Scielo RSS <![CDATA[Revista de la ciencia del suelo y nutrición vegetal]]> vol. 10 num. 1 lang. es <![CDATA[SciELO Logo]]> <![CDATA[<strong>KINETIC AND THERMODYNAMIC BEHAVIORS OF SOIL UREASE AS AFFECTED BY UREASE INHIBITORS</strong>]]> The kinetic characteristics of soil urease have attracted great attention, but little information was available on its kinetic and thermodynamic behaviors as affected by urease inhibitors and temperature. With black soil (Pachic Udic Mollisol) in Heilongjiang Province of Northeast China as a test soil, an incubation test was conducted to investigate the effect of urease inhibitors (hydroquinone, HQ; phenyl phosphorodiamidate, PPD; N-(n-Butyl) thiophosphoric triamide, NBPT) on kinetic and thermodynamic behaviors of soil urease at 10°C, 20°C and 30°C. The results showed that all tested inhibitors increased Km and decreased Vmax, behaving as mixed inhibitors to soil urease. With increasing temperature, the Km and Vmax values increased significantly. With incubation time, Km decreased, while Vmax significantly increased. Compared with control, treatment HQ decreased soil urease thermodynamic parameters Ea, AH, and Qi0, but in PPD and NBPT treatments, the parameters increased slightly. The Qio and AH of soil urease decreased slightly with increasing temperature. Among test inhibitors, PPD and NBPT were more effective in influencing the kinetic and thermodynamic behaviors of urease in black soil. The variations in kinetic and thermodynamic parameters indicated that the effects of urease inhibitors on soil urease are greater on kinetic behaviors rather than on thermodynamic ones. <![CDATA[<strong>TILLAGE EFFECT ON SOIL ORGANIC MATTER, MYCORRHIZAL HYPHAE AND AGGREGATES IN A MEDITERRANEAN AGROECOSYSTEM</strong>]]> Arbuscular mycorrhizal fungi (AMF) and their product glomalin (GRSP) play a decisive role in the soil aggregation, affecting the carbon (C) dynamics in agroecosystems. Tillage affects the AMF activity and GRSP content, influencing the stability and the soil C forms as well. The aim of this study was to compare the effect of no tillage (NT) and conventional tillage (CT) on: i) arbuscular mycorrhizal hyphal length and GRSP content; ii) the nature of soil organic matter by means of physical fractionation (free paniculate organic matter [fPOM]; occluded paniculate organic matter [oPOM] and mineral-associated soil organic matter [Mineral]), as well as chemical fractionation (fulvic acid, humic acid and humin), and iii) the relationships between AMF parameters, soil carbon and water stable aggregates (WSA) in a Mollisol of Central Chile managed for 6 years under NT and CT using a wheat-corn rotation. Higher values in the AMF hyphal length, GRSP and WSA in NT compared with CT were observed. Significant relationships were found between GRSP and WSA (r = 0.66, p < 0.01) and total mycelium and GRSP (r = 0.58, p< 0.05). The total carbon increased 44% under NT compared with CT. The chemical fractionation showed percentage greater than 95% for humim in both treatments. Physical fractionation indicates that the higher part of the SOC (89.4 - 95.1%) was associated with the mineral fraction. <![CDATA[NITROUS OXIDE EMISSION FROM FARM DAIRY EFFLUENT APPLICATION IN GRAZED GRASSLAND]]> Intensification in dairying and increased production of farm dairy effluent (FDE) has raised concerns about gaseous nitrogen (N) losses and their environmental implications. This study was undertaken to monitor changes in mineral-N and soil water-filled pore-space (WFPS) in relation to N(2)0 emission from application of FDE to dairy-grazed pasture. Pasture was irrigated with FDE in September 2003 (first irrigation) and January 2004 (second irrigation), preceded by grazing events. The N(2)0 emission rate increased after application of FDE. Total amounts of N(2)0 emitted from FDE application for first and second irrigation were 2% and 4.9%, respectively, of the total N added through effluents. Difference in emission rates between the two irrigation events were attributed to difference in time lapse between the grazing event and FDE application. When FDE was applied immediately after grazing (second irrigation) higher emissions were observed. <![CDATA[<strong>COMPARATIVE ANALYSIS OF SPLIT-WINDOW ALGORITHMS FOR ESTIMATING SOIL TEMPERATURE</strong>]]> The ability to estimate soil temperature (Ts) from satellite information is highly useful, since this is one of the main input variables in various models designed for estimating biophysical parameters. A comparative analysis is made of various Split-Window algorithms used to estimate soil temperature from data provided by the Advanced Very High Resolution Radiometer (AVHRR) sensor on board of satellites of the National Oceanic and Atmospheric Administration (NOAA). The algorithms compared are those proposed by: Prata and Platt (1991); Uliveri et al. (1992); Sobrino et al. (1993); Caselles et al. (1997); Sobrino and Raissouni (2000). The temperature estimates were validated with data of the soil temperature in situ recorded in a data logger installed in a meteorological station belonging to La Araucania Region, Chile. The results showed that the algorithm proposed by Sobrino and Raissouni (2000) come the closest to the in situ data. However, there are no statistically significant differences between the different algorithms evaluated. <![CDATA[<strong>THE EFFECT OF COMPOST AND SEWAGE SLUDGE ON SOIL BIOLOGIC ACTIVITIES IN SALT AFFECTED SOIL</strong>]]> Saline soil was amended with 13.3 and 26.6 g kg-1 of Municipal Solid Waste (MSW) compost or sewage sludge, and arylsulphatase (ARY), phosphatase (PHO), dehydrogenase (DEH), (β-glucosidase ((β-GLU), urease (URE) and catalase (CAT) activities as well as physical-chemical properties were determined after 70 day of incubation under laboratory conditions. MSW compost and sewage sludge significantly improved soil physical-chemical properties, especially carbon and nitrogen contents. Accordingly, overall enzyme activities were substantially promoted in presence of both amendments and the higher increases were measured at 13.3 g kg-1 of MSW compost (increases by 107%, 43%, 20%, 11%, and 148% for, DEH, (3-GLU, PHO, URE, and CAT, respectively). Lower beneficial effects occurred at 26.6 g kg-1 of sewage sludge possibly because of the increased salinity or the presence of trace elements by sewage sludge application. As a general response, MSW compost supplied at 13.3 g kg-1 seems to be a useful strategy to enhance biologic activities of salt-affected soil. <![CDATA[<strong>USE OF SLUDGE FROM KRAFT MILL WASTEWATER TREATMENT AS IMPROVER OF VOLCANIC SOILS</strong>: <strong>EFFECT ON SOIL BIOLOGICAL PARAMETERS</strong>]]> Sludge from kraft mill wastewater treatment was applied on two soils derived from volcanic ashes and, the effect on biological parameters of the soils was evaluated. The soils used in this study were an Andisol belonging of Gorbea Series and an Ultisol belonging of Collipulli Series. The sludge was added at rates of 0, 10, 20, 30 and 50 t ha-1. Previously, germination of red clover (Trifolium pratense), white clover (Trifolium repens), alfalfa (Medicago sativa) and ryegrass (Lolium perenne) was tested to assess phytotoxicity of the sludge. The different soil-sludge mixtures were incubated at controlled temperature for 60 days and microbial respiration, microbial biomass carbon, fluorescein diacetate hydrolysis and acid phosphatase activity were evaluated throughout the incubation time. All biological parameters evaluated were sensitive enough to shown the effect of sewage sludge application on soil microorganisms. The sludge application at different rates increased significantly (PO.05) the microbial activity and enzymatic activity of the sludge amended soils. The maximum levels of activity were observed between 15 and 30 days after sludge application in both Gorbea soil and Collipulli soil, obtaining the highest values when were applied between 30 and 50 t ha-1. The results of this study suggest that sludge from kraft mill wastewater treatment may have potential as a beneficial soil amendment for improving biological properties of the soils. <![CDATA[ATRAZINE EFFICIENCY IN AN ANDISOL AS AFFECTED BY CLAYS AND NANOCLAYS IN ETHYLCELLULOSE CONTROLLED RELEASE FORMULATIONS]]> Atrazine, a herbicide used for the control of broadleaf weeds of different crops, was incorporated in ethylcellulose controlled release formulations (CRFs) by using the solvent evaporation technique. Allophanic clays and nanoclays were incorporated as matrix modifying agents. The formulations were characterized by scanning electron microscopy (SEM) and infrared spectroscopy (FTIR), and their behavior was determined in aqueous phase. Dissipation studies and soil columns experiments with CRFs were also carried out, and compared with commercial formulations (CFs). In addition, a short-term bioassay was performed to evaluate the effect of CRFs and CFs on the emergence and growth of field mustard (Brassica campestris L.) under greenhouse conditions. The matrix modifiers (clays and nanoclays) showed little influence on the particle morphology and atrazine encapsulation efficiency. Furthermore, these matrix modifiers had a slight effect on the atrazine release into water, its dissipation and its behavior in soil compared with the formulation without them. All CRFs increased the atrazine herbicidal activity and reduced their loss by leaching in soil. Although some similarities were found in the efficiency to reduce the seedling emergence between CRFs and CFs, a greater death of seedlings was observed in the CRFs, especially when nanoclays were added into the formulation. These facts denote an advantage of CRFs over CFs due to prolonged bio-efficiency, and longer applications intervals will be produced, minimizing the harmful impact on the environment. <![CDATA[<strong>PHOSPHORUS-MOLYBDENUM RELATIONSHIP IN SOIL AND RED CLOVER <i>(Trifolium pratense </i>L.) ON AN ACID ANDISOL</strong>]]> We studied the phosphorous (P) and molybdenum (Mo) relationship in soil and red clover (Trifoliumpratense L.) in a non limed and limed acid Andisol of Southern Chile. In soil, we evaluated the effect of different liming (0 and 2000 mg kg-1), P (0, 200 and 400 mg kg-1), and Mo (0, 0.58 and 0.96 mg kg-1) doses supply on soil available Mo. In addition, the availability of P and Calcium (Ca) in treated soils was determinated. In red clover, we studied the Mo and P shoot concentrations and dry matter yield in response to the different treatments applied to the soil. Also, we measured the changes produced by Mo uptake in shoot Cu concentrations. The results showed that both, lime and more strongly P and Mo additions significantly (P ≥ 0.05) increased soil Mo availability. In contrast, soil available P was not significantly (P ≥0.05) affected by liming and Mo treatments. A significant high correlation (r = 0.579, at P ≥ 0.05) was observed among soil Mo availability and shoot Mo concentrations, as well as between soil available P and shoot concentration of P (r = 0.844, at P ≥ 0.01). In this study for all fertilization treatments, shoot Cu concentrations reached values which are considered as normal for forage species. We also shown that the simultaneous applications of high P and Mo rates could be produce red clover shoot Cu/Mo ratios that should provoke Mo-induced Cu deficiency (Molybdenosis) for the cattle. Red clover yield was no significantly different in limed and non limed soils. Nevertheless, red clover yield production increased at increasing rates of P and Mo in both, non limed and limed soil. The major practical implication of these results is that the application of Mo doses equal or superior to 200 g ha-1 to acid Andisols, are recommendable to obtain appropriate Mo shoot content on red clover. In addition, our results shown that P supply to these soils, rather than liming, is necessary to obtain sufficient values of shoot Mo concentrations in red clover.