Rolando Demanet

Effect of liming and gypsum on soil chemistry, yield, and mineral composition of ryegrass grown in an acidic Andisol

Abstract Changes in the chemistry of the acidic Chilean Andisols in response to various ameliorant treatments (gypsum, dolomitic, and calcitic limestone) and their effects on ryegrass (Lolium perenne) production were studied in laboratory incubation and greenhouse experiments. Dolomitic and calcitic limestone alone and in combination with gypsum increased pH significantly and, at the same time, decreased exchangeable aluminum (Al) concentration to low concentrations. Gypsum alone increased pH slightly and reduced Al concentration by 50%, but its effect on ryegrass yield was similar to calcitic and dolomitic limestone. The Al/calcium (Ca) ratio was not a good predictor of the Al toxicity for plant growth but the Al/sulfur (S) ratio in the soil showed a good relationship with dry matter yield. The Ca + magnesium (Mg) + potassium (K) content in shoots was highly correlated with dry matter yield.

Effects of lime and gypsum on pasture growth and composition on an acid Andisol in Chile, South America

The effects of amending an acid Andisol with lime and gypsum on soil pH, aluminum (Al) saturation, the plant-availability of sulfur (S) and phosphorus (P), and the growth, botanical, and chemical composition of a ryegrass/white clover pasture were measured in a field trial in southern Chile. The combined amendment of limestone, dolomite and gypsum raised soil pH slightly, decreased Al saturation from 20 to less than 1% and increased the concentration of plant available P, S, calcium (Ca), magnesium (Mg), and potassium (K) in the soil. The growth of a recently-sown rye grass–white clover pasture increased by 50% and the proportions of ryegrass, white clover and weed species changed from 12.6, 0.2, and 87% to 75, 7.7, and 17%, respectively. Plant chemical analysis suggested that, while N, P, and S concentrations in mixed pasture were less than critical values in spring, S was the most limiting nutrient in pastures from both the amended and control areas.

UREASE ACTIVITY AND NITROGEN MINERALIZATION KINETICS AS AFFECTED BY TEMPERATURE AND UREA INPUT RATE IN SOUTHERN CHILEAN ANDISOLS

Se realizaron estudios de incubacion para evaluar el efecto de la temperatura y niveles de suministro de urea sobre la actividad ureasa y la cinetica de mineralizacion de N en dos Andisoles del Sur de Chile. Nuestros resultados mostraron que la actividad ureasa fue mas alta en el suelo Piedras Negras (PNS) que en el suelo Freire (FS) a 24 y 48 h, y la enzima fue activada cuando la temperatura incremento desde 5 a 21 °C. La actividad ureasa siguio una cinetica simple de Michaelis-Menten. En PNS, la constante de Michaelis-Menten (Km) disminuyo, mientras que la velocidad maxima de reaccion de la enzima (Vmax) y la eficiencia catalitica aumentaron cuando la temperatura fue elevada hasta 21 °C a 24 y 48 h de incubacion del suelo. En FS, la actividad ureasa fue la mas alta a las 24 h, y esta disminuyo a las 48 h como consecuencia del agotamiento del sustrato. Por otra parte, los datos de cinetica de mineralizacion de N estrechamente se ajustaron a un modelo exponencial simple. A etapas tempranas de la incubacion, cantidades similares de N mineralizado (Nmin) fueron encontradas en ambos suelos. Sin embargo, Nmin fue 27 a 64 % mas alto en PNS que FS al final del experimento. Estos resultados tuvieron directa relacion con el contenido de materia organica del suelo, la temperatura y el nivel suministro de urea. En PNS, nosotros observamos que 47 a 80 % de Nmin permanecio como NH4+-N, mientras que en FS N03--N represento entre 80 y 96 %. Tales diferencias en la dinamica de transformacion de N estuvieron de acuerdo con la variacion del pH registrada durante el periodo experimental. Estos hechos tienen implicancias practicas para el manejo de los sistemas agricolas en una localidad en particular, debido a que la dinamica de la mineralizacion de N en Andisoles es principalmente controlada por el contenido de materia organica y las propiedades biologicas de suelos, asi como por la temperatura y el nivel de suministro de urea al sistema suelo-planta.

Effect of liquid cow manure on andisol properties and atrazine adsorption.

Application of animal manure amendments to agricultural soils is a common practice to improve soil fertility through the addition of essential plant nutrients. This practice may increase the potential for atrazine (2-chloro-4-ethylamino-6-isopropylamino-1, 3, 5-triazine) leaching due to competition for adsorption sites between the pesticide and dissolved organic carbon (DOC) added through manure. We evaluated the influence of liquid cow manure (LCM) application on soil properties, atrazine adsorption, and the physicochemical controlling mechanisms in an Andisol. The LCM was applied at rates equivalent to 0, 100,000, 200,000, and 300,000 L ha(-1), resulting in treatments S-0, S-100, S-200, and S-300, respectively. The LCM application increased DOC and pH of the soils immediately on addition, but pH returned to S-0 values 30 d after application. The LCM application did not modify atrazine adsorption with the two lowest application rates (S-100 and S-200), but atrazine adsorption was decreased in S-300 (K(f) = 0.96) compared with the control (S-0) (K(f) = 1.19), possibly due to the competitive adsorption of DOC with the pesticide. The Fourier-transformed infrared analysis showed that LCM increased aliphaticity and presence of N-containing groups and polysaccharide-like groups in amended soils; however, these properties did not modify the atrazine interaction in the studied amended soils. Interestingly the addition of DOC to soil at the high application rate (S-300) reduced atrazine adsorption in this rich OM Andisol despite the LCM not raising the concentration of stable organic matter. The application of high rates of liquid manure containing DOC incurs an increased risk of pesticide leaching.

Effect of calcitic and dolomitic lime on physicochemical properties of a Chilean Andisol

Abstract Changes in surface reactivity produced by different types of liming in a Chilean Andisol were determined. Barros Aranas soil with 53% aluminum (Al) saturation and 4.8 pH was incubated with different amounts of calcitic and dolomitic lime. Each cmol of calcitic or dolomitic lime applied per kg of soil increased the pH with 0.13 and 0.16 units, respectively. Consequently, the decrease in Al saturation was higher with dolomitic than with calcitic liming material. The zero point of charge (ZPC) increased from 4.2 in unlimed soil to 4.6 and 4.8 in limed soil, while the point of zero salt effect (PZSE) decreased from 4.5 to 4.0 and 3.5 with calcitic and dolomitic lime, indicating an increase in negative charge. But, isoelectric point (IEP) values measured by electrophoretic migration suggested that the external charge only changed by treatment with calcitic liming materials. In both treatments, the acidity constant decreased, and consequently phosphorus (P) adsorption capacity also decreased.

Nitrogen losses under different cattle grazing frequencies and intensities in a volcanic soil of Southern Chile.

Chilean livestock production systems have intensified over the last years, with increasing amounts of N fertilizer inputs creating the potentiality for environmental damage through N pollution of water and air, so that alternative production strategies have been developed to reduce such environmental impacts. This study assesses N losses under different grazing frequencies and intensities on permanent pasture (Lolium perenne L., Festuca arundinacea Schreb., Dactylis glomerata L., and Trifolium repens L.) on an Andisol in Southern Chile. Four grazing strategies were evaluated: frequent-heavy (FH), frequent-light (FL), infrequent-heavy (IH), infrequent-light (IL), and a no grazing control (C) treatment, and each with three replicates in a randomized complete block design. Results of the experiment indicate that N leaching losses were greater in the FH treatment (58.7 kg available N ha -1 ; p < 0.05) and with most of the leaching occurring in spring (39%). On average, N ammonia (NH3) losses were 10% greater in the frequent grazing treatments in relation to the infrequent grazing treatments, since there were no significant differences (P ≤ 0.05) among individual grazing events for FH, FL and IH. Results indicate that grazing frequency affects leaching losses while grazing intensity affects ammonia emissions from the grassland. Grazing with dairy cows in Southern Chile should consider this environmental constraint to ensure sustainable production over time.

Effect of dairy manure rate and the stabilization time of amended soils on atrazine degradation

The application rate of liquid cow manure (LCM) in the field and the stabilization time of amended soils before application of pre-plant herbicides are factors that determine their efficiency. This study includes evaluation of residual atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine) in soil and amended soils with equivalent rate of 100,000; 200,000; and 300,000 L ha(-1) of LCM and the effect of pre-incubation time of amended soils on atrazine degradation. The study was carried out under controlled conditions using an Andisol with previous historical application of atrazine. The respiratory activity and fluorescein diacetate (FDA) studies indicated that the time necessary for stabilization of amended soils is over 20-30 d. During the measurement of respiratory and FDA activity, no significant differences were observed when atrazine was applied. The half-life of atrazine ranged from 5 to 8d and the relative distribution of degradation products seem to be affected by the application of LCM. The pre-incubation time of amended soil and LCM dose would not affect atrazine degradation rate, when the soil has a history of herbicide application. However, repeated applications of LCM in a long period of time could change the soil pH and increase the content of dissolved organic carbon (DOC) which could further contribute to a faster degradation of atrazine. Both effects would reduce the effectiveness of atrazine in weed control.

Effect of cow slurry amendment on atrazine dissipation and bacterial community structure in an agricultural Andisol.

Atrazine is a commonly used herbicide for maize production in Chile, but it has recently been shown to be ineffective in soils that receive applications of cow slurries generated from the dairy industry. This effect may be caused either by the sorption of the pesticide to organic matter or more rapid degradation in slurry-amended soils. The objectives of this study were to evaluate the effects of cow slurry on atrazine dissipation, the formation of atrazine metabolites and the modification of bacterial community in Andisol. The cow slurry was applied at doses of 100,000-300,000 Lha(-1). After 4 weeks, atrazine was applied to the slurry-amended soils at concentrations of 1-3 mg kg(-1). The amounts of atrazine and its metabolites were determined by high performance liquid chromatography (HPLC). The soil microbial community was monitored by measurement of CO(2) evolution and changes in bacterial community using PCR-DGGE of 16S rRNA genes. The results show that cow slurry applications had no effect on atrazine dissipation, which had a half-life of 15-19 days. The atrazine metabolites were detected after 20 days and were significantly higher in soils amended with the slurry at both 20 and 40 days after application of the herbicide. Respiration rates were elevated after 10 days in all soils with atrazine addition. Both the atrazine and slurry amendments altered the bacterial community structures, indicated by the appearance of specific bands in the DGGE gels after 10 days. Cloning and sequencing of the 16S rRNA genes from the DGGE gels showed that the bands represented various genera of beta-proteobacteria that appeared in response to atrazine. According to our results, further field studies are required to explain the lower effectiveness of atrazine in weed control. These studies may include the effect of dissolved organic carbon on the atrazine mobility.

MOVEMENT OF N0(3)-N AND NH4-N IN AN ANDISOL AND ITS INFLUENCE ON RYEGRASS PRODUCTION IN A SHORT TERM STUDY

En suelos acidos, el uso de fertilizantes amoniacales acelera los procesos de acidificacion y disminuye la produccion y persistencia de las pasturas. El nitrogeno (N) es el principal factor limitante del crecimiento vegetal en la mayoria de los sistemas agricolas, pero tambien es uno de los principales problemas ambientales del mundo. En Chile, no han sido reportados estudios sistematicos en el primer periodo de crecimiento de la pastura ni las perdidas de N por lixiviacion asociadas. Los objetivos de este estudio fueron: (i) evaluar el efecto de la fuente de N a dosis crecientes de aplicacion sobre el rendimiento y calidad de ballica (Lolium perenne) y (ii) cuantificar en el corto plazo las perdidas potenciales de N por lixiviacion y los cambios de pH a traves del perfil del suelo bajo condiciones de campo. Se realizo un experimento de campo durante la temporada primavera-verano 2000-2001 en un Andisol del Sur de Chile bajo riego. Se aplico urea y nitrato de sodio en dosis de 0, 150 y 300 kg N ha-1. La pastura fue cortada tres veces y se determino la produccion de materia seca (DM) y la concentracion de N foliar. Ademas, se determino el pH del suelo y las concentraciones de N-NH4+ y N-N03 para los 0-10 cm, 10-20 cm y 20-40 cm de profundidad, y se estimaron las maximas perdidas potenciales de N por lixiviacion. La produccion de DM aumento en 128 % a medida que el suministro de N se incremento de 0 a 300 kg N ha-1. La fuente de N no mostro ningun efecto sobre el rendimiento. La urea y el nitrato de sodio generaron una concentracion de N foliar mas alta a medida que la dosis de N aumento, y no se observo un efecto acidificante de la urea sobre la produccion de DM y la calidad de la pastura. La aplicacion de nitrato de sodio y urea (300 kg N ha-1) genero la mayor concentracion de N-NH4+ y N-N03 en las capas mas profundas del suelo. Para los 20-40 cm de profundidad, las maximas perdidas potenciales de N a traves del perfil del suelo fueron alrededor de 90 kg N ha-1 y correspondieron al periodo de menor tasa de crecimiento de la pastura

Improving selenium status in plant nutrition and quality

Abstract Selenium (Se) is an essential micronutrient for human health due to its antioxidant capabilities. The Se content around the world is highly variable from 0.005 mg kg -1 in areas from China and Finland to 8,000 mg kg in seleniferous soils from Tuva-Russia. However, about one billion of people in the world wide are Se deficient. During the last decade, studies related with strategies for Se biofortification in food plants for human nutrition have significantly increased because this metalloid is incorporated into human metabolism mainly as a constituent of food plants. Similarly, Se biofortification is important in pastures for increasing the Se content in cattle to enrich meat and to prevent disease associated to Se deficiency as white muscle disease. In China, two endemic diseases have been related to Se deficiency: Keshan and Keshin–Beck diseases.Agronomic biofortification by using inorganic Se sources is a current practice in countries as China, Finland, and USA. In Chile, fertilization by using chemical compounds with Se is an uncommon practice due the edaphoclimatic characteristics of Andisols, which represent around 60% of agricultural soils of southern Chile. Recent studies showed that microorganisms as bacteria and arbuscular mycorrhizal fungi play an important role in the transformations and Se availability, representing an interesting biotechnological alternative to Se biofortification.This review is focalized to describing Se behavior in soil-plant system and the possible strategies to improving Se content, including the use of microorganisms as biotechnological tools for increasing plant nutrition and quality. Specific attention will be devoted to volcanic soils of Southern Chile, where different factors concur to enhance the Se-deficiency problem.