M. Flores

Intensificación agropecuaria evaluada por indicadores de sustentabilidad ambiental

espanolSe compararon 19 establecimientos agropecuarios, (superficie total 3654 hectareas), mediante indicadores de sustentabilidad agro-ambiental, para evaluar como el proceso de adopcion de tecnologias de produccion influye en un agro-ecosistema con incipiente intensificacion en el uso de la tierra, en la zona semiarida central de Argentina. Se identificaron prioridades de capacitacion y extension para productores segun escala de produccion. Originariamente el area correspondia a pastizales y bosques de calden (Prosopis caldenia) con ganaderia vacuna. Se aplicaron como variables: uso de la tierra por cultivos anuales (CA), y como indicadores: consumo de energia fosil (EF) y eficiencia de su utilizacion (EEF), balances de nitrogeno (BN) y fosforo (BP), riesgo de contaminacion por plaguicidas (RPL), riesgo de erosion (RE), cambio de stock carbono en suelo (CSC) y balance de gases efecto invernadero (GEI), evaluandolos segun escala de gravedad. Los predios fueron analizados individualmente y agrupados segun tamano (81 ha). Se observaron diferencias significativas (p2 Mj EF utilizado/Mj EF producto) y valores negativos de BP en el 68% de los predios (hasta -14,4 kg P/ha/ano), relacionandolo a la incorporacion de soja sin restitucion por fertilizantes. Los BN no senalan riesgo de contaminacion (entre -4,7 a 41,7 kg N/ha/ano). El CSC presento valores problematicos en campos chicos, por la utilizacion de labranzas convencionales para cultivos forrajeros. El GEI reflejo las mayores emisiones de metano en los predios grandes, debido al sistema pastoril de alimentacion. Las actividades de capacitacion deberian orientarse segun escala. La utilizacion de indicadores permitio conocer el impacto de practicas agropecuarias a nivel de predio y de zona, segun escala de produccion, mostrando que la actual intensificacion del sector no ha impactado aun gravemente al medio. EnglishThe aim of the study was to evaluate how technology adoption processes influence agro-ecosystems with incipient land use intensification, in a rural semiarid area of San Luis province, Argentina, using environmental sustainability indicators at farm and regional level. For this purpose a comparison of 19 farms (3654 ha) was carried out. Training and extension priorities for producers were identified during this study. The original vegetation corresponded to grassland and Prosopis caldenia forests with beef cattle production. The environmental sustainability indicators were: Land use -% of annual crops (CA)- (a variable); Fossil energy use(EF); fossil energy use efficiency (EEF); nitrogen balance (BN); phosphorus balance(BP); pesticide contamination risk (RPL); soil erosion risk (RE); changes in soil carbon stock (CSC) and greenhouse gases balance (GEI), evaluated according to severity scale. Farms were analyzed individually and grouped by size (81 ha). Statistically significant differences (p2 Mj EF used/Mj EF product), and negative values of BP in the 68% of the farms (up to -14.4 kgP/ha/year). Both can be related to soybean introduction without extensive fertilizers use. Nitrogen balance do not indicate contamination risk (between -4.7 and 41.7 kg N/ha/year). Conventional tillage in forages is the cause of high CSC values in small farms. The methane emissions in big farms, were reflected by the higher values of GEI indicator because of their grazing systems. Training activities should be farm scale oriented . The use of these indicators has made it possible to understand the impact of agricultural practices at farm and at regional level in relation to production scale. These indicators show that todays Villa Mercedes farm area intensification has not had a serious impact on their environment yet.

Influence of Water Temperature and Heat Stress on Drinking Water Intake in Dairy Cows

Grazing animals are exposed to heat stress and there should be conditions to facilitate water intake. Three experiments were carried out to determine the relationship between water intake, water temperature, and heat stress for Holstein pastured dairy cows. Experiment 1: Drinking behavior of 13 cows was evaluated (for 3 consecutive days) and four time periods were established according to the temperature humidity index (THI): (H1:05:00 to 10:59 h, H2:11:00 to 16:59 h, H3:17:00 to 22:59 h, and H4:23:00 to 04:59 h). The highest mean percentage of drinking bouts (53.2%) was registered in H2 (THI: 74.91 to 83.95). Drinking bout means among time periods were different (p 0.05). Recorded water intake in T1 (18 L) was lower than in T2 (35.9 L), although body heat dissipation was higher (T1 = 672.64 kJ d -1 , T2 = 620.76 kJ d -1 ).