + compound fertilizer (NTC) and CT + compound fertilizer (CTC), respectively. Results showed that N fertilization significantly increased (p < 0.01) N₂O emissions, NH₃ volatilization and N leaching from rice fields in both years. In general, there was no significant difference in N₂O emissions and NH₃ volatilization between NT0 and CT0 in both years, while NTC had significantly higher (p < 0.05) N₂O emissions and NH₃ volatilization compared to CTC. Over the two rice growing seasons, NTC showed 32% and 47% higher N₂O emissions, and 29% and 52% higher NH₃ losses than CTC. Higher (p < 0.05) N₂O emissions from NTC than CTC were presumably due to higher soil organic C and greater denitrification. Total N and NO₃^? concentrations were higher (p < 0.05) in CTC than NTC, but larger volumes of percolation water in NTC than CTC resulted in no significant difference in leakage of total N and NO₃^?. Hence, application of N fertilizer in combination with NT appeared to be ineffective in reducing N losses from N fertilizer in paddy fields.     

Headwater streams: neglected ecosystems in the EU Water Framework Directive. Implications for nitrogen pollution control

The European Union Water Framework Directive (WFD) aims to achieve the “good status” of waters by 2015, through monitoring and control of human impacts on “bodies of surface water” (BSWs), discrete elements for quality diagnosis and management. Headwater streams, however, are frequently neglected as they are not usually recognised as BSW. This poses limitations for the management of river catchments, because anthropogenic impacts on headwaters can constrain the quality of downstream rivers. To illustrate this problem, we compared nitrate levels and land use pressures in a small agricultural catchment with those recorded in the catchment in which it is embedded (Ega), and in the Ebro River Basin (NE Spain) comprising both. Agriculture greatly influenced water nitrate concentration, regardless of the size of the catchments: R² = 0.91 for headwater catchments (0.1–7.3 km²), and R² = 0.82 for Ebro tributary catchments (223–3113 km²). Moreover, nitrate concentration in the outlet of a non-BSW small river catchment was similar to that of the greater downstream BSW rivers. These results are of interest since, despite representing 76% of the length of the Ega catchment hydrographical network, only 3.1% of the length of the headwater streams has been identified as BSWs. Human activities affecting headwater streams should therefore be considered if the 2015 objective of the WFD is to be achieved.