Mollisol Soil Research Articles

Effect of biosolid incorporation on arsenic distribution in Mollisol soils in central Chile

The effect of biosolid incorporation on arsenic distribution in Mollisol soils in central Chile was studied. Two soils were sequentially extracted for arsenic with a five-step method that accounts for the following arsenic forms: non-specifically adsorbed (F1), specifically adsorbed (F2), amorphous and poorly crystallized Fe and Al oxides (F3), well-crystallized Fe and Al oxides (F4) and residual (F5). The arsenic residual fraction was predominant in Pintué soil, whereas in Graneros soil, arsenic was mostly associated to amorphous Fe and Al oxides. Graneros soil exhibited a higher As(V) adsorbing capacity than Pintué soil, which relates to the higher clay and iron and aluminum oxides contents, confirming that these components participation is essential for the adsorption of this metalloid. Biosolid application at a rate of 100 Mg ha −1 caused an increase in arsenic bound to amorphous Fe and Al oxides and in the residual fraction, in Pintué soil. When Pintué soil was spiked with arsenic, aged for two months, and treated with biosolid (100 Mg ha −1), the content of arsenic in the most labile fractions decreased, thus showing a favorable effect in its application to soils with few specific sites for arsenic adsorption. Arsenic speciation was carried out in the first two fractions of the sequential extraction procedure. As(V) was the main form in both fractions. Biosolid incorporation at a rate of 100 Mg ha −1 caused a significant increase in organic arsenic forms.

Effect of biosolid incorporation to mollisol soils on Cr, Cu, Ni, Pb, and Zn fractionation, and relationship with their bioavailability

Biosolid application to soil may be a supply of nutrients and micronutrients but it may also accumulate toxic compounds which would be absorbed by crops and through them be incorporated to the trophic chain. The present study deals with the effect of biosolid application on Cr, Cu, Pb, Ni, and Zn in agricultural soils. The procedure used is sequential extraction so that the availability of those metals may be estimated and related to their bioavailability as determined through two indicator plants grown in greenhouse: ryegrass ( Lolium perenne L.) and red clover ( Trifolium pratense). Results showed that biosolid application to soil increased total Cu and Zn content. Sequential extraction showed that the more labile Zn fractions increased after biosolid application to soil. This was confirmed when assessing the total content of this metal in shoot and root of the plants under study, since a higher content was found in plant tissues, while no significant differences were found for Cu, Cr, Ni, and Pb.

Factors Affecting Triadimefon Degradation in Soils

The degradation of triadimefon [1-(4-chlorophenoxy)-3,3-dimethyl-1-(1H-1,2,4-triazol-1-yl)butan-2-one] was studied in two soils, mollisol and inseptisol, under varying conditions of moisture and temperature, and the role of cow manure amendment and soil sterilization on fungicide degradation was ascertained. The soil moisture content affected the pathway followed for triadimefon degradation. In nonflooded soils (60% water-holding capacity), triadimefon was reduced to triadimenol, and in flooded soils, it was metabolized to the diol derivative [1-(1H-1,2,4-triazol-1-yl)-3,3-dimethylbutan-2-one-1,4-diol]. In nonflooded soils, triadimefon was more persistent in soil having more organic carbon content (mollisol), and the amendment of cow manure (5%) further enhanced its persistence. On the contrary, in flooded soil systems, the higher the soil organic carbon content was, the less persistent was the fungicide, and amendment of cow manure further enhanced its degradation. Triadimefon degradation was faster at 35 degrees C than at 27 degrees C. Triadimefon degradation in soils was mediated by the microorganisms, and no triadimefon degradation was observed in sterile soils. Triadimefon (1 mg/kg) did not affect soil phosphatase activity in either of the soils; however, soil dehydrogenase activity was significantly reduced, especially in mollisol soil.

