Latossolo Vermelho-Amarelo Research Articles

Atributos físicos do solo submetido a ensilagem com diferentes conjuntos mecanizados

ABSTRACT The evaluation of the physical attributes of the soil in cultivated areas is essential for understanding the impacts of agricultural operations, especially those with intense machine traffic. Therefore, the present study aimed to evaluate the physical attributes of the soil submitted to silage with different mechanized sets. A randomized block design was adopted with three treatments: forage harvester with a one-row cutting platform (T1), forage harvester with a three-row cutting platform (T2), and T2 with a forage harvester with a conveyor wagon. Before ensiling and 24 hours after the operation, intact samples of soil classified as Latossolo Vermelhoamarelo álico, intact, were collected to determine the micro, macro, and total porosity, soil density, and volumetric soil water content according to the methodology proposed by the Brazilian Agricultural Research Corporation (Embrapa). After ensiling, the resistance to soil penetration was measured with an electronic manual penetrometer, before and after ensiling, at the A horizon of the soil in the layers of 0.0-0.2 m and 0.2-0.4 m. We analyzed the data by establishing the confidence interval using the t-test at 10% probability. The sets reduce the macroporosity and total porosity of the soil in the 0.0-0.2 m and 0.2-0.4 m soil layers. T2 promoted greater total density in the 0.0–0.2 m layer. The silage increased the resistance to soil penetration to a depth of 0.15 m.

INDICATOR ATTRIBUTES OF SOIL QUALITY IN AREAS UNDER DIFFERENT LAND USE SYSTEMS, IN THE WESTERN AMAZON

The anthropization of natural environments, when performed inadequately, promotes the disruption of the ecological balance and can influence the fauna, flora and biodiversity in general, including the edaphic environment and its components. The objective was to evaluate the soil attributes in areas with different types of vegetation cover and different forms of soil management. The study was carried out in native forest area (Subperennial Equatorial Forest) and cultivated area (annual species), in Porto Velho, Rondônia, Brazil. Samples were collected in two layers (0-10 and 10-20cm), on a Latossolo Vermelho-Amarelo, to evaluate microbial biomass by the fumigation-extraction (FE) method, as well as the chemical and physical soil attributes. It was possible to verify a significant increase in soil density and reduction of moisture and improvement of chemical attributes resulting from the use of the area. The organic matter content decreased sharply in the managed area (25%), compared to the forest, in the superficial layer (0-10cm). Microbial C-biomass under the native forest showed 54% higher mean value (883 mgC g-1) compared to the managed area (410 mgC g-1) in the superficial layer. The microbial N-biomass ranged from 21.3 to 19.5 mgN.g-1 in the native forest area, and from 9.3 to 11.5 mgN g-1 in the managed area, respectively in the 0-10 and 10-20cm layers. In the native forest area, the addition of organic matter to the soil by the vegetation litter was an important conditioning factor for the microbial community, demonstrating the use of this attribute as an indicator of soil quality.

Load-bearing capacity and critical water content of the coffee plantation soil with management in full sun and shaded

New management practices applied to coffee crops may influence the soil’s capacity to tolerate vertical stresses. This paper aimed to evaluate the influence of two coffee crop management systems on the soil load-bearing capacity and critical soil water content to agricultural machinery traffic. This study was performed in the experimental area of the Federal Institute of the Southeast of Minas Gerais – Rio Pomba college, in Rio Pomba city, Minas Gerais, Brazil. Dystrophic Red-Yellow Oxisol (Latossolo Vermelho-Amarelo distrófico) (LVA7) [...]

