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1.
Getaneh K. Ayele Azalu A. Gessess Meseret B. Addisie Seifu A. Tilahun Tigist Y. Tebebu Daregot B. Tenessa Eddy J. Langendoen Charles F. Nicholson Tammo S. Steenhuis 《Land Degradation \u0026amp; Development》2016,27(2):270-280
Gully erosion reduces agricultural productivity by destroying valuable land resources, increases sediment concentrations, reduces water quality, and fills up reservoirs. Gully rehabilitation has proven to be challenging especially in the high‐rainfall areas of the Ethiopian Highlands and has therefore had limited success. This paper describes a successful low‐cost gully rehabilitation effort with community participation in the Birr watershed in the Blue Nile basin that begun in early 2013. Initially, farmers were reluctant to participate for religious reasons, but with the aid of local priests and respected elders, community discussions, and a visit to a rehabilitated gully, a consensus was reached to rehabilitate a 0·71‐ha upland gully. The rehabilitation measures consisted of regrading the gully head at a 45° slope, constructing low‐cost check dams from locally available materials, and planting Pennisetum purpureum grass and Sesbania sesban. At the end of the first post‐implementation rainy season, 2,200 tons of soil was conserved by the constructed check dams and newly planted vegetation, compared with soil losses of 680 and 560 tons in two untreated, nearby gullies. In 2014, an additional 3,100 tons of soil was conserved. In 2013, the marginal rate of return (MRR) on the gully rehabilitation investment was 2·6 based on the value of increased forage production alone. When we include trapped soil nutrient values, the rehabilitation MRR was increased to 10. Although these numbers are impressive, the best proof of the success was that farmers on their own initiative rehabilitated an additional five gullies in 2014. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
2.
Wetting front instability resulting in fingered flow has been found in both wettable and nonwettable soils. Understanding how and when this phenomenon occurs under field conditions is greatly limited. Laboratory research has resulted in a number of expressions for finger diameter. In this paper we test the applicability of one of these equations for three different soils in the Netherlands where detailed soil sampling of moisture content was done earlier. In addition, information needed for finger prediction, such as the main wetting and drying loops of the soil moisture characteristic curves and the unsaturated and saturated soil conductivities, were measured in the laboratory. Results show that predicted finger diameters for the two sandy soils agreed well with the observed moisture patterns, while for the loess soil the wetting front was flat as predicted. The finger diameters in dry soil were based on the main wetting loop and in the wet soils were dependent on the main drying loop. 相似文献
3.
Olga Singurindy Marina Molodovskaya Brian K. Richards Tammo S. Steenhuis 《Water, air, and soil pollution》2008,195(1-4):285-299
Urine-treated soils make a significant contribution to gaseous N losses to the atmosphere. Our goal was to investigate the influence of clay type and content on ammonia (NH3) and nitrous oxide (N2O) emissions from urine under different wetting–drying soil conditions and to relate these results to urine-N transformation processes in soil. Three types of silt loam soils and synthetic sand–clay aggregates with three different clay-dominated materials (kaolinite, montmorillonite and vermiculite) were used in this laboratory study. Bulk soil, 4–4.75 mm and 9.5–11.2 mm aggregates were incubated with synthetic urine at 50% and 75% saturation under aerobic conditions. Repeated urine application affected the properties of the aggregates depending on the type of clay present. Greater clay content increased aggregate stability and reduced NH3 volatilization. The variation in clay ammonium (NH4 +) fixation capacities was reflected in NH3 volatilization as well as in the onset of N2O emissions, occurring first from kaolinite-dominated and last from vermiculite-dominated soils. Nitrous oxide production was greater in aggregates than in bulk soil, a difference that consistently increased with repeated urine applications for kaolinitic and vermiculitic treatments. A dual-peak N2O emission pattern was found, with the second maximum increasing with the number of urine applications. Emission of 15N-labeled N2 was found at 75% saturation in kaolinite and vermiculite-dominated samples. Anaerobic conditions were less pronounced with montmorillonite-dominated samples because shrink–swell action caused aggregate breakage. 相似文献
4.
