Dealing with double-counting in tiered hybrid life-cycle inventories: a few comments

Strømman et al. (2009) developed a method for dealing with double-counting in tiered hybrid LCA. Their algorithms identify overlaps of physical and monetary flows in the process and input–output parts of their hybrid data base, and then remove double-counted monetary flows in the input–output system using structural path analysis. Strømman's adjustment criterion is that the set of input–output paths to be removed should have the same monetary value as the process system flow that it overlaps with. I comment on Strømman's methods with respect to the accuracy of the correspondence between process and input–output systems. I argue that the set of double-counted paths to be removed from the input–output system is better selected on the basis of sector definitions than monetary value.     

A new maniraptoran dinosaur from China with long feathers on the metatarsus

The unusual presence of long pennaceous feathers on the feet of basal dromaeosaurid dinosaurs has recently been presented as strong evidence in support of the arboreal–gliding hypothesis for the origin of bird flight, but it could be a unique feature of dromaeosaurids and thus irrelevant to the theropod–bird transition. Here, we report a new eumaniraptoran theropod from China, with avian affinities, which also has long pennaceous feathers on its feet. This suggests that such morphology might represent a primitive adaptation close to the theropod–bird transition. The long metatarsus feathers are likely primitive for Eumaniraptora and might have played an important role in the origin of avian flight.Electronic Supplementary Material  Supplementary material is available for this article at     

Chemical and spectral characterization of soil phosphorus under three land uses from an Andic Palehumult in West Cameroon

Phosphorus (P) is one of the main limiting plant nutrients in most tropical soils. Acquiring quantitative information on soil P status is essential for evaluating its sustainable management in agroecosystems. The objective of this study was to evaluate how land-use shifts from semi-permanent food crop systems (CF) to plantations of tea (Camellia sinensis) (TP) and Eucalyptus grandis (EP) impact on both organic and inorganic P species. Determination of phosphorus status combined a P sequential fractionation procedure and ³¹P nuclear magnetic resonance (NMR) spectroscopy. Sequentially extracted pools included available P by 0.5 M NaHCO₃, Al/Fe-P by 0.1 M NaOH, Ca-P by 0.5 M HCl and residual P by 0.5 M H₂SO₄ after ignition at 550 °C. Soil total P (STP) varied significantly across land uses (P<0.05) with the lowest mean value (1025.6±23.1 mg kg⁻¹) occurring under CF and the highest (1698.0±86.1 mg kg⁻¹) under TP. The largest P-pools were NaOH-P (47–51% of total soil P) and H₂SO₄-P (25–32%). NaHCO₃-P_i under fertilized land uses (CF and TP) was greater than 12 mg kg⁻¹ indicating that these systems were sustainable. Unfertilized EP was P-deficient, probably as the result of organic-matter accretion and subsequent P immobilization in organic forms. ³¹P NMR revealed that 88–89% of P compounds in NaOH extract were organic with monoester-P accounting for 59.1–60.8%. This was followed by diester-P (9.8–12.4%), teochoic acid (8.4–10.1%), orthophosphate (8.8–9.7%), unknown compounds (7.4–8.4%), pyrophosphate (1.1–4.6%) and phosphonate (0–1.3%). EP had higher diester-P and no phosphonate compound whereas CF had substantial amount of pyrophosphate (4.6%) and less orthophosphate and teochoic acid. These results indicate that these last P compounds are easily mineralizable P forms participating actively in plant P nutrition.     