Boron Dynamics in Agricultural Soils of the Cerrado: Study on Sources, Doses and Leaching

The objectives of this study were: to evaluate the leaching potential of B in a Latossolo Vermelho-Amarelo (Oxisol) as a function of sources and doses of this micronutrient; among the sources tested (boric acid, ulexite and the commercial source H2 Boro), to determine the one with the lowest leaching potential; to evaluate leaching losses at different doses in each soil layer evaluated; and to identify chemical and physical variables of soils that influence B leaching. For that, two experiments were conducted in a greenhouse. The first one tested B leaching in the soil, with the three sources under study and five doses of B (0; 12; 24; 36; and 48 kg ha-1), whereas the second experiment evaluated the influence of soil physical and chemical attributes on B leaching using soils randomly collected in 22 localities in southeastern Goiás, Brazil. Regardless of the dose applied, ulexite led to the lowest soluble B content in the profile of the analyzed soils and also in the leachate. Boric acid was the only source that showed a different behavior in relation to B content in the different soil layers and in the leachate. In the soil layer from 21 to 30 cm, ulexite is the source with the lowest soluble B content. The behaviors of the more soluble sources, in this case boric acid and H2 Boro (H2 Agrosciences - Monoethanolamine borate), regardless of the dose, are very similar, being highly leachable in the profile of the Oxisol used. Soils with clayey texture and higher values of H+Al and CEC were able to retain higher B contents in the upper portion their profiles (layers from 0 to 10 cm and 11 to 20 cm), but soils with sandy texture and higher values of sum of bases showed greater B losses by leaching.

SORPTION OF INDAZIFLAM IN BRAZILIAN SOILS WITH DIFFERENT pH VALUES

ABSTRACT Pre-emergence herbicides, such as indaziflam, have agronomic efficiency when available in the soil solution, mainly in the superficial layer (0-10 cm), the region with the highest concentration of weed seed bank. However, information about the sorption of indaziflam in Brazilian soils still is scarce, since most studies available in the literature were conducted in soils of temperate regions. The objective of this study was to estimate the sorption of indaziflam using high-performance liquid chromatography (HPLC) and bioassay in a Latossolo Vermelho-Amarelo (Oxisol) and in a Cambissolo (Inceptisol), at pH values of 5.1 and 6.1. In the biossay, Sorghum bicolor was used as an indicator plant. Quantitative indaziflam data were obtained by HPLC, and the sorption and desorption coefficients were determined in the soils using Freundlich isotherms. Increasing the pH of the two soils from 5.1 to 6.1 resulted in reductions of C50 and sorption coefficient values. Desorption, a parameter estimated only by HPLC, showed an inverse behavior to that of sorption, that is, the lowest desorption was observed in the condition of highest sorption. It is concluded that the increase in pH of the studied soils reduces indaziflam sorption, influencing the recommendations of this herbicide, from both the agronomic and the environmental points of view. When the goal is to verify the presence or absence of indaziflam in the studied soils, the bioassay technique has satisfactory efficiency. Chromatographic assay is necessary when quantifying the concentration of this herbicide in the soil.

SPATIAL AUTOCORRELATION OF PHYSICAL ATTRIBUTES OF AN OXISOL

Studies that seek to identify a smaller number of soil attributes that represent others can generate less expenditure of time and financial resources for monitoring cultivated areas. Thus, this study aimed to analyze the spatial distribution and spatial autocorrelation of physical attributes of an Oxisol (Latossolo Vermelho Amarelo, Brazilian Soil Classification System). The evaluated attributes consisted of soil density (SD), total porosity (TP), free porosity (FP), field capacity (FC), permanent wilt point (PW), and total water availability (TW). Semivariogram adjustments and semivariance estimates were performed to characterize the structure and magnitude of the spatial dependence of soil attributes. The attributes were distributed on thematic maps and the spatial autocorrelation was estimated by the Moran index, which quantifies the degree of autocorrelation. TP showed a high positive correlation with PWP. Soil TW showed a high positive correlation with SD and a high negative correlation with FP. In turn, FP showed a high negative correlation with SD. The results showed spatial dependence for all attributes, standing out the apparent soil density and permanent wilt point, which were good evaluators of strong spatial dependence.