Martin V. Bauer Christian Marx Fabienne V. Bauer Dominique M. Flury Tammo Ripken Bernhard Streit 《Weed Research》2020,60(4):241-250
Research and development activities on non-chemical weed control methods to date have mainly focused on mechanical and thermal applications. Selectivity in mechanical weed control is obtained using dynamically actuated harrows. Selectivity in thermal weed control is obtained through a certain heat tolerance of the crop. In conservation agriculture (CA), weed emergence is partially suppressed by constant soil cover with crops or cover crops. Large amounts of plant residues therefore remain on the soil, which make mechanical methods inefficient or difficult to implement. And thermal methods need to prevent not only crop damage but also fire from situationally dry plant residues. In this review, technologies that can potentially be used for in-crop weed control in CA are discussed. The technologies reviewed include spot-flaming, electric resistance heating, electromagnetic irradiation and steam/hot water application. Their evaluation focuses on efficiency and specificity (spatial precision). This review indicates that existing equipment does not fulfil the spatial precision required in CA and that further research and development is required on this topic. In particular, the authors suggest further research on the use of laser diodes, micro-flames and capacitive coupling of electric fields. It seems that the use of automated imaging systems for weed/crop differentiation is a prerequisite in CA to enable automatisation of weed control. 相似文献
5.
Agricultural production in the North China Plain with rainfall of less than 500 mm·yr−1 has been steadily increasing over the past 40 years, with the groundwater levels decreasing at a rate of over 1 m·yr−1. In this paper, it is demonstrated theoretically that the water level in the aquifer can be expressed as a function of agricultural production and the sum of water added as rainfall and imported from outside the basin. Therefore, the most effective measures to halt groundwater depletion are importing water, decreasing cropping intensity and growing less thirsty crops. Irrigation improvements, mulching and agronomic measures that could increase the yield per unit area have less of an impact on solving the declining groundwater levels. 相似文献
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7.
Carla Sofia Santos Ferreira Rory Peter Dominic Walsh João Pedro Carvalho Nunes Tammo S. Steenhuis Manuel Nunes João Luís Mendes Pedroso de Lima Celeste Oliveira Alves Coelho António José Dinis Ferreira 《Journal of Soils and Sediments》2016,16(11):2580-2593
Purpose
Relatively little is known in the Mediterranean environment about changes in streamflow during urban development in partially urbanized peri-urban catchments. This paper explores the modification of streamflow regime as a consequence of the construction of an enterprise park, a major road, and expansion of residential areas, leading to urban areas increase from 32 to 40 % in a small catchment (6.2 km2), located in the periphery of one of the main cities in central mainland Portugal.Materials and methods
The study was carried out over five hydrological years (October 2008–September 2009 to October 2012–September 2013), including two initial years of pre- and three following years of post-additional urban development. Streamflow was recorded by a V-notch weir at the catchment outlet at 5-min intervals. Rainfall was recorded at a weather station 0.5 km north of the catchment and by five tipping-bucket raingauges installed in January 2011 within the study catchment. Streamflow was converted into runoff and split into baseflow and stormflow components by applying a mathematical low-pass digital filter. Streamflow differences were investigated through changes in (i) annual runoff coefficients, (ii) annual baseflow index, (iii) seasonal baseflow index and stormflow coefficient, and (iv) storm event analysis.Results and discussion
Annual runoff coefficient ranged from 14 to 21 % and storm runoff coefficient from 9 to 14 %, both between the driest 2011/12 and wettest 2012/13. Although these differences were influenced by inter-annual weather variability, a comparison between years with similar rainfall before and after additional urban development showed a 43 % increase in storm runoff. Impacts on streamflow were also noticed through changes on hydrograph: (i) regression lines of storm runoff against rainstorm parameters exhibited higher vertical positions in 2012/13 than 2008/09, (ii) gradual increase in peak flow but with a clear distance between pre- and post- additional urbanization, (iii) quicker response time from 60–75 min to 40–45 min between both periods, and (iv) decrease in recession time from 21–29 h to 7–9 h for the same periods.Conclusions
The dispersed urban pattern and permeable soils provide many overland flow sinks, favouring relatively low storm runoff of the catchment. Nevertheless, the enlargement of impervious surfaces (from 12.8 to 17.0 %) and particularly the storm drainage system installed in new urban areas led to great changes on rainfall–runoff event responses. Urban planning should consider the landscape mosaic of peri-urban areas in order to maximize water infiltration and minimize the impacts on streamflow regime.8.
