摘要:

Total nitrogen was determined in sediments by the high temperature combusion (∼ 2600°C) method of Dumas, using an induction furnace system. Nitrogen analyses were carried out on six chemical compounds and 18 sediment samples. The reproducibility and accuracy of the analyzer were evaluated. The automated system gave the same total nitrogen values in the sediment samples as the conventional Kjeldahl procedure.

ISSN:0038-075X    

出版商:OVID    

年代:1977

数据来源: OVID

摘要:

The relative persistence of endrin in soils as related to flooding and alternate “anaerobic” (flooded unstirred) and “aerobic” (flooded stirred) conditions was studied in three soils by radiotracer technique. More rapid degradation of endrin occurred in all three soils under flooded conditions than under nonflooded conditions. Autoradiography revealed the formation of six breakdown products in flooded soils as compared to four compounds in nonflooded soils after 25 days of incubation. The breakdown products, detected at the end of 25 days of preincubation under flooded unstirred (predominantly anaerobic) conditions, decreased to low levels following incubation under unstirred conditions for another 30 days. By contrast, when the flooded soils were stirred for 30 days after 25 days of unstirred conditions, undecomposed endrin and some of its breakdown products detected at the end of unstirred conditions persisted and accumulated. The data demonstrated that aerobic conditions in non-flooded soils and in flooded soils subjected to an unstirred cycle increased the persistence of endrin and its breakdown products.

ISSN:0038-075X    

出版商:OVID    

年代:1977

数据来源: OVID

摘要:

Strain specific fluorescent antibodies were used to enumerate two serotypes ofNitrobacter winogradskyiin the rhizosphere and rhizoplane of wheat and soybeans treated with 100 ppm nitrogen. Serotype “agilis” predominated over serotype “Winogradsky” at all times in the soil studied. No significant inhibition or stimulation ofNitrobactermultiplication occurred during the six week growth period, but rhizosphere to rhizoplane shifts occurred. Ammonia nitrogen stimulated early multiplication ofNitrobacter, but the effect was short-lived; soybean meal maintained a greaterNitrobacterpopulation throughout.

ISSN:0038-075X    

出版商:OVID    

年代:1977

数据来源: OVID

摘要:

A detailed investigation has been carried out to determine, through tissue analysis, the nutritional status of 55 plant species of the Egyptian wild flora collected from the desert area of Burg El-Arab, west of Alexandria. The data obtained resulted in classifying the different species into 17 groups, each being specifically rich in a given element. The relationship between the level of elements and the kind of habitats has also been discussed.

ISSN:0038-075X    

出版商:OVID    

年代:1977

数据来源: OVID

摘要:

The total phosphorus contents of 68 soils representing the major agricultural soils of Southeastern Nigeria have been fractionated into aluminum, iron, calcium, and organic and residual phosphates, and the fractions correlated with percentage yield of maize(zea mays)and with available phosphorus determined by two chemical methods.Total phosphorus content varied between a minimum value of 51 ppm P and a maximum value of 2646 ppm P. Organic phosphorus accounted for between 30 and 78.8 percent of the extractable phosphorus, followed by iron phosphate, aluminum phosphate, and calcium, phosphate in decreasing order of abundance. The bulk of the inorganic phosphorus in the soils was in the residual form, except in the extremely sandy soils with low iron oxide content.Percentage yield of maize correlated positively with each of aluminum phosphate (r= 0.562), iron phosphate (r= 0.546), calcium phosphate (r= 0.491), and organic phosphates (r= 0.455), the correlation coefficient in each case being significant at the 0.1 percent level, suggesting that all four forms contribute to the available phosphorus for the maize crop.Aluminum phosphate correlated positively and very highly significantly with resinextractable P (r= 0.786) and with dilute acid/fluoride-extractable P (r= 0.903), suggesting that the bulk of the available P so determined was aluminum phosphate. There was evidence that iron phosphate also contributed to the extracted available P but that calcium and organic phosphates were relatively unimportant.

ISSN:0038-075X    

出版商:OVID    

年代:1977

数据来源: OVID

摘要:

In a growth-chamber experiment, spinach yield response to low boron application and phytotoxicity of higher rates to corn were related to plant availability of applied B and B adsorption by a weathered upland, a recent alluvial, and a muck soil. Boron application to the different soils enhanced the correlated plant tissue B and hot-water-soluble soil B concentrations at different rates to reflect the effects of soil properties such as specific surfaces area, organic matter content, and extractable Al and Fe on soil adsorption of applied B. Boron application significantly affected plant tissue Ca, Mn, and P concentrations.

ISSN:0038-075X    

出版商:OVID    

年代:1977

数据来源: OVID

摘要:

Studies with32P-tagged mono-, di-, or tricalcium phosphate (MCP, DCP, TCP) showed that on application to moist aerobic acid soils, a considerable proportion of the applied phosphates even from DCP and TCP were converted to Al-P and/or Fe-P due to gradual dissolution by the H+ions of the system, resulting in increased Olsen or Bray P. Dry matter production of rice and utilization of applied P was found to be higher when the P carriers were applied to moist acid soils 2 weeks before flooding than when these were applied at flooding. The reasons for this differential response to time of application have been explained. There appears scope for making the citrate soluble and insoluble phosphates as efficident as water soluble phosphates for growing rice on acid soils by their application to the moist soil 2 weeks before flooding.

ISSN:0038-075X    

出版商:OVID    

年代:1977

数据来源: OVID

摘要:

A rating scale was developed to quantitatively evaluate several important morphological properties of soils. The rating scale was used in the following two ways: 1) to determine the relative distinctness of horizons and 2) to determine the relative development of a soil profile. The determination of relative distinctness of horizons was made by a comparison of adjacent horizons, while the determination of the relative profile development was made by a comparison of the C horizon to the horizons above it in the profile. The rating scale was effective in evaluating pedological development of soils developed in a humid-temperate climate. Additional morphological factors may be needed to evaluate pedological development of soils developed in other climatic regimes.

ISSN:0038-075X    

出版商:OVID    

年代:1977

数据来源: OVID

摘要:

The favourable effect of growing rice for the reclamation of sodic soils was examined in a pot experiment.Rice increased the percolation rate even in the highly sodic soil. This seems due to the physical presence of roots which facilitate the movement of water along its surfaces. However, the reclamation efficiency per unit amount of water did not increase, because the water moved mainly through the macropores and not through the entire mass.Biological activity of rice roots lowered the soil pH and decreased the loss of organic matter during the process of leaching. Rice plants resulted in high cumulative removal of soil exchangeable sodium caused by mobilisation of native insoluble CaCo3as a result of increased hydrolysis and CO2liberated by plant roots. In sodic soils as well as in a Na-resin-sand-CaCO3system it was observed that the reclaiming effect of rice was more biochemical in nature rather than through increased permeability alone.

ISSN:0038-075X    

出版商:OVID    

年代:1977

数据来源: OVID

摘要:

Breakthrough curves observed in miscible displacement experiments with finite soil columns often show some asymmetry or tailing. Part of this tailing can be caused by irregulaties in the flow field at the entrance of the column. We observed this effect using entrance plates with well-defined defects so that the incoming flow was not strictly one-dimensional. The resulting tailing created ab additional dispersion which could be as large as the dispersion present in the absence of tailing. A model was also developed where a single parameter was used to describe the extent of tailing. For a given defect the tailing effect increases as the column length decreases. Hence, particularly for short columns, the hydraulic conductivity of the entrance plate should not be greater than that of the soil, and the plate should be checked for occlusions, cracks, or other defects.

ISSN:0038-075X    

出版商:OVID    

年代:1977

数据来源: OVID