Abstract: Increasing diffuse nitrate loading of surface waters and groundwater has emerged as a major problem in many agricultural areas of the world, resulting in contamination of drinking water resources in aquifers as well as eutrophication of freshwaters and coastal marine ecosystems. Although empirical correlations between application rates of N fertilizers to agricultural soils and nitrate contamination of adjacent hydrological systems have been demonstrated, the transit times of fertilizer N in the pedosphere–hydrosphere system are poorly understood. We investigated the fate of isotopically labeled nitrogen fertilizers in a three–decade-long in situ tracer experiment that quantified not only fertilizer N uptake by plants and retention in soils, but also determined to which extent and over which time periods fertilizer N stored in soil organic matter is rereleased for either uptake in crops or export into the hydrosphere. We found that 61–65% of the applied fertilizers N were taken up by plants, whereas 12–15% of the labeled fertilizer N were still residing in the soil organic matter more than a quarter century after tracer application. Between 8–12% of the applied fertilizer had leaked toward the hydrosphere during the 30-y observation period. We predict that additional exports of 15N-labeled nitrate from the tracer application in 1982 toward the hydrosphere will continue for at least another five decades. Therefore, attempts to reduce agricultural nitrate contamination of aquatic systems must consider the long-term legacy of past applications of synthetic fertilizers in agricultural systems and the nitrogen retention capacity of agricultural soils.

Abstract: Horses were first domesticated about 6,000 years ago on the vast Eurasian steppe extending from Mongolia to the Carpathian Mountains. Yet only in the last two decades have scientists begun to explore the specific mental capacities of these animals. Responding to a surge of interest in fields from ethology to comparative psychology and evolutionary biology, Michel-Antoine Leblanc presents an encyclopedic synthesis of scientific knowledge about equine behavior and cognition. The Mind of the Horse provides experts and enthusiasts alike with an up-to-date understanding of how horses perceive, think about, and adapt to their physical and social worlds.
Much of what we know—or think we know—about “the intelligence of the horse” derives from fragmentary reports and anecdotal evidence. Putting this accumulated wisdom to the test, Leblanc introduces readers to rigorous experimental investigations into how horses make sense of their world under varying conditions. He describes the anatomical and neurophysiological characteristics of the horse’s brain, and offers an evolutionary perspective by comparing these features with those of other species. A horseman himself, Leblanc also considers the opinions of renowned riding masters, as well as controversies surrounding the extraordinary powers of the horse’s mind that have stirred in equestrian and scientific circles.
Although scientists understand more today about how horses think than at any time in our species’ long acquaintance with these animals, much remains in the dark. The Mind of the Horse brings together the current state of equine research and will likely stimulate surprising new discoveries.