Astrid R. Jacobson Sondra Klitzke Murray B McBride Philippe Baveye Tammo S. Steenhuis 《Water, air, and soil pollution》2005,160(1-4):41-54
Silver (Ag) and thallium (Tl) are non-essential elements that are toxic to many biota at trace levels, but are rarely studied in soil environments. Ag sorbs strongly to soils, especially those rich in organic matter whereas Tl sorption is influenced by clay content. However, the mobility and bioavailability of Tl and Ag are ultimately affected less by the soil sorptive capacity than by the ease with which these elements desorb from soils. In that context, the strength of Ag and Tl sorption to illite-rich mineral soils with differing textures and an organic peaty-muck soil, from New York State, was investigated by studying their desorption using, as a sink for the metals, a resin (Duolite G-73) containing a thiol functional group. Desorption was monitored over time (1 h, 4 weeks) from soils previously equilibrated with Tl+ or Ag+ for 24 h (steady-state) or for up to 1 year. Within 24 h, 60% of the sorbed Tl was recovered by the resin. Within 2 weeks, 80–100% of the Tl desorbed from all four soils equilibrated for both 24 h and 1 year periods. Ag was not effectively recovered from the resin. However, qualitative review indicates that more Ag was desorbed after the 24 h sorption period than after the 1 year period. More Ag desorbed from the sandy soil than from the peaty-muck soil or the mineral soils with higher clay contents. However, within two weeks silver was mobilized from the peaty-muck soil. The observed release of Ag and Tl from soils, coupled with their toxicity at trace levels to a broad range of soil organisms, suggests that they may pose an environmental concern when present in soils at elevated concentrations. 相似文献
9.
In horse breeding, quality assessment of semen before insemination is often requested. Non‐laboratory‐based techniques for objective analysis of sperm motility are thus of interest. The aim of this study was evaluating a portable device for semen analysis (Ongo sperm test) and its comparison with computer‐assisted semen analysis (CASA). Semen was collected from 10 stallions, diluted to 100, 50 and 25 × 106 sperm/ml and analysed for total (TM) and progressive motility (PM). The final sperm concentration influenced total motility analysed by Ongo (p < 0.05) which was higher at 100 × 106 sperm/ml when compared to 25 × 106 sperm/ml (p < 0.05) but not when compared to 50 × 106 sperm/ml (n.s.). Sperm concentration did not influence total motility when assessed by SpermVision (n.s.). Agreement between methods was evaluated by correlation analysis and Bland–Altman plot. Intra‐assay variation of Ongo was 5.2% ± 3.0 for TM and 6.9% ± 3.4 for PM. Correlation between Ongo and CASA was r = 0.79, 0.88 and 0.83 for 100, 50 and 25 × 106 sperm/ml for TM, and r = 0.87, 0.89 and 0.87 for PM, respectively (all p < 0.001). At the 100 and 25 mio/ml dilutions, the difference between the two systems deviated significantly from 0, while no such bias existed at the 50 mio/ml dilution (TM Ongo 85.0%, CASA 82.3%; PM Ongo 64.1%, CASA 66.1%). The 95% confidence interval was 19.9%, 18.9% and 19.2% ± mean for TM and 20.7%, 17.4% and 20.3% ± mean for 100, 50 and 25 × 106 sperm/ml, respectively. In conclusion, Ongo sperm test sperm motility data were strongly correlated with data obtained by CASA. In addition, at a concentration of 50 × 106 sperm/ml values measured with both systems were close to identical. At this concentration, which is recommended in equine AI, Ongo and CASA can be used interchangeably. 相似文献
10.
Louis‐Pierre Molleyres Alfred Rindlisbacher Tammo Winkler Vijaya Kumar 《Pest management science》1999,55(4):494-497
An Erratum for this article has been published in Pest Management Science 56(5) 493 (2000). In the course of the screening for novel, naturally occurring pesticides from the plant family Meliaceae, an extract of the stem bark of Aglaia roxburghiana was found to exhibit significant insecticidal activity. In addition to rocaglamide, a known insecticide isolated from several species of the genus Aglaia, 15 new natural products were isolated from this plant. Isolation and structure elucidation of the natural products is described. The outstanding insecticidal activities of some of the compounds as well as a structure–activity relationship study are presented. © 1999 Society of Chemical Industry 相似文献