Showing papers on "Soil organic matter published in 1974"

Loss-on-Ignition as an Estimate of Soil Organic Matter

Abstract: Loss-on-ignition at 430C of calcareous and noncalcareous soils has been compared with organic matter contents estimated by a wet oxidation method. The presence of CaCO₃ did not affect the magnitude of the ignition-loss and the gravimetric method provides both a reliable and simple estimation of soil organic matter.

Effects of neutral salts on carbon and nitrogen mineralisation of organic matter in soil

Abstract: In an incubation experiment the mineralisation of gulmohur (Delonix regia L.) leaves added to soil was studied at increased salt concentrations. CO2 evolution and total carbon mineralisation decreased with increased concentrations of salt mixture (NaCl+CaCl2) from 0.1 to 5.1 per cent, and the process of nitrification was completely inhibited between 0.6–0.9 per cent salt. The loss of nitrogen was about 10.4 per cent from control up to 0.6 per cent salt and about 17.8 per cent from 0.9 to 5.1 per cent salt. The formation of ammonium was of the same order of magnitude under all treatments. Extractable carbon varied between 27–32 per cent of the total carbon in the soil and humic/fulvic acid carbon ratio varied between narrow limits of 0.41–0.58 in saline and non-saline soils.

Effects of cultivation on the organic matter of grassland soils as determined by fractionation and radiocarbon dating

Abstract: The effects of cultivation on the net mineralization of carbon and nitrogen in a lacustrine Brown clay (Sceptre) and two Orthic Black soils on glacial till (Oxbow) were assessed with the aid of fractionation and radiocarbon dating techniques. Fractionation of the soil organic matter of comparative virgin and cultivated soils by acid hydrolysis and peptization in dilute NaOH showed that the distribution of carbon and nitrogen among fractions of these soils was similar. There was no measurable alteration in the mean residence time (MRT) of the soil during the first 15 to 20 yr of cultivation, during which time the Sceptre soil had lost 19% of its carbon and the Oxbow, 35%. However, the MRT increased from 250 yr before present (BP) to 710 years BP after 60 yr of cultivation of the Oxbow soil. The losses for nitrogen were 10% lower than for carbon in the Oxbow soil due to the recycling of nitrogen in the soil. The rate of loss of carbon from the Oxbow soil during the cultivation period was simulated by expres...

Decomposition of elephant dung in an arid, tropical environment.

Abstract: Carbon dioxide evolution from elephant dung and bare soil was measured in relation to the chemical composition of the decomposing organic material, temperature and moisture. Carbon mineralisation from the dung was extremely rapid during the first 48 hours after deposition but micro-organism activity became progressively more limited by moisture after this initial period, and was at a comparatively low rate after two weeks when the dung was dry. Under high moisture controlled conditions CO2 evolution from the dung was primarily temperature limited, but a decrease in the carbon mineralisation rate and the temperature response over the 14 day experimental period suggested that the availability of carbon and nutrient resources also became limiting to micro-organism activity. Carbon dioxide evolution from the soil was negligible under normal conditions but both the soil and dry dung showed a rapid increase in CO2 evolution rates following the addition of water. The implication of these results for the dynamics of soil organic matter during the wet and dry seasons and for the ecology of dung beetles is discussed.

Whole-tree Harvesting Depletes Soil Nutrients

Abstract: This paper reports the effects of whole-tree harvesting of eight cottonwood stands on the soil nutrient pool. The data indicate possible site degradation by depletion of soil reserves of N, P, and K but not Ca and Mg on a range of alluvial site conditions in Alabama. Foresters must establish the rate of nutrient removal in intensive tree cropping systems for a variety of species and sites and develop prescriptions to minimize the impact.

The influence of net charge on water dispersible clay and sorbed sulphate

Abstract: The variation of net electric charge with pH at four electrolyte concentrations has been determined on samples from four horizons of a krasnozem soil in north Queensland. A potentiometric titration technique was employed, which allowed the estimation of the zero point of charge (zpc) for each sample. Variation in zpc was related to organic matter content and clay mineralogical composition. The charge distribution characteristics explain the amounts of water dispersible clay and phosphate extractable sulphate in this soil.

Effect of zero-tillage on organic carbon and total nitrogen content, and their distribution in different N-fractions in loessial soils

Abstract: In order to evaluate the effect of reduced tillage intensity on the accumulation of organic matter in Grey-brown podsolic soils near Gottingen (German Federal Republic), stratified soil analyses were made in three field trials after at least 5 years of experimenting. On old arable soil, zero-tillage increased the content of organic C of the 0–30 cm layer by mean annual rates of 0.59–1.30 tons/ha, and correspondingly the content of total N by 53.8–72.4 kg/ha. Killing a sod and cropping the former grassland with annual field crops, but without disturbing the soil, caused a mean annual loss of 2.29 tons/ha and 162.4 kg N/ha. This indicates that reduced tillage cannot preserve the original high content of soil organic matter maintained by a living sod. On arable soil, zero-tillage caused a mode of nitrogen distribution which is similar to that found in grassland soil. The N-content of fraction V (containing total amino-acid N and unknowns) increased at the expense of the ammonium-N (fraction I). The relative increase or loss of total N in the 0–5 cm layer, as caused by tillage and cropping practices, was most pronounced in fraction V, ranging between 53 and 67%.

Identification of the wound infection-potentiating factors in soil.