Ant–plant–herbivore interactions in the neotropical cerrado savanna

The Brazilian cerrado savanna covers nearly 2 million km² and has a high incidence on foliage of various liquid food sources such as extrafloral nectar and insect exudates. These liquid rewards generate intense ant activity on cerrado foliage, making ant–plant–herbivore interactions especially prevalent in this biome. We present data on the distribution and abundance of extrafloral nectaries in the woody flora of cerrado communities and in the flora of other habitats worldwide, and stress the relevance of liquid food sources (including hemipteran honeydew) for the ant fauna. Consumption by ants of plant and insect exudates significantly affects the activity of the associated herbivores of cerrado plant species, with varying impacts on the reproductive output of the plants. Experiments with an ant–plant–butterfly system unequivocally demonstrate that the behavior of both immature and adult lepidopterans is closely related to the use of a risky host plant, where intensive visitation by ants can have a severe impact on caterpillar survival. We discuss recent evidence suggesting that the occurrence of liquid rewards on leaves plays a key role in mediating the foraging ecology of foliage-dwelling ants, and that facultative ant–plant mutualisms are important in structuring the community of canopy arthropods. Ant-mediated effects on cerrado herbivore communities can be revealed by experiments performed on wide spatial scales, including many environmental factors such as soil fertility and vegetation structure. We also present some research questions that could be rewarding to investigate in this major neotropical savanna.     

Influence of no-tillage on the distribution and lability of phosphorus in Finnish clay soils

No-tillage (NT) is a method adopted to reduce erosion and particulate phosphorus (P) load from arable land to watercourses. However, it has been found to increase the loss of dissolved P with surface runoff, but the reasons for that have rarely been examined in detail. The objective of the present study was to determine the chemical factors explaining this response by investigating the impact of NT on the type and distribution of P reserves as well as on organic carbon (C) in the 0–35 cm topsoil layer of clay soil profiles (Vertic Cambisols). Soil samples were taken from two experimental fields (Jokioinen and Aurajoki) at 0–5, 5–20 and 20–35 cm depths in conventionally tilled (CT) and non-tilled (for 4–5 years) plots. The plots had been cultivated and fertilized according to the common field practices in Finland (15–18 kg P and 100–128 kg N ha⁻¹ year⁻¹).Inorganic and organic P reserves characterized by a modified Chang and Jackson fractionation procedure were not significantly affected by the cultivation methods. However, in the uppermost soil layer (0–5 cm) in NT of the Jokioinen field, the labile P determined by water extraction (P_w) increased significantly, whereas the increase in P extracted with acid ammonium acetate (P_AAC) remained statistically insignificant. The increase in labile P coincided with a significant increase in organic carbon (C), which supports the theory that competition between organic anions and phosphate for the same sorption sites on oxide surfaces will enhance the lability of soil P. In the Aurajoki field with distinct soil cracking, P_w and P_AAC were not affected by NT in the uppermost soil layer, but they increased in the deepest soil layer (20–35 cm) concomitantly with an increase in Al-bound P and organic C. However, the increases were not statistically significant. In both fields, soil acidification due to the repeated application of N fertilizers at a shallow soil depth as well as the accumulation of organic C lowered pH of the uppermost soil layer in NT compared to the deeper soil layers. The results indicated that even short-term NT can increase the labile P in clay soil. However, further studies are needed to assess the long-term changes in lability of surface soil P and, consequently, the possible need for readjustment of the fertilization level in NT.     

Enhanced adaptability of Sesbania rostrata to Pb/Zn tailings via stem nodulation

Sesbania rostrata is wellknown for its stem nodulation, but the roles of stem nodulation in root nodulation and adaptation of S. rostrata to Pb/Zn-enriched tailings environment has been poorly understood. We investigated the e ects of inoculating (with stem nodule treatment) and non-inoculating (without stem nodule treatment) Azorhizobium caulinodans on the growth, root nodulation, and N fixation of S. rostrata grown on three di erent types of soil substrata: Pb/Zn tailings, garden soil amended tailings, and garden soil. The results showed that plant height, stem basal diameter, biomass, chlorophyll content, nitrogen content and N-accumulation per plant were 2.3%–4.9%, 2.2%–7.7%, 27.8%–72.2%, 17.1%–23.5%, 12.3%–34.2%, and 43.1%–131.2%, respectively, higher in treatments with stem nodule than those without stem nodule for the same soil substrate. With respect to soil substrata, all measurements had consistently higher values in tailings than in amended tailings and garden soil, indicating that the poorer the soil condition, the greater the contribution of stem nodule. In contrast, the number and fresh weight of root nodules on plants without stem nodule were 6.9–11.6 times and 5.8–29.0 times higher than those with stem nodule, respectively, especially with respect to the plants grew on Pb/Zn tailings. In general, stem nodulation favored plant growth and nitrogen fixation of S. rostrata, but suppressed root nodulation. With the ability of stem and root nodulation, S. rostrata can be used as a pioneer plant species for remediation of Pb/Zn tailings.     

