Marta Alfaro

Fate of Mycobacterium avium subsp. paratuberculosis after application of contaminated dairy cattle manure to agricultural soils

ABSTRACT Details regarding the fate of Mycobacterium avium subsp. paratuberculosis (basonym, Mycobacterium paratuberculosis) after manure application on grassland are unknown. To evaluate this, intact soil columns were collected in plastic pipes (lysimeters) and placed under controlled conditions to test the effect of a loamy or sandy soil composition and the amount of rainfall on the fate of M. paratuberculosis applied to the soil surface with manure slurry. The experiment was organized as a randomized design with two factors and three replicates. M. paratuberculosis-contaminated manure was spread on the top of the 90-cm soil columns. After weekly simulated rainfall applications, water drainage samples (leachates) were collected from the base of each lysimeter and cultured for M. paratuberculosis using Bactec MGIT ParaTB medium and supplements. Grass was harvested, quantified, and tested from each lysimeter soil surface. The identity of all probable M. paratuberculosis isolates was confirmed by PCR for IS900 and F57 genetic elements. There was a lag time of 2 months after each treatment before M. paratuberculosis was found in leachates. The greatest proportions of M. paratuberculosis-positive leachates were from sandy-soil lysimeters in the manure-treated group receiving the equivalent of 1,000 mm annual rainfall. Under the higher rainfall regimen (2,000 mm/year), M. paratuberculosis was detected more often from lysimeters with loamy soil than sandy soil. Among all lysimeters, M. paratuberculosis was detected more often in grass clippings than in lysimeter leachates. At the end of the trial, lysimeters were disassembled and soil cultured at different depths, and we found that M. paratuberculosis was recovered only from the uppermost levels of the soil columns in the treated group. Factors associated with M. paratuberculosis presence in leachates were soil type and soil pH (P < 0.05). For M. paratuberculosis presence in grass clippings, only manure application showed a significant association (P < 0.05). From these findings we conclude that this pathogen tends to move slowly through soils (faster through sandy soil) and tends to remain on grass and in the upper layers of pasture soil, representing a clear infection hazard for grazing livestock and a potential for the contamination of runoff after heavy rains.

Ganadería y contaminación difusa, implicancias para el sur de Chile

Producto de los tratados de libre comercio firmados por Chile, que auguran la apertura de mercados para la exportacion de productos lacteos y carnicos, se espera que la actividad ganadera del Sur del pais se incremente e intensifique. A pesar del conocimiento tecnico disponible para el incremento de la productividad del rubro, poco se sabe con certeza sobre el impacto ambiental de esta actividad, en especial sobre cursos de agua, a pesar de que los rios y lagos de la region son ademas la base de otras actividades economicas de importancia, como la acuicultura y el turismo. En paises desarrollados se ha demostrado que existe una fuerte relacion causa-efecto entre la actividad ganadera y la polucion difusa de cursos de agua superficiales, en especial de su eutroficacion por altas concentraciones de nitrogeno (N) y fosforo (P). Realizando un analisis de los mecanismos que controlan dichas perdidas, es posible plantear un escenario futuro para la Region de Los Lagos, en el sur de Chile. El mayor uso de insumos, el incremento de la carga animal, la falta de normas de manejo mejoradas y la incorporacion de zonas de mayor pendiente o con implementacion de drenaje artificial a la actividad permiten prever un bajo nivel de eficiencia en el uso del N y P que ingresan como fertilizantes a los sistemas ganaderos de la region, incrementandose sus perdidas y pudiendo generarse con ello la subsecuente eutroficacion de los cursos de agua aledanos.

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.

Nitrogen, phosphorus and potassium losses in a grazing system with different stocking rates in a volcanic soil.

A B S T R A C T In Chile there is little information on nutrient losses in livestock systems. The experiment was carried out between 2004 and 2006. Two stocking rates (3.5 and 5.0 steers ha -1 ) were tested under rotational grazing with Black and White Friesian steers on a permanent pasture (67.5 kg N and 40 kg P ha -1 yr -1 ). To quantify surface runoff losses (N, P, K), three surface lysimeters (5 x 5 m) per treatment were established. N and K leaching losses were estimated with ceramic cups. Runoff and leachate samples were individually analyzed for available and total N, reactive (RP) and total P, and K. Dissolved organic N (DON) and organic P (OP) were estimated as the difference between total and available forms. The stocking rate did not increase total N, P and K losses (P > 0.05). Losses in surface runoff were < 0.5 kg N, < 0.05 kg P and < 0.6 kg K ha -1 yr -1 , respectively, due to the low amount of runoff measured. Nitrogen leaching losses were high (11 up to 71 kg ha -1 yr -1 ) and K leaching losses were low (3 to 5 kg ha -1 yr -1 ). Nitrogen in runoff was mainly lost as DON (50%). Nitrogen leaching losses were mainly as nitrate (70%). Phosphorus was lost as RP (70%). Thus, stocking rates of 5.0 steers ha -1 are plausible, but fertilizer application should be avoided in rainfall periods during the year to reduce incidental nutrient losses.

