Efficacy of multivariate analysis and zone soil sampling to study relationships between site variables affecting crop yield and yield response to phosphorus and potassium fertilization

Crop yield and yield response to fertilization is frequently heterogeneous within-fields. A better understanding of this variability and the development of cost-effective soil sampling techniques to better represent plant nutrient levels are needed to improve nutrient management practices. Two studies were conducted in Iowa to address this general objective.;One study focused on correlations between several site variables and their relationship with soybean [Glycine max (L.) Merr.] yield using two multivariate techniques. Soil and crop variables were measured at five fields using a dense, 0.2-ha grid-point sampling approach. Factor analysis grouped correlated variables into three common factors across fields, which represented conditions for early crop growth, interactions between intrinsic soil properties and landscape position, and P and K availability. These factors explained 10--65% of the yield variability across fields. Principal component analysis explained a similar portion of the yield variability, but relationships between site variables were more difficult to interpret.;In the second study, soil-test P and K results from samples collected using a dense grid sampling approach (0.08--0.24-ha) before applying P or K treatments to long strips in seven fields was used to assess the effectiveness of various zone sampling approaches. Zones were delineated using a systematic, 1.0 grid-cell approach, soil survey maps, remotely sensed soil electrical conductivity, elevation, and slope. The efficacy of the zoning approaches was assessed based on soil-test values and corn (Zea mays L.) and soybean yield response to fertilization. We used yield monitors, global positioning systems, and geographical information systems software. Zones based on elevation and (or) electrical conductivity identified field areas with high and low yield. However, soil-test values and crop response to fertilization seldom differed across zones, except for the grid-sampling approaches. A systematic 1.0-ha grid-cell approach was more effective for identifying field areas with different crop response to fertilization, but the numerous samples required may result in excessive soil testing costs. Because long-term nutrient removal with harvest also is a key element for P and K fertilizer management, less costly zoning approaches used in conjunction with yield maps could be useful for improving long-term nutrient management

Scouting Benefits and Developing Innovations in Temperate Grassland to Sustainable Agriculture Production

Agricultural intensification raises concern about land use and future effects to natural resources. The world demand for grain, meat and forest products is increasing constantly. Changes are occurring at large scale, being a compromise for policy makers to contribute to identify opportunities to readdress the productive scenario. There is available technology to reduce impacts, without restricting necessarily productivity. Grasslands provide a large series of economical and ecological benefits to the agricultural systems, being the literature exhaustive in examples. Ley-farming and cover crops technologies are good examples of environmentally sound soil management practices. The society is also worried about an improper use of the natural resources involved. The drastic increase in the grain crops area leaded by soybean in Uruguay, determined that the government implemented Sustainable Soil Use and Management Plans, based on erosion estimation using the USLE-RUSLE model adapted locally by research conducted over more than 50 years on a series of long term experimental platforms. There is an opportunity for this type of local innovative initiatives to be widely diffused, adopted or adapted. In essence, grasslands will continue playing a key role in maintaining a sustainable production

Efficacy of multivariate analysis and zone soil sampling to study relationships between site variables affecting crop yield and yield response to phosphorus and potassium fertilization

Crop yield and yield response to fertilization is frequently heterogeneous within-fields. A better understanding of this variability and the development of cost-effective soil sampling techniques to better represent plant nutrient levels are needed to improve nutrient management practices. Two studies were conducted in Iowa to address this general objective.;One study focused on correlations between several site variables and their relationship with soybean [Glycine max (L.) Merr.] yield using two multivariate techniques. Soil and crop variables were measured at five fields using a dense, 0.2-ha grid-point sampling approach. Factor analysis grouped correlated variables into three common factors across fields, which represented conditions for early crop growth, interactions between intrinsic soil properties and landscape position, and P and K availability. These factors explained 10--65% of the yield variability across fields. Principal component analysis explained a similar portion of the yield variability, but relationships between site variables were more difficult to interpret.;In the second study, soil-test P and K results from samples collected using a dense grid sampling approach (0.08--0.24-ha) before applying P or K treatments to long strips in seven fields was used to assess the effectiveness of various zone sampling approaches. Zones were delineated using a systematic, 1.0 grid-cell approach, soil survey maps, remotely sensed soil electrical conductivity, elevation, and slope. The efficacy of the zoning approaches was assessed based on soil-test values and corn (Zea mays L.) and soybean yield response to fertilization. We used yield monitors, global positioning systems, and geographical information systems software. Zones based on elevation and (or) electrical conductivity identified field areas with high and low yield. However, soil-test values and crop response to fertilization seldom differed across zones, except for the grid-sampling approaches. A systematic 1.0-ha grid-cell approach was more effective for identifying field areas with different crop response to fertilization, but the numerous samples required may result in excessive soil testing costs. Because long-term nutrient removal with harvest also is a key element for P and K fertilizer management, less costly zoning approaches used in conjunction with yield maps could be useful for improving long-term nutrient management.</p

Vulnerabilidad al cambio climático en los sistemas de producción agrícola en América Latina y el Caribe: "Desarrollo de respuestas y estrategias"

El objetivo de la propuesta fue formular un plan de acción con recomendaciones para el desarrollo de respuestas y estrategias con el fi n de contribuir a una mejor adaptación a los impactos del clima y el cambio climático en los sistemas de producción agrícola de Urugua

Ajuste del modelo de erosión WEPP para un Argisol Subéutrico y un Brunosol Éutrico en el Uruguay. [WEPP soil erosion model adjustment for an abruptic argiudoll and a vertic argiudoll in Uruguay].

RESUMEN:Los modelos de estimación de erosión son herramientas útiles para la planificación de sistemas productivos sustentables. El modelo Water Erosion Prediction Project (WEPP) estima erosión laminar y en canalículos, así como la carga y deposición del sedimento, con distribución temporal y espacial. Esto permite estimar no sólo los efectos in situ sino también los efectos fuera del sitio, como ser deposición en cauces de agua, pudiéndose aplicar en estudios ambientales. Si bien este modelo está basado en los procesos físicos que ocurren en el suelo, es preciso realizar ajustes sitio-específicos. El objetivo de este estudio fue ajustar el modelo WEPP, para suelos representativos de la zona agrícola litoral oeste y lomadas del este del Uruguay. Se utilizaron datos de parcelas experimentales de escurrimiento de INIA La Estanzuela y Palo a Pique, y se compararon los valores de erosión estimados por WEPP y USLE/RUSLE con los medidos en términos de promedios anuales. Además se contrastó la erosión estimada con WEPP con la medida a escala anual. WEPP estimó la erosión de ambos sitios con alto nivel de precisión, comparable al de USLE (R2=0,97 y 0,98 respectivamente). El índice Nash-Sutcliffe de 0,92 indica que su desempeño es muy bueno. Para continuar esta línea de investigación resulta necesario realizar medidas de variables físicas del suelo o desarrollar ecuaciones de pedotransferencia alternativas..-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.SUMMARY.Erosion estimation models are helpful tools for planning sustainable agriculture systems. The model Water Erosion Prediction Project (WEPP) estimates rill and interrill erosion, as well as sediment load and deposition, including temporal and spatial distribution. This enables the estimation of both in-site and off-site effects such as deposition in water bodies, making it useful for environmental studies. Although this model is based on the physical processes that occur in the soil, site-specific adjustments are needed. The aim of this study was to adjust the WEPP model for the representative Uruguayan agriculture soils of the West coast and East rolling plains. We used the data base of the runoff plots from INIA La Estanzuela y Palo a Pique, and we compared erosion values estimated with WEPP and those estimated with USLE/RUSLE, in terms of annual means. In addition, erosion estimated with WEPP was compared with the data measured at an annual scale. WEPP estimated erosion with high precision in both sites, comparable to USLE (R2 =0.97 y 0.98 respectively). A Nash-Sutcliffe value of 0.92 indicates a very good performance. To continue this research line, measures of local soil physical variables or the development ofalternative pedotransfer equations will be needed

Nicarbazin as an oral contraceptive in eared doves

Eared doves (Zenaida auriculata) are responsible for substantial losses in cereal and oil crops as well as in dairy and feedlot production in the southern cone of South America. Various strategies have been shown to be effective in reducing damage at the farm scale, but in some scenarios, it is necessary to also incorporate population control methods due to excessive bird population size. An alternative approach to reduce pest bird populations is the use of contraceptive methods, minimizing the impact on the environment and non-target populations. Nicarbazin is registered in the United States as a contraceptive for Branta canadensis and Columba livia. The aim of this study was to measure the effect of nicarbazin on the reproductive performance of eared doves in captivity. This study included eleven caged pairs of nesting eared doves in three experimental phases (pre-treatment, treatment, recovery). Each pair was exposed to nicarbazin bait for 4 h per day. The contraceptive used was OvoControlP® (0.5% nicarbazin) ground with a millstone into particles of 0.5–3.0 mm. Daily bait consumption and reproductive variables per pair (egg laying and 14-day-old fledgling) were recorded, and levels of 4,4′dinitrocarbanilide were measured in feces and unhatched eggs. Median consumption was 4.2 g of bait/pair/day. We observed a 62% reduction in the number of viable eggs and successful nestlings in the treatment phasein contrast to pre-treatment (V = 36; p = 0.006). There were no significant differences (V = 0; p = 1) in the number of viable eggs between the pretreatment and recovery phases. Median daily bait consumption by pairs producing zero or one nestling (4.4 and 5.0 g/pair/day respectively) was significantly higher than that of pairs that had two nestlings (3.4 g/pair) during the treatment phase (t = 2.0; p = 0.002). Nicarbazin was effective in reducing reproductive performance of eared doves, and its effect was reversible when the treatment finished

Variable root:shoot ratios and plant nitrogen concentrations discourage using just aboveground biomass to select legume service crops

Aims: Comparing different winter legume species by plant traits that determine their contributions to ecosystems as service crops. Since root biomass determines soil organic matter formation and biological nitrogen fixation (BNF) increases soil organic nitrogen stock, those plant traits are more suitable than shoot biomass to select service crops. Methods: We evaluated shoot and root biomass and BNF (using 15N natural abundance method) of 10 winter legume service crop species under field conditions, in two consecutive years. Results: The legumes significantly varied in shoot (3.4 to 9.1 Mg ha−1 year−1) and root biomass (0.8 to 1.3 Mg ha−1 year−1) and in the proportion and the amount of biologically fixed nitrogen (36–61% and 43–121 kg of N ha−1, respectively). Whereas shoot biomass varied between years, root and BNF were rather constant determining a low correlation between the variables. Among the evaluated species, Trifolium pratense and T. alexandrinum were the top-ranked species for the evaluated conditions, showing the largest amount of root biomass (~ 1.3 Mg ha−1 year−1) and BNF (~ 112 kg of N ha−1 year−1). Conclusions: Selecting service crops species aimed to increase soil organic matter based only on shoot biomass may be insufficient. As a consequence, we highlight the importance of performing breeding programs aimed to increase, in addition to crop yield or shoot biomass production, other plant traits such as root biomass or biological nitrogen fixation that provide key regulating and supporting ecosystem services.Fil: Pinto, Priscila. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; ArgentinaFil: Rubio, Gerardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones en Biociencias Agrícolas y Ambientales. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones en Biociencias Agrícolas y Ambientales; ArgentinaFil: Gutiérrez, Félix. Instituto Nacional de Investigacion Agropecuaria;Fil: Sawchik, Jorge. Instituto Nacional de Investigacion Agropecuaria;Fil: Arana, Santiago. No especifíca;Fil: Piñeiro, Gervasio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina. Universidad de la República; Urugua

Guía de buenas prácticas agrícolas para sistemas con agricultura de secano en Uruguay

La presente guía tiene como objetivo identificar y promover los conocimientos disponibles para una producción agrícola segura y sustentable, para fomentar el bienestar social y la mejora continua de las condiciones de trabajo en el sector. La aplicación de bpa se fundamenta en la identificación de peligros y la determinación de las prácticas más apropiadas para la prevención y control de estos. Esta guía será utilizada como una herramienta para orientar a los actores del sector (productores, técnicos y trabajadores en general), sobre las prácticas que se deben llevar adelante para una producción agrícola responsable, más allá de las normas legales establecidas, de manera de garantizar la mayor productividad y fomentar la confianza de los mercados extranjeros en la inocuidad de los productos uruguayos

Expansión agrícola 2000-2010 en Argentina, Bolivia, Paraguay, Uruguay y Chile: Caracterización espacial mediante series temporales de índices de vegetación

 In South America major landscape transformations occurred in the last decades as a consequence of technological improvements and new international market and prices conditions. Grasslands, shrublands and forests were cleared mainly for soybean production for export. Based on remote sensing and GIS techniques, we analyzed MODIS products time series, to detect the major cropping systems in 5 countries of South America. We mapped annual crop areas for the 2000/01 and 2010/growing seasons, we evaluated in a spatially explicit way the changes between these periods, and we developed hypotheses in order to understand the changes. There was a 43% increase in the cropped area between growing seasons, with a heterogeneous spatial distribution. The most notable changes at the regional level were a 66% decreased in the area cover by winter crops as unique practice, and increases of 62% for summer crops and 52% in the double cropped area. The methodology used was adequate to carry out analyzes that combine a large expanse of territory and time.En Sudamérica ocurrieron, en las últimas décadas grandes transformaciones del paisaje. Como consecuencias de mejoras tecnológicas, de nuevas condiciones en el mercado y precios internacionales, tanto pastizales como bosques o arbustales fueron transformados, principalmente para la producción de soja con fines de exportación. A partir de teledetección y Sistemas de Información Geográfica se analizaron series temporales de productos del sensor MODIS, y se detectaron los principales sistemas de cultivos de 5 países de Sudamérica. Se cartografíaron las áreas de cultivos anuales para los ciclos productivos 2000/01 y 2010/11; se evaluó de manera espacialmente explícita los cambios ocurridos entre los mencionados ciclos; y se elaboraron hipótesis a fin de entender dichos procesos de cambios. Se observó un incremento del 43% de la superficie cultivada entre ciclos, con una distribución espacial heterogénea. Los cambios más destacables a nivel regional fueron la disminución del 66% cultivos de invierno como práctica única, y los incrementos del 62% de los cultivos de verano y del 52% en la superficie de doble cultivos. La metodología planteada fue adecuada para llevar a cabo análisis que combinan una gran extensión de territorio y tiempo