Preconsolidation stress of gibbsitic and kaolinitic Oxisols under a multipractice conservationist coffee system

Our goal was to analyze the impact of a multipractice soil conservationist system on coffee production in tropical soils (LATOSSOLO VERMELHO-AMARELO caulinítico/kaolinitic Haplustox and LATOSSOLO VERMELHO-gibbsítico/gibbsitic Acrustox) in Minas Gerais, Brazil. In the experimental area, the soil management involved a set of multiple conservationist practices during cultivation for more than 3.5 yrs. Soil samples were collected at 0-5, 10-15, and 20-25 cm depths at two positions: planting rows and between rows. The soil physical and mechanical properties were determined, with a focus mainly on the preconsolidation stress model (preconsolidation stress versus matric tension). For the purpose of analysis, a split-split plot experimental design was implemented. A linear mixed regression model (LMR) was fitted, and Wald’s test was performed (P < 0.05). An improvement of soil physical quality for both Oxisols was observed at the planting row position. The effects of multipractice soil management after 3.5 yrs of cultivation in association with increased gibbsite content could promote new soil structure organization, as revealed by LMR, resulting in more resilient soils (between rows) and increasing the resistance to external pressures on gibbsitic Acrustox. Overall, the findings herein are in concordance with global trends towards conservationist practices that may alleviate soil compaction in agricultural systems to maintain environmental sustainability.

SPATIALITY OF SOIL CHEMICAL ATTRIBUTES IN A BANANA CULTIVATION AREA IN WEST BAHIA

ABSTRACT Irrigated fruit growing in the São Francisco Valley has been standing out in the Northeast region of Brazil and the incorrect management of fertilization has caused problems of physical and / or chemical degradation of the soil. The work aimed to evaluate the spatial variability of the chemical attributes of a Latossolo Vermelho-Amarelo (Oxisol) grown with banana (Musa spp). The study was carried out in the irrigated perimeter of Nupeba in Riachão das Neves / BA. In an area cultivated for 18 years with silver banana fertigated by micro sprinkling. In April 2017 simple soil samples were collected at depths of 0 -0.20 m and 0.20 -0.40 m, from an experimental grid consisting of 40 georeferenced points and spaced every 10 meters. The soil samples determined: pH (H2O); Organic carbon; Phosphorus (P); Potassium (K+); Calcium (Ca2+); Magnesium (Mg2+) and Potential acidity (H + Al) and the sum of bases (BS), cation exchange capacity (CEC) and base saturation (V%) were calculated. The results of the analyses were evaluated using descriptive statistics and the geostatistics technique. The descriptive analysis identified the normality of the data. The spatial variability was confirmed, allowing the making of maps. The analyzed area has low fertility (V <55%) and the inadequate management of soil correction and fertilization can reduce the availability of nutrients for the implanted crop, making the soil susceptible to degradation with the use of irrigation. The distribution maps allow the visualization of the area, allowing the application of inputs with varying rates, aiming at homogenizing the soil fertility.

OPERATIONAL PERFORMANCE OF AN AGRICULTURAL TRACTOR UNDER DIFFERENT TIRE INFLATION PRESSURES IN THE SUBSOILING OPERATION

For the agricultural tractor's best performance, it must be correctly adapted to the job. Among other factors, the adequacy of tire inflation pressure is one of the most important and may influence the operation's efficiency and productivity. This study aimed to evaluate an agricultural tractor's operational performance with different tire inflation pressures in the subsoiling operation. The study was carried out in an experimental area of the Agricultural Machinery and Mechanization Laboratory of the experimental farm “Água Limpa,” belonging to the University of Brasília. The experimental design used was in randomized blocks with the following values, 206.8 kPa (30 psi), 137.9 kPa (20 psi), and 68.9 kPa (10 psi), of inflation pressure for agricultural tractor tires. The mechanized set used was a tractor model TM7020 2WD MFWD pulling a subsoiler with five shanks, SPCR model, in a Latossolo Vermelho-Amarelo. The higher inflation pressure resulted in greater slippage, advance, hourly fuel consumption, and lower speed and operational field capacity.

