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991.
Changes in vegetation and soil properties because of agricultural abandonment may affect soil nitrogen (N) and associated processes. We investigated soil N (total N: TN, inorganic N: NH4–N and NO3–N) and denitrification potential in cropland, pine plantations and abandoned agricultural land along a secondary succession sequence (grassland→shrubland→secondary forest) in a headwater catchment in the Qinling Mountains, northwest China. The results show that the soil denitrification potential differed significantly among the five land‐use types with the highest potential in the secondary forest, followed by grassland, shrubland, cropland and plantations. The denitrification potential of the 20‐ to 40‐cm layer was significantly lower compared with the topsoil (0–20 cm) across all land‐use types. TN, soil organic matter (SOM) and NH4–N increased significantly with stand age, whereas there was an opposite trend in soil pH. However, the denitrification potential did not relate to stand age in a linear manner. We conclude that changes in soil TN, SOM and pH during vegetation succession following agricultural abandonment are critical controls on the denitrification potential. 相似文献
992.
Swine manure and wood shavings used as a drying bed were removed from a High-Rise? hog facility following two production cycles. The manure was composted in aerated pilot-scale vessels for four weeks or a mechanically turned windrow for ten weeks. Total dry matter losses during the pilot-scale studies were 30 and 32.5 % for continuously and intermittently aerated systems, respectively. Compost from both systems was stable with emission rates of 0.07-0.11 mgCO2 h?1 gvs?1. Moisture, O2, CO2 and NH3 use/losses during the process as well as chemical properties of the initial and composted manure are presented. Incorporation of the compost at a 5% amendment rate (v/v) into a standard pine bark container medium significantly (P = 0.05) increased growth of two woody plant species. Higher amendment rates were toxic to some plants due to high initial NH4+ concentrations in the medium. The compost significantly (P=0.05) increased growth and suppressed Pythium root rot of poinsettia when incorporated at 10% (v/v) into a standard sphagnum peat mix. The compost can be utilized as a value-added disease-suppressive product in the ornamentals industry. 相似文献
993.
J. G. Wesseling C. R. Stoof C. J. Ritsema K. Oostindie & L. W. Dekker 《Soil Use and Management》2009,25(3):274-283
To gain more insight into the hydrological behaviour of coarse-textured soils, the physical properties of artificially created soil mixtures with different texture were determined. The mixtures were prepared according to the specifications of the United States Golf Association (USGA) for constructing putting greens. In addition, the effect of 10 vol.% organic matter addition was studied. The soil moisture retention and hydraulic conductivity relationships of the different mixtures were determined and their hydrological behaviour was studied using the numerical model SoWaM. Both texture and organic matter addition substantially affected the hydraulic properties. Hydraulic conductivity significantly increased with increasing coarseness while moisture retention decreased. On the other hand, organic matter addition reduced saturated hydraulic conductivity by a factor of 10 to 100 and distinctly increased moisture retention capacity. The amounts of total available water were increased by the addition of organic matter between 144% (slightly coarse texture) and 434% (very coarse texture). Results indicate that the mixtures can contain only 2–16% plant available water and therefore need frequent irrigation to maintain plant growth. Addition of organic matter seems a good solution to reduce the irrigation water requirements but it increases the risk of ponding or runoff because of large reductions in the saturated hydraulic conductivity sometimes to below the rate of 3.6 m/day recommended by the USGA. 相似文献
994.
995.
Martin Körschens 《Archives of Agronomy and Soil Science》2013,59(2):77-92
Im Statischen Düngungsversuch Bad Lauchstädt werden nach Erweiterung der Versuchsfrage seit 1978 die Prüffaktoren: Stalldung (2 Stufen), Corg‐Gehalt im Boden (6 Stufen) und Mineral‐N‐Mengen (5 Stufen) in der Fruchtfolge Kartoffeln, Winterweizen, Zuckerrüben, Sommergerste geprüft. Nur bei Sommergerste konnte eine Ertragswirkung des Stalldungs im Vergleich zu ausschließlicher Mineraldüngung nachgewiesen werden. Die jährlichen Veränderungen der Corg‐ und Nt‐Gehalte im Boden betrugen bei jeweils extremen Änderungen des Düngungsregimes bis zu 0, 012% Corg bzw. 0,0013% Nt. 相似文献
996.
997.