NITROGEN LEACHING LOSSES ON A VOLCANIC ASH SOIL AS AFFECTED BY THE SOURCE OF FERTILISER

ABSTRACT An intact lysimeters study was carried out to measure the potential nitrogen (N) losses onan andisoil of Southern Chile with different fertilisers. The treatments tested were: fishslurry (FS), dairy slurry (DS), potassium nitrate (IF) and a control treatment (C), with no Naddition. An equivalent amount of 150 kg of total N ha -1 was applied to each lysimeter andthen the equivalent to 1260 mm of rainfall was irrigated over a 90 days period. Leachatesamples were analysed for nitrate, nitrite, ammonia and organic N (No). Total N losseswere calculated as the product between drainage and the respective N concentration in theleachates. Lowest N losses were obtained in the control and FS treatments (66 kg N ha -1 )and the greatest amount was obtained in the IF treatment (261 kg N ha -1 ). Nitrogen wasmainly lost as nitrate and No (each was 49% of the total N losses). High soil organic matterof andisoils can be more relevant than fertiliser for N leaching losses. Palabras claves: Lodo de pescado, purines de lecheria, fertilizante inorganico, calidad deagua

Intensification of grassland and forage use: driving forces and constraints

Abstract. The increasing demand for safe and nutritional dairy and beef products in a globalising world, together with the needs to increase resource use efficiency and to protect biodiversity, provide strong incentives for intensification of grassland and forage use. This paper addresses the question: ‘Does intensification of grassland and forage use lead to efficient, profitable and sustainable ecosystems?’ We present some notions about intensification of agricultural production, and then discuss the intensification of grassland-based dairy production in The Netherlands, Chile and New Zealand. Finally, we arrive at some conclusions. External driving forces and the need to economise (the law of the optimum) provide strong incentives for intensification, that is, for increasing the output per unit surface area and labour. The three country cases illustrate that intensification of grassland use is a global phenomenon, with winners and losers. Winners are farmers who are able to achieve a high return on investments. Losers are small farmers who drop out of the business unless they broaden their income base. The relationship between intensification and environmental impact is complex. Within certain ranges, intensification leads to increased emissions of nutrients and greenhouse gases to air and use of water per unit surface area, but to decreased emissions when expressed per unit of product. The sustainability of a grassland-based ecosystem is ultimately defined by the societal appreciation of that system and by biophysical and socioeconomic constraints. In conclusion, intensification may lead to more efficient and profitable and, thereby, more sustainable grassland ecosystems. This holds especially for those systems that are currently not sustainable because they are either underutilised and of low productivity or over-exploited and unregulated, and as long as the adapted systems meet societal and ecological constraints.

Effect of Soil Slope on the Appearance of Mycobacterium avium subsp. paratuberculosis in Water Running off Grassland Soil after Application of Contaminated Slurry

ABSTRACT The study assessed the effect of soil slope on Mycobacterium avium subsp. paratuberculosis transport into rainwater runoff from agricultural soil after application of M. avium subsp. paratuberculosis-contaminated slurry. Under field conditions, 24 plots of undisturbed loamy soil 1 by 2 m2 were placed on platforms. Twelve plots were used for water runoff: 6 plots at a 3% slope and 6 plots at a 15% slope. Half of the plots of each slope were treated with M. avium subsp. paratuberculosis-contaminated slurry, and half were not treated. Using the same experimental design, 12 plots were established for soil sampling on a monthly basis using the same spiked slurry application and soil slopes. Runoff following natural rainfall was collected and analyzed for M. avium subsp. paratuberculosis, coliforms, and turbidity. M. avium subsp. paratuberculosis was detected in runoff from all plots treated with contaminated slurry and one control plot. A higher slope (15%) increased the likelihood of M. avium subsp. paratuberculosis detection but did not affect the likelihood of finding coliforms. Daily rainfall increased the likelihood that runoff would have coliforms and the coliform concentration, but it decreased the M. avium subsp. paratuberculosis concentration in the runoff. When there was no runoff, rain was associated with increased M. avium subsp. paratuberculosis concentrations. Coliform counts in runoff were related to runoff turbidity. M. avium subsp. paratuberculosis presence/absence, however, was related to turbidity. Study duration decreased bacterial detection and concentration. These findings demonstrate the high likelihood that M. avium subsp. paratuberculosis in slurry spread on pastures will contaminate water runoff, particularly during seasons with high rainfall. M. avium subsp. paratuberculosis contamination of water has potential consequences for both animal and human health.