Soil Water Storage Temporal Stability With and Without Outliers

The knowledge on the temporal stability of spatial variability of soil water storage in the crops’ root zone is of fundamental importance for soil and water management. The objective of this work was to characterize the temporal distribution of water storage in a Latossolo vermelho amarelo and identify field locations with spatial patterns of high, intermediate and low soil water storage, in 13 samplings every 14 days. The assessed period included periods of drying and water recharge of the soil, along which soil water content was determined at 60 sampling points arranged in a 5 × 5 m grid covering an area of 1250 m2 (25 × 50 m). Soil water content was determined by means of a neutron probe, at soil depths of 0.2, 0.4, 0.6, 0.8 and 1.0 m. Soil water storage was calculated by Simpson’s rule and data were analyzed by the temporal persistence of the spatial pattern. Maximum values of soil water storage were obtained at the portion of the area with water flux concentration (sampling points 4, 28 and 57), with and without outliers, and low values of soil water storage were obtained at the highers levels of the site (sampling points 12, 18 and 19), with and without outliers. The sites representing the mean soil water storage were 32, 51 and 11, considering outliers, and 8, 11 and 53, without considering outliers.

Yield and Nutrient Demand and Efficiency of Eucalyptus under Coppicing Regime

Eucalyptus stands can be managed by coppicing, however, in several Brazilian regions reduced yield has been observed with harvesting successions. This reduction can be attributed to reduced nutrient availability, among other factors. This study aimed to: to assess the nutritional demand of the Eucalyptus stand under a coppice regime; the effect of fertilization on the production of wood, distribution and compartmentalization of nutrients in eucalyptus stands managed by coppice; the effect of the height and number of shoots, on the occasion of the sprouting, in the production of eucalyptus managed by coppice and to compare the productivity of high eucalyptus wood with coppice management regime. The trial was conducted for clone GG157 (Eucalyptus urophylla hybrid), in Latossolo Vermelho-Amarelo (Oxisol), of the Cerrado region in Minas Gerais State, Brazil. Trees were originally planted at the 3.8 × 2.4 m spacing and, after the first harvesting, at age 84 months, the stand was managed by coppicing. Treatments consisted of: (a) fertilization or not; (b) one, two or four poles per stump; and (c) selection of 1-, 2- or 4-m-high poles and repeated three times. Sixty months after treatment application, plots of 80 trees were used for the assessments. The gain in trunk yield with fertilization and the combination between the height of poles at the time of pole selection and number of poles left varies between 140.2% for thinning when the pole is 2 m high and maintains 1 pole per strain and 128.6% when the plants are 1 m high and maintain 1 pole per strain. Not supplying nutrients in the coppicing system leads to lower accumulation of nutrients in the tree and reductions in both wood and trunk yields. Trees in the coppicing system use nutrients for trunk production more efficiently than those in high forest. Earlier pole selection enables the best use of growth resources, resulting in increased yield. Adequate nutritional management of coppiced stands results in the maintenance or increase of yield compared to the first rotation.

Tensile strength values for the degrees of soil consistency using human perception and TS-Soil device

Tensile strength of aggregates, defined as the force per unit of area required to cause rupture of aggregates, is useful to quantify the effects of both use and management on soil quality. The present study considered the hypothesis that the evaluator’s perception, combined with the force applied to break the aggregate, measured by the TS-Soil device, can be used to define ranges of tensile strength for the degrees of dry soil consistency. The objective in this study was to define ranges of tensile strength for the degrees of dry soil consistency. For this purpose, aggregates (mean diameter of 22 mm after preparation) were collected in five horizons: A and Bi of a Cambissolo Háplico (Cambisol), Bt with a cohesive character of an Argissolo Vermelho Amarelo (Lixisol), Bt of a Luvissolo Crômico (Luvisol) and Bw of a Latossolo Vermelho-Amarelo (Ferralsol). One hundred aggregates of each horizon were evaluated for tensile strength, measured in the TS-Soil device, and, concomitantly, when pressed, were analyzed by an evaluator to assign the following scores to their consistency: 1- loose, 2- soft, 3- slightly hard, 4- hard, 5- very hard, and 6- extremely hard. Data were initially analyzed by descriptive statistics. Then, evaluator’s scores and tensile strength measured by the TS-Soil device were considered to define the ranges of values for the degrees of dry soil consistency. The following tensile strength (kPa) ranges were obtained: >0 to <21 for soft consistency, ≥21 to <38 for slightly hard, ≥38 to <65 for hard, ≥65 to <110 for very hard and ≥110 for extremely hard. It was concluded that the TS-Soil device makes it possible to combine the evaluator’s perception with the force applied to break the aggregate, enabling the definition of ranges of values for the degrees of dry soil consistency, and that the qualitative perception (evaluator) associated with tensile strength values (TS-soil device) gives better quality to the process of evaluating dry soil consistency.

