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1.
Practical agriculturists all over the world have reported losses of nitrogen from the fields when nitrogenous fertilizers are applied. They have observed that whole of the nitrogen is not utilized by the plants but a major Portion is lost as nitrogen gas. The inorganic mtrogen compounds -ammonia and nitratessUffer several types of loss from the soil. They may be taken up by growing plants, they may be assimulated into the bodies of microorganisms and so brought back into the organic nitrogen reservoir, they may be converted into volatile compounds and lost into the air or they may be leached out of soil. 相似文献
2.
《Communications in Soil Science and Plant Analysis》2012,43(17-18):2929-2940
Abstract Plant samples were taken from a corn field at an early and later sampling dates in an 82.5 ft. grid. The samples were analyzed for phosphorus (P) using both an acid‐digest method and a simple acetic‐acid extraction. Values for P composition were compared to soil Bray PI levels taken from the same locations. Mapping from the plant analysis methods and soil PI values were compared. Acid‐digest P levels were significantly correlated with soil P levels at each sampling. Acetic acid extracts were significantly correlated with soil P only at the late sampling. Acetic acid and acid‐digest P were strongly correlated with each other at the early sampling and also significantly correlated at the late sampling. Plant analysis using both methods may be useful in mapping relative P uptake levels throughout a field, but the levels may or may not be related to soil PI levels. Some ground truthing with soil sampling may be neccessary to interpret plant analysis P before fertilizer application is directed. 相似文献
3.
The objective of this study was to determine if a combination of commercially available mucin and an 8 microm microporous membrane insert can be used to replace the 15 kDa molecular weight cutoff (MWCO) dialysis membrane used in an established in vitro digestion/Caco-2 cell culture system. Although the current model with the 15 kDa membrane correlates well with human studies, use of mucin may improve the system as the mucus layer is suspected to play a physiological role in Fe absorption. Use of mucin may also enable more complete assessment of iron bioavailability from large molecular weight forms of Fe such as heme and ferritin Fe. A range of foods or Fe (i.e., FeCl(3) +/- ascorbic acid, cooked beef, red bean, white bean, soybean, horse spleen ferritin and plant-type ferritin) were subjected to in vitro digestion. In the presence of mucin, significantly more Fe was taken up from the heme Fe (86%) and ferritin (91%) samples and significantly less Fe was taken up from the white bean samples ( approximately 70%) relative to the 15 kDa membrane. The results indicated that the forms of iron interact with mucin. The mucus layer has a significant effect on Fe uptake. Further refinement and characterization of the mucin method is needed before it can be deemed to be a suitable replacement for the dialysis membrane. 相似文献
4.
《Communications in Soil Science and Plant Analysis》2012,43(5):273-286
Abstract Micronutrients are applied alone to soils or with macronutrient fertilizers. Foliar application of Fe and other micronutrients is also practiced, and Mo is usually applied as a seed treatment. Since the soil application rates of B, Cu, Mn, and Zn are low, they are usually applied with macronutrient fertilizers by incorporation during the manufacturing process, bulk blending with or coating onto granular fertilizers, or with fluid fertilizers. Chemical reactions between the micronutrient source and the macronutrient fertilizer may occur in the manufacturing process, in storage, or after soil application. These reaction products may vary widely, so care must be taken in selecting and processing micronutrient sources and macronutrient carriers so the resulting products will be available to plants. In general, plant availability of B sources is not affected during reaction. Care must be taken to apply boronated fertilizers uniformly and to avoid excessive rates, because the range between B deficiency and toxicity is very narrow. Crop response to Cu, Mn, and Zn varies with the micronutrient rate and source, macronutrient carrier, and method of application. 相似文献
5.
Abstract. Total concentrations of heavy metals in soils were measured before and after the catastrophic floods of 1997, which devastated most districts within the commune of Racibórz in southern Poland. The assays covered lead, zinc, cadmium, chromium, nickel and copper. Analyses on soil samples taken in 2002, after the floods, were compared with those of 1992, taken as part of regular monitoring. There was an increase in the mean concentrations of heavy metals as a consequence of the flooding. Only a small part of this increase may be due to changes in the method of analysis between the two dates. The mean concentrations of heavy metals after flooding did not exceed the permissible levels for Polish soils. Permission was therefore granted to continue using much of the flooded land for farming. However, the investigations located a number of places where heavy metals were above permissible levels. Some of these were a consequence of the floods, but others were considered to be due to contamination from previous industry. Where high concentrations were found, land was excluded from agricultural use. 相似文献
6.