Objectives : To describe a method of faecal smear production and to determine the sensitivity and specificity of faecal smear for detection of parasitic larvae using Baermann sedimentation as a gold standard Methods : Faecal smears were produced from samples submitted to the Royal Veterinary College Diagnostic Laboratory Service for Baermann sedimentation. An inexperienced and an experienced assessor each examined the smear for larvae for a maximum of five minutes. Results : One hundred and eighty six samples were analysed of which 28 were positive for Angiostrongylus vasorum on Baermann sedimentation. The experienced assessor had a faecal smear sensitivity of 61% and a specificity of 100%. The inexperienced assessor had a faecal smear sensitivity of 54% and a specificity of 95%. Clinical Significance : Faecal smear is an effective and cheap aid to diagnosis of canine angiostrongylosis which can be readily performed in general practice. Its use leads to a rapid detection of infection compared to other available methods. This could lead to swifter treatment of the disease and a decrease in inappropriate diagnostics. A further diagnostic method, such as Baermann sedimentation, is recommended whether the faecal smear result is positive or negative. 相似文献
998.
M. A. Kader S. Sleutel S. A. Begum K. D’Haene K. Jegajeevagan S. De Neve 《Soil Use and Management》2010,26(4):494-507
After decades of searching for a practical method to estimate the N mineralization capacity of soil, there is still no consistent methodology. Indeed it is important to have practical methods to estimate soil nitrogen release for plant uptake and that should be appropriate, less time consuming, and cost effective for farmers. We fractionated soil organic matter (SOM) to assess different fractions of SOM as predictors for net N mineralization measured from repacked (disturbed) and intact (undisturbed) soil cores in 14 weeks of laboratory incubations. A soil set consisting of surface soil from 18 cereal and root‐cropped arable fields was physically fractionated into coarse and fine free particulate OM (coarse fPOM and fine fPOM), intra‐microaggregate particulate OM (iPOM) and silt and clay sized OM. The silt and clay sized OM was further chemically fractionated by oxidation with 6% NaOCl to isolate an oxidation‐resistant OM fraction, followed by extraction of mineral bound OM with 10% HF (HF‐res OM). Stepwise multiple linear regression yielded a significant relationship between the annual N mineralization (kg N/ha) from undisturbed soil and coarse fPOM N (kg N/ha), silt and clay N (kg N/ha) and its C:N ratio (R2 = 0.80; P < 0.01). The relative annual N mineralization (% of soil N) from disturbed soils was related to coarse fPOM N, HF‐res OC (% of soil organic carbon) and its C:N ratio (R2 = 0.83; P < 0.01). Physical fractions of SOM were thus found to be the most useful predictors for estimating the annual N mineralization rate of undisturbed soils. However, the bioavailability of physical fractions was changed due to the disturbance of soil. For disturbed soils, a presumed stable chemical SOM fraction was found to be a relevant predictor indicating that this fraction still contains bio‐available N. The latter prompted a revision in our reasoning behind selective oxidation and extraction as tools for characterizing soil organic N quality with respect to N availability. Nonetheless, the present study also underscores the potential of a combined physical and chemical fractionation procedure for isolating and quantifying N fractions which preferentially contribute to bulk soil N mineralization. The N content or C:N ratio of such fractions may be used to predict N mineralization in arable soils. 相似文献
999.
K.H. Finger 《New Zealand veterinary journal》2013,61(3)
Extract In Europe, during the 18th century, the farm animal population was seriously reduced by the spread of disease due to increased travel and wars between states. At that time, there were no specialists in animal health, but this need was soon met by the founding of veterinary schools in France, Germany and England. 相似文献
1000.
R. C. Misra H. K. Sahoo D. R. Pani D. C. Bhandari 《Genetic Resources and Crop Evolution》2013,60(7):2033-2054
The subterranean parts of many wild plants form an important constituent of traditional diet of the tribal inhabitants of Similipal Biosphere Reserve, Odisha especially in times of food scarcity during critical periods. However, no specific study has been made so far on this aspect. The present study was conducted during 2008–2012 as a search for sources of food and to assess the dietary diversity, consumption pattern, culinary uses and prioritized species of wild tuberous plants sustained by local tribes. The exploration and germplasm collection missions along with intensive botanical survey, focus group discussions, structured household interview and market survey were conducted in 30 villages interacting with 102 key informants of core and buffer zones. A total of 55 wild edible tuberous species representing 37 genera and 24 families were inventoried including 17 species used during food deficiency to meet seasonal shortages. The analyzed data contributed 5 use categories, 4 preparation methods, 7 kinds of food items, 10 species as children snacks, 35 species of pharma-foods and 20 prioritized species. Ten species were domesticated by tribes thus reducing threats on wild tubers and 20 species were traded in local markets to generate additional income exemplifying economic benefits from wild tubers. Seventeen species were identified as novel uses of food items from India. The findings suggested that the nutritional profile along with pharmaceutical attributes of preferred wild food plants be analyzed for recommending suitable species for better nutrition and development of nutraceuticals. Further, many genetic resources of these wild tuberous species of agri-horticultural importance constitute the wild genepool hence their economic and breeding potential along with desirable attributes need to be investigated for utilization in crop improvement programmes. 相似文献