Soil Index Table

Values are in tons per acre (t ha in parentheses) ground/magnesium limestone or chalk of neutralizing value 50-55, with fineness of 40% passing through a 150 pm (No. 100) sieve, and to bring the top 20 cm (8 in) of soil to the optimum pH of 5.5 (5.8 for peaty soil). 

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There are many different types of soil, and extractant formulations have been fine-tuned to suit the soil. The particular extractant may also be chosen on the basis of familiarity over the years, and because it is easier to compare results with those previously obtained, and hence make recommendations to correct deficiencies based on experience. Usually one is not interested in the total amount of a soil nutrient, rather in the amount that is in a form available to the roots of the plant. Regional advisory laboratories over a long period may have developed index tables relating to the found concentration of nutrient in local soil types and the corrective amount of fertilizer required. It would probably be wise to adopt the same methods that have been used to... 

Analyses will be those in common use for soils from fields for both grass and arable crops. MAFF/ADAS (now DEFRA) methods and Index Tables are reproduced by permission of the Controller of Her Majesty s Stationery Office (Ref. 20001327). Analyses for nitrogen mineralization are included. Special consideration will be given to composts and recycled urban waste. 

The new Defra nitrogen recommendations continue to use Soil Nitrogen Supply (SNS) as their basis but the system has been fully revised with clearer definitions of soil type and revised index tables. Defra defines SNS as the amount of nitrogen (kg N/ha) in the soil (apart from that applied for the crop in manufactured fertilisers and manures) that is available for uptake by the crop throughout its entire life, taking accoimt of nitrogen losses . It is calculated using the equation ... 

As a soil develops, P appears in different forms, and both the distribution of P among these forms and the total amount of P present in the soil provides a useful index of the extent of soil development. In a climosequence of New Zealand soils in tussock grassland, for example, total P (P ) mainly declined with increasing soil development (Table 1) with lowest levels in the three podzolised members. The proportion of available P (0.5 M H2SOj -soluble P) also declined across the sequence, while the proportion in organic forms increased. Levels of P that can occur in soils vary widely from near zero to over 0.2%. In some New Zealand soil chronosequences, P levels have been shown to reach a maximum eventually which is maintained up to soil ages of about 20,000 years. Levels then decline as a result of leaching losses, such as occur in the humid tropics. 

Potassium nitrate is being used increasingly on intensive crops such as tomatoes, potatoes, tobacco, leafy vegetables, citms, and peaches. The properties that make it particularly desirable for these crops are low salt index, nitrate nitrogen, favorable N K20 ratio, negligible CU content, and alkaline residual reaction in the soil. The low hygroscopicity of KNO (Table 9) leads to its use in direct appHcation and in mixtures. It is an excellent fertilizer but the high cost of production limits its use to specialty fertilizers. 

The partition index (IR, which will be discussed in details below) of Cd, Cu, Cr, Ni and Zn in both soils rapidly increased from time zero (calculated value) to one day and further to one year. This was especially true for Cr, Cu and to some extent Ni and Cd (Table 6.5). This result indicates that added trace metals are initially and rapidly transferred from the labile EXC fraction into the more stable fractions. Furthermore, IR of trace metals in native arid soils incubated under the saturated paste regime decreased at the end of year. This indicates mobilization of trace elements in these soils as saturation (Table 6.5). Also, it can be seen that IR decreased, for any given time, with an increase of the loading level (Table 6.5, Fig. 6.5). This means that higher additions of soluble metals result in higher metal content in the labile fractions and lower metal binding intensity in soils. 

Table 6.5. Reduced partition index (IR) of trace metals in arid-zone soils incubated under saturated paste regime (after Han and Banin, 1997. Reprinted from Water Air Soil Pollut, 95, Han F.X., Banin A., Long-term transformations and redistribution of potentially toxic heavy metals in arid-zone soils. I Incubation under saturated conditions, p 411, Copyright (1997), with permission from Springer Science and Business Media)...

Table 3. Soil fertility index (SFI) degradation or soil evaluation factor (SEF) reflecting the land ...

For the purposes of this example, it was assumed that the waste was placed 4 m deep and covered with a cap and soil that was at least 3 m thick. As a consequence, the assumed scenario was an onsite drilling event. The dose analysis assumes a two-fold volume increase (50 percent dilution) of the drill tailings by uncontaminated material. The mixture of waste and uncontaminated cover material is spread on the surface of the site, and individuals working in the area are exposed to the tailings for 1,000 h. The thickness of the layer of contaminated drill tailings is assumed to be about 5 cm and the area to be about 3.3 m2. Using dose as a surrogate for risk, analysis of this scenario yields a dose of0.002 mSv from all radionuclides. Since the assumed allowable dose is 20 mSv (see Table 7.1), the risk index would be 0.002/20 = 10 4, which is well below the value of unity, and the waste would be classified as low-hazard. 

As an alternative to the assumption of a one-time exposure for 1,000 h at the time of facility closure, permanent occupancy of a disposal site following loss of institutional control could be assumed (see Section 7.1.3.4). The assumption of chronic lifetime exposure would affect the analysis for hazardous chemicals that induce deterministic effects only if estimated intakes due to additional pathways, such as consumption of contaminated vegetables or other foodstuffs produced on the site, were significant. Based on the results for lead in Table 7.8, an intake rate from additional pathways of about 50 percent of the assumed intake rate by soil ingestion, inhalation, and dermal absorption would be sufficient to increase the deterministic risk index above unity. The importance of additional pathways was not investigated in this analysis, but they clearly would warrant consideration. The increase in exposure time during permanent occupancy does not otherwise affect the analysis for chemicals that induce deterministic effects, provided RfDs are appropriate for chronic exposure, because chronic RfDs incorporate an assumption that the levels of contaminants in body organs relative to the intake rate (dose) are at steady state. 

In drinking water, color may be used as an index of large quantities of organic chemicals from plants and soil organic matter. Metals such as copper, iron, and manganese may also introduce color (Table 13.8). 

Since at pH 2 virtually all the 4-amino-3,5,6-trichloropicolinic acid will be in the free acid form, this partition coefficient—and therefore the sorption index—would be constant if extraction is the mechanism by which the free acid is absorbed. Table IV shows reasonable constancy for the sorption index over a wide range of organic contents except for the first three soils—i.e., soils 3, 4, and 7. There are at least two possible causes for failure of this relationship in these cases other components contributing significantly to sorption, and analytical uncertainty in or-... 

The kinetic data on desorption of Cd by phosphate, as related to the amount of Cd released during the initial 30-minute reaction period and the overall diffusion coefficients obtained from the desorption kinetics of Cd by mol NH4CI from the soils, reflect well the phytoavailable Cd in the two soils, as shown by the Cd availability index and the grain Cd content of two durum wheat cultivars, Kyle and Arcola, grown on the two soils (Table 5.6). 

The kinetics of Cd release, as influenced by the LMMOLs, play an important role in plant Cd uptake. The kinetic rate constant of Cd release, as obtained from desorption kinetics of Cd by LMMOLs and the amount of Cd released by renewal of LMMOLs from the soil, followed the same trend as the cadmium availability index and Cd grain content of durum wheat grown on the soils (Table 5.7). These reports highlight the significance of Cd desorption kinetics in understanding Cd dynamics and phytoavailability. 

From a quantitative point of view, the global PAH concentration can be estimated with the use of PAH index previously defined in Chapter 4. The value of the ratio 254 nm 288 nm gives information on the distribution of PAH in the contaminated soils, namely that as higher is this ratio, and higher is the proportion of light PAHs. Table 7 collects the data related to the two studied contaminated soils. 

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