Proxy global assessment of land degradation 总被引：3，自引：0，他引：3
Land degradation is always with us but its causes, extent and severity are contested. We define land degradation as a long-term decline in ecosystem function and productivity, which may be assessed using long-term, remotely sensed normalized difference vegetation index (NDVI) data. Deviation from the norm may serve as a proxy assessment of land degradation and improvement – if other factors that may be responsible are taken into account. These other factors include rainfall effects which may be assessed by rain-use efficiency, calculated from NDVI and rainfall. Results from the analysis of the 23-year Global Inventory Modeling and Mapping Studies (GIMMS) NDVI data indicate declining rain-use efficiency-adjusted NDVI on ca. 24% of the global land area with degrading areas mainly in Africa south of the equator, South-East Asia and south China, north-central Australia, the Pampas and swaths of the Siberian and north American taiga; 1.5 billion people live in these areas. The results are very different from previous assessments which compounded what is happening now with historical land degradation. Economic appraisal can be undertaken when land degradation is expressed in terms of net primary productivity and the resultant data allow statistical comparison with other variables to reveal possible drivers. 相似文献
7.
F. G. Bell D. D. Genske N. Hytiris P. Lindsay 《Land Degradation \u0026amp; Development》2000,11(5):419-437
Contaminated ground represents a problem in all the industrialized countries of the world. Contaminated ground may give rise to hazards and that implies a degree of risk which also involves a problem of definition. The investigation of a site which is suspected of being contaminated differs somewhat from a routine site investigation. Sampling of soils, groundwater and gas producing material may be required. Various precautions may be necessary in doing this and operatives may have to wear protective clothing. The first case history considered involves a site investigation for a relief sewer in Glasgow, Scotland. As the site investigation progressed it ran into made‐ground which contained chemical waste. The presence of this waste meant that the nature of the investigation changed and much more stringent safety precautions had to be taken. It also meant that the initial location of the sewer tunnel had to be repositioned at greater depth in uncontaminated sandstone rather than in the superficial deposits above. Two further case histories associated with coal mining in the Ruhr district of Germany are included. The methods involved in investigating these two sites are described, as is their rehabilitation. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
8.
Abdelfattah Badr Hanaa H. El-Shazly Linda E. Watson 《Genetic Resources and Crop Evolution》2008,55(1):21-31
The origin and ancestry for Egyptian clover, Trifolium alexandrinum, was examined using AFLP data. The data support a close relationship of T. alexandrinum accessions from Syria and Egypt to T. apertum, T. berytheum, and T. salmoneum. However, crossability and geographic distributions suggest that T. apertum is an unlikely progenitor. In contrast, T. salmoneum appears to be the most probable progenitor for Syrian material of Egyptian clover, although a close relationship to T. berytheum was also revealed. The ability of these species to cross freely indicates that T. salmoneum and T. berytheum may be regarded as the primary ancestors from, which man domesticated Egyptian clover through artificial selection in Syria.
Following domestication, the earlier forms of the crop species could have been taken into rain-fed cultivation in Palestine
and irrigated cultivation in Egypt. In this regard, the domestication of Egyptian clover may be analogous to other crops,
such as barley and wheat, which were also domesticated in the Fertile Crescent and taken into cultivation in the Nile Valley.
It appears that genetic improvement of the crop occurred in Egypt after cultivation, and that the varieties that were developed
in Egypt were later distributed worldwide. 相似文献
9.
Darriet P Pons M Lamy S Dubourdieu D 《Journal of agricultural and food chemistry》2000,48(10):4835-4838
Musty, earthy odors are highly detrimental to the aromatic quality of wines. A characteristic aroma of freshly tilled earth, damp cellar was studied in some red and white wines of different origins. The extraction and purification of the wines marked by this odor have shown after analysis by gas chromatography-olfactometry a unique strong odorous zone having the same odor as the one perceived at tasting. The compound responsible for this odorous zone was identified by gas chromatography-mass spectrometry as geosmin (trans-1,10-dimethyl-trans-9-decalol), which possesses a distinctive earthy odor. Geosmin may be present in wines at levels higher than the racemic geosmin olfactory perception threshold, thus suggesting its contribution to their off-aroma. Moreover, the presence of this compound in juice taken from freshly crushed grapes suggests that microorganisms that develop on the grapes may contribute to the presence of this compound in wines. 相似文献
10.
