Effect of sieving on ex-situ soil respiration of soils from three land use types

This study aims to investigate the effect of sieving on ex situ soil respiration (CO2 flux) measurements from different land use types. We collected soils (0–10 cm) from arable, grassland and woodland sites, allocated them to either sieved (4-mm mesh, freshly sieved) or intact core treatments and incubated them in gas-tight jars for 40 days at 10 °C. Headspace gas was collected on days 1, 3, 17, 24, 31 and 38 and CO2 analysed. Our results showed that sieving (4 mm) did not significantly influence soil respiration measurements, probably because micro aggregates (< 0.25 mm) remain intact after sieving. However, soils collected from grassland soil released more CO2 compared with those collected from woodland and arable soils, irrespective of sieving treatments. The higher CO2 from grassland soil compared with woodland and arable soils was attributed to the differences in the water holding capacity and the quantity and stoichiometry of the organic matter between the three soils. We conclude that soils sieved prior to ex situ respiration experiments provide realistic respiration measurements. This finding lends support to soil scientists planning a sampling strategy that better represents the inhomogeneity of field conditions by pooling, homogenising and sieving samples, without fear of obtaining unrepresentative CO2 flux measurements caused by the disruption of soil architecture

Assessment of carbon in woody plants and soil across a vineyard-woodland landscape

<p>Abstract</p> <p>Background</p> <p>Quantification of ecosystem services, such as carbon (C) storage, can demonstrate the benefits of managing for both production and habitat conservation in agricultural landscapes. In this study, we evaluated C stocks and woody plant diversity across vineyard blocks and adjoining woodland ecosystems (wildlands) for an organic vineyard in northern California. Carbon was measured in soil from 44 one m deep pits, and in aboveground woody biomass from 93 vegetation plots. These data were combined with physical landscape variables to model C stocks using a geographic information system and multivariate linear regression.</p> <p>Results</p> <p>Field data showed wildlands to be heterogeneous in both C stocks and woody tree diversity, reflecting the mosaic of several different vegetation types, and storing on average 36.8 Mg C/ha in aboveground woody biomass and 89.3 Mg C/ha in soil. Not surprisingly, vineyard blocks showed less variation in above- and belowground C, with an average of 3.0 and 84.1 Mg C/ha, respectively.</p> <p>Conclusions</p> <p>This research demonstrates that vineyards managed with practices that conserve some fraction of adjoining wildlands yield benefits for increasing overall C stocks and species and habitat diversity in integrated agricultural landscapes. For such complex landscapes, high resolution spatial modeling is challenging and requires accurate characterization of the landscape by vegetation type, physical structure, sufficient sampling, and allometric equations that relate tree species to each landscape. Geographic information systems and remote sensing techniques are useful for integrating the above variables into an analysis platform to estimate C stocks in these working landscapes, thereby helping land managers qualify for greenhouse gas mitigation credits. Carbon policy in California, however, shows a lack of focus on C stocks compared to emissions, and on agriculture compared to other sectors. Correcting these policy shortcomings could create incentives for ecosystem service provision, including C storage, as well as encourage better farm stewardship and habitat conservation.</p

Quality of groundwater and surface water in the Farming with a Future project, 2002