Increasing land pressure in East Africa: The changing role of cassava and consequences for sustainability of farming systems

Increasing land pressure during the past three to four decades has transformed farming systems in the mid-altitude zone of East Africa. Traditional millet-, cotton-, sugarcane- and/or banana-based farming systems with an important fallow and/or grazing component have evolved into continuously cultivated cassava or cassava/maize-based systems. Within three to four decades, cassava cultivation increased from 1–11 to 16–55% of cropped fields in our six study sites. Declining soil fertility, and not labour or food shortage, was apparently the primary trigger for this transformation. The land use changes have increased nutrient offtakes and reduced nutrient recycling rates. Cassava and maize now account for 50–90% of nutrient removal. Whereas single-season fallows were the most important source of nutrient recycling on cropped fields in the past, currently cassava litterfall and maize stover contribute roughly 70% of nutrient recycling, with 50–70% of N, P and K recycled in cassava litterfall. This may explain why many farmers reason that cassava ‘rests’ the soil. With increasing land use pressure farmers progressively use cassava as an ‘imitation fallow’ throughout their farm. Farmers increasingly target cassava to poor fertility fields characterized by low pH and available P. High cassava intensities are nonetheless maintained on more fertile fields, probably to guarantee regeneration of soil fertility on all fields. Once cassava is targeted to poor fertility soils, farmers have run out of low-input management options and need to intensify management to maintain system productivity. As cassava is now used by more farmers and on a larger acreage than fallowing in the studied farming systems, cassava cropping could perhaps serve as an excellent entry point to strengthen system sustainability.     

Optimum autonomous photovoltaic solution for the Greek islands on the basisof energy pay-back analysis

Although autonomous photovoltaic (PV) systems are identified as renewable energy technologies able to satisfy the electrification needs of remote consumers, they are strongly accused of their life-cycle energy requirements. To support the specific systems' sustainable character one should be able to ensure minimum period of energy pay-back. In this context, an optimum sizing methodology is developed for stand-alone PV-battery systems in order to obtain configurations of minimum energy content. The proposed methodology is applied to three representative islands across the Greek territory and the results obtained are favourably compared with the up to now – commonly used – diesel-electric generator solution.     

Acid deposition critical loads modeling for the simulation of sulfur exceedance and reduction in Guangdong, China

The current acid deposition critical loads in Guangdong, China were calculated using the PROFILE model with a 3 km × 3 km resolution. Calculations were carried out for critical loads of potential acidity, actual acidity, sulfur and nitrogen, with values in extents of 0–3.5, 0–14.0, 0–26.0 and 0–3.5 kmol/(hm2·year), respectively. These values were comparable to previously reported results and reflected the influences of vegetation and soil characteristics on the soil acid buffering capacity. Simulations of S...     

The San Francisco Bay-Delta: A failure of decision-making capacity

The paper reviews the history of Bay-Delta decision-making in California in order to highlight the continuity between what happened with CALFED and what happened in the preceding decades since water project deliveries began in 1949. Throughout this period, there has been intense conflict about whether and how to transfer water from the Bay-Delta to users elsewhere—a conflict marked by a fundamental opposition of interests among stakeholders. We document how the State of California has failed to organize itself effectively to resolve this conflict and make a decision on how to manage the Delta. The strategy consistently adopted by the State was to encourage the main parties – agricultural and urban water diverters, and fisheries and other instream-protection interests – to work out a solution among themselves, rather than imposing one externally. However, economic theory suggests that a bargaining solution is unlikely to exist because of the extreme opposition of interest among the parties. The Bay-Delta history amply confirms this theoretical prediction. Thus, the State's strategy of relying on voluntary agreement to resolve the issue is fundamentally misconceived and is, at some level, an abdication of its responsibility.     

