Scielo RSS <![CDATA[Journal of soil science and plant nutrition]]> vol. 14 num. 3 lang. es <![CDATA[SciELO Logo]]> <![CDATA[<b>Improving maize residue use in soil fertility restoration by mixing with residues of low C-to-N ratio</b>: <b>effects on C and N mineralization and soil microbial biomass</b>]]> The application of organic residues with wide C-to-N ratio on soils is known to cause nitrogen immobilization unless applied with nitrogen fertilizer. Considering that fertilizer usage is limited in low input agricultural systems in Africa. we determined whether it was possible to alleviate N immobilization of Zea mays (maize) by applying together with Tithonia diversifolia or Vicia faba green manure with low C-to-N ratio. The effect of sole Z. mays application on soil microbial biomass and carbon mineralization were also compared with when mixed with T. diversifolia or V. faba. The objectives were achieved using laboratory incubation experiments conducted over 84 days. As expected. the application of sole Z. mays residues resulted in an initial net N immobilization that lasted for 28 days. Relative to sole Z. mays. the application of Z. mays with either V. faba or T. diversifolia increased N mineralization by 58% and 55% respectively. It was also evident. that in comparison with sole Z. mays. soil microbial biomass and C mineralization were significantly higher in soils that received residues of V. faba and T. diversifolia either alone or in combination with Z. mays. The study showed that V. faba and T. diversifolia either alone or in combination with Z. mays residues had relatively high N concentration and narrow C-to-N ratio. which accounted for the increased N mineralization and improved microbial biomass and C mineralization. We inferred from the results of our study that N supplies from V. faba and T. diversifolia could be substantial in alleviating delayed decomposition and N immobilization of Z. mays residues. <![CDATA[<b>Influence of integrated soil fertility management in wheat and tef productivity and soil chemical properties in the highland tropical environment</b>]]> Soil fertility depletion and soil quality decline have been threatening the ecological and economic sustainability of crop production. In order to improve soil fertility and nutrient management approaches, on-farm integrated soil fertility management (ISFM) trials were conducted to evaluate the effects of organic and inorganic fertilizers on wheat (Triticum estivum L.) and tef (Eragrostis tef) yield and soil fertility in the highland Nitisol area of Ethiopia during 2010 and 2011 cropping seasons. The treatments were five selected combinations of N and P, manure and compost. These included control, farmers' practice (23/10 kg NP ha-1), recommended NP rate (60/20 kg NP ha-1), 50% of recommended NP rate (30/10 NP kg ha-1) + 50% manure and compost as inorganic N equivalence (3.25 tons ha-1). and 50% manure + 50% compost as N equivalence. Results revealed that yields of wheat and tef, and some soil chemical properties significantly responded to the different soil fertility management treatments. The application of 60/20 kg NP ha-1 and 30/10 kg NP ha-1 with 50% manure and compost as N equivalence increased mean grain yield of wheat by 151 and 129% respectively compared to the control, and by 85 and 68% respectively compared to the farmers' treatment (23/10 kg NP ha-1). Similarly, the same treatments increased tef grain yield by 141 and 122% compared to the control, and by 44 and 33% compared to the farmers' treatment.The application of compost or manure with half the recommended NP fertilizer rate resulted in a comparable yield as that of full NP dose, which could beconsidered as an alternative option for sustainable soil health and crop productivity. In conclusion, the two year result showed that the application of ISFM may optimize yield of wheat and tef as well as improve the fertility status of the soil. <![CDATA[<b>Biometric and biochemical attributes of alfalfa seedlings as indicators of stress induced by excessive cadmium</b>]]> The biometric and biochemical attributes of alfalfa (Medicago sativa L.) seedlings were studied after their exposure to 0-120 µM cadmium for 28 days using hydroponic culture. The growth, photosynthetic area and pigment contents (chlorophyll a, b and total) declined significantly (p < 0.05) in the presence of high cadmium concentrations (90 and 120 µM). A steady increase in lipid peroxidation assessed via MDA production was observed with increasing levels of cadmium. Cadmium uptake by the plant tissues was concentration dependent. The roots accumulated 1020 µg g-1 of cadmium which was two folds than leaves. An enhanced production up to 600 µg g-1 of proline was observed at higher levels of cadmium. Though, cadmium toxicity was expressed in terms of decline in growth variables, chlorophyll content and oxidative damage but restricted transfer of the metal to the aerial tissue and greater production of proline