Sown biodiverse pastures consist of diverse mixes of up to twenty different species or varieties of

seeds In botany, a seed is a plant structure containing an embryo and stored nutrients in a protective coat called a ''testa''. More generally, the term "seed" means anything that can be sown, which may include seed and husk or tuber. Seeds are the ...

, and are rich in

legumes Legumes are plants in the pea family Fabaceae (or Leguminosae), or the fruit or seeds of such plants. When used as a dry grain for human consumption, the seeds are also called pulses. Legumes are grown agriculturally, primarily for human consu ...

. They are more productive than natural

grasslands A grassland is an area where the vegetation is dominated by grasses (Poaceae). However, sedge ( Cyperaceae) and rush ( Juncaceae) can also be found along with variable proportions of legumes such as clover, and other herbs. Grasslands occur ...

, and are also richer in number of species. The seed mix is designed specifically for each location after soil analysis. Species in the mix is adapted to soil physical and chemical characteristics, as well as to local climate conditions, and therefore there is no single representative mix. However, some very common sown species in SBP are ''

Trifolium subterraneum ''Trifolium subterraneum'', the subterranean clover (often shortened to sub clover), subterranean trefoil, is a species of clover native to Europe, Southwest Asia, Northwest Africa and Macaronesia. The plant's name comes from its underground s ...

'', '' Trifolium incarnatum'', '' Trifolium resupinatum'', ''

Ornithopus ''Ornithopus'', the bird's-foot, is a genus of flowering plants in the legume family, Fabaceae. It includes six species and one natural hybrid native to Europe, Macaronesia, the eastern Mediterranean, northwest Africa, and Iran, and from southern ...

'' spp., ''

Biserrula pelecinus ''Biserrula'' is a genus of flowering plants in the family Fabaceae, found in Portugal (including Madeira and Selvagens), the Canary Islands, all the Mediterranean countries, the Arabian peninsula, and in east Africa as far south as Tanzania. ''B ...

'', annual ''Medicago'' spp., and grass species of the genera ''

Lolium ''Lolium'' is a genus of tufted grasses in the bluegrass subfamily (Pooideae). It is often called ryegrass, but this term is sometimes used to refer to grasses in other genera. They are characterized by bunch-like growth habits. ''Lolium'' ...

'', ''

Dactylis ''Dactylis'' is a genus of Eurasian and North African plants in the bluegrass subfamily within the grass family. ''Dactylis'' is native to North Africa, they are found throughout the world, and are an invasive species. They are known in English ...

'' and ''

Phalaris Phalaris () was the tyrant of Akragas (now Agrigento) in Sicily in Magna Graecia, from approximately 570 to 554 BC. History Phalaris was renowned for his excessive cruelty. Among his alleged atrocities is cannibalism: he was said to have eaten ...

''. The mixes of sown species are often enriched with seeds from spontaneous plants such as ''Plantago'' spp., ''Vulpia'' spp. and ''Bromus'' spp.. Legumes are thus very common in these mixtures and cover more than 50% of first-year SBP. As pasture settlement progresses, legumes increase and eventually dominate. Percentage of legumes in the plant cover of a mature SBP (more than 5 years) is around 25–30%. Legumes are inoculated with bacteria of the genus ''

Rhizobium ''Rhizobium'' is a genus of Gram-negative soil bacteria that fix nitrogen. ''Rhizobium'' species form an endosymbiotic nitrogen-fixing association with roots of (primarily) legumes and other flowering plants. The bacteria colonize plant ce ...

'' which induce

nitrogen-fixing Nitrogen fixation is a chemical process by which molecular dinitrogen () is converted into ammonia (). It occurs both biologically and abiological nitrogen fixation, abiologically in chemical industry, chemical industries. Biological nitrogen ...

nodules in the roots of legumes. The fixated atmospheric nitrogen is then used by grasses thus making the overall system self-sufficient in terms of nitrogen. Given the species variability, there are fewer gaps in plant cover throughout the plots (it is ensured that the species most suited for each spatial condition will thrive). The higher plant productivity of SBP implies increased atmospheric carbon capture through

photosynthesis Photosynthesis ( ) is a system of biological processes by which photosynthetic organisms, such as most plants, algae, and cyanobacteria, convert light energy, typically from sunlight, into the chemical energy necessary to fuel their metabo ...

. Part of the biomass produced is stored in soils due to the high density of yearly renewed roots. Storage is in the form of non-labile

soil organic carbon Soil carbon is the solid carbon stored in global soils. This includes both soil organic matter and inorganic carbon as carbonate minerals. It is vital to the soil capacity in our ecosystem. Soil carbon is a carbon sink in regard to the global carb ...

(SOC), which is part of the

soil organic matter Soil organic matter (SOM) is the organic matter component of soil, consisting of plant and animal detritus at various stages of decomposition, cells and tissues of soil microbes, and substances that soil microbes synthesize. SOM provides numerou ...

(SOM) pools. SOM pools are also increased by leaves’ senescence, and by animals returning undigested fibre to the soil. Sown biodiverse pastures were developed in

Portugal Portugal, officially the Portuguese Republic, is a country on the Iberian Peninsula in Southwestern Europe. Featuring Cabo da Roca, the westernmost point in continental Europe, Portugal borders Spain to its north and east, with which it share ...

in the 70’s decade. They have been installed throughout some regions of the country in the past decade, as well as in some minor areas in Spain and Italy.Carneiro, J.P., Freixial, R.C., Pereira, J.S., Campos, A.C., Crespo, J.P., Carneiro, R. (Eds.), 2005. Relatório Final do Projecto AGRO 87 (Final Report of the Agro 87 Project, in Portuguese). Estação Nacional de Melhoramento de Plantas, Universidade de Évora, Instituto Superior de Agronomia, Direcção Regional de Agricultura do Alentejo, Fertiprado, Laboratório Químico Agrícola Rebelo da Silva.

References

{{Reflist *Teixeira, R.F.M., Domingos, T., Costa, A.P.S.V., Oliveira, R., Farropas, L., Calouro, F., Barradas, A.M., Carneiro, J.P.B.G. (2011). Soil organic matter dynamics in Portuguese natural and sown rainfed grasslands. Ecological Modelling 222, 993-2001. *Teixeira, R. (2010). Sustainable Land Uses and Carbon Sequestration: The Case of Sown Biodiverse Permanent Pastures Rich in Legumes. PhD Thesis. Technical University of Lisbon. Grasses