SOIL CLASSES AND REGIONAL ORGANIC RESIDUES AFFECT NUTRITION, MORPHO-PHYSIOLOGY AND QUALITY OF COPAIBA SEEDLINGS

ABSTRACT Besides being used in the wood industry, copaiba has medicinal properties. However, continuous and excessive extraction both of wood and of oil may impair the regeneration and make the product scarce. It is very important to produce quality seedlings, both for sustainable exploitation and for the recovery of degraded and disturbed areas. The purpose of the present study was to evaluate the initial growth and nutrition of Copaiba seedlings, incorporating organic residues into different classes of soils. The treatments were disposed in a design of entirely randomized blocks using the 5x4 factorial scheme, with four organic residues (rice husks in natura, carbonized rice husks, goat manure, carnauba residue), plus a treatment with soil only and four classes of soil (Latossolo Vermelho-Amarelo, Neossolo Quartzarenio, Gleissolo Haplico e Argissolo Vermelho-Amarelo), with four repetitions. At 90 days, the morpho-physiological variables of the seedling and macronutrient contents of the aerial part were evaluated. As to the morpho-physiological variables, the carnauba residue was outstanding among the residues tested in the present study. There was an increase in the quantities of P, K, Ca and Mg in the aerial part of copaiba seedlings resulting in the combination between the organic residues and the soil classes.

Potassium Dynamics in Ruzigrass Rhizosphere

Ruzigrass (Urochola ruziziensis) has a large capacity to take up K from the soil, including non-exchangeable forms, and can play an important role in nutrient cycling in integrated production systems. However, K transport to roots of brachiarias is not well known, nor the nutrient dynamics in the rhizosphere, where a concentration gradient may be established towards the non-rhizospheric soil, creating a favorable environment for the release of non-exchangeable K. This study aimed to evaluate the effect of ruzigrass on K dynamics in the rhizosphere and on non-exchangeable K release. Ruzigrass was grown in pots filled with a Latossolo Vermelho Amarelo (Typic Hapludox) that was collected at 0.00-0.20 and 0.20-0.60 m layer from a cultivated area and fertilized with 0, 30, and 60 mg kg−1 of K, plus a treatment with forest soil, used as control. Thirty days after plant emergence, soil samples were taken at the following distances from the roots: 0.5, 1.0, 1.5, 3.0, 5.0, and 10.0 mm. For the highest exchangeable K rate (60 mg dm−3), the exchangeable K level was higher from 0 to 0.5 mm of the roots for both soils (0.00-0.20 and 0.20-0.60 m). Therefore, more K was transported to the rhizosphere than the plant could take up. A depletion of exchangeable K observed in the rhizosphere resulted in the release of K from non-exchangeable forms, as observed in the soils from 0.00-0.20 (60 mg dm−3) and 0.20-0.60 m (without application of K). Ruzigrass grown on low K soils without fertilizer application results in a larger exchangeable K depletion zone than in soils that were fertilized or originally high in exchangeable K, showing a high potential for K cycling in the system.