in response to higher metal content seems to alleviate cadmium toxicity. Thus, ability of alfalfa plants to tolerate high cadmium concentrations can be a manifestation of effective defensive mechanism derived from differential accumulation of metal in plant tissues in addition to enhanced production of proline. <![CDATA[<b>Intercropping with grasses helps to reduce iron chlorosis in olive</b>]]> Grasses are more efficient than dicots in acquiring Fe from calcareous soils. We studied whether intercropping with grasses alleviates Fe chlorosis in olive and whether the effect persists in succeeding dicot crops. Three different pot experiments were conducted. In the first, olive plants were intercropped with 6 different grass species (purple false brome, annual ryegrass, compact brome, goatgrass, barley and red fescue); in the second, the two species best performing in the previous experiment were studied in various calcareous soils and; in the third, chickpea and peanut were grown in pots previously used to cultivate the two grasses. Intercropping with purple false brome and barley increased leaf chlorophyll concentrations and/or boosted growth of olive trees on three different calcareous soils. Olive growth was adversely affected by intercropping in one soil as a result of competition for water. Intercropping increased Fe, Mn, Cu and Zn leaf contents in olive. Also, grass cropping generally raised available levels of soil Fe, Mn, Cu and Zn; this effect, however, resulted in no substantial alleviation of Fe chlorosis in succeeding chickpea or peanut crops. Intercropping with purple false brome and barley appears to be a promising remedy for Fe chlorosis in olive orchards affected by Fe chlorosis. <![CDATA[<b>Response of bacterial community to simulated nitrogen deposition in soils and a unique relationship between plant species and soil bacteria in the Songnen grassland in Northeastern China</b>]]> Nitrogen (N) deposition greatly affects the above ground biological composition of grasslands and soil properties. However, its influence on the relationship among soil, plant and bacterial communities remain controversy. We calculated Shannon-wiener index to measure the soil bacterial diversity based on denaturing gradient gel electrophoresis, and investigate the roles of vegetation and soil properties on the soil bacterial community under N addition. A three-year simulated N deposition experiment was conducted in a forbs community dominated by Leymus chinensis (Trin.) Tzvel. and Artemisia scoparia Wald. Et. Kit. N was added at five levels (0, 23, 46, 69, 92 kg ha-1 yr-1). Our results showed that N addition increased the soil microbial biomass carbon (SMBC) and soil bacterial diversity. Moderate N (23, 46, 69 kg ha-1 yr¹) addition increased the soil bacterial diversity, whereas excess N (92 kg ha-1 yr-1) addition inhibited it. The SMBC and soil bacterial diversity were related to richness of plant functional groups. In particular, SMBC had positive correlation with biomass of annuals and biennials, suggesting that the effects of the plant community on the soil bacteria could be explained by a relationship between the soil bacterial community and a subset of plant species rather than all species. <![CDATA[<b>Detection of <i>Neofusicoccum nonquaesitum</i> causing dieback and canker in highbush blueberry from Southern Chile</b>]]> Due to increased incidence of wood fungi from genus Neofusicoccum in highbush blueberry (Vaccinium corymbosum L.) established in various locations in Southern Chile. The objective of this study was the identification of Neofusicocum species in two highbush blueberry cultivars from commercial orchards in Southern Chile. During 2011-12 season, stems with basal cankers and twigs with dieback were collected from cultivars Brigitta and Elliott grown in Panguipulli (39°30'S; 72° 19'W) and Teodoro Schmidt (38°58'S; 73°02'W). Tissues were kept in humid conditions and from cirrus conidia were taken and incubated in PDA medium. The mycelia had a cottony consistency, with colour ranging from greyish-white to black; sub-epidermal pycnidia were eruptive, ostiolate, and brown to black in colour. The unicellular conidia were hyaline, smooth-bordered, coenocytic and septate (1-3), with dense granular content, fusiform and elipsoidal with truncated point, measuring 27.2 - 29.4 (±3.0) μm x 7.7 - 8.4 (±0.9) μm; length/width ratio (L/W) = 3.6 ±0.6 (n=100). The morphometric characteristics corresponded to those of Neofusicoccum nonquaesitum and corroborated genetically (100% homologation) by rDNA sequencing ITS and was recorded in CABI under number IMI-500168. Whereas, the sequencing was deposited into Genbank (accession number JX217819.1). The pathogenicity of the fungus was consistent in twigs and stems of highbush blueberry cultivars Brigitta and Elliott. <![CDATA[<b>Spatial variability of the hydraulic properties of a drip irrigated andisol under blueberries</b>]]> The objective of the present investigation