Reside0ntial solar water heating as a potential Clean Development Mechanism project: A South African case study

A community-based Clean Development Mechanism (CDM) project – asolar water heating project in a low-income community in South Africa –is analysed to illustrate the methodological and policy challenges that faceimplementation of the Kyoto Protocol to the United Nations FrameworkConvention on Climate Change. We evaluate four baseline options, andthree potential CDM interventions. The emissions reductions range from –670 to +5 929 Mg CO₂ per year, with all option but oneshowing positive emission reductions. Using metered solar water heatingwith liquefied petroleum gas back-up as the CDM intervention, and electricstorage geysers as the baseline, the annual emissions reductions are 5686 Mg CO₂. The cost-effectiveness from the national perspective,which is the incremental life cycle costs divided by the lifetime emissionsreductions, is –$18 per Mg CO₂ From the perspective of theCDM investor, however, the cost-effectiveness is $5.2 per mgCO₂, assuming that the investor receives all of the carbon credits forproviding the incremental capital investment. From our analysis, weconclude that using the current technology (kerosene stoves) as a baselineis probably not appropriate because it does not reflect likely future trendsand also penalises the community for their poverty and current lack ofinfrastructure. We also highlight the importance of credit sharing, and howit affects the cost-effectiveness of the project from the CDM investor'sperspective. The lessons from this analysis are important for the currentinternational policy debate on how to preferentially treat small-scale CDMprojects.     

Wood waste management practices and strategies to increase sustainability standards in the Australian wooden furniture manufacturing sector

This study assesses the wood waste generation and its associated true cost which Australian wooden furniture manufacturing companies encounter and are exposed to. The assessment aims to create awareness and facilitate understanding within the wooden furniture manufacturing industry about how much wood is wasted into the production process and how this is translated in financial terms, how wood waste can be reduced, what can and can't be recycled and what services are available to assist businesses with recycling. The results indicate that during processing, 7% up to 40–50% of the annual supply of wooden raw material become residues. The costs connected directly to these wastes represent 2–8% of the turnover.     

Agricultural intensification within agroforestry: The case of coffee and wood products

Compared to the environmental and conservation value as refuges for biodiversity, less is known about the social and economic value of shaded coffee systems. The agroforestry system can serve as a source of non-coffee products for diverse purposes. This study focuses on the role of shade trees in smallholder coffee farms, examining the wood products derived from the shaded coffee system. Data presented from surveys with 185 growers in Peru and 153 growers in Guatemala show that the consumption and sale of all non-coffee products account for a fifth to a third of the total value realized from the agroforestry system. Fuelwood and construction materials account for much of this value. Differences seen between countries can be traced to agricultural intensification – the degree to which the coffee agroforestry system is “technified” (i.e., managed with a reduced shade tree cover and diversity, high-yielding cultivars, agrochemical inputs, etc.) – as well as the relative demand for wood resources and farmers’ access to natural forest systems.     

Carbon values,reforestation, and `perverse' incentives under the Kyoto protocol: An empirical analysis

Economic incentives for sequestering atmospheric carbon dioxide (CO₂) in forests may be an effective way to meet greenhouse gas (GHG) reduction commitments under the Kyoto Protocol (KP). But concerns have been raised that the KP may create unintended incentives to excessively harvest existing forests if regenerated forests qualify for carbon (C) credits under the reforestation provision of Article 3.3. This paper combines an analytical model of the optimal forest rotation with both timber and C as priced outputs with data on timber and C growth and yield to different forest settings in the U.S. C prices of $50 per megagram (Mg) – the highest price evaluated– can considerably lengthen forest rotations (40 years or more), raise forest land values (as much as $1,900 per hectare), and sequester more C in the long run (up to 60 percent per acre), relative to the base case of no C compensation. However, if C payments are made for the regenerated stand only, in some situations, it is optimal to immediately harvest an otherwise premature stand at C prices as low as $20/Mg. The strength of perverse incentives to accelerate harvesting of existing forest varies by forest type, region, C price level, and institutional factors relevant to the compensation system. If C compensation were extended to existing stands, as may be possible under Article 3.4 of the KP, the perverse incentives for prematurely harvesting existing stands would not exist.     