Soil Water Retention in the Semiarid Region of Brazil

From the physics point of view, soil structure is a dynamic attribute that is affected by genetic conditions and anthropogenic changes and requires an integrated approach. Soil water retention curve is one of the main tools used in soil structure evaluations. The objective of this work was to evaluate the structural and chemical attributes of soils of different classes and agroecosystems in the Terra de Esperança Settlement (Governador Dix Sept Rosado, Rio Grande do Norte, Brazil) to distinguish these environments. Disturbed and undisturbed soil samples were collected in horizons of 10 soil profiles of the soil classes: Cambissolo Háplico (Haplustepts), Latossolo Vermelho-Amarelo (Eutrustox), Chernossolo Rêndzico (Calciustolls), and Neossolo Flúvico (Usticfluvents). The soil physical attributes evaluated were granulometry, soil density, total porosity, aeration porosity, macroporosity, microporosity, field capacity, permanent wilting point, available water, and water retention curve. The results were expressed in averages of four replicates per horizon (in laboratory) by multivariate analysis, which detected the most sensitive attributes for the distinction of the environments. The soil physical attributes of the different classes and its inorganic fractions, especially silt and clay, were determinant to distinguish the environments; they affected the microporosity; aeration porosity; and available water. The source material of the Chernossolo Rêndzico, which is rich in calcium and magnesium, affected its physical attributes, characterized by the predominance of the silt fraction. Clay was the determinant fraction of the Cambissolo Háplico, and Neossolo Flúvico; and the sand fraction on the surface layer, and clay fraction in the Bw horizon were determinant of the Latossolo Vermelho-Amarelo. The more expressive physical attributes were soil density, sand content, macroporosity (Latossolo Vermelho-Amarelo), microporosity, field capacity, available water, permanent wilting point, total organic carbon, mass-based moisture, volume-based moisture, clay, aeration porosity (Cambissolo Háplico, and Neossolo Flúvico), and silt (Chernossolo Rêndzico).

Selection of Indicator Species of the Tembotrione Sorption in Soils with Different Attributes

ABSTRACT: Studies on herbicide behavior in soils may be performed using biological and chemical methods. The efficiency of the biological method depends on the indicator species sensitivity to low herbicide concentrations in the soil solution. Among the herbicides commonly used in Brazil for corn cultivation, tembotrione stands out. In the last agricultural seasons, the intoxication of some crops when cultivated in succession to corn has been reported, which may be attributed to tembotrione recommendations without the knowledge of their interactions with colloids of tropical soils. In this research, we selected an indicator plant species of tembotrione residues in the soil after sorting 12 species. The sorption of this herbicide was estimated in two Oxisols (Latossolo Amarelo and Latossolo Vermelho-Amarelo, Brazilian Soil Classification) and in a Histosol (Organossolo, Brazilian Soil Classification) with different attributes. Initially, after sorting the 12 plant species, the two most efficient in detecting tembotrione in the soil were selected. In the second stage, the most sensitive species was selected. In the third stage, tembotrione sorption was assessed in the three soils by using the selected species. Among the 12 species, Beta vulgaris and Brassica oleracea var. capitata were the most efficient in detecting tembotrione at low concentrations in the soil, being B. vulgaris (beet) the most sensitive. Thus, due to its ease of cultivation, high sensitivity, and fast initial growth, beet can be used as an indicator species of tembotrione presence in the soil solution. The sorption of this herbicide was higher in the Histosol and it is directly related to the organic matter content.

CHANGES IN CHEMICAL PROPERTIES BY USE AND MANAGEMENT OF AN OXISOL IN THE AMAZON BIOME

ABSTRACT The proper soil use and management are essential for a sustainable production, thus the pursuit for systems that minimize damages to the environment and improve soil fertility is continuous. The objective of this study was to evaluate changes in soil fertility by the use and management of an Oxisol (Latossolo Vermelho-amarelo, SiBCS) in the Amazon biome. The soil uses and management systems evaluated were native forest, native pasture, minimum tillage system and conventional tillage system. The chemical atributes of the soil layers 0.00-0.10, 0.10-0.20, 0.20-0.30 and 0.30-0.40 m were evaluated. The soil pH (CaCl2) and the contents of organic matter, available phosphorus and exchangeable potassium, calcium, magnesium and aluminum were evaluated and the saturation by Al, effective cation exchange capacity and soil potential were determined. The highest pH values were found in the native pasture area, and the highest exchangeable aluminum contents were found in the layers 0.00-0.10 and 0.10-0.20 m of the conventional tillage system. The highest phosphorus availability was found in the layer 0.00-0.10 m of the native forest area. The highest potassium availability was found in the minimum tillage system. The lowest calcium and magnesium values were found in the layers 0.00-0.10 and 0.10-0.20 m of the conventional tillage system. The highest soil organic matter content was found in the layer 0.00-0.10 m of the native forest area. The nutrient availability for plants decreases in soils managed using the conventional tillage system. Soil uses and management systems of little soil disturbance are recommended to minimize environmental degradation in the Amazon biome.