Abstract: Even the most trivial combat wound is regularly contaminated with soil. Unless this foreign body is adequately cleansed from the wound the risk of subsequent infection is great. The causal factors for this deleterious effect of soil have, until now, been unknown. Results of this study have led to the identification of the factors in soil that potentiate the development of infection. When an injury contained as few as 100 bacteria, the addition of 5 mg of soil led to infection. When this soil sample was fractionated, it was found that the infection-potentiating factors (IPFs) resided predominantly in the clay or organic soil fractions or both. The type of cation adsorbed by the surface of the IPF did not influence its toxic effects on tissues. Silicate clay fractions contain several colloidal clay minerals: montmorillonite, illite, and kaolinite. Montmorillonite clay enhanced the development of infection more than did illite or kaolinite. The IPFs in organic and clay fractions of soil can be characterized by their large surface area and high cation exchange capacity. This physical property of the IPFs ensures an active chemical exchange between the wound and the IPFs which may account for their deleterious effects. Isolation and identification of the factors in soil that potentiate infection will enable us to develop technics for the efficient removal of these agents based on modern pedologic methods.

Salt content of lateritic profiles in the Darling Range, Western Australia

Abstract: Soil cores from some 40 complete laterite profiles as deep as 40 m in the Darling Range, W.A., have been examined for salt content, and in some cases, pH. The sites cover a range of topographic situations from divides to valley floors, and of rainfall from 560 to 1350 mm per annum. Increases in surface soil salinity and in the salt concentration of water yields following clearing of the native hardwood forest are related to the amounts of soluble salts stored in the lateritic pallid zones. Storage increases as rainfall decreases in all slope situations. In low rainfall areas (<800 mm per annum) the salt stored under unit area of landscape in the profile down to bedrock is five times greater than in high rainfall areas (G1000 mm per annum). One area with an annual rainfall of 600 mm has an estimated storage of nearly a million kg of total salts per ha and marked increases in surface soil salinity have occurred within 10 years of clearing. Although in the past, increasing soil salinity has mainly affected agricultural land, the present emphasis on bauxite mining in the forested areas of the Darling Range, particularly in the drier parts, poses new problems in revegetating the exposed saline and acid pallid zone clays after mining operations have ceased.

Direct Measurement of the Composition of Soil Components Which Retain Added Arsenate

Abstract: The combined use of autoradiography, electron microscopy and electron probe microanalysis provided a direct method of defining the location of arsenate added to a soil and of identifying the soil component mainly responsible for its retention. In the soil examined, arsenate was retained by the goethite particles which also held the native phosphorus.

A high sample volume procedure for the colorimetric determination of soil organic matter

Abstract: A modified procedure for routine determination of soil organic matter is described. The procedure employs a wet combustion method of reducing the carbon in soil organic matter with dichromate in an acid media. The modification will permit 700–800 organic matter determinations per day with samples containing less than 8% 0M without undue difficulty.

Assessment of available soil sulphur in an 35s growth chamber experiment

Abstract: Growth chamber and laboratory studies of four selected soils differing in C:N:S ratios and the percentage of total S present as HI-reducible S in the soil organic matter showed that: (1) the yield response of alfalfa to applied S occurred when the 0.01 M CaCl2-extractable soil SO4—S was less than 3.3 μg/g, (2) mineralization of soil organic S was unaffected by the addition of 25 μg S/g to the soils, and (3) the amount of S mineralized was not directly related to the quantity of total S, HI-S or the percentage of total S present as Hi-reducible S. It was noted that the largest amount of S mineralized occurred from the soil with the lowest C:N:S ratios.

MICROBIAL MECHANISM OF EFFECTS OF WATER PERCOLATION ON Eh, IRON, AND NITROGEN TRANSFORMATION IN THE SUBMERGED PADDY SOILS

Abstract: Effects of percolating of water through the submerged paddy fields were analyzed by laboratory experiments. Soil samples were taken from the surface layer of three kinds of paddy soil with varying amounts of easily decomposable organic substances. The air-dried soil samples put in glass vessels were incubated under submerged conditions. One series of the submerged soil was percolated with water (percolated plot) and another series was held under stagnant water (nonpercolated plot). Complex nature of the effects of the percolating water on the soil dynamics is fairly well clarified. If a soil contains large amount of easily decomposable organic substances, both supply of molecular oxygen and removal of water-soluble toxic substances are considered to enhance microbial activities and lead to increase in formation of ammonium and ferrous iron and decrease in Eh of the soil. Meanwhile, if a soil contains small amount of easily decomposable organic substances, supply of molecular oxygen will oxidizes ...

Soil organic matter and the adsorption and decomposition of the herbicides atrazine and linuron

Abstract: Soil was subjected to a variety of treatments so as to provide a series of materials with different organic residues. These preparations were inoculated with an aqueous extract of untreated soil, then incubated at 20°C with atrazine or linuron and rates of herbicide degradation were followed. The rates were lowest when virtually all the organic matter had been removed by peroxidation. The most rapid break-down occurred in samples which had been successively extracted with ethanol + toluene, hot water, dilute acid and dilute alkali. It is suggested that the organic residue left after this sequence contained hydrolysed materials that were easily metabolized and hence could support the most active microbial population. There was no relationship between extent of adsorption and decomposition rate.

Salt and water movement in relatively dry soil

Abstract: When dry crystalline salt is placed in contact with relatively dry soil, water is found to accumulate in the soil immediately adjacent to the salt, and dissolved salt moves into this wetter region. A recent paper by Parlange presents a theory modelling the salt and water movement in such situations. To allow this theory to be checked against experiment, basic data on water potentials and water and salt diffusivities as functions of water content for the particular soil used are necessary. Such data, as well as data showing salt and water movement in soil near crystalline salt, are reported and used to check the Parlange theory. The theory is shown to have some limited success in predicting the salt movement into the soil, but to inadequately explain the water distribution in the wetter region adjacent to the crystalline salt. It is suggested that this failure is due to significant water movement in the vapour phase into the wetter soil, which is not accounted for in the theory.