Lidia Giuffré

A comparison of indexing methods to evaluate quality of soils: the role of soil microbiological properties

The study evaluates and compares two procedures for selecting soil quality indicators (used for the construction of soil quality indices, SQI) by using diverse chemical, physical, and biological properties, and evaluates the role of soil microbiological properties in the construction of SQI. Different soil environments were selected from an extensive agricultural production site in the rolling pampa, Buenos Aires, Argentina. The plots included an undisturbed soil, a grassland soil, and continuous tilled soils with four different surface horizon depths (25, 23, 19, and 14 cm). Various properties were measured, and a minimum dataset was chosen by principal component analysis (PCA) considering all measured soil properties together (procedure A), or the PCA was performed separately according to classification as physical, chemical, or biological soil properties (procedure B). The measured soil properties involved physical, chemical, and biochemical properties determined by standard protocols used in routine laboratory analysis (simple SQI, SSQI) or more laborious protocols to determine microbial community structure and function by phospholipid fatty acid (PLFA) and catabolic response profile (CRP), respectively (complex SQI, CSQI). The selected properties were linearly normalised and integrated by the weight additive method to calculate SSQI A, SSQI B, CSQI A, and CSQI B indices. Two microbiological SQI (MSQI) were also calculated; MSQI 1 considered only biological properties according to the procedure used for calculating SQI; MSQI 2 was calculated by considering three selected microbiological parameters representing the size (microbial biomass carbon), activity (soil basal respiration), and functional diversity (evenness, determined by CRP) of the microbial communities. All of the constructed indices show the same differences among the study sites. The inclusion of CRP and PLFA data in the indices slightly increased, or did not increase, the index sensitivity. Microbiological indices had the same sensitivity as the indices integrated by physical, chemical, and biological properties. An evaluation of the SQI constructed by both procedures found no difference in sensitivity. However, SQI constructed by procedure B allowed evaluation of the effects of management practices on physical, chemical, and biological soil properties.

Soil phosphorus mobilization in different taxonomic orders

Changes in P fractions using Hedleys sequential fractionation of organic and inorganic soil P, were studied in soils covering a wide range of developmental stages and original materials. A greenhouse experiment was performed in order to make an exhaustive P uptake by Lolium perenne and to study soil phosphorus mobilization from different fractions. Samples were obtained at 30, 60 and 90 days from sowing, with two fertilization rates added as KH2PO4. The exhaustion produced by plants resulted in different patterns of mobilization according to soil characteristics. For control soils the contents of inorganic labile fraction (LIP) decreased at the end of the experience in Mollisol (31%), Vertisol (24%) and Andisol (17%). The mobilization of organic P was greater for Ultisol and Andisol (77 and 75% respectively) than for the other soils. Fertilization affected mainly inorganic P, with a significant increase in contents of LIP in Entisol (46%) and moderately resistant inorganic P (MRIP) in Andisol (15%). Inorganic P/organic P relationship tended to increase during the experiment, while labile P/moderately resistant P increased in Entisol and Mollisol. Mobilisierung von Phosphor bei verschiedenen taxonomischen Ordnungen Veranderungen von organischen und anorganischen Phosphorformen wurden nach der Hedleyschen sequentiellen Fraktionierung bei verschiedenen Bodenordnungen analysiert. Umfassende Gefasversuche wurden mit Weidelgras im Gewachshaus durchgefuhrt. Bodenproben wurden 0, 30 und 90 Tage nach dem Auflaufen der Keimlinge gesammelt. Aus der P-Aufnahme der Pflanzen ergaben sich in Abhangigkeit von den Bodeneigenschaften verschiedene Mobilisierungsmuster. Bei den Kontrollboden nahm der Gehalt an anorganischen labilen P-Formen beim Mollisol (31%), Vertisol (24%) und Andisol (17%) ab. Die Mobilitat organischer P-Formen waren beim Ultisol (77%) und beim Andisol (75%) am hochsten. P-Dungung beeinflust hauptsachlich den anorganischen P-Gehalt: Eine signifikante Erhohung der mobilen anorganischen P-Form wurden beim Entisol (46%) und der masig gebundenen anorganischen P-Form beim Andisol (15%) beobachtet. Das Verhaltnis anorganische/organische P-Fraktion zeigte wahrend des Experimentes eine zunehmende Tendenz, wohingegen sich das Verhaltnis mobile/masig gebundene P-Form beim Entisol und Mollisol erhohte.