In Farming with a Future (FwF) farmers, together with extension officers and researchers, work towards sustainable production systems for arable crops, open air vegetables, flower bulbs and ornamental trees. Systematic measurements of water quality on the participating farms are conducted by RIVM; for the first time in 2002. The results of these measurements are presented and discussed in this report. Special attention is paid to the concentration of several forms of nitrogen (N) and phosphorous (P), and the relationships with land use and the physical environment. The groundwater of 15 of the 37 farms investigated presented nitrate concentrations (farm averages) below the boundary value of 50 mg/l (as NO3). Groundwater of the farms with arable crops on clay soils and of those with flower bulbs presented the lowest nitrate concentrations as compared to groundwater of the other farm sectors. The highest concentrations were found in groundwater of farms with open air vegetables, followed by the farms with ornamental trees. These differences are partly explained by differences in the physical environment. Farms on 'wet' soils, including all flower bulb farms and arable farms on clay, present lower concentrations than farms on naturally well-drained soils with a deep groundwater table. However, when physical environments appear to be comparable (sandy soils), farms with open air vegetables generally present higher groundwater nitrate concentrations than farms with arable crops. With respect to groundwater P-concentrations, among the participating farms, the ones with flower bulbs clearly present the highest values, (average farm average total-P = 7,4 mg/l), followed by those with arable crops on clay soils (average 0,61 mg/l) and a few farms with arable crops on sandy soils. The most important factors determining the high groundwater P-concentrations on the farms with flower bulbs seem to be the small phosphate retention capacity of the sandy dune soils where flower bulbs are produced; heavy applications of manure and fertilisers (especially in the past); the shallow groundwater level and the practice of deep tillage. Ditch water samples were taken on 5 farms with arable crops on clay and 3 farms with flower bulbs. In all cases, farm average total-N concentrations exceeded the FwF goal for surface water (2,2 mg/l). With respect to total-P, farm average concentrations where within the FwF goal (0,15 mg/l) on 3 of the farms with arable crops on clay, but exceeded this goal on all flower bulb farms investigated. It is questioned however, to which extent the FwF goals for surface water may be applied to each farm individually. Differences between the quality of groundwater, drain water and ditch water seem to be primarily related to the period of sampling, as well as to the residence time of the water in the soil.In Telen met Toekomst (TmT) werken agrarische ondernemers, samen met adviseurs en onderzoekers, aan duurzame bedrijfssystemen voor akkerbouw, vollegrondsgroenteteelt, bloembollen en boomteelt. In 2002 heeft het RIVM voor het eerst systematisch waterkwaliteitsmetingen verricht op de deelnemende bedrijven. De resultaten van deze metingen worden in dit rapport gepresenteerd en besproken. Hierbij wordt vooral gekeken naar de concentraties van verschillende vormen van stikstof en fosfaat en de verbanden met landgebruik en omgevingsfactoren. De bedrijfsgemiddelde nitraatconcentratie in het grondwater (of bodemvocht) was op 15 van de 37 onderzochte bedrijven lager dan de grenswaarde van 50 mg/l (als NO3). Het grondwater bij de akkerbouwers-op-klei en de bollentelers vertoont de laagste nitraatconcentraties in vergelijking met de andere sectoren. De volle-gronds-groente-telers springen er uit met de hoogste waarden, gevolgd door de boom-telers. Deze verschillen kunnen deels verklaard worden door omgevingsspecifieke factoren. Bedrijven op 'natte' gronden, waaronder alle bollentelers en akkerbouwers-op-klei, vertonen lagere concentraties dan bedrijven op van nature goedgedraineerde gronden met een diepe grondwaterstand. Echter, ook onder ogenschijnlijk vergelijk-bare omstandigheden vertoont het grondwater van de bedrijven in de vollegronds-groenteteelt in het algemeen hogere nitraatconcentraties dan bij de akkerbouwers op zand. Voor wat betreft P in het grondwater, springen de bollentelers er duidelijk uit met de hoogste concentraties (gemiddeld totaal-P = 7,4 mg/l), gevolgd door de akkerbouwers-op-klei (gemiddeld 0,61 mg/l) en enkele akkerbouwers-op-zand. De belangrijkste factoren die verantwoordelijk lijken te zijn voor de hoge fosfaatconcentraties in het grondwater van de bollentelers zijn het geringe fosfaatvastleggend vermogen van de betreffende duingronden; de hoge fosfaatoverschotten (met name in het verleden); de hoge grondwaterstand en de diepe grondbewerking. Het bemonsterde slootwater voldeed op geen enkel van de 5 akkerbouw-op-klei- en 3 bollen-bedrijven aan de TmT-doelstelling voor totaal-N in oppervlaktewater (2,2 mg/l). Voor wat betreft totaal-P voldeed het slootwater op 3 van de akkerbouw-op-klei bedrijven maar op geen van de bollen-bedrijven aan de doelstelling van 0,15 mg/l. Het is echter de vraag in hoeverre deze doelstellingen voor elk van de bedrijven van toepassing zijn. Verschillen tussen grond-, drain- en slootwater lijken vooral te maken te hebben met de periode van bemonsteren en de verblijftijd in de bodem van het betreffende water

Quality of groundwater and surface water in the Farming with a Future project, 2002