不同品种冬小麦磷效率性状与农学性状关系的研究 总被引：4，自引：0，他引：4
通过两年的田间试验,对冬小麦农学性状和磷效率性状之间的关系进行了研究。结果发现,植株较高或抽穗期推迟较多的品种中磷效率性状好的品种较多;产量构型中更多地依靠单一产量因素获得产量的品种对低磷敏感。研究还发现,在缺磷严重的条件下(OlsenP=2.4mg.kg)扬花期的生物量、光合叶面积和穗粒数与冬小麦的磷效率相关性较好;在缺磷较轻的条件下(OlsenP=6.6mg.kg)成穗数与冬小麦的磷效率相关性较好。这些性状有可能作为筛选磷高效材料的辅助选择指标。 相似文献
11.
12.
Lawrence Band 《CATENA》1985,12(4):281-290
Specially designed instruments were used to sample surface water and sediment discharge on a set of small hillslopes. The data set produced is unique as it includes simultaneous observations of surface water and sediment discharge, local surface declivity and drainage area at several points over the slope surface, and the precipitation intensity taken a number of times through natural storm events. The data are used to parameterize an empirical sediment transport law, expressing sediment transport as a power function of the local declivity and surface water discharge. A good fit to the observed data is achieved, suggesting that these field techniques may be used to parameterize the equation for different soils. A dynamic catena effect involving surface grain size, local declivity and the form of the sediment transport equation is recognized that may have significant implications for the form of sediment transport and long-term hillslope development. 相似文献
13.
Specially designed instruments were used to sample surface water and sediment discharge on a set of small hillslopes. The data set produced is unique as it includes simultaneous observations of surface water and sediment discharge, local surface declivity and drainage area at several points over the slope surface, and the precipitation intensity taken a number of times through natural storm events. The data are used to parameterize an empirical sediment transport law, expressing sediment transport as a power function of the local declivity and surface water discharge. A good fit to the observed data is achieved, suggesting that these field techniques may be used to parameterize the equation for different soils. A dynamic catena effect involving surface grain size, local declivity and the form of the sediment transport equation is recognized that may have significant implications for the form of sediment transport and long-term hillslope development. 相似文献
14.
15.
The process of humic acid formation during humification of plant residues (clover leaves and roots as well as timothy roots) was studied. According to some characteristics (elementary composition, IR-spectra, the content of COOH-groups) the newly-formed humic acids may be defined as “young forms”. The comparison of the new forms with more mature soil humic acids revealed the following specific features of the latter: (a) a higher degree of aromatic nuclei condensation; (b) a higher content of carboxyl groups; and (c) a more uniform structure.The authors discuss some defects of the methods used for extraction of humic acids from fresh and slightly humified plant residues by alkaline solutions. An artificial formation of humus-like substances and their extraction as admixtures together with true humic acids are inevitable with these methods. This should be taken into account in studying and systematizing such forms of humic acids. 相似文献
16.
G. D. TOWNER 《European Journal of Soil Science》1980,31(4):607-621
The time taken for a tensiometer to reach equilibrium with the soil-water pressure is a function not only of the tensiometer characteristics but also of the soil-water transport properties. When. in an appropriate system of units. the numerical value of the conductance of the tensiometer cup is small compared with that of the hydraulic conductivity of the soil, and the sensitivity of the pressure ‘gauge’ is large compared with the differential water capacity of the soil. then the precision of the measurements is such that the observed response may be indistinguishable from that of a tensiometer in bulk water. referred to as ‘tensiometer limited’. The theory developed in this paper for a hemispherical tensiometer cup shows that tensiometer-limited conditions can be achieved in practice. Moreover. such conditions would often correspond to a rapid response system. It is suggested that it might be advantageous in the design of a field recording system to choose a tensiometer-limited system even if it is not the fastest realisable one in order that its response is completely predictable from the known tensiometer characteristics. independent of the unknown soil properties. which may be changing. 相似文献
17.