English

The use of mathematical models is an alternative way to understand how management practices affect soil organic matter (SOM) dynamics because such models yield results on time scales that would be impossible to observe in field studies. The aim of this study was to parameterise and calibrate the application Century 4.0 in terms of the edaphoclimatic conditions of a Latossolo Vermelho-Amarelo of the Araripe Plateau and simulate the soil C dynamics in each compartment. The study was conducted in the Araripe National Forest (Floresta Nacional do Araripe ― FLONA). The soils are classified as Latossolos Vermelho-Amarelos with a medium clayey texture and a clay fraction consisting of kaolinite with iron and aluminium oxides. The physical and chemical properties of the soils were obtained at a depth of 0.00-0.20 m in 2012 and 2013. The best total organic carbon (TOC) result was an error of only 3% between the measured and simulated values, which was obtained with a PRDX (4) adjustment of 140 g m-2 C. After correcting for the C decay rate in the passive (PC), slow (SC) and active compartments (AC), absolute errors lower than 10% were obtained for the C values. The abiotic correction factors specific to each compartment were 0.89 for the active and passive compartments and 1.12 for the slow compartment. The sensitivity analysis indicates that all compartments are sensitive to variations in maximum and minimum temperature and that the clay content affects the TOC and the passive compartment. &nbsp; Key words: Century model calibration, soil carbon compartments.

Agricultural potential of areas under pasture in southern Tocantins

Improper soil use leads to inefficient exploitation of natural resources, destruction of land resources, poverty and other social problems. Therefore, the objective of this study was execute a survey and soil classification of an area under pasture in a farm in southern Tocantins. The area was divided according to the existing soil spots to perform the soil classification following the methodology of the Brazilian System of Soil Classification and its agricultural potential. At the studied area were found four soil classes, which were studied and classified as Plintossolo Argiluvico Distrofico petroplintico , Cambissolo Haplico Tb Eutrofico , Latossolo Vermelho-Amarelo Distrofico tipico and Gleissolo Melânico Ta Eutrofico with agricultural potential in the subgroups 1(a)bC, 4P, 1aBC and 3(bc), respectively. The terrain was underutilized, being used for pasture cultivation, at the same time it could be used for cultivation of annual plants.

Soil microbiological properties and available nitrogen for corn in monoculture and intercropped with forage

Abstract The objective of this work was to evaluate the effects of corn (Zea mays) in monoculture and intercropped with forage on soil microbiological properties and nitrogen availability under no-tillage in the Cerrado (Brazilian savanna). The experiment was carried out from the 2007/2008 to the 2010/2011 crop season, in a Latossolo Vermelho-Amarelo distrófico (Typic Haplustox). A randomized complete block design with three replicates was used, with the following treatments: corn in monoculture; corn intercropped with Panicum maximum; corn intercropped with Urochloa humidicola; P. maximum in monoculture; and U. humidicola in monoculture. Soil samples were taken at 0.00-0.05, 0.05-0.10, 0.10-0.20, and 0.20-0.30-m soil depths, in the begining and in the end of the last crop season. The intercropping systems of corn increased soil nitrogen availability, but did not alter total nitrogen and organic carbon contents in the soil, when compared to corn in monoculture. Corn intercropped with P. maximum increased soil microbial biomass nitrogen and microbial nitrogen quotient, in comparison to corn in monoculture, as well soil as microbial biomass carbon in the surface soil layer, when compared to corn intercropped with U. humidicola.