Model evaluation of different mechanisms driving freeze–thaw N2O emissions

N₂O emissions from soil contribute significantly to global warming. Pulse emissions of N₂O from soils during freeze-thawing were recently recognized as important atmospheric sources. In this modelling study we explore three different hypotheses for explaining freeze–thaw related N₂O emissions: (1) soil frost or snow cover may reduce gas diffusion and create anaerobic conditions that stimulate N₂O production via denitrification, (2) microbes that die of frost deliver easy decomposable organic carbon and nitrogen to the soil, which stimulates microbial growth and vigorous N₂O production during freeze–thaw, and (3) the enzyme nitrous oxide reductase, which is responsible for the reduction of N₂O to N₂ during denitrification, is more sensitive to low temperatures than other enzymes, so that N₂O becomes the dominating end-product of denitrification at low temperatures. These hypotheses were tested with a biogeochemical model that combines hydrology and physics calculations with a newly developed, parameter-poor biochemistry module. The model was first calibrated with field datasets on soil–atmosphere fluxes of N₂O, NO and CO₂ and soil NO₃ and NH₄ concentrations that were measured in a spruce forest in Southeast Germany in the years 1994–1997. Subsequently, additional model mechanisms were implemented that allow the model to describe the outlined mechanisms potentially driving freeze–thaw N₂O fluxes. After each implementation the model was recalibrated. We were able to mimic dimension and timing of high N₂O emissions when either one of the first two hypotheses were assumed, but found no confirmation for the third. The best model fit was achieved by combining hypothesis one and two, indicating that freeze–thaw N₂O emissions are not mono-causal.     

Phosphorus and nitrogen in soil, plants, and overland flow from sheep-grazed pastures fertilized with different rates of superphosphate

Eutrophication of waterways through delivery of phosphorus (P) and nitrogen (N) from farmland is a problem in many countries. Loss of nutrients from grazed grassland via overland flow is well demonstrated, but the sources of these nutrients and the processes controlling their mobilization into water are not well understood. Much of the nutrient loss in overland flow from grazed pastures may be due to generally increased fertility of the soil–plant system (i.e. background or ‘systematic’ nutrient loss) rather than to immediate loss after fertilizer application [Nash, D., Clemow, L., Hannah, M., Barlow, K., Gangaiya, P., 2005. Modelling phosphorus exports from rain-fed and irrigated pastures in southern Australia. Aust. J. Soil Res. 43, 745–755]. The main aim of this study was to measure the effects of long-term (25 years) superphosphate (Ca(H₂PO₄)₂ + 2CaSO₄) fertilizer application (0–23 kg/(ha year)) on P and N in soil, plants, and potential background P and N movement in overland flow (generated using a rainfall simulator) from sheep-grazed pastures in southern Australia. Measurements were taken in autumn, under dry soil conditions, and in winter, under wet soil conditions, 12 and 15 months after the last fertilizer applications, respectively. Superphosphate application caused a strong increase in plant P, soil total P, Olsen P, and Colwell P; and a weaker increase in plant N, soil total N, and inorganic N (ammonium and nitrate). Soil P and N were concentrated in the surface 25 mm of soil. Soil water-extractable P, calcium chloride-extractable P, and calcium chloride organic P were in general only poorly associated with fertilizer application. The concentration of P and, to a lesser extent, the concentration of N in overland flow increased with increasing fertilizer application and showed strong seasonal differences (0.06–0.77 mg P/L and 0.6–5.5 mg N/L in autumn; 0.04–0.20 mg P/L and 0.4–1.7 mg N/L in winter). The P in overland flow was predominantly dissolved reactive P in autumn and particulate P in winter. The N in overland flow contained significant proportions of dissolved organic N, dissolved inorganic N (ammonium and nitrate), and particulate N. The concentrations of P and N in overland flow usually exceeded State water quality targets (<0.04 mg P/L and <0.90 mg N/L), suggesting that background losses of nutrients from these pasture systems could contribute to the eutrophication of waterways.     