Effect of Nitrogen Inhibitors on Nitrous Oxide Emissions and Pasture Growth After an Autumn Application in Volcanic Soil

Una gama de tecnologias estan disponibles para reducir las emisiones de gases de efecto invernadero desde sistemas agricolas. Entre estas, la aplicacion de inhibidores de transformacion del N es considerada prometedora para reducir emisiones de oxido nitroso (N2O) en suelos de cultivo y praderas. Un diseno de bloques completos al azar con seis repeticiones se utilizo para cuantificar el efecto de inhibidores de ureasa (UI) y nitrificacion (NI) sobre emisiones de N2O y produccion de pradera permanente sobre un Andisol despues de la aplicacion otonal de urea. Las emisiones de N2O se midieron periodicamente durante 8 semanas en camara estacionaria de PVC. Se analizaron N mineral, rendimiento de MS, concentracion de N, y absorcion de N. Los resultados muestran que la aplicacion de fertilizante (40 kg N ha-1) aumento significativamente las emisiones de N2O en 281% sobre el tratamiento control (P < 0,05) y genero 10-29% de reduccion de emisiones. Ambos inhibidores redujeron la produccion de N-nitrato en el Andisol serie Osorno por detener la hidrolisis de urea o el proceso de nitrificacion. Se midieron aumentos en produccion (8-13%), concentracion N (7-9%) y absorcion N (46-56%) con la adicion de inhibidores del N con urea sobre el tratamiento control. Los factores de emision medidos bajo condiciones de campo en Chile por la aplicacion otonal de urea e inhibidores del N (aplicados solos o combinados) fueron muy bajos (0,052-0,114%) en comparacion con los valores reportados en literatura y valores por defecto del Panel Intergubernamental para el Cambio Climatico (IPCC) (1%). El uso de estas tecnologias puede contribuir al objetivo establecido a nivel nacional de reducir las emisiones de gases de efecto invernadero en un 20% para el ano 2020.

NITROGEN RUNOFF AND LEACHING LOSSES IN BEEF PRODUCTION SYSTEMS UNDER TWO DIFFERENT STOCKING RATES IN SOUTHERN CHILE

En la Region de los Lagos de Chile se produce el 60% de la leche y el 45% de la carne del pais, esperandose un aumento de la produccion en un futuro cercano. Existe escasa informacion local sobre los impactos ambientales de esta creciente produccion agropecuaria. Un experimento de campo fue llevado a cabo durante el 2004 para medir las perdidas de nitrogeno (N) por lixiviacion y arrastre superficial en sistemas de produccion de carne de la zona basados en el pastoreo. Para el pastoreo se utilizo terneros Holstein-Friesian de 220 kg de peso vivo inicial, organizados en dos tratamientos con cargas de 3,5 y 5 terneros ha-1. Las muestras de agua fueron colectadas durante 6,5 meses con lisimetros superficiales y capsulas ceramicas, y analizadas para nitrato y amonio. Las perdidas totales de N fueron calculadas como el producto de la concentracion de N en las muestras y la cantidad de drenaje disponible, para cada fecha de muestreo. Se observo diferencias significativas en las perdidas totales de N entre los dos tratamientos (11,1 y 29,9 kg N ha-1, respectivamente; P=0.05). La principal via de perdida de N fue la lixiviacion, la cual contribuyo con un 99% del total de N perdido (P=0.05). El nitrato fue la principal forma para la perdida de N por arrastre (71%) y lixiviacion (99%). La concentracion promedio de nitrato en los lixiviados estuvo siempre bajo el limite de la Directiva de la Union Europea. Sin embargo, la concentracion de nitrato en muestras de arrastre tuvo un maximo de 116 ± 13.8 y 82 ± 22.4 mg L-1 para los tratamientos de 3.5 y 5 terneros ha-, respectivamente. Bajo las condiciones experimentales estudiadas, las perdidas de N desde sistemas de produccion de carne fueron bajas. Esto fue relacionado con la baja cantidad de N aplicado como fertilizantes, y las propiedades fisicas y quimicas de suelos volcanicos

INVENTORY OF AMMONIA EMISSIONS FROM LIVESTOCK PRODUCTION IN LOS LAGOS AND LOS RÍOS REGIONS, CHILE

This paper presents the first inventory of ammonia emissions from livestock production in Los Lagos and Los Rios Regions of Chile. The inventory was focused in this area because is where cattle production is concentrated. This study aimed to quantify the amount of N losses due to ammonia volatilization from livestock production in these regions of the country, and to provide its spatial representation identifying their main sources. Calculations have been carried out for 1997 and 2007, and also projections to 2017 and 2027 were obtained. Calculated emissions were 6097 and 6206 t NH3-N for 1997 and 2007, respectively. Major sources of NH3-N emissions were cattle accounting for more than 85%, followed by horses and pigs. Farm management practices as grazing, housing, manure storage and land spreading of manure accounted for 87%, 9%, 3%, and 2%, respectively, of total annual emissions. Projections suggest that emissions could increase up to 6344 and 6516 t NH3-N for 2017 and 2027, respectively. Emissions are much lower than those reported for developed European countries. However, intensification of cattle production systems may lead to an increase of ammonia emissions which could impact the temperate forest of Southern Chile characterized by low nutrient fluxes.