Written By Lila Taheraly
I have always thought that diversity is key.
My parents come from two different continents.
I grew up watching the French National soccer team winning the World Cup in 1998 and the European Cup in 2000 with the slogan “Black, Blanc, Beur” referring to the three different skin colors of the players.
Diversity is everywhere.
Try to find two identical papayas at the farmers market.
Try to handwrite the same word exactly the same way.
Even twins have different moles or different eyebrow lines.
Diversity is life.
So when I read this article published in Nature Plants in April 2015, I felt happy. Diversity could also be great in agriculture. It could be promising and profitable!
What did these researchers do?
For one year, they grew five different grassland species on 124 small plots, half of which were exposed to drought during six weeks. The plots received either monocultures or polycultures and displayed different degrees of genetic diversity. The configuration allowed them to study separately the influence of species diversity and the influence of genetic diversity on biomass production and on temporal stability of the production.
Researchers harvested six times during the year, weighed their harvest and compared the results.
Their results proved that polycultures produced more than monocultures, especially when subject to drought, regardless of the number of genotypes per species present. With irrigation, plots with several species presented a superior yield of 200g/m² than plots with one species, i.e. 0.8tonne/acre. For plots under drought conditions, the difference was 3.2tonnes/acre.
Conversely, the temporal stability of production increased only with the number of genotypes present under both drought and non drought conditions, and was unaffected by the number of species.
How do they explain these results? With diversity, plants are more likely to produce their peak biomass at different dates. This process is called growth asynchrony. They will use water and nutrients at different moments. They will share the available resources more easily.
The article shows that species diversity and genetic diversity can play different roles for livestock optimization: species diversity impacts biomass production especially under drought conditions and genetic diversity impacts production stability. Both could be considered in agronomic systems to increase the productivity and resilience, especially in a context of rising hazardous environmental events.
We can notice that this is not the main direction that global agriculture followed for the last fifty years. The great news is that the tools that have been developed to improve monocultures for decades could help today to define and improve species mix which would increase yields and better resist hazardous conditions.
Maybe diversity could also be agriculture’s opportