摘要:

SummaryBarley, rye, and cabbage have been used as test plants to measure labile soil phosphate by the Larsen procedure. In some soils higher values are given by rye and cabbage than by barley. These differences are believed to reflect the greater ability of cabbage and rye to lower the free energy of phosphate in the external medium. Thus, in soils contai&ncaring large quantities of labile phosphate at a low potential, sources of phosphate that are inaccessible to barley are accessible to the other two species.

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1958.tb01902.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY

摘要:

SummaryThe distribution of soil inorganic phosphorus in soils was found to measure the degree of chemical weathering, the chemical weathering sequence being calcium phosphate, aluminium phosphate, iron phosphate, and occluded phosphate. The latter category includes reductant soluble iron phosphate and aluminium‐iron phosphate occluded in iron oxides. For example, three horizons of one Chernozem profile, a Dark Brown soil, and the calcareous C1 horizon of a Grey‐Brown Podzolic soil containqd 68–95 per cent. of their inorganic phosphorus in the form of calcium phosphate, the other forms decreasing exponentially in the sequence. The inorganic phosphorus of two Latosols increased exponentially in the order calcium phosphate (1%), aluminium phosphate (0–3%), iron phosphate (10–13 %), and occluded (reductant soluble) phosphate (66–78%). Three samples of podzolized soils contained intermediate, sigmoidal distributions of the four phosphates.In two Miami silt loam profiles, the 0–002 N H2SO4‐extractable‐phosphorus test was much higher in the subsoils down to 31/2 ft. than in the surface soil, and was correlated mostly with the calcium‐phosphate content, somewhat with aluminium and iron phosphate, and none at all with occluded phosphates which constituted a high percentage of the total phosphorus. The higher content of available phosphorus in the subsoils and release of phosphorus in the surface soil by de‐ crease of A1 and Fe activity through liming most probably explain the lack of crop response to added phosphate fertilizer even though the surface soil had a low phosphorus test.Application of phosphate fertilizer to Almena silt loam greatly increased the amount of aluminium and iron phosphate at three lime levels: only a slight increase of calcium phosphate occurred; at tge highest lime level. The amount of occluded phosphate remained unchanged by liming or fertilization. The relatively small increase of calcium phosphate through phosphate application is attributable partly to crop removal but is shown to be due mostly to formation of the less soluble iron and

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1958.tb01903.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY

摘要:

SummaryPhosphate residues in the soil were subdivided into three fractions on the basis of isotopic exchange of orthophosphate ions between the soil and the soil solution. It was observed that the total labile phosphorus was a smaller fraction of the total phosphorus in the heavier soils (c. 20 per cent. clay) than in the lighter soils (1–10 per cent. clay), This could be partly attributed to a higher organic‐phosphorus content in the heavier soils. In comparable soils, recent manuring with superphosphate increased the ratio of the rapidly labile phosphate to the total labile phosphate; in the soils of lower clay content, this ratio was higher than the corresponding ratios in the heavier soils. The recovery of phosphorus added at a moderately heavy rate was estimated by this method of fractionation in soils incubated for periods up to 3 months after treatment. Recovery of added phosphorus in the total labile fraction was incomplete for the calcareous soils, as compared to a I00 per cent. recovery in a neutral soil of similar clay content. Moreover, a redistribution of phosphorus with time was observed in the calcareous soilswithinthe total labile fraction, no such effect being observed with the neutral soil. This was attributed to the presence of internal surfaces on the calcium carbonate pres

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1958.tb01904.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY

摘要:

SummaryThe yields of syringaldehyde, vanillin, and p‐hydroxybenzaldehyde obtained by alkaline‐nitrobenzene oxidation of soil organic matter indicate the extent to which lignin‐derived material is present. A number of soils, peats, and peat fractions have been oxidized by this method and the phenolic aldehydes formed have been separated and determined by a‐ micro‐technique. The results indicate the presence in soil organic matter of significant amounts of syringyl, guaiacyl, and p‐hydroxyphenyl residues which are almost certainly derived from lignin. The yields of aldehydes from mineral soils accounted for about 0.5–1.0 per cent. of the total organic carbon; from peats for about 1.0–4.0 per cent. There was evidence of a correspondence between the relative amounts of the three aldehydes obtained from the soil organic matter and from the parent plant material. The results for a peat profile indicated a tendency for the yield of aldehydes to increase with depth of the horizon; the reverse was found with a pine‐forest soil profile. Peat fractions all gave some aldehydes on oxidation, but there were marked differences in the levels; the highest yield, almost 7 per cent., was obtained from a humic‐acid fraction soluble in ethanol‐benzene. Hydrolysis of the humic‐acid fractions with dilute hydrochloric acid markedly depressed the yields of aldehydes

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1958.tb01905.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY

摘要:

SummaryA technique is described for the identification of clay minerals, the layers of which are difficult to expand or collapse by the usual treatment with glycerol and KCl. Samples are extracted for 3 to 6 hours in normal sodium citrate at pH 7–3 and 100° C. The citrate is renewed hourly. After the citrate extraction the inter‐ layer spaces of some minerals can be expanded with glycerol and CaCl2Basal spacings of minerals previously identified as ‘dioctahedral vermiculite’ expand to 16–18 A. after this treatment; hence, their identity is questioned.The widespread occurrence in the north‐eastem United States of clay minerals with 14‐A. spacing necessitates this extraction for correct

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1958.tb01906.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1958.tb01907.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY

摘要:

SummaryA field and greenhouse study has been made of the effect of nitrogen on the utilization of fertilizer phosphorus by cereal grains. A marked increase in utilization when nitrogen was mixed with either NH4H2PO4or Ca(H2PO4)2was shown to occur only when the nitrogen was in the ammonium form. Nitrate sources of nitrogen were relatively ineffective. Placement of nitrogen was important as increased uptake only occurred when the ammonium ion was intimately associated with the phosphorus fertilizer. This stimulative effect of the ammonium ion on phosphorus uptake occurred at a very early stage of crop growth.Rapid ammonium‐ion absorption by young cereal seedlings occurred irrespective of whether the ammonium source of nitrogen was mixed with, or separated from, the phosphorus carrier. Thus the ammonium ion appears to be the dominant factor; it indirectly influences the plant's ability to take up phosphorus, rather than altering in any way the availability of the applied phosphorus fertilize

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1958.tb01908.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY