Bioavailability of Macro and Micronutrients Across Global Topsoils: Main Drivers and Global Change Impacts

Understanding the chemical composition of our planet\u27s crust was one of the biggest questions of the 20th century. More than 100 years later, we are still far from understanding the global patterns in the bioavailability and spatial coupling of elements in topsoils worldwide, despite their importance for the productivity and functioning of terrestrial ecosystems. Here, we measured the bioavailability and coupling of thirteen macro- and micronutrients and phytotoxic elements in topsoils (3–8 cm) from a range of terrestrial ecosystems across all continents (∼10,000 observations) and in response to global change manipulations (∼5,000 observations). For this, we incubated between 1 and 4 pairs of anionic and cationic exchange membranes per site for a mean period of 53 days. The most bioavailable elements (Ca, Mg, and K) were also amongst the most abundant in the crust. Patterns of bioavailability were biome-dependent and controlled by soil properties such as pH, organic matter content and texture, plant cover, and climate. However, global change simulations resulted in important alterations in the bioavailability of elements. Elements were highly coupled, and coupling was predictable by the atomic properties of elements, particularly mass, mass to charge ratio, and second ionization energy. Deviations from the predictable coupling-atomic mass relationship were attributed to global change and agriculture. Our work illustrates the tight links between the bioavailability and coupling of topsoil elements and environmental context, human activities, and atomic properties of elements, thus deeply enhancing our integrated understanding of the biogeochemical connections that underlie the productivity and functioning of terrestrial ecosystems in a changing world

Condensed Tannin in Drinking Water Reduces Greenhouse Gas Precursor Urea in Sheep and Cattle Urine

Ingestion of small amounts of condensed tannin (CT) by ruminants may provide benefits including reduction of ammonia and nitrous oxide emissions by reducing urine urea excretion. However, providing grazing ruminants with sufficient amounts of CT- containing forages is difficult, and an alternative may be to provide CT in their drinking water. We conducted three trials to determine if urine urea levels in sheep and cattle decrease after they drink water containing CT. In two initial trials, blood serum urea was measured as a surrogate for urine urea when lambs or steers drank tap water containing low to higher amounts of quebracho tannin (QT). Serum urea concentration was measured after lambs drank the treatments for 7 d or steers for 4-6 d. Lambs consumed pellets (16% crude protein [CP] as fed) at 3.5% of body weight, and steers were fed cubes (15% CP as fed) at 3% of body weight. Mean serum urea concentration in sheep was reduced when they consumed water with QT (P = 0.03) and was also reduced for cattle (P < 0.001). In a third trial with a Latin-square design, four wethers were fed pellets (22% CP, DM basis) and given tap water or tap water with low, medium, or high amounts of QT, and their urine urea excretion was measured. There was a linear effect of QT intake on daily urine urea excretion as a percentage of nitrogen intake (P = 0.03). Reductions in daily urea excretion as a percentage of nitrogen intake were 3.5%, 6.6%, and 12.6%, respectively, for the low, medium, and high QT intake. Small amounts of QT in the drinking water of grazing ruminants can reduce their urine urea excretion./La ingestión de pequen ̃as cantidades de taninos concentrados (TC) por los rumiantes podría traer beneficios incluyendo, la reducción de emisiones de amonia y oxido nitroso al reducir la excreción de urea por la orina. Sin embargo, proveer a los rumiantes en pastoreo con suficiente cantidad de TC en el forraje es difícil y una alternativa podría ser agregar el TC en los abrevaderos. Realizamos tres pruebas para determinar sí el nivel de urea en la orina en ovinos y bovinos disminuía después que estos animales bebieran agua con TC. En dos pruebas iniciales, se medio suero sanguino con urea como sustituto de orina de corderos y novillos que bebieron agua conteniendo baja y alta cantidad de tanino de quebracho (TQ). Se midió el suero de urea concentrado después de que los corderos bebieron del tratamiento por 7 días y los novillos de 4 a 6 días. Los corderos consumieron el 3.5% de su peso vivo de suplemento en forma de pellets (16% de PC) y los novillos suplemento en forma de cubos (15% de PC) en cantidad correspondiente al 3% de su peso vivo. La media de la concentración de suero de urea en borregas se redujo cuando consumieron agua con TQ (P = 0.03), y también se redujo en bovinos (P < 0.001). En una tercera prueba con diseño de Cuadro Latino, cuatro corderos se alimentaron con pellets (22% PC, en base a materia seca) y tuvieron acceso a agua sin TQ o agua con cantidades bajo, media y alto de TQ y se medio las excreciones de urea en la orina. Hubo un efecto linear en el consumo de TQ y las excreciones diarias de urea en la orina como un porcentaje del consumo de nitrógeno (P=0.03). La reducción de excreciones diarias de urea en la orina como porcentaje de consume de nitrógeno fueron 3.5%, 6.6%, y 12.6% respectivamente para el bajo, medio y alto consumo de TQ. Cantidades pequeñas de TQ en el agua de beber para ovinos en pastoreo puede reducir la excreción de urea en la orina.The Rangeland Ecology & Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform August 202