Michael J. S. Tevesz Gerald Matisoff Stephen A. Frank Peter L. McCall 《Water, air, and soil pollution》1989,47(1-2):65-70
Vital effects may be important in determining metal levels in bivalves and must be taken into account before the environmental ‘meaning’ of the data may be interpreted. Manganese concentrations in shells and soft tissues of several species of freshwater bivalves from three recent environments in northern Ohio and one archeological site from southern Ohio were determined by neutron activation analysis and show a species effect where Fusconaia flava Mn levels > Anodonta grandis grandis levels ≥ all Lampsilis species levels. Manganese is concentrated by a factor of 2 to 25 in soft tissues compared to shells. In addition, within-taxon variability of Mn concentration is high. The high intraspecies variability points to the necessity of processing many individuals before reliable numbers may be obtained. 相似文献
18.
Ethylene formation in submerged soils and ethylene degradation by rice roots and soils were investigated. Ethylene was formed in rice soils in amounts which may deleteriously affect the growth of rice seedlings. Ethylene formation was markedly enhanced when organic materials such as glucose or rice straw were added to the soil. The rice roots, especially those taken from lowland and rice fields, showed notable ethylene-degradation activity; the rhizosphere microorganisms of the lowland rice appeared to be responsible for the ethylene-degradation activity. Lowland soils which have been continually submerged for a long time also showed ethylene-degradation activity. Upland soil and soil recently submerged, however, showed little degradation activity. 相似文献
19.
《Communications in Soil Science and Plant Analysis》2012,43(7):609-618
Abstract Measurements of leaf water potential taken in the Snake Range of Nevada indicate that bristlecone pine (Pinus longaeva Bailey) may be adapted to maintain lower internal water stress than some of its competitors. This characteristic may account in part for the tree's dominance on harsh timberline sites. 相似文献
20.
Concentrations of metals in the environment have greatly increased in the past decade since large quantities of pollutants are released annually in to the atmosphere. Exposure of the population atmospheric pollutants is believed to be responsible for the development of a number of illnesses and there is an increasing need for bio-indicators which may serve as monitors of pollutants such as heavy metals. Many animal and plant species are used as bio-indicators. Certain species of trees are used as bio-indicators because they add an additional temporal dimension. By their growth rings, trees may reflect annual variations in metal concentrations in the environment. In general, conifers are preferred because of the primitive nature of their wood which decreases the lateral transfer of contaminants between rings and, thus, gives them a better potential for the evaluation of environmental contamination. The aim of this work is to evaluate black spruce (Picea mariana) as an historical indicator of Al deposition from the atmosphere. The territory studied extends to a radius of 10 km around the Alcan aluminum refinery at Jonquiere, Quebec, Canada. The sampling strategy was designed to determine the variability within an individual tree and to determine local and regional differences. Using an incremental corer, xylem samples were taken from trees at six sites at 5 and 10 km from the refinery. At each site, three samples were taken from each of five trees separated by 100 m. The wood samples, containing from 30 to 50 rings, were sliced into two-year sections which were dried and analysed for Al by neutron activation. This involved irradiation of each section in the neutron flux of a nuclear reactor followed by gamma-ray spectroscopy with a germanium detector. The Al concentrations were thus determined in over two thousand xylem sections with a precision of 5% at levels as low as 0.2 µg g?1. The calculation of Kendall's τ for the Al concentrations in the three samples from each tree revealed correlations in 85% of the trees from the four sites situated along the line of the prevailing winds from the refinery. For the other two sites correlations were found in 40% of the trees. Higher Al levels were found in the growth rings of more recent years at all the sites. At each site the inter-tree variations in the Al concentrations in wood of a given age were about 50%. Among the six sites, the lowest concentrations were found by an SNK test, at the two which were away from the line of prevailing winds from the refinery. The highest concentrations were found at the site 10 km west of the refinery. This site is also 5 km from a paper mill. These results suggest that the trees most exposed to atmospheric contamination will contain high concentrations of Al. However, the temporal fluctuations of Al concentrations have not yet been related to fluctuations in industrial contamination. Moreover, the Al concentrations accumulated in the growth rings of black spruce could be related to the quantity of Al available in the soil, to the atmospheric release of NOX and SOX and to the natural pH of the soil which can induce chemical transformations, more particularly those related to the speciation and bio-availability of this metal. Although other variables must be taken into account, it appears that black spruce may be a useful historical monitor of environmental Al contamination once the relation between xylem concentration and atmospheric deposition is determined. 相似文献