Available from: DLV Adviesgroep nv, Postbus 7001, 6700 CA WageningenIn Telen met Toekomst (TmT) werken agrarische ondernemers, samen met adviseurs en onderzoekers, aan duurzame bedrijfssystemen voor akkerbouw, vollegrondsgroenteteelt, bloembollen en boomteelt. In 2002 heeft het RIVM voor het eerst systematisch waterkwaliteitsmetingen verricht op de deelnemende bedrijven. De resultaten van deze metingen worden in dit rapport gepresenteerd en besproken. Hierbij wordt vooral gekeken naar de concentraties van verschillende vormen van stikstof en fosfaat en de verbanden met landgebruik en omgevingsfactoren. De bedrijfsgemiddelde nitraatconcentratie in het grondwater (of bodemvocht) was op 15 van de 37 onderzochte bedrijven lager dan de grenswaarde van 50 mg/l (als NO3). Het grondwater bij de akkerbouwers-op-klei en de bollentelers vertoont de laagste nitraatconcentraties in vergelijking met de andere sectoren. De volle-gronds-groente-telers springen er uit met de hoogste waarden, gevolgd door de boom-telers. Deze verschillen kunnen deels verklaard worden door omgevingsspecifieke factoren. Bedrijven op 'natte' gronden, waaronder alle bollentelers en akkerbouwers-op-klei, vertonen lagere concentraties dan bedrijven op van nature goedgedraineerde gronden met een diepe grondwaterstand. Echter, ook onder ogenschijnlijk vergelijk-bare omstandigheden vertoont het grondwater van de bedrijven in de vollegronds-groenteteelt in het algemeen hogere nitraatconcentraties dan bij de akkerbouwers op zand. Voor wat betreft P in het grondwater, springen de bollentelers er duidelijk uit met de hoogste concentraties (gemiddeld totaal-P = 7,4 mg/l), gevolgd door de akkerbouwers-op-klei (gemiddeld 0,61 mg/l) en enkele akkerbouwers-op-zand. De belangrijkste factoren die verantwoordelijk lijken te zijn voor de hoge fosfaatconcentraties in het grondwater van de bollentelers zijn het geringe fosfaatvastleggend vermogen van de betreffende duingronden; de hoge fosfaatoverschotten (met name in het verleden); de hoge grondwaterstand en de diepe grondbewerking. Het bemonsterde slootwater voldeed op geen enkel van de 5 akkerbouw-op-klei- en 3 bollen-bedrijven aan de TmT-doelstelling voor totaal-N in oppervlaktewater (2,2 mg/l). Voor wat betreft totaal-P voldeed het slootwater op 3 van de akkerbouw-op-klei bedrijven maar op geen van de bollen-bedrijven aan de doelstelling van 0,15 mg/l. Het is echter de vraag in hoeverre deze doelstellingen voor elk van de bedrijven van toepassing zijn. Verschillen tussen grond-, drain- en slootwater lijken vooral te maken te hebben met de periode van bemonsteren en de verblijftijd in de bodem van het betreffende water.In Farming with a Future (FwF) farmers, together with extension officers and researchers, work towards sustainable production systems for arable crops, open air vegetables, flower bulbs and ornamental trees. Systematic measurements of water quality on the participating farms are conducted by RIVM; for the first time in 2002. The results of these measurements are presented and discussed in this report. Special attention is paid to the concentration of several forms of nitrogen (N) and phosphorous (P), and the relationships with land use and the physical environment. The groundwater of 15 of the 37 farms investigated presented nitrate concentrations (farm averages) below the boundary value of 50 mg/l (as NO3). Groundwater of the farms with arable crops on clay soils and of those with flower bulbs presented the lowest nitrate concentrations as compared to groundwater of the other farm sectors. The highest concentrations were found in groundwater of farms with open air vegetables, followed by the farms with ornamental trees. These differences are partly explained by differences in the physical environment. Farms on 'wet' soils, including all flower bulb farms and arable farms on clay, present lower concentrations than farms on naturally well-drained soils with a deep groundwater table. However, when physical environments appear to be comparable (sandy soils), farms with open air vegetables generally present higher groundwater nitrate concentrations than farms with arable crops. With respect to groundwater P-concentrations, among the participating farms, the ones with flower bulbs clearly present the highest values, (average farm average total-P = 7,4 mg/l), followed by those with arable crops on clay soils (average 0,61 mg/l) and a few farms with arable crops on sandy soils. The most important factors determining the high groundwater P-concentrations on the farms with flower bulbs seem to be the small phosphate retention capacity of the sandy dune soils where flower bulbs are produced; heavy applications of manure and fertilisers (especially in the past); the shallow groundwater level and the practice of deep tillage. Ditch water samples were taken on 5 farms with arable crops on clay and 3 farms with flower bulbs. In all cases, farm average total-N concentrations exceeded the FwF goal for surface water (2,2 mg/l). With respect to total-P, farm average concentrations where within the FwF goal (0,15 mg/l) on 3 of the farms with arable crops on clay, but exceeded this goal on all flower bulb farms investigated. It is questioned however, to which extent the FwF goals for surface water may be applied to each farm individually. Differences between the quality of groundwater, drain water and ditch water seem to be primarily related to the period of sampling, as well as to the residence time of the water in the soil.Plant Research Internationa

