Volumen 18, Número 1 (Junio, 2000)
Efectos de la labranza convencional sobre la sortividad y conductividad hidráulica saturada en Udoles del sureste de la provincia de Buenos Aires
Conventional tillage effects on sorptivity and saturated hydraulic conductivity on Udolls of the south-east of Buenos Aires province
FN Cabria & JP Culot
Pág. 1-8
The objectives of this study were to compare soil infiltration in three soil series, to assess the long- term effect that the conventional tillage has on saturated hydraulic conductivity and to determine whether saturated hydraulic conductivity (Ks) in the principal horizons of the sequum is isotropic or not. With this purpose, sorptivity (S), final infiltration (it) and saturated hydraulic conductivity (KsA and KsB) were determined. Applying Schwartzendruber equation to infiltration data ob- tained with the concentric rings methodology, S and it were calculated. Undisturbed soil samples in two directional axis, parallel and perpendicular to soil surface were collected and KsA and KsB using Klute, and Dirksen methodology were determined. The results showed that: 1) the soils are different when characterized by S and Ks. 2) conventional tillage has an effect on KsA and KsB on the long term. 3) KsA and KsB magnitudes are co-linear to soil effective depth. 4) Saturated hy- draulic conductivity decreased in surface and subsurface horizons under conventional tillage. 5) S is increased in the superficial horizons under conventional tillage. 6) Saturated hydraulic conduc- tivity is isotropic in surface horizonS but not in argillic horizonS.
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Métodos rápidos de estimación de nitrógeno potencialmente mineralizable en suelos
Rapid methods for assessing potentially mineralizable soil nitrogen
HE Echeverria, NF San Martín & R Bergonzi
Pág. 9-16
The objective of this study was to relate potentially mineralizable soil nitrogen (N) obtained by means of long-term aerobic incubations (No), with nitrogen mineralizated using more rapid and simple methods such as KCl digestion (Nq) and short-term anaerobic incubations at 40 oC (Na). A preliminar experience, carried out on 23 soil samples of the southeastern Buenos Aires Province, allowed to determine that a close association between nitrogen mineralization after 7 and 14 days of anaerobic incubations (Na) exists. Consequently, Na was incubated during 7 days. Measure- ments were made during 1994 to 1997 in the topsoil of soils submitted to contrasting management systems of the Pampean Region. Nq had the lowest range in samples taken in 1994 and 1995. This indicated its low sensitivity, showing no differences between managements. In both years the relationships between No and Nq were similar; however slopes were different suggesting that Nq was not a good predictor of No. Short-term anaerobic incubations at 40 oC and No were correlated in both years, and the slopes of the fitting equations obtained in each year were not different (P less than 0,05). This relationship was confirmed with soil samples taken during 1996 and 1997. The fitting equa- tion for the four analysed years was No = 1,37 Na + 83,17 (r2 = 0.65), which can be used to estimate No with a rapid incubation method (Na).
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Estimación del nitrógeno mineralizado para un cultivo de trigo en distintas secuencias de cultivos
Estimation of soil nitrogen mineralization for spring wheat in different crop sequences
GA Studdert, LS Carabaca & HE Echeverría
Pág. 17-27
Nitrogen fertilization diagnosis for wheat should include not only the evaluation of available nitro- gen at sowing but also the nitrogen to be mineralized during the crop growing season. Soil nitrogen availability dynamics depends on the size of soil potentially mineralizable nitrogen (N0), which in turn is dependent on long term soil management, and on the characteristics of the plant material returned to the soil, determined by on the preceding crop. It has been hypothesized that a model based on N0 to estimate nitrogen mineralization, would not be effective since N0 does not take into account the material returned to the soil. In a field experiment at Balcarce, nitrogen nutrition and yield of wheat sown after four preceding crops (soybean, wheat, sunflower, and maize) within four long term crop sequences with a high frequency of each of them was studied. In a laboratory experi- ment soil organic carbon, N0 and mineralization constant (k) were determined. Grain yield, aboveground dry matter and nitrogen accumulation and other nitrogen nutrition indicators showed the following order as a function of the preceding crop: soybean>wheat> sunflower>maize. Soil organic carbon, N0 and mineralized soil nitrogen estimated with the model showed the opposite order due to the long term effect of the sequences. Soybean residues decomposition released nitro- gen and maize residues provoked nitrogen immobilization that altered wheat nitrogen nutrition and were not taken into account by the model. Nitrogen mineralization estimation should include the short term effect of preceding crops in the sequence.
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Fijación y movilidad de cadmio y cinc en tres tipos de suelos ácidos de Galicia, España
Retention and mobility of cadmium and zinc in three acid soils of Galicia, Spain
J Estévez, ML Andrade, P Marcet & MJ Montero
Pág. 28-35
The retention and mobility of Cd and Zn were studied in three acid soils of Galicia, Spain. Soils were treated with 500 mg kg-1 of cadmium, 1000 mg kg-1 of zinc and a mixture of both elements. Total contents of both metals were determined by acid digestion using a microwave oven, and their available contents by NH4COO CH3 extraction. Significant differences were found in all the three soils. Stronger retention was found in the soil with higher organic matter contents, finer texture, more effective cationic exchange capacity, and lower percentage of Al saturation. Zn mobility was greater than Cd mobility in all three soils. High concentrations of one of the metal favours mobility and inhibits the retention of the other.
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Landfarming of petroleum wastes in a cold dry climate of Tierra del Fuego.(Effects on soil and vegetation)
Cultivo de residuos de petroleo en un clima frio y seco de Tierra del Fuego (Efectos en el suelo y la vegetación)
R Mendoza & R Portal
Pág. 36-43
The effect of adding organic oily wastes on plant cover and on soil water content was studied in a soil covered by a community of low forage value in Tierra del Fuego (Argentina). Oily wastes were mixed with the top 3 cm of the soil in May 1993 at rates of 1.51 and 3.03 % (w/w basis). In December 1993, half of each plot was fertilized with N and P, and changes in species abundance and total cover were evaluated in December of 1994 and 1995. Soil samples at 0-3, 3-6 and 6-9 cm depths were taken in December of 1993-1995, and analyzed for pH, water content, and total petro- leum hydrocarbon (TPH). The oily wastes increased water content and pH in the soil. Fertilization increased plant growth but both fertilization and oily waste increased plant cover. TPH in soil decreased from 3 % to 0.18 % during the experimental period, but fertilization did not affect the decrease in TPH with time. The results, combined with the annual rainfall and the water table elevation at the site, suggests that the risk of contaminating the water table is relatively low. It is concluded that landfarming could be applied as a remedial action in soils of Tierra del Fuego. In addition, amending the soil with oily waste in dry heath ecosystems increased water conservation and this effect promoted plant growth.
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Modelo de fertilización nitrogenada y fosforada para trigo en el Sudoeste Bonaerense, Argentina
Model for nitrogen and phosphours fertilization of wheat in southwestern Buenos Aires, Argentina
MM Ron & T Loewy
Pág.44-49
In the southwest of Buenos Aires Province (Argentina) nitrogen and phosphorus deficiencies are important wheat yield limiting factors. The objective of this paper was to develop a model which predicted yield response to nitrogen (0 to 60 kg N ha-1), applied at two different times (sowing or tillering) or in a split application, and to include the interaction with phosphorus (16 kg P ha-1), applied with the seed. For each of 19 experiments, placed on farmers’ fields, a function of the form y=b0 +b1 Ns +b2 Nm +b3 Ns2 +b4 Nm2 +b5 NsxNm +b6 P +b7 NsxP+b8 NmxP +b9 NsxNmxP, was fitted. In the equation y denotes yield; N and P, fertilizer rates; subscripts s and m, time of application and b0 to b9, coefficients. Dependent variables of yield response to N and P and interac- tions were derived from this equation. Independent variables were pH, organic matter (MO) and soil extractable phosphorus (BK). Dummy variables of soil texture, wheat cycle and climatic year were also included. Yield response to N and P depended mainly on climatic year and BK, respec- tively, as shown in previous papers. Interactions accounted for ± 500 kg wheat ha-1. N-P interaction was greater for soils of low organic matter and cultivars of intermediate and short vegetative cycle. Interaction between the two N fractions of a split application was related to pH and the higher yield response potential of the intermediate cycle cultivar. The results indicate that it is more convenient to split the N rate, particularly for long and intermediate cycle cultivars.
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Biominerales de oxalato de calcio en suelos de Laguna de los Padres, Buenos Aires, Argentina
Calcium oxalate biominerals in soils of Laguna de Los Padres, Buenos Aires, Argentina
M Osterrieth , F Oyarbide & V Bordas
Pág. 50-58
The general mineralochemical characteristics of calcium oxalate: whewellite (CaC2O4 .H2O) and weddellite (CaC2O4. (2+X) H2O) from litter layer and minerals horizons of the Pampean Plains soil are described by first time in Argentine. The studies are carried out using polarisation microscopy and scanning electron microscopy plus energy dispersive microanalysis. The results indicate a pre- dominance of weddellite crystals such as twinned tetragonal dipyramid and bipyramid crystals arranged as rossetes and druses with sizes varing between 5 and 10μm in the litter layer of the acacia forest. The whewellite, pseudo-rhombohedra, isodiametric crystals, appear as individual 5μm diameter crystals and rossetes 5 to 10μm diameters crystals, can be found in the A horizons of forest and grass praire. A direct relation has been found between: humidity degree, development of the litter layer and fungi colonisation, with respect the amount and development of biominerals.
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Metales pesados por aplicación de biosólidos en un Hapludol de Tucumán, República Argentina
Effect of biosolids application on heavy metal contents of an Hapludol of Tucuman, Argentina
S Ratt0, L Marbán & C Magnavacca
Pág. 59-63
Heavy metal soil content was measured in a Tucuman Hapludol after two consecutive years of biosolids application. Total Cd, Cr, Cu, Ni, Pb, Zn soil contents were measured at 0-10cm, 10-20cm and 20-30 cm depths. Three doses of biosolids were surface applied at 0, 3.5 and 10 Mg ha-1. The biosolid was obtained from a treatment plant and was irradiated with 3 kGy for disinfecting. Cu, Pb, Zn, and Ni contents increased significantly up to 10 cm depth with the lower dose and up to 20 cm with the higher one. Cr and Cd did not change. While Environmental Protection Agency (EPA) rules indicate that Pb would be limiting after 85 years of application, soil’s heavy metal data con- tent suggest that after 10 years of repeated application Ni can be the most hazardous element followed by Pb and Zn. According to the Commission of the European Communities (CEU) rules the critical elements in soils using this type of biosolids for 10 consecutive years are Ni, Zn and Pb in that order.
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Relaciones entre la producción de grano y la concentración de nitratos en seudotallos de variedades de trigo
Relationship between the grain yield and the stems nitrate concentration of wheat varieties
RA Strada, HE Echeverría & GA Studdert
Pág. 64-68
Plant analysis is a valuable tool for evaluating nitrogen availability to wheat because it combines soil and environmental effects. The aim of this work was to determine the relationships between nitrate concentration at tillering, in stems of wheat varieties with similar growth cycles, with wheat grain yield. In 1997, two nitrogen fertilization trials were carried out with two sowing times and four wheat varieties. In both experiences the average grain yield was 6,7 Mg ha-1, and its variation was linearly related to the nitrogen fertilization rate (R2=0,78). Average responses to the 120 and 60 kg ha-1 nitrogen rates were 21 and 25 kg of grain per kg of nitrogen, respectively. Protein contents were inversely associated with grain yield (R2=0,45), and were higher for the first sowing date. Seed size decreased with increment of the nitrogen fertilization rate. The nitrate concentration decreased with plant age and with the reduction in the nitrogen fertilization rate. The effect of variety was less important. Thresholds of stem nitrate concentration were determined to achieve 95% of maximum yield: 7,9, 4,8 and 2,5 g kg-1 for double ridge, glumme primordium and terminal spikelet, respectively. Wheat stem nitrate concentration at tillering is a promising estimator of the crop nitrogen nutrition status.
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Minerales de arcilla en fracciones limo de horizontes superficiales de suelos de diferente mineralogía
Clay minerals in the silt-size fraction in superficial soil horizons of different mineralogical composition
N Peinemann, NM amiotti, P Zalba & MB Villamil
Pág. 69-72
Particle size fractions were separated by sedimentation from the A horizon of soils developed on two types of loess (II, IV), on an alluvial material (III) and on a basaltic rock (I). X-ray powder diffraction traces were used to identify the mineralogical composition of the isolated fractions and their CEC was determined. The obtained data showed the following clay type dominance for each soil: kaolinite (I), illite (II), smectite (III) and illite-smectite interstratified (IV). Clay minerals could be detected in all the analized size-fractions decreasing their content as the fraction increases in size. The same behavior was found concerning charge and size of the fractions as demonstrated by the CEC values. The CEC of the silt fractions displayed the following order: kaolinite (less than)smectite (less than) interstratified (less than) illite. When considering the relationship between the clay content and the charges originated in the coarse fraction, it could be observed that this relationship remained constant in the soil where kaolinite prevails, increased in the illitic soil and decreased in the soil with smectite and interstratified. Therefore, it is concluded that in soil I kaolinite is responsible for the entirety of the charges generated in the silt fraction. In soil II, the charge surplus could be attributed to the illite along with other coarser soil minerals. In soils II and IV, the mentioned reduction could be ex- plained through the aggregation of phyllosilicates forming pseudo-silts which probably makes part of the charges inaccessible as to participate in cation exchange reactions.
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