was to identify the spatial variability of hydraulic properties of a volcanic ash soil under irrigated Blueberry crops, in order to improve the irrigation efficiency in a very sensitive crop by excess or lack of water. Undisturbed samples (230 cm³) were collected in area of 945 m² (grid: 72 points separated by 3.2 and 6.4 m) between 1 and 7 cm depth in an Acrudoxic Fulvudands to determine the bulk density (Bd), total porosity (TP), the volume of water-filled pore space (ea(6kPa)), plant available water (PAW), permanent wilting point (PWP) and saturated hydraulic conductivity (Ks). Along with sampling, volumetric water content (θ(Field)) was measured using a TDR (grid: 120 points spaced by 1.4 and 3.2 m). From all results contour maps were developed, using geostatistical tools. The coefficient of variation of (θ(Field)), Ks, (ea(6kPa)) and PAW showed a moderate variability (15 % - 35 %). The dependence degree (DD) was considered as weak for (θ(Field)), moderate for(6kPa) ), ea(6kPa), PAW and high for Bd, TP, Ks and (θ(0.1kPa). The properties with largest DD were soil structure-dependent, whereas, the lowest values were observed for those related to soil texture (in this case θ(Field), which were close to the PMP). The spatial variability was related to the high water storage capacity and the ability of the soil to conduct water with different intensities, what is related to the amount of water-filled macropores. <![CDATA[<b>Growth and nutrient status of olive plants as influenced by foliar potassium applications</b>]]> Olive (Olea europaea L.) plants were sprayed (one, two or three times) with nutrient solutions containing KCl, KNO3 and K2SO4 with the same amount of K (0, 1, 2 and 3% w/v). The weight of the plants was unaffected by salt type, number of sprays or K concentration of salts, whereas the dry matter percentage was significantly increased in the plants treated with K2SO4. Furthermore, the application of K2SO4 led to a significantly higher N concentration in leaves than that of KCl. K-salts increased K concentration in plants in the following order: KCl> KNO3> K2SO4 and three foliar applications were significantly more efficient than one. Moreover, irrespective of plant part, K spray application frequency significantly affected Fe and Zn concentrations in the plants studied. Finally, although KCl increased Cl concentrations more than KNO3 and K2SO4, the former fertilizer was the most efficient to improve the K status of the olive cv. Chondrolia Chalkidikis. <![CDATA[<b>Responses of nitrogen metabolism to copper stress in <i>Luffa cylindrica</i> roots</b>]]> Pot experiments were performed to investigate the responses of nitrogen metabolism to copper stress in Luffa cylindrica roots. Four treatments were used, in which varying copper concentrations (25, 50, 75 and 100 µM ) were added to MS medium. The fresh weights of the roots decreased gradually with the increasing copper concentrations. At the lower concentrations, the ammonium and nitrite levels increased compared with the control, but the nitrate concentrations significantly decreased with 75 and 100 µM copper. Compared with the control, nitrate reductase activity levels gradually increased with increasing copper concentrations of up to 50 µM, and nitrite reductase activity levels significantly decreased. Copper stress led to variable increases in the activities of glutamine synthetase and glutamate synthase compared with the controls. The NADH- glutamate dehydrogenase (NADH-GDH) and NAD-glutamate dehydrogenase (NAD-GDH) activities were affected by the copper treatments, but that of NAD-GDH was significantly reduced by 100 µM copper. The activities of alanine aminotransferase (AlaAT) and aspartate aminotransferase (AspAT) showed varying changes following the copper treatments. The present results indicate that Luffa cylindrica shows altered activities of enzymes associated with nitrogen metabolism during copper stress, enabling it to monitor and adapt to changes in its N status and supply, thereby minimizing the harmful effects of the stress. <![CDATA[<b>Thermal stability of organic carbon in soil aggregates of maize-wheat system in semi arid India</b>]]> Understanding the stability and carbon retention ability of aggregates under common cropping sequences is essential to ascertain terrestrial carbon storage. Surface soil samples (0-15 cm) were collected and dry sieved to separate the macro (&gt;250µm) and micro sized aggregates (<250µm). The separated aggregates were subjected to 60 days incubation at four different temperatures (25, 30, 35 and 40 °C). Nutrient management was more prominent than tillage in determining water stable aggregates. 