Amplifying the benefits of agroecology by using the right cultivars
Are currently selected cultivars adapted to conditions of agro-ecological systems recommended for the preservation of soils and provision of ecosystem services?
A study conducted by IRD and CIAT researchers suggests that selection criteria should include responsiveness to soil fauna activities (earthworms) and heterogeneous distribution of nutrient sources (biochar application) to the set of genetically determined traits (efficiency of nutrient use, allocation to grain production, resistance to environmental stress and diseases) that are generally selected for.
Five different rice cultivars, some rather rustic (O. sativa cv.Azucena, Donde lo Tiren, O. Glaberrima, others the result of more sophisticated selection processes (L30, Nippon bare), increased their respective total biomass and grain productions by up to 437% in response to earthworms, biochar application or a combination of both. While all cultivars responded positively to earthworm and biochar application, some invested in the production of more leaves (Azucena, DLT) while others produced more grains (O. Glaberrima, L30).
• The same maximum total biomass could be obtained with (in O. glaberrima) or without fertilization (in Donde lo tiren) but with both earthworms and biochar;
• The highest absolute grain biomasses were obtained with the combination of fertilization, earthworms and biochar (in O. glaberrima and Line 30);
• With fertilization, choosing the best combination of cultivar and treatment allowed a 353% relative increase in the total grain biomass (biochar and earthworms in Nipponbare); Without fertilization, choosing the best combination of cultivar and treatment allowed a 437% relative increase in the total grain biomass (biochar earthworms in Azucena).
• Overall, choosing the best combination of treatments and cultivar multiplied by more than four the mean relative increase in grain production calculated over all the combinations of treatments and cultivars (with and without fertilization).
Rapidly developing agro-ecological practices are expected to prevent soil degradation, enhance biodiversity, provide the high level of ecosystem services required to mitigate the effects of Global Change and reduce the reliance of agriculture on agrochemicals as they will become more expensive and scarce. These practices will require cultivars that interact more closely with soil organisms and soil organic inputs to increase agriculture sustainability. Unravelling the physiological mechanisms at hand and genes involved in these interactions is only in its very preliminary stages but is a promising research avenue to better understand and more efficiently exploit this positive feedback loop.
Noguera Diana, Kam-Rigne Laossi, Patrick Lavelle, Maria Elena Cruz de Carvalho, Neusa Asakawa, Cesar Botero, and Sébastien Barot. In press. Amplifying the benefits of agroecology by using the right cultivars. Ecological Applications. [doi:10.1890/10-2204.1]
Blouin et al., 2005. Ecol. Lett., 8 (202-208); Laossi et al. 2008, Pedobiologia (51)397-407; Jana et al., 2010. Soil Biol Biochem (42) 244-252.
Contacts: Diana.Noguera@ird.fr; Sebastien.Barot@ird.fr; P.LAVELLE@CGIAR.ORG;