A synthesis of nitrogen transformations and transfers from land to the sea in the Yaqui Valley agricultural region of northwest Mexico

Abstract

1] Intensification of agricultural systems represents one of the most significant land use changes of the last century. High fertilizer inputs have been a key component of intensification and have contributed to increases in crop yield in most areas, but they can also cause profound alterations in the biogeochemical functioning of the soil, water, and air resources of these systems, particularly with regard to the nutrient nitrogen (N). Comprehensive studies linking field-scale fertilization with regional N fates and consequences for water resources are surprisingly sparse, particularly in the rapidly developing tropics and subtropics. Here we synthesize 15 years of research in wheat fields, drainage canals, estuaries, and coastal waters of the Yaqui Valley region of Sonora, Mexico. Although a relatively low proportion (<4%) of total N inputs are exported via surface water to the coast, the episodic nature of these losses can have significant ecological consequences. For instance, gaseous and dissolved N fluxes from agricultural fields are among the highest observed, and N-rich runoff from the Yaqui Valley fuels phytoplankton blooms in coastal waters. Reductions in N losses with improved timing of fertilizer application relative to crop demand are possible without negatively affecting crop yield or quality and may help to move this and similar regions closer to sustainability.

Calidad De Sedimentos Asociada a Actividades Antrópicas en Lagunas Costeras Semiáridas Subtropicales De La Costa Central Este Del Golfo De California

“…En la parte norte tenemos la laguna Lobos, principal cuerpo receptor de un drenaje colector (L8), mientras que en la parte sur está la laguna Tóbari, que recibe vertimientos de aguas residuales agrícolas (T5-T9), camaronícolas (T12-T16) y de asentamientos humanos (T6 y T8) (Ahrens et al 2008).…”

“…Alrededor del 40 % de la superficie de la Tierra ha sido convertida en tierras de cultivo o pastizales (Foley et al 2005). Desde 1950 la intensificación de los sistemas agrícolas ha impactado a los ecosistemas costeros tropicales y subtropicales, especialmente a causa de sus drenajes (Ahrens et al 2008). En 1985 en Europa y América del Norte esta actividad económica ya afectaba al 56 -65 % de los humedales (OECD/IUCN 1996).…”

“…En esta zona, la actividad agrícola que se desarrolla en el Valle del Yaqui es la más importante (Beman et al 2005, Ahrens et al 2008. Su práctica inició de manera intensiva durante los años de 1960 y 1970, durante la "Revolución Verde" (Cleaver 1972).…”

Coastal Lagoons and Estuaries in Mexico: Processes and Vulnerability

“…The identification of the conceptual relationships among vulnerability, resilience, and adaptive capacity in the management of Mexican coastal ecosystems is currently lacking (Bezaury-Creel 2005;Seingier et al 2011), particularly in the context of global climate change including increases in temperature and sea level (McGranahan et al 2007). This gap in the availability of data, information, and models is not surprising given the absence of comparative regional studies (Rivera-Monroy et al 2008;Vidal and Filograsso 2008), for example, on the influence of TCs in controlling water resource availability and their effect on nutrient and carbon cycling in the coastal zone (Ahrens et al 2008;Seingier et al 2011) or the economic impact of eutrophication on the sustainability of ecosystems services provided by coastal wetlands (e.g., Contreras-Espinosa and Warner 2004;Camacho-Valdez et al 2013) such as commercial fisheries (Yanez-Arancibia and Day 2004a;Aburto-Oropeza et al 2008;Martínez Arroyo et al 2011;Aguilar Ibarra et al 2013). We foresee the contribution of the six papers included in this special section as a step in both closing the knowledge gap and the development of an integrated research agenda for the implementation of long-term socio-ecological studies (Burgos et al 2007;Jardel et al 2013) in estuaries and tropical lagoons, not only in Mexico, but also in other tropical latitudes.…”

“…Major human activities altering coastal hydrological patterns in Mexico include road construction, urban development, coastal tourism, and oil and gas exploration (Ruiz-Luna and BerlangaRobles 2003;Murray 2007;Vidal and Filograsso 2008). These alterations may lead to increased water residence times that exacerbate eutrophic conditions in coastal waters already affected by agricultural activities (i.e., fertilizers) and untreated sewage loads (e.g., Paez-Osuna et al 1998;Ahrens et al 2008).…”