100% organic treated plots in bed planting and mineral fertilizers + crop residues in conventional tillage gave maximum mean weight diameter values of 1.01 and 0.95 respectively. Irrespective of the treatments, microaggregates were found to be poorer in carbon content, but richer in their capacity to retain it by way of larger activation energies. The Q10 values were found to be higher in microaggregates than macroaggregates for all treatments, confirming the thermal sensitivity hypothesis of stable carbon fractions. <![CDATA[<b>Fractions, uptake and fixation capacity of phosphorus and potassium in three contrasting soil orders</b>]]> A controlled greenhouse experiment was conducted to study the fraction, uptake and fixation of phosphorus (P) and potassium (K) in three soils with contrasting characteristics. The experiment was carried out in two phases, viz., sorghum-Sudangrass depletion and test crop experiment with maize with three levels of fertility status (depleted, original and fertilized with 40 mg kg-1 P and K) and two levels of rhizospheric status (rhizosphere and non rhizosphere). Clay was separated by ultrasonic vibration followed by fractionation into colloidal and non colloidal clay and short-range order (SRO) minerals, P and K fixation were measured in these clays. Phosphorus and potassium fractions and uptake were measured in soil samples. The results showed that, available and non-exchangeable potassium was highest in Vertisol and Inceptisol, respectively. Calcium-P was the dominant fraction in soil and highest in Inceptisol. Maximum K-fixation capacity for both the clay fractions was found in Vertisol (32.57% for colloidal clay and 37.94% for non colloidal clay), depleted soils (30.58% for colloidal clay and 31.04% for non colloidal clay) and rhizosphere (28.34% for colloidal clay and 29.59% for non colloidal clay). Phosphorus fixation was highest in Alfisol (58.72% for colloidal clay and 67.26% for non colloidal clay), depleted fertility status (53.41% for colloidal clay 55.45% for non colloidal clay) and non-rhizosphere (52.53% for colloidal clay and 54.26% for non colloidal clay) for both the clays. Phosphorus fixation was positively correlated with different pools of iron and aluminum compounds whereas, potassium fixation showed positive significant correlation with amorphous ferri-alumino silicate content. <![CDATA[<b>Soil assessment for urban agriculture</b>: <b>a Vancouver case study</b>]]> With the expansion of urban agriculture in many North American cities, there is a current need to evaluate the soil and urban environment to assess potential risks of metal contamination in urban grown food. In this study, a university farm, a community garden, and a brownfield located in Vancouver, BC were characterized with respect to soil metal concentrations, atmospheric deposition of metals, and bioaccumulation of metals in Poa pratensis. Wet and dry deposition were collected over five months. Aqua regia and HCl extractions were used to evaluate total and labile metal fractions of Zn, Pb, Ni, Mn, and Cu. Highest soil metal concentrations, atmospheric deposition flux, and bioaccumulation in Poa were found at the community garden, followed by the brownfield site, and the University of British Columbia Farm. Concentrations of Ni and Mn seem to be associated with soil parent material, while Zn, Pb, and Cu were indicators of industrial activity. Concentrations of metals in atmospheric deposition were not an immediate concern but their potential accumulation in the soil requires attention. The framework developed by the case study identified three factors meaningful for assessing metal contamination on an urban agriculture site: site history, atmospheric deposition trends, and parent material. <![CDATA[<b>Establishment of empirical relations between fuel moisture content and the normalised difference vegetation index</b>]]> The object of the present research is to establish empirical relations between the Fuel Moisture Content (FMC) and the Normalised Difference Vegetation Index (NDVI) in pasture samples. The study area was the Carillanca Experimental Centre belonging to the Institute ofAgriculture and Livestock Research (Instituto de Investigaciones Agropecuarias - INIA), Araucanía Region, Chile. The study period ran from November 2011 to January 2012, in order to determine the variation in vegetation moisture content from spring, when plant cover is most vigorous, to summer when it declines to a minimum due to the summer drought. The application of a linear adjustment model produced correlation coefficients higher than 0.6. <![CDATA[<b>The impact of CO<sub>2</sub> enrichment on fiber dimension and lignocellulose properties of three varieties of kenaf <i>(Hibiscus cannabinus L.)