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排序方式: 共有252条查询结果,搜索用时 15 毫秒
71.
72.
Rodomiro Ortiz Minna Nurminiemi Sten Madsen Odd Arne Rognli Åsmund Bjørnstad 《Euphytica》2002,126(2):283-289
Accurate assessments of genetic gains ensuing from plant breeding for the most important agronomic characteristics in Nordic
spring barley (Hordeum vulgareL.) are not available. Hence this research was aimed to determine the rate of genetic improvement in the Nordic barley breeding
pool. This study included 90, 2-row spring barley cultivars released (1942–1988) and29, 6-row spring barley cultivars released(1930–1991)
adopted by Nordic farmers that were tested in four Nordic locations for three consecutive years. Relative genetic gain owing
to plant breeding was 13% in2-row barley and 34% in 6-row barley for grain yield. The absolute gain for this characteristic
was 13 ± 3 kg ha-1 year -1 in 2-row barley, and22 ± 3 kg ha-1 year-1 in6-row barley. Improved yield was achieved in Nordic barley by reducing plant height(0.20 ± 0.04 cm year-1 for 2-rowbarley and 0.16 ± 0.06 cm year-1for 6-row cultivars), thereby reducing significantly lodging (0.5 ± 0.1%year-1 and 0.4 ± 0.1year-1), and increasing significantly the harvest index (0.0008 ± 0.0002year-1 and 0.0018 ± 0.0002year-1). Additionally, in 2-row spring barley cultivars resistance to powdery mildew (0.19 ± 0.08% year-1)and thousand-kernel weight (0.07 ±0.03 g year-1) were also significantly enhanced, whereas hectoliter weight was improved (0.06 ± 0.02 kg year-1)in 6-row barley cultivars in the period investigated.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
73.
The dynamic properties of a flexible net sheet exposed to waves and current were investigated by using a numerical model. The net was modelled by dividing it into super elements, and the structural and hydrodynamic forces were calculated for each element. The movement of the net was found from time integrating the equation of motion at each node. The model was used to study the influence of different parameters on the behaviour of the net. Through six different cases the impact of the following five parameters were investigated: (i) floater movement, (ii) wave period/height, (iii) current velocity, (iv) net solidity and (v) bottom weight. 相似文献
74.
In two separate experiments, juvenile Arctic charr (Salvelinus alpinus) were held at three different water depths (12, 24 and 37 cm) and at three different stocking densities (10, 50 and 100 kg/m3). Mortalities from swim bladder stress syndrome (SBSS) were noted over 2 months. Low water depth caused high mortality while stocking density did not induce the stress syndrome to any notable degree. An analysis of catecholamines in the blood plasma of a small number of fish indicated elevated dopamine levels in stressed fish. 相似文献
75.
Heidi Moe Tim Dempster Leif Magne Sunde Ulf Winther & Arne Fredheim 《Aquaculture Research》2007,38(1):91-99
Escapes of cod (Gadus morhua) from sea cages represent an economic problem for farmers and a potential environmental problem. We estimate that 0–6% of cod held in sea‐cage farms in Norway were reported to have escaped each year from 2000 to 2005, which is a high proportion compared with salmon. We interviewed employees at 19 coastal sea‐cage cod farms in Norway to investigate both how and why cultured cod escape and to document cage handling and management strategies that were effective in minimizing escapes. Based on the interviews, we describe five working hypotheses that may explain why a greater proportion of cod than salmon escape: (1) cod are more willing to escape than salmon; (2) cod bite the net cage and create wear and tear; (3) net cages have insufficient technical standards for cod culture; (4) cod are placed in sea cages at considerably smaller sizes than salmon; and (5) cod are more popular feed for predators. Preliminary testing of the hypothesis that cod bite netting and create holes was done by placing pre‐damaged net panels with cut twines and control panels inside sea cages. Holes in the pre‐damaged net panels increased in size over a period of 3 months. The type of damage indicated that biting of netting twines was the likely cause. 相似文献
76.
Kjell Johansson Mats Aastrup Arne Andersson Lage Bringmark Ake Iverfeldt 《Water, air, and soil pollution》1991,56(1):267-281
As a result of air pollution, the content of Hg in fish has significantly increased in a large part of Scandinavia and North
America. In this paper, the occurence and fluxes of Hg in Swedish forest soils and waters are reviewed and synthesized. The
main objective is to describe and evaluate the present transport of anthropogenic Hg from atmospheric deposition, through
the terrestrial compartment and running waters to lake basins and also to comprehend the main factors influencing these fluxes.
The transportation and distribution. of Hg in forest soils and waters is closely related to the flow of organic matter. The
content of Hg in humic matter is higher in southern and central areas compared to the north of the country. Compared to background
concentrations, the Hg content has increased in the southern and central part by about a factor of 4–7, while the overall
increase in the north is by about a factor of 2 to 3. The increased content of Hg in forest soils may have an effect on organisms
and biological processes in the soil. Regarding budget calculations for whole catchment areas and for the mor layer of the
soil, a reduction of about 80% from present atmospheric wet deposition must be obtained to reach “critical load” with respect
to conditions in Scandinavia. 相似文献
77.
Martina I. Gocke Axel Don Arne Heidkamp Florian Schneider Wulf Amelung 《植物养料与土壤学杂志》2021,184(1):51-64
Background : In search for more sustainable crop production, the subsoil has recently come into focus as considerable reservoir of nutrients and water. Aims : Dimensions of subsoil phosphorus (P) reserves are yet largely unknown but crucial for identifying regions suitable to include subsoil into sustainable management strategies. Methods : We analyzed stocks of total and plant‐available (calcium acetate lactate‐extractable) P in 96 representative soil profiles of German arable land down to 1 m depth. Results : We found that the German arable soils stored, on average, 8 t ha?1 of total P, of which nearly 500 kg ha?1 were readily plant‐available. Notably, one third of plant‐available P was located below the plow layer and one fifth even at depths below 0.5 m. The depth gradients of plant‐available P stocks were affected more by major reference soil group than by texture. Generally, Chernozem but also Anthrosol, Gleysol and Fluvisol exhibited the largest P stocks in German cropland. The contribution of plant‐available P to total P stocks was larger in sandy and extremely acidic (pH < 4.5) soils compared with more fine‐grained and slightly acidic to alkaline soils, possibly because fertilization compensated for overall lower total P stocks at these sites. Generally, the more P was stored in topsoils, the more P was stored also in subsoils. Conclusions : A hypothetical crop utilization of 10% from plant‐available P stocks and 0.1% from total P stocks from shallow subsoil could compensate for P fertilization by ca. 8 kg ha?1, but the rate of plant‐available P replenishment in subsoil likely remains the crucial factor for the role of subsoil P stocks in crop nutrition. Generally, the large P reserves found in subsoil could act as an ‘insurance' system for crops. 相似文献
78.
Zhang Nina Xiaoning Andringa Joke Brouwer Jitske Alba Juan M. Kortbeek Ruy W. J. Messelink Gerben J. Janssen Arne 《Journal of pest science》2022,95(3):1343-1355
Journal of Pest Science - It has become clear that omnivorous predators can induce plant defences that affect the performance and host plant choice of herbivores. They are also known to induce the... 相似文献
79.
80.
Peer?B.?MortensenEmail author Louise?Schlüter Arne?Jensen Henning?F.?Aaser Kjeld?S.?Hansen 《Journal of Soils and Sediments》2004,4(2):101-106