Managing erosion and water quality in agricultural watersheds by small detention ponds

Terrace-contouring systems with on-site water detention cannot be installed in areas of complex topography, small parceling and multi-blade moldboard plow use. However, field borders at the downslope end may be raised at the deepest part where runoff overtops to create detention ponds, which can be drained by subsurface tile outlets and act similar to terrace-contouring systems. Four of such detention ponds were monitored over 8 years. Monitored effects included the prevention of linear erosion down slope, the sediment trapping from upslope, the enrichment of major nutrients in the trapped and delivered sediments, the amount of runoff retained temporarily, the amount of runoff reduced by infiltration, the decrease in peak runoff rate and the decrease in peak concentrations of agrochemicals due to the mixing of different volumes of water within the detention ponds. The detention ponds had a volume of 30–260 m³ ha⁻¹ and trapped 54–85% of the incoming sediment, which was insignificantly to slightly depleted (5–25%) in organic carbon, phosphorus, nitrogen and clay as compared to the eroding topsoil, while the delivered sediment was strongly enriched (+70–270%) but part of this enrichment already resulted from the enrichment of soil loss. The detention ponds temporarily stored 200–500 m³ of runoff. A failure was never experienced. Due to the siltation of the pond bottom, the short filled time (1–5 days) and the small water covered area, infiltration and evaporation reduced runoff by less than 10% for large events. Peak runoff during heavy rains was lowered by a factor of three. Peak concentrations of agrochemicals (Terbutylazin) were lowered by a factor of two. The detention ponds created by raising the downslope field borders at the pour point efficiently reduced adverse erosion effects downslope the eroding site. They are cheap and can easily be created with on-farm machinery. Their efficiency is improved where they are combined with an on-site erosion control like mulch tillage because sediment and runoff input are reduced. Ponds had to be dredged only after the first year when on-site erosion control was not fully effective.     

Environmental cross-compliance mitigates nitrogen and phosphorus pollution from Swiss agriculture

In 1993 the Swiss agricultural policy was revised with – amongst other goals – the objective of improving the environmental performance of agriculture. A voluntary agri-environmental scheme to promote integrated production (IP) was introduced. In 1999 the IP standards were integrated in cross compliance requirements and termed Proof of Ecological Performance (PEP). We evaluated the effectiveness of this policy in terms of reducing diffuse nitrogen (N) and phosphorus (P) pollution of ground and surface water. We combined monitoring schemes covering the reference period from before the introduction of IP/PEP (1990–1992) with the evaluation of cause/effect relationships in selected case-study areas. The evaluation showed an overall reduction of diffuse N and P pollution from agriculture even though some goals were not reached. Nitrate leaching declined, but only a 3–4 mg L⁻¹ reduction was observed rather than the intended decrease of 5 mg L⁻¹. The P pollution of surface waters from agriculture decreased by only 10–30% instead of 50%. The intended reduction of the nitrogen surplus of Swiss agriculture by 33% was not attained, but the P surplus of Swiss agriculture was more than halved. IP/PEP practices that improved N and P management included reduced N and P fertiliser inputs and pig and poultry feedstuffs with reduced N and P contents, both of which are a consequence of the requirement of equilibrated farm nutrient balances, as well as increased use of cover cropping and of conservation tillage systems.     

Crop residue removal and fertilizer N: Effects on soil organic carbon in a long-term crop rotation experiment on a Udic Boroll