</i></b>]]> The effects of two different carbon dioxide levels on fiber yield, fiber dimension and lignocelluloses properties of three varieties of kenaf (Hibiscus cannabinus L.) namely Fuhong (FH991), V36 and Kohn-Kaen60 (KK60) were assessed in a growth house experiment at faculty of Agriculture, Universiti Putra Malaysia. Seeds were sown in polyethylene bags containing top (loamy soil). Carbon dioxide enrichment treatment started when the seedlings reached four weeks and plants were exposed to 400 and 800 µmol mol-1 of CO2. A factorial experiment was arranged in a split plot using a randomized complete block design (The CO2 chamber is perpendicular to sunrise and sunset) with CO2 levels as the main plot, and different varieties as sub-plot replicated three times. Different CO2 levels had significant impact on fiber dimension, fiber yield and lignocellulose properties of bast and core fiber for all three varieties. Result indicated that increasing CO2 concentration from 400 µmol mol-1 to 800 µmol mol-1 positively affected fiber of all varieties under study. Increase in fiber length and slight reduction in fiber diameter at 800 mol-1 resulted in higher fiber quality for paper production purposes. These results provide significant insights into opportunities for growing of kenaf under enriched CO2 concentration. <![CDATA[<b>Response to organic fertilization in mango cultivars</b>: <b>Manila, Tommy Atkins and Ataulfo</b>]]> The objective was evaluating the response to mineral (230-0-300 and 230-0-0 g NPK tree-1) and organic: vermicompost, bokashi and chicken manure (5 and 10 t ha-1) fertilizers in soil nutrimental content (pH, MO, macro and micronutriments), trunk diameter, flowering, and yield of three mango cultivars: 'Manila', 'Tommy Atkins', and 'Ataulfo'. For soil variables were design completely random and other variables a split-plot in completely random. Differences between contents of N, K, Ca, Cu and Zn were showed in soil. Differences were showed between cultivars in trunk diameter. Flowering showed differences among cultivars and fertilizers. Regarding yield in 2010, only 'Tommy Atkins' fruits were harvested, showing differences between fertilizers and control. In 2011, were differences among cultivars and fertilizers, chicken manure and mineral fertilizers outperformed the control. In 2012, 'Tommy Atkins' outperformed 'Ataulfo'. It is concluded that chicken manure 10 t ha-1, were similar to nitrogen doses on soil contents of N, K, Cu and Zn; fertilizer do not have influence in the trunk diameter; on flowering and yield, bokashi and chicken manure 10 t ha-1, were similar to nitrogen doses. <![CDATA[<b>Effect of liquid humus and calcium sulphate on soil aggregation</b>]]> An Ultic Haploxeralf soil collected from ridges built into the slopes of the Coastal Mountain Range of Central Chile was used in applications of humic and fulvic acids (HFA) extracted from sludge from sewage treatment plants, in combination with gypsum (CaSO4). A total of 12 treatments were applied by combining four doses of HFA (0, 20, 30 and 40 t ha-1) with three doses of gypsum (0, 1.2 and 6.0 t ha-1). The effect of these treatments was assessed using three indicators of the degree of soil aggregation: macroporosity (MA), bulk density (Da) and microinfiltration (MI). The experiment was set up in a laboratory using a completely randomised design (CRD). Factorial variance analysis was also performed using two factors: gypsum in three doses and HFA in four doses. For all three indicators, MA, Db and MI, it can be seen that there is interaction between the HFA treatments and the gypsum treatments in the studied soil. The macroporosity increased with HFA treatments with 20 or 30 t ha-1 (9%) and with gypsum of 1.2 t ha-1 plus 20 t ha-1 HFA (11%). It can also be seen that the gypsum treatments have no effect on Db when HFA is not applied. Microinfiltration is the variable that shows the greatest effects from the treatments applied. The results also clearly show that high amounts of HFA (40 t ha-1) and of gypsum (6.0 t ha-1) cancel out the differential effects and cause negative effects on the three indicators for the studied soils. The use of liquid humus and its combination with calcium sulphate (20/1.2 t ha-1) improves soil aggregation. <![CDATA[<b>Land use and seasonal effects on a Mediterranean soil bacterial community</b>]]> To evaluate the effects of management practices and seasons on a soil bacterial community and the composition of ammonia-oxidizing bacteria (AOB), molecular screenings were compared among Mediterranean (Sardinia) soils with different plant covers and different agricultural practices, namely cork oak forest, tilled/non-tilled vineyard, hay crop and pasture. We compared the fingerprints from both independent replicates and pooled samples to ascertain the best approach for studying the environmental effects on bacterial composition. The soil microbial biomass, which was estimated from the amounts of extracted soil dsDNA, was 2 to 3 folds higher in the spring than in the autumn; in the spring, it was negatively correlated with the intensity of land use. A 16S rDNA DGGE experiment confirmed that both the land use and season markedly affect the composition of the soil bacterial community. Tilled vineyard soil exhibited the lowest similarities in community structures, suggesting that tillage induced the most marked disturbance among the tested land management methods. Distinct AOB populations were found for each type of land use; among