Carbon dioxide level and form of soil nitrogen regulate assimilation of atmospheric ammonia in young trees.

The influence of carbon dioxide (CO2) and soil fertility on the physiological performance of plants has been extensively studied, but their combined effect is notoriously difficult to predict. Using Coffea arabica as a model tree species, we observed an additive effect on growth, by which aboveground productivity was highest under elevated CO2 and ammonium fertilization, while nitrate fertilization favored greater belowground biomass allocation regardless of CO2 concentration. A pulse of labelled gases ((13)CO2 and (15)NH3) was administered to these trees as a means to determine the legacy effect of CO2 level and soil nitrogen form on foliar gas uptake and translocation. Surprisingly, trees with the largest aboveground biomass assimilated significantly less NH3 than the smaller trees. This was partly explained by declines in stomatal conductance in plants grown under elevated CO2. However, unlike the (13)CO2 pulse, assimilation and transport of the (15)NH3 pulse to shoots and roots varied as a function of interactions between stomatal conductance and direct plant response to the form of soil nitrogen, observed as differences in tissue nitrogen content and biomass allocation. Nitrogen form is therefore an intrinsic component of physiological responses to atmospheric change, including assimilation of gaseous nitrogen as influenced by plant growth history

Nitrogen Use Efficiency of Coffee at the Vegetative Stage as Influenced by Fertilizer Application Method.

Nitrogen (N) is the most limiting nutrient for coffee production in Colombia. An adequate supply is especially important during the vegetative period of growth, since any deficiency during this short period is known to have lasting effects on subsequent coffee bean production. Urea fertilizer is commonly applied on the soil surface since steep slopes hamper incorporation into soil, a practice which increases the risk of N volatilization. Little information is available on N recovery during early growth stages under different fertilizer application practices. The aim of this study was therefore to provide a comparison of 15N uptake during the early vegetative growth stage under surface-applied and incorporation practices at two contrasting locations. The highest proportion of plant N derived from fertilizer (Ndff) occurred 60 days following application at the site with greater precipitation and soil organic matter, where surface application also increased the Ndff in roots and stems after 120 days. Although fertilizer N supplied approximately 20-29% of total plant N after 4 months, this fertilizer-derived N corresponded on average to only 5% of the total application, indicating that very little fertilizer (relative to how much is applied) reaches plants during this time. Apart from the difference in Ndff observed at the wetter site, there was no effect of application method on dry weight and macronutrient content in different plant components, root to shoot ratio, and leaf 13C content. However, site effects were registered for most of these measurements, with the exception of total nutrient uptake. Similarly to Ndff trends, lower root/shoot ratio and higher concentrations of N, K, and Mg in aboveground biomass were found in the site with higher rainfall and soil organic matter, likely resulting from higher soil water and N availability. These findings provide new information useful as a direction for further research looking toward increasing NUE during the vegetative stage in Colombian coffee crops

Respuesta del café a la fertilización con zinc en suelos de la zona cafetera colombiana

Aunque el zinc (Zn) es un microelemento esencial para la nutrición del café por su efecto directo sobre el crecimiento y porque sus deficiencias en las etapas vegetativas son cada vez más comunes, son pocas las investigaciones relacionadas con este nutriente en Colombia. Por ello, con el objetivo de evaluar la respuesta del café variedad Colombia renovado por zoca a la fertilización con zinc (Zn), se realizó una investigación en tres localidades: Venecia, Gigante y Timbío. Los tratamientos consistieron en tres dosis de Zn (5, 10 y 20 kg.ha-1), aplicadas al suelo en forma de óxido (ZnO), y tres dosis de Zn (0,045, 0,09 y 0,18 kg.ha-1), aplicadas vía foliar como quelato, además de un testigo sin aplicación de Zn. Durante el primer año, la aplicación edáfica se realizó a los dos y ocho meses después del zoqueo, y a partir del segundo año, cada seis meses con la recomendación NPK según el análisis de suelo. La aplicación foliar se realizó a los 60 y 90 días después del pico de floración tanto para la cosecha principal como para la mitaca de cada sitio. Se midió la producción anual de café cereza y acumulada durante cuatro años. Para las condiciones del estudio la fertilización edáfica o foliar de Zn no tuvo efectos significativos en la producción de café cereza pero si se registraron aumentos en los niveles de Zn en el suelo y en las hojas

Carbon dioxide level and form of soil nitrogen regulate assimilation of atmospheric ammonia in young trees.

The influence of carbon dioxide (CO2) and soil fertility on the physiological performance of plants has been extensively studied, but their combined effect is notoriously difficult to predict. Using Coffea arabica as a model tree species, we observed an additive effect on growth, by which aboveground productivity was highest under elevated CO2 and ammonium fertilization, while nitrate fertilization favored greater belowground biomass allocation regardless of CO2 concentration. A pulse of labelled gases ((13)CO2 and (15)NH3) was administered to these trees as a means to determine the legacy effect of CO2 level and soil nitrogen form on foliar gas uptake and translocation. Surprisingly, trees with the largest aboveground biomass assimilated significantly less NH3 than the smaller trees. This was partly explained by declines in stomatal conductance in plants grown under elevated CO2. However, unlike the (13)CO2 pulse, assimilation and transport of the (15)NH3 pulse to shoots and roots varied as a function of interactions between stomatal conductance and direct plant response to the form of soil nitrogen, observed as differences in tissue nitrogen content and biomass allocation. Nitrogen form is therefore an intrinsic component of physiological responses to atmospheric change, including assimilation of gaseous nitrogen as influenced by plant growth history