Weathering controls on mechanisms of carbon storage in grassland soils

On a sequence of soils developed under similar vegetation, temperature, and precipitation conditions, but with variations in mineralogical properties, we use organic carbon and 14C inventories to examine mineral protection of soil organic carbon. In these soils, 14C data indicate that the creation of slow‐cycling carbon can be modeled as occurring through reaction of organic ligands with Al3+ and Fe3+ cations in the upper horizons, followed by sorption to amorphous inorganic Al compounds at depth. Only one of these processes, the chelation of Al3+ and Fe3+ by organic ligands, is linked to large carbon stocks. Organic ligands stabilized by this process traverse the soil column as dissolved organic carbon (both from surface horizons and root exudates). At our moist grassland site, this chelation and transport process is very strongly correlated with the storage and long‐term stabilization of soil organic carbon. Our 14C results show that the mechanisms of organic carbon transport and storage at this site follow a classic model previously believed to only be significant in a single soil order (Spodosols), and closely related to the presence of forests. The presence of this process in the grassland Alfisol, Inceptisol, and Mollisol soils of this chronosequence suggests that this process is a more significant control on organic carbon storage than previously thought.

CHARACTERIZATION OF HUMIC SUBSTANCES ISOLATED FROM CLAY- AND SILT-SIZED FRACTIONS OF A CORN RESIDUE-AMENDED AGRICULTURAL SOIL1

In a small-plot field study on a Waukegan silt loam soil, annual applications of 20 g N m{sup {minus}2} were made each May for 8 years before planting corn (Zea mays L.). Subplots were fertilized with 0.8 g {sup 15}N m{sup {minus}2}. Soil treatment in the fall either incorporated the chopped corn stover after grain harvest, using a rototiller, or the stover was removed from the plots. Soil samples taken in the fall were ultrasonicated, separated into clay- and silt-sized fractions, and extracted exhaustively with 0.1 mol L{sup {minus}1} sodium pyrophosphate (Na{sub 4}P{sub 2}O{sub 7}) + 0.1 mol L{sup {minus}1} NaOH (pH 12.6). Humic (HA) and fulvic (FA) acids were isolated using the International Humic Substances Society (IHSS) procedures. A variety of analytical methods were employed. The most useful information was obtained from amino acid (AA) and neutral sugar (NS) analyses, and from cross polarization magic angle spinning (CPMAS) {sup 13}C-NMR and {delta}{sup 13}C data. Overall, the corn residue amendments did not have a large effect on the composition of the humic substances (HS) from the different sized separates, but there were differences in the relative abundance of some AA and NS in the HAs and FAs. The NMR andmore » {delta}{sup 13}C data provided evidence of some compositional differences and extent of humification between the HS from the clay- and silt-sized separates. The conclusion reached is, therefore, that the silt-sized particles were microaggregates of clay-sized particles, and the HS in these microaggregates were partially protected from bioalteration. These HS bore greater resemblance to the plants of origin than did those associated with the clays. The composition of the HAs and that of the FAs were similar to that of the Mollisol soil standard of the IHSS, but they were different from humic samples from other non-Mollisol soil types.« less

Evaluación de un Modelo de Simulación de Crecimiento Aplicado a Genotipos de Soya (Glycine max. L. Merr) bajo Condiciones Tropicales

<p>El modelo de simulación de crecimiento y producción de soya (Glycine max. (L) Merr) Soygro V5-42, fué validado a nivel del trópico con datos experimentales de un ensayo en el cual se evaluaron dos genotipos Soyica P-33 e ICA-Ariarii-1, con diferente hábito de crecimiento, bajo dos densidades de plantas, en el Centro de Investigación Palmira de la Corporación Colombiana de Investigación Agropecuaria Corpoica, localizado a 3°32' de latitud norte y 76°17' de longitud oeste, en un Mollisol, clasificado como Isohipertérmico Aquico Hapludoll. Las salidas del modelo fueron sensibles a los ajustes en trece coeficientes genéticos, los cuales se calibraron sistemática e iterativamente. La calibración del modelo presentó una estrecha relación entre lo observado y lo simulado para las principales variables de respuesta. Su validación con base en datos de experimentos de campo anteriores, presentó una relación muy estrecha R> = o.86, entre lo observado y lo simulado; lo cual indicó, que el modelo explica acertadamente la variación en las épocas de siembra y las densidades de plantas. Como resulta do de la simulación del efecto de las épocas de siembra con variaciones de clima, bajo diferentes ambientes (3 localidades), se encontró que el modelo se ajusta a las condiciones de siembra utilizadas por los agricultores en Colombia.</p><p> </p><p><strong>Evaluation of a Growth Simulation Model Applied to Soybean Genotypes (<em>Glycine </em><em>max</em><em>.</em>L. Merr) Under Tropical Conditions</strong></p><p>The crop growth simulation model of soybean ( <em>Glycin</em><em>e </em><em>max </em>(L) Merr) Soygro V5.42, was tested under tropical conditions, using experimenta l data from a field experiment in which two genotypes (Soyica P-33 and Soyica Ariari-1) with different growth h abit, were grown under two plant densities, at the Palmira Research Centre of the Corporación Colombiana de Investigación Agrop ecua ria, located at 3°32' north latitude and 76°17' west longitude, on a Mollisol soil classified as Isohyperterthermic Aquic Hapludoll. Thirtheen genetic coefficients were calibrated and showed sensitivity to the model. The validation of the model was made using previous experimental data from the same genotypes. The narrow line observed vs predicted seed yield was close to the 1:1 slope, indicating that, the simulating was not skewed. Thus, the model explained well the variation due to planting dates and plant spatial distribution in the field. The simulation of planting dates effects in relation to climatic variation at three different soybean production regions, is in agreement with the traditional planting dates used by the soybean growers of Colombia.</p>

