Humification

... Tetramethylammonium hydroxide (TMAH) is the most widely used alkylating agent (Challinor, 1989, Challinor, 2001, Saiz-Jimenez et al., 1993, Martin et al., 1994, Martin et al., 2001, Hatcher and Clifford, 1994, Hatcher et al., 1995, Clifford et al., 1995, del Rio and Hatcher, 1996 ...

... Tetramethylammonium hydroxide (TMAH) is the most widely used alkylating agent (Challinor, 1989, Challinor, 2001, Saiz-Jimenez et al., 1993, Martin et al., 1994, Martin et al., 2001, Hatcher and Clifford, 1994, Hatcher et al., 1995, Clifford et al., 1995, del Rio and Hatcher, 1996 ...

Chemical and spectroscopic methods were used to characterize organic matter transformations during the composting process. Four different residue mixtures were studied: P1-garden trimmings (GT) only, P2-GT plus fresh cattle manure, P3-GT plus orange pomace and P4-GT plus filter cake. The thermophilic phase was not reached in P1 compost, but the P2, P3 and P4 composts showed all three typical process phases. The thermophilic phase and CEC/C ratio stabilized after 90 days, while C/N ratio and the ash content stabilized after 60 days. The increasing E 4 /E 6 ratio indicated oxidation reactions occurring during the process in the material from P2, P3 and P4. The 13 C NMR and FTIR results suggested extraction of both pectin and lignin in the HA-like fraction. The CEC/C ratio, temperature and E 4 /E 6 ratio showed that within 90 days P2, P3 and P4 composts were humified. However, material from P1 did not show characteristics of humified compost. From these data, it is apparent that C/N ratio and ash content are not reliable methods for monitoring the composting process.

To assess the effect of continuous organic material (OM) application on soil humic acids, the amount and chemical characteristics of humic acids in various types of soils (n ¼ 10) were compared between plots treated with farmyard manure (FYM) or rice straw compost (RSC) plus chemical fertilizer (CF) and plots treated with CF alone. The degree of humification (degree of darkening), molecular size distribution and 13 C cross polarization/magic angle spinning nuclear magnetic resonance spectra of humic acids from CF-treated soils showed wide variation among the soils. Humic acid content was generally larger in OM þ CF soils than in corresponding CF soils, and the stable C isotopic ratio suggested partial replacement of indigenous humic acids with OM-derived ones even where no apparent increase in humic acid content was observed. The rate of OM application and the indigenous humic acid content were related positively and negatively, respectively, to the apparent accumulation rate of humic acids among soils. The degree of humification of humic acids was generally smaller in OM þ CF soils than in CF soils. Humic acids extracted from FYM and RSC exhibited chemical characteristics typical of humic acids having a smaller degree of humification, which suggested the contribution of OM-derived humic acids to the differences between OM þ CF and CF soil humic acids, such as larger average molecular sizes and smaller and larger proportions of aromatic C and O-alkyl C, respectively, relative to total C in the OM þ CF soil humic acids. Little change was observed in the chemical characteristics of humic acids when the degree of humification of indigenous humic acids was small. The effect of OM application on the chemical characteristics of humic acids was most conspicuous in soils containing humic acids having an intermediate degree of humification, possibly resulting from the combination of accelerated degradation of indigenous humic acids and the accumulation of OM-derived humic acids.

Organic matter protection, defined here as slowing of the oxidation of organic matter, is thought to result from a variety of mechanisms, which can be placed into two classes. Recalcitrant organic-organic linkages often account for protection on shorter time scales; biota intentionally create many of these linkages, leading to bselectively preservedQ organic matter, and various humification reactions may produce others. On longer time scales, exclusion of biota or their digestive agents accounts for most protection, induced by factors such as clay mineral protection and anoxia. Longer term protection likely proceeds through a succession of different mechanisms, acting cooperatively. The papers of this session address kinetic and structural aspects of organic matter protection, in response to factors such as the hydrochemical cycle, organomineral aggregates, molecular aspects of nitrogen, and exposure to oxygen.

A fractional precipitation method with 0.01 mol L-1 NaOH-ethanol solutions was used to assess the temporal change in the composition of humic acids (HAs) in upland field soils with respect to the degree of humification as expressed by the degree of darkening. A Typic Hapludult (Togo) and Pachic Melanudand (Kuriyagawa) with and without the application of cattle manure were examined. Humic acids were fractionated into five to eight fractions, and a fraction precipitated at a lower ethanol concentration tended to have a larger degree of humification in each soil. The slight increase in the degree of humification of Togo HAs in both the manured (40 Mg ha-1 year-1) and non-manured plots after 10 years was exhibited as a shift in the dominant fraction. The distribution pattern in the fractionation of Kuriyagawa HAs was similar between the initial soil and the manured (80 Mg ha-1 year-1) and non-manured plot soils after 19 years. However, the degree of humification of the dominant fraction that was precipitated at the lowest ethanol concentration (200 mL L-1) was smaller in the manured plot soil than in the initial and non-manured plot soils. In another Kuriyagawa soil with manure applied at 160 Mg ha-1 year-1 for 19 years, the amounts of three HA fractions with smaller degrees of humification were larger than those in the other Kuriyagawa soils, and the dominant fraction was observed at a higher ethanol concentration (400 mL L-1). Thus, fractional precipitation was effective in assessing changes in the degree of humification of HAs induced by agricultural practices, including manure application.

and his staff at the Chico Basin Ranch for allowing us access to the fens at the ranch, and John B. Gilmore for providing laboratory and financial assistance. Mark Chenault and his family deserve our appreciation for providing room and board to Kevin Gilmore while he was processing samples at the Arizona ams Facility. Several people provided comments that greatly improved the ideas and presentation of this field note. We would like to thank Kay Wall at ero Resources for technical editing and Craig E. Colten at the Geographical Review, Max Canestorp, and two anonymous reviewers for their constructive comments on our manuscript. As always, we take full responsibility for any errors and omissions.

Responses of termite assemblages to the conversion of semi-deciduous forest into teak plantations were studied in the Lama Forest Reserve in Benin, West Africa. Four belt transect surveys were run in each of the two forest types, adopting a modified termite diversity assessment ...

SUMMARY: Decomposition and humification of powdered plant material of Leptochloa fusca L. Kunth and Sesbania aculeata Pets. by eight soil fungi was studied in pure culture. Maximum decomposition was caused by Sporotrichum pruinosum, and maximum humification by ...