Optimizing alfalfa productivity and persistence versus greenhouse gases fluxes in a continental arid region

Abstract

Alfalfa in China is mostly planted in the semi-arid or arid Northwest inland regions due to its ability to take up water from deep in the soil and to fix atmospheric N2 which reduces N fertilizer application. However, perennial alfalfa may deplete soil water due to uptake and thus aggravate soil desiccation. The objectives of this study were (1) to determine the alfalfa forage yield, soil property (soil temperature (ST), soil water content (SWC), soil organic carbon (SOC) and soil total nitrogen (STN)) and greenhouse gas (GHG: methane (CH4), nitrous oxide (N2O), and carbon dioxide (CO2)) emissions affected by alfalfa stand age and growing season, (2) to investigate the effects of soil property on GHG emissions, and (3) to optimize the alfalfa stand age by integrating the two standard criteria, the forage yield and water use efficiency, and the total GHG efflux (CO2-eq). This study was performed in alfalfa fields of different ages (2, 3, 5 and 7 year old) during the growing season (from April to October) in a typical salinized meadow with temperate continental arid climate in the Northwest inland regions, China. Despite its higher total GHG efflux (CO2-eq), the greater forage yield and water use efficiency with lower GEIhay and high CH4 uptake in the 5-year alfalfa stand suggested an optimal alfalfa stand age of 5 years. Results show that ST, SOC and RBM alone had positive effects (except RBM had no significant effect on CH4 effluxes), but SWC and STN alone had negative effects on GHG fluxes. Furthermore, results demonstrate that in arid regions SWC superseded ST, SOC, STN and RBM as a key factor regulating GHG fluxes, and soil water stress may have led to a net uptake of CH4 by soils and a reduction of N2O and CO2 effluxes from alfalfa fields. Our study has provided insights into the determination of alfalfa stand age and the understanding of mechanisms regulating GHG fluxes in alfalfa fields in the continental arid regions. This knowledge is essential to decide the alfalfa retention time by considering the hay yield, water use efficiency as well as GHG emission.

Carbon-sink potential of continuous alfalfa agriculture lowered by short-term nitrous oxide emission events

“…The net CH 4 sink was significantly greater in site year 4 than all other years (Table 1, p < 0.001). Sinks measured here were larger than others alfalfa ecosystem estimates 10,31,56 , likely from the lower detection limit of the CRDS and automated chambers. In contrast to expectations, decreases in bulk soil O 2 concentrations did not appear to drive significant increases in net CH 4 production or decreases in the CH 4 sink (Fig.…”

Freezing and thawing cycles affect nitrous oxide emissions in rain-fed lucerne (Medicago sativa) grasslands of different ages

“…Lucerne (Medicago sativa) is an important crop in dryland farming systems of the Loess Plateau, China, and has been shown to produce high N 2 O emissions (Bremner, 1997;IPCC, 2013;Ning et al, 2020). The Loess Plateau occupies more than 70% of the farmland in north-western China and is characterized by near-surface soil freeze/thaw cycles in early spring and late autumn (Han, Tsunekawa & Tsubo, 2010).…”

Propuesta híbrida para la captación y medición de CO2 edáfico empleando cámaras de incubación estáticas y secuestramiento de gases

“…Otros autores proponen mediciones en laboratorio, basados en el mismo principio químico de secuestro de gases empleando respirómetros e incubaciones en condiciones controladas, donde se determina la absorción del CO 2 en una solución de hidróxido de potasio (KOH), a través de ecuaciones estequiométricas [18,19]. Sin embargo, como se mencionó antes, la metodología mayormente usada a nivel mundial para la captación de GEI edáficos es la cámara de incubación [20,21] y se combina con diferentes equipos o procedimientos para su posterior medición o cuantificación.…”