A CLASSIFICATION OF SOILS IN BUR OAK WOODLANDS IN THE FOOTHILLS OF THE BLACK HILLS, SOUTH DAKOTA

Soils were classified in riparian bur oak (Quercus macrocarpa) woodlands in the foothills of the Black Hills, South Dakota. The soils in these gallery forests represented a blending of grassland (Mollisol) soils and forested (Alfisol) soils. Four soillandscape units were identified: (i) relatively young soils on steep slopes (usually Ustochrepts); (ii) soils adjacent to stream channels that were subject to episodic flooding and burial by new layers of alluvium or colluvium (Fluventic Mollisols); (iii) low relief, concave surfaces on stable floodplains away from stream channels (Cumulic Mollisols); (iv) Alfisols and Mollisols with argillic horizons on stable surfaces up off the floodplain. The actual taxonomic classification of similar pedons was often quite different, reflecting changes over time in the overstory and understory. In general, soil types and vegetative communities were poorly correlated. Soil pedons may provide a glimpse of history that helps us to understand past processes in formation, but this knowledge may not be very useful in understanding current plant distribution patterns.

Effect of inoculum rate on the performance of chickpea (Cicer arietinum L.) Rhizobium strains in the field

The influence of three inoculum rates on the performance of three chickpea (Cicer arietinum L.) Rhizobium strains was examined in the field on a Mollisol soil. Increasing amounts of inoculum improved the performance of the strains. A normal dose (104 cells per seed) applied at different intervals gave non-significant increases in nodulation, nitrogenase activity (acetylene reduction assay), nitrogen uptake and grain yield. A ten-fold increase in inoculum increased nodule number, shoot dry weight, nitrogenase activity (ARA) and grain yield, but increases over the control were significant only for nodule dry weight and nitrogen uptake by shoot and grain. The highest level of inoculum (100 × normal) significantly increased nodule dry weight, grain yield, total nitrogenase activity (ARA) and nitrogen uptake by shoot and grain. Strain TAL 620 was more effective than the other two. Combined nitrogen (60 kg N ha−1) suppressed nodulation and nitrogenase activity (ARA).

Competition Among Rhizobium spp. for Nodulation of Leucaena leucocephala in Two Tropical Soils

The successful nodulation of legumes by a Rhizobium strain is determined by the competitive ability of that strain against the mixture of other native and inoculant rhizobia. Competition among six Leucaena rhizobial strains in single and multistrain inoculants were studied. Field inoculation trials were conducted in an oxisol and a mollisol soil, both of which contained indigenous Leucaena-nodulating rhizobia. Strain-specific fluorescent antibodies were used for the identification of the strains in Leucaena nodules. Mixtures of three recommended inoculum strains for Leucaena spp. (TAL82, TAL582, and TAL1145) were used in peat-based inocula either alone or with one of the three other strains isolated from the sites, B213, B214, and B215. Each of these latter three strains was also used as single-strain inocula to study their competition with the native rhizobia in the two soil systems. In the oxisol soil, strains B213 and B215, when used as single-strain inocula, outcompeted the native rhizobia and formed 92 and 62% of the nodules, respectively. Strain B214 was the least competitive in oxisol soil, where it formed 30% of the nodules, and the best in mollisol soil, where it formed 70% of the nodules. The most successful competitor for nodulation in multistrain inocula was strain TAL1145, which outcompeted native and other inoculum Leucaena rhizobia in both soils. None of the strains in single or multistrain inoculants was capable of completely overcoming the resident rhizobia, which formed 4 to 70% of the total nodules in oxisol soil and 12 to 72% in mollisol soil. No strong relationship was detected between the size of the rhizosphere population of a strain and its successful occupation of nodules.