Efecto de diferentes técnicas de manejo de residuos de la cosecha forestal en algunas propiedades de un suelo Kandiudult en el Noreste argentino

El objetivo de este trabajo fue evaluar el efecto de diferentes tecnicas de manejo de residuos de Pinus ellioti Engelm en indices de calidad de suelo en un Kandiudult de Misiones, Argentina, en condiciones de altas temperaturas y precipitaciones. Los tratamientos fueron: T1) extraccion manual de los residuos y reforestacion; T2) quema y reforestacion; T3) conservacion de los residuos y reforestacion; T4) conservacion de los residuos y desarrollo de bosque secundario. El diseno estadistico fue en bloques completamente al azar con cuatro repeticiones, en bloques de 840 m2. Las muestras de suelo fueron extraidas un ano y medio despues de implantados los tratamientos, por ser importante el monitoreo a corto plazo, dado que los cuatro primeros anos son clave en las plantaciones de pinos en esta region . La remocion total de los residuos se tradujo en menores valores de las formas de carbono total (Ct) (P < 0,05). La quema, a corto plazo, produjo un aumento significativo de fosforo extractable (Pe) (P < 0,05). La conservacion de los residuos provoco un aumento significativo de nitrogeno total (Nt), equivalente al de la quema, y valores mas altos de carbono total (Ct) y carbono liviano (Cl) (P < 0,05).

ANTHROPOGENIC EFFECT ON SOIL ORGANIC PHOSPHORUS FRACTIONS IN TROPICAL ECOSYSTEMS

Total organic phosphorus (P), labile organic P, and total carbon were determined in composite surface soil samples, with three replicates, in a Kandihumult from Misiones province, Argentina. The analysis was performed on <0.1 mm, 2–0.5 mm, and >8 mm aggregate fractions obtained by dry sieving. Representative situations were selected to evaluate changes in P dynamics by soil use: a native subtropical forest, a degraded agroecosystem with a 50-year yerba mate plantation (Ilex paraguariensis Saint Hill.), and a similar plantation with a 6-year associated elephant grass (Pennisetum purpureum Schumach). Native pristine soil from the forest presented the highest content of phosphorus in more humified fractions (<0.1 mm). Fifty-year cultivation of “yerba mate” produced a degraded agroecosystem with 10% decrease of total organic phosphorus forms in humified fractions. Six-year-old elephant grass mulch incorporation increased total organic phosphorus both in more humified fractions and in macroaggregates (>8 mm), due to addition of decomposable organic materials. Labile organic phosphorus was higher under stress conditions.

A Study on the Effec t of Soil Amendments and Environmental Conditions of Stevia rebaudiana in Urban Soils of Buenos Aires, Argentina

The leaves of wild Stevia plants contain several different natural glycoside compounds responsible for producing the sweet taste sensation. It is used as a sweetener, and has some important properties as regulation of sugar level in blood, and other medical issues. The objective of this work is to study the effects of different soil amendments and the location of the culture, inside or outside a greenhouse, on Stevia rebaudiana growth and final dry weight, at an urban soil. A complete randomized design with 4 replications was used. The effect of two factors on Stevia growth were evaluated: the application with organic amendments and the location, at field and at greenhouse conditions. Amendments treatments were control, liquid vermicompost, compost and vermicompost. The height and diameter of Stevia plants were measured at T2 (vegetative state) and T3 (flowering, ) and final plant dry weight was also weighed at T3. Inside the greenhouse Stevia plants had a higher development, measured by height and diameter growth and by final dry weight accumulation, due to higher temperatures and drip irrigation. Solid amendments, compost and vermicompost, presented higher values of the measured parameters, height, diameter and dry matter, with statistically significant differences from the control and liquid vermicompost; values of these latter treatments did not differ statistically from each other. Differences in diameter growth were more closely related to final dry weight than height growth, which suggests that diameter is a suitable variable to use as an early indicator of growth conditions. In this trial Stevia adapted to existing conditions of the urban soil, slightly acid, non saline and well supplied in organic matter, and completed its cycle properly, with good potential as an organic grown crop.

Moderately resistant phosphorus forms in subtropical ultisol of argentina

Abstract The efficiency of phosphorus (P) fertilization may be improved through knowledge of soil P fraction changes with time. This study examined: i) the distribution of P fractions according to Hedleys fractionation scheme and ii) the sequential changes in soil organic P (OP) and inorganic P (IP) in a typical Kandihumult, under favorable conditions for mineralization and under depletion conditions, with and without P fertilization. Soil P fractions considered were IP‐resin, IP‐ and OP‐bicarbonate, and IP‐ and OP‐hydroxide. The soil is characterized by the predominance of moderately resistant P, in organic and inorganic fractions. In the presence of favorable conditions for mineralization, a substantial decrease in moderately resistant organic P was observed, enhanced even more by fertilizer incorporation. The decrease of total extracted P (TPe) before depletion situations was mainly produced in the moderately resistant fraction, that registered a decrease of 23% (of this value 65% were due to OP). The main fate of the fertilization, in both situations (active mineralization as well as depletion) was moderately resistant inorganic phosphate.