Biochemical proxies indicate differences in soil C cycling induced by long-term tillage and residue management in a tropical agroecosystem

Background &amp; aim: A potential benefit of conservation agriculture (CA) is soil organic carbon (SOC) accrual, yet recent studies indicate limited or no impact of CA on total SOC in tropical agroecosystems. We evaluated biochemical indicators of soil C cycling after 9&nbsp;years (18 seasons) of contrasting tillage with and without maize residue retention in western Kenya. Methods: Potential activities of C-cycling enzymes (β-glucosidase, GLU; β-galactosidase, GAL; glucosaminidase, GLM; cellobiohydrolase, CEL), permanganate-oxidizable C (POXC), and soil organic matter (SOM) composition (by infrared spectroscopy) were measured. Results: POXC tended to be greater under reduced tillage and residue retention, but did not significantly differ among treatments (≤ 2% of SOC). Despite no significant differences in SOC concentrations or stocks, activities of all 4 C-cycling enzymes responded strongly to tillage, and to a lesser extent to residue management. Activities of GLU, GAL, and GLM were greatest under the combination of reduced tillage and residue retention relative to other treatments. Reduced tillage produced an enrichment in carboxyl C&nbsp;=&nbsp;O (+6%) and decreased polysaccharide C-O (−3.5%) relative to conventional tillage irrespective of residue management. Conclusions: Though enzyme activities and POXC are typically associated with SOC accrual, changes in soil C cycling at this site have not translated into significant differences in SOC after 9&nbsp;years. Elevated enzyme activities may have offset potential SOC accumulation under CA. However, the ratio of C-cycling enzyme activities to SOC was higher under reduced tillage and residue retention relative to other treatments, indicating that stoichiometric scaling of SOC and enzyme activities does not explain absence of significant differences in SOC among tillage and residue managements. Potential factors that may explain the low SOC accrual rates in this tropical agroecosystem included the low, albeit realistic, levels of residue retention, nutrient limitations, and high temperatures favoring decomposition

Retinopathy in type 2 diabetes mellitus is associated with increased intima-media thickness and endothelial dysfunction

Background  Microangioathy and macroangiopathy in type 2 diabetes mellitus (T2DM) frequently coexist. Both types of vascular complications share traditional risk factors. It is not clear whether the presence of microangiopathy, such as diabetic retinopathy (DR), constitutes a predictor of atherosclerosis in T2DM. Here we described the search for the association between DR and intima-media thickness (IMT) in T2DM. We also compared endothelial function in subjects with and without DR. Material and methods  We examined 182 consecutive patients with T2DM for at least 5 years (mean age at examination 56·3 ± 6·52 years). We assessed (i) IMT of carotid artery by ultrasound and (ii) endothelial function by flow-mediated dilatation (FMD) method as well as by measurement of concentrations of von Willebrand factor (vWF) and s-ICAM-1. All patients underwent ophthalmological examination. Statistical analysis included Student's, Mann–Whitney, chi-square, Fisher tests and multiple regression. Results  DR was found in 71 (39·0%) subjects. IMT was higher in patients with DR than those without DR (0·87 mm vs. 0·79 mm, respectively, P = 0·0001). FMD was lower in the complication group than in subjects without DR (8·38% vs. 10·45%, respectively, P = 0·0023). Concentrations of s-ICAM-1 and vWF were not different between the groups. In multiple regression analysis, DR was among the predictors of increased IMT (P = 0·016) and decreased FMD (P = 0·002). We did not find a significant association of DR with vWF and s-ICAM-1 (P = 0·09 and P = 0·11, respectively). Conclusions  DR is associated with increased IMT and endothelial dysfunction in T2DM. Impaired endothelial function may be a common denominator of pathogenesis of microvascular complications and atherosclerosis in T2DM