Effects of Heating on Soil Chemical Properties and Growth and Nutrient Composition of Corn and Millet

AbstractHeating or burning has a wide variety of effects on soils, the magnitude of which is determined largely by the temperature to which the soil is heated and on soil properties. In parts of Africa, the practice is used on soils in the field to improve crop production. The objective of this study was to determine the effect of heating Alfisol and Mollisol soil materials on their chemical properties and on the early growth and nutrient composition of corn (Zea mays L.) and millet (Setaria italica) grown in the greenhouse. Heating the soils to 110°C decreased pH, but the pH increased when the soils were heated to 200 or 250°C. Organic matter and extractable Mg decreased while extractable NH+4 and Mn and electrical conductivity (EC) increased greatly with heating. The effects on soil‐test P and K and extractable Ca were small and variable, but the soils were already higb in these elements. Increases in extractable NH+4 and Mn, EC, and pH probably came from both the destruction of soil organic matter and release from inorganic compounds in the soils. Heating soils to 110°C resulted in greater growth of both corn and millet, but heat treatments of 200 and 250°C suppressed growth. The increase in the growth of corn and millet was attributed primarily to moderate increases in extractable NH+4 at 110°C. The suppression of growth with heat treatments of 200 and 250°C was thought to be due largely to excessive amounts of NH+4. Extensive work on NH+4 shows that certain levels of this form of N may be toxic to plants. Heating of soil was shown to be both heneficial and detrimental to the growth of plants. Crops may benefit from nutrients released when soils are heated, provided the amounts are not excessive. The detrimental effects observed in this study would not usually be noticeable under field practice, because only a small proportion of the soil volume is heated.

Water‐repellent Soil Clods and Pellets as Mulch1

AbstractWater‐repellent clods and pellets of a Mollisol soil, Nunn clay loam, were tested in laboratory and field experiments to determine the potential for use in place of gravel as a mulch for reducing soil water evaporation. Solutions of two hydrophobic compounds, dialkyl quaternary ammonium chloride (Arquad), and sodium methyl silanolate (R‐20), were used either as a dip for soil clods and pellets or for mixing with the soil to form pellets. Seven treatments were tested for endurance in the laboratory by the wet sieve, alternate freezing and thawing, and alternate wetting and drying methods. The treatments were also exposed to the ambient climate. The most stable treatments, R‐20 dipped clods, R‐20 mixed pellets, and Arquad mixed pellets, were compared with treatments of gravel and bare soil in evaporation tests to determine the efficiency in reducing soil water loss. The three soil clod and pellet treatments were durable for over 1 year, and each reduced cumulative evaporation with time compared with a bare soil. First‐day evaporation rates after a 5.0‐cm water application showed bare soil was higher than gravel by 79%, R‐20 mixed pellets by 73%, R‐20 dipped clods by 63%, and Arquad mixed pellets by 36%. The R‐20 mixed‐pellet, mulch‐reduced soil water evaporation rate with nearly the same efficiency as gravel and could save about 30% more precipitation for plant use than a bare soil.

A comparison of the effectiveness of various extractants for determining humus quality in a calcareous soil

Abstract Humic substances from an Argentinian chesnut (Mollisol) soil were extracted with Na‐Dowex A‐1 resin, 0.1 N NaOH and 0.1 M Na4P2O7 without decalcification and with 0.1 N NaOH after decalcification. Humic to fulvic (Ch/Cf) acid and E4/E6 ratios of the extracts were determined and compared. A simpler and more rapid procedure than the classical ones for extracting and characterizing soil humus is proposed. The procedure is based on the use of a chelating resin as extractant and on the direct determination of analytical properties of humus in aliquots of the extract.