Biofuels can be produced by converting cellulose in crop residues to ethanol. This has recently been viewed as a potential supplement to non-renewable energy sources, especially in the Americas. A 50-yr field experiment was analyzed to determine the influence of (i) removing approximately 22% of the above-ground wheat (Triticum aestivum L.) residue each crop year, and (ii) N and P fertilization on soil carbon (C) in the top 15 cm depth of a fallow–wheat–wheat (F–W–W) rotation. The study was conducted from 1958 to 2007 on a clay soil, at Indian Head in sub-humid southeast Saskatchewan, Canada. Soil C concentrations and bulk densities were measured in the 0–7.5 and 7.5–15 cm depths in 1987, 1996 and 2007 and soil C changes were related to C inputs estimated from straw and root yields calculated from regressions relating these to grain yields. Two soil organic matter models [the Campbell model and the Introductory Carbon Balance Model (ICBM)] were also used to simulate and predict the effects of the treatments on soil C change over time, and to estimate likely soil C change if 50% or 95% of above-ground residues were harvested each crop year. Crop residue removal reduced cumulative C inputs from straw and roots over the 50-yr experiment by only 13%, and this did not significantly (P > 0.05) reduce soil C throughout the experiment duration. However, after 50 yr of applying N fertilizer at recommended rates, soil C increased significantly by about 3 Mg ha⁻¹ compared to the non-fertilized treatment. The simulated effect of removing 50% and 95% of the above-ground residues suggested that removing 50% of the straw would likely have a detectable effect on the soil C, while removing 95% of the straw certainly would. Measurements and model simulations suggest that adoption of no-tillage without proper fertilization will not increase soil C. Although it appears that a modest amount of residue may be safely removed from these Udic Borolls (Black Chernozems) without a measurable effect on soil C, this would only be feasible if accompanied by appropriate fertility management.     

Exploring diversity in soil fertility management of smallholder farms in western Kenya: I. Heterogeneity at region and farm scale

The processes of nutrient depletion and soil degradation that limit productivity of smallholder African farms are spatially heterogeneous. Causes of variability in soil fertility management at different scales of analysis are both biophysical and socio-economic. Such heterogeneity is categorised in this study, which quantifies its impact on nutrient flows and soil fertility status at region and farm scales, as a first step in identifying spatial and temporal niches for targeting of soil fertility management strategies and technologies. Transects for soil profile observation, participatory rural appraisal techniques and classical soil sampling and chemical analysis were sampled across 60 farms in three sub-locations (Emuhaia, Shinyalu, Aludeka), which together represent much of the variability found in the highlands of western Kenya. Five representative farm types were identified using socio-economic information and considering production activities, household objectives and the main constraints faced by farmers. Soil fertility management and nutrient resource flows were studied for each farm type and related to differences in soil fertility status at farm scale. Farm types 1 and 2 were the wealthiest; the former relied on off-farm income and farmed small pieces of land (0.6–1.1 ha) while the latter farmed relatively large land areas (1.6–3.8 ha) mainly with cash crops. The poorest farm type 5 also farmed small pieces of land (0.4–1.0 ha) but relied on low wages derived from working for wealthier farmers. Both farm types 1 and 5 relied on off-farm earnings and sold the least amounts of farm produce to the market, though the magnitude of their cash, labour and nutrient flows was contrasting. Farms of types 3 and 4 were intermediate in size and wealth, and represented different crop production strategies for self-consumption and the market. Average grain yields fluctuated around 1 t ha⁻¹ year⁻¹ for all farm types and sub-locations. Grain production by farms of types 4 and 5 was much below annual family requirements, estimated at 170 kg person⁻¹ year⁻¹. Household wealth and production orientation affected the pattern of resource flow at farm scale. In the land-constrained farms of type 1, mineral fertilisers were often used more intensively (ca. 50 kg ha⁻¹), though with varying application rates (14–92 kg ha⁻¹). The use of animal manure in such small farms (e.g. 2.2 t year⁻¹) represented intensities of use of up to 8 t ha⁻¹, and a net accumulation of C and macronutrients brought into the farm by livestock. In farms of type 5, intensities of use of mineral and organic fertilisers ranged between 0–12 kg ha⁻¹ and 0–0.5 t ha⁻¹, respectively. A consistent trend of decreasing input use from farm types 1–5 was generally observed, but nutrient resources and land management practices (e.g. fallow) differed enormously between sub-locations. Inputs of nutrients were almost nil in Aludeka farms. Both inherent soil properties and management explained the variability found in soil fertility status. Texture explained the variation observed in soil C and related total N between sub-locations, whereas P availability varied mainly between farm types as affected by input use.