Identifying grass-legume bicultures to increase above and belowground biomass production and improve traditional fallows in crop rotations of the Andean Highlands

2021 Spring.Includes bibliographical references.In the high Andes of Peru, intensification of crop rotation and agricultural land-use is reducing the practice and duration of traditional fallow (based on natural establishment of native vegetation). These fallows represent one of the main traditional soil management practices to sustain long-term productivity, while also providing key forage resources in these mixed crop-livestock systems. Improved forage-based fallows, with the intentional seeding of more productive annual and perennial forages, offer great potential for producing forage and contributing to soil restoration under intensified contexts; however, there remains a gap in knowledge about which plant species can best optimize tradeoffs between forage production and belowground inputs to support long-term soil fertility and contribute to the multifunctionality of Andean agroecosystems. To address this issue, a pot study was conducted with two contrasting soils to evaluate the above and belowground productivity of all possible grass-legume pairs involving five grasses (oat (Avena sativa), ryegrass (Lolium multiflorum), festulolium (Lolium x Festuca genera), brome grass (Bromus catharticus), and orchardgrass (Dactylis glomerata), and four legumes (vetch (Vicia dasycarpa ), red clover (Trifolium pratense), black medic (Medicago lupulina), and alfalfa (Medicago sativa)) in comparison to the performance of each species in monoculture. Grass-legume bicultures resulted in significant overyielding, producing 65% and 28% more total dry biomass and total N uptake on average than species in monoculture, respectively. Grass-legume shoot biomass production yielded 67% more compared to monocultures, while root biomass was on average 58% higher in bicultures than in monocultures. For aboveground biomass, production differences between grass-legume bicultures were significantly influenced by the species of legume present, while belowground biomass was more affected by the grass species present in the bicultures. Roughly 80% of the mixtures achieved a mean land equivalent ratio (LER) > 1.0. When examining total biomass production, the most successful bicultures were oat-vetch (LER=1.87), vetch-festulolium (LER=2.31), vetch-orchardgrass (LER=1.87), oat-red clover (LER=1.62), and red clover-ryegrass (LER=1.46). When examining partial LERs (the component of the LER attributed to each species), we found that overyielding in bicultures was mainly driven by increases in the biomass of the component grass species. Our findings suggest that mixtures of key functional species (e.g. grass and legume, annual and perennial species) offer greater promise in improved fallows compared to monocultures of the respective species. Additionally, I suggest that strategically designed improved fallow mixtures, with emphasis on perennial species that support long-term root inputs, can best support soil health and the multifunctionality of Andean agroecosystems

Las mezclas de gramíneas y leguminosas muestran el potencial de aumentar la producción de biomasa aérea y subterránea en los barbechos andinos basados en el forraje

Descargue el texto completo en el portal de la revista Agronomy: https://doi.org/10.3390/agronomy12010142Los suelos altoandinos están amenazados por la intensificación de los sistemas de cultivo. Los barbechos mejorados basados en el forraje ofrecen una gran promesa para abordar este problema, pero es necesario investigar para entender mejor el potencial de las mezclas de especies frente a los monocultivos para apoyar múltiples objetivos de los agricultores, especialmente la producción de forraje y la conservación del suelo. Hemos utilizado un estudio en maceta para cuantificar la producción de biomasa aérea y subterránea, así como la absorción total de N de las mezclas de gramíneas y leguminosas entre cinco gramíneas: (1) avena (Avena sativa), (2) ryegrass (Lolium multiflorum), (3) festulolium (Lolium × Festuca genera), (4) bromo (Bromus catharticus), y (5) hierba de la huerta (Dactylis glomerata), y cuatro leguminosas: (1) veza (Vicia dasycarpa), (2) trébol rojo (Trifolium pratense), (3) medicago negro (Medicago lupulina), y (4) alfalfa (Medicago sativa) en relación al rendimiento de cada especie en monocultivo dentro de dos suelos de los Andes centrales peruanos. Los bicultivos de gramíneas y leguminosas demostraron un rendimiento superior, produciendo un 65% y un 28% más de biomasa seca total y de absorción total de N en promedio que los monocultivos. La biomasa aérea de los bicultivos estuvo significativamente influenciada por la especie de leguminosa presente, mientras que la biomasa subterránea estuvo más afectada por la especie de hierba en la mezcla. Al evaluar el crecimiento de cada especie por separado, nuestros resultados indican que el exceso de rendimiento fue impulsado más por el mayor crecimiento de las gramíneas en relación con las leguminosas. Nuestros resultados indican que la combinación de grupos funcionales clave (p. ej., gramíneas y leguminosas, anuales y perennes) es muy prometedora para el desarrollo de barbechos mejorados que apoyen la salud del suelo y la productividad en los agroecosistemas andinos.Soils of the Andean highlands are under threat from cropping system intensification. Improved forage-based fallows offer great promise to address this issue, but research is needed to better understand the potential of species mixtures vs. monocultures to support multiple farmer objectives, especially forage production and soil conservation. We used a pot study to quantify above- and belowground biomass production as well as the total N uptake of grass–legume pairs between five grasses: (1) oat (Avena sativa), (2) ryegrass (Lolium multiflorum), (3) festulolium (Lolium × Festuca genera), (4) brome grass (Bromus catharticus), and (5) orchard grass (Dactylis glomerata), and four legumes: (1) vetch (Vicia dasycarpa), (2) red clover (Trifolium pratense), (3) black medic (Medicago lupulina), and (4) alfalfa (Medicago sativa) relative to the performance of each species in monoculture within two soils from the central Peruvian Andes. Grass–legume bicultures demonstrated significant overyielding, producing 65% and 28% more total dry biomass and total N uptake on average than monocultures. Aboveground biomass of bicultures was significantly influenced by the species of legume present, while belowground biomass was more affected by the grass species in the mixture. When evaluating the growth of each species separately, our findings indicate that overyielding was driven more by the enhanced growth of grasses relative to legumes. Our findings indicate that combining key functional groups (e.g., grass and legume, annual and perennial) offers great promise for developing improved fallows for supporting soil health and productivity in Andean agroecosystems