these types, the cork oak forest proved to be a protective habitat for AOB against environmental changes. Our results suggest that the comparative community level and group-specific fingerprinting enabled an accurate evaluation of multiple factors in soil bacterial structures when performed with both independent and pooled replicates. <![CDATA[<b>Foliage applied boron improves the panicle fertility, yield and biofortification of fine grain aromatic rice</b>]]> Boron (B) deficiency in rice field is becoming a common problem in South Asia. Correcting B deficiency in rice has potential to improve the rice productivity. Foliage application of B is an easy and effective way to resolve this problem. This study was conducted to evaluate the influence of foliage applied (0.16, 0.24, 0.32, 0.40 and 0.48 M) B on leaf elongation, tillering, water relations, yield and B grain enrichment of rice cultivars Super Basmati and Shaheen Basmati. Foliage applied B improved leaf elongation, tillering, leaf chlorophyll contents, water relations, grain yield, yield-related traits and B grain contents with simultaneous decrease in panicle sterility. However, foliage application of 0.32 M B was the most effective in this regard. An increase in leaf and grain B contents was observed with increase in B concentration in the foliar spray. There was no difference between the cultivars for grain yield; however, Shaheen Basmati had more grain weight, and grain and leaf B contents than Super Basmati. Boron foliage application (0.32 M B) proved an effective way to correct B deficiency in rice. Improvement in grain yield by B application was attributed to increase in grain size and decrease in panicle sterility. <![CDATA[<b>Soil microbial properties in <i>Eucalyptus grandis</i> plantations of different ages</b>]]> Eucalyptus plantations are increasingly used in Brazil to produce wood and energy, although the long-term consequences for ecosystem processes have rarely been evaluated. We investigated the soil microbial properties (soil microbial C, N, respiration, carbon use efficiency, and microbial C-to-N ratio) among Eucalyptus grandis plantations of differing ages (1 to 4 years) in Northeast Brazil. An adjacent native forest was used as a reference. In general, soil microbial properties decreased in initial years of land-use change, but recovered to conditions comparable to an adjacent native forest after four years in the rainy season, but not in the dry season. The varying effects of Eucalyptus plantations and native forests between seasons may reflect differences in soil microbial communities with different responses to environmental conditions. Our results highlight the importance of long-term monitoring and microbial community analysis in order to adequately assess and understand the impacts of exotic forest plantations on soil microbial properties. <![CDATA[<b>Soil organic matter quality in three Mediterranean environments (a first barrier against desertification in Europe)</b>]]> The aim of this study was to establish the effect of parent material, climate conditions and vegetation type on soil organic matter (SOM) quality in different Mediterranean environments as an essential step for assessing soil stability; ecosystems in the first barrier against desertification in the western Mediterranean region. Thirty-six samples were taken from the organic-mineral horizon of unreclaimed soils with calcareous, acid metamorphic and calcareous/volcanic substratums; and from beneath three vegetation types (natural forests, reforested forests and scrublands) in areas of significant ecological value. The humus fractions and soil respiratory activity of bulk soil samples were studied, and some structural features of the humic acids extracted were characterized by elemental analysis and visible and infrared spectroscopies. Results indicate that SOM in the surface horizons of the calcareous and calcareous/volcanic areas showed higher biogeochemical transformation, where microbial synthesis in humic acids formation, including condensation mechanisms, prevails. In contrast, the acid metamorphic area showed the greatest differences, and would be considered more fragile in terms of organic matter stability to changes in the biogeochemical system. The results also indicate some differences due to the type of vegetation on soil humus chemistry. Under reforested forests of Pinus in an edaphic acid environment, humic acids showed a marked aliphatic character, displayed higher 2920 cm-1 IR band, well defined typical lignin patterns, and higher E4/E6 ratio, i.e., accumulation of inherited macromolecular substances. The SOM beneath scrubland and natural Quercus forests may be said to be more decomposed (active breakdown of biomacromolecules) than beneath Pinus, humic acids exhibited higher aromaticity and were associated with accumulation of newly formed perylenequinonic chromophors of fungal origin, i.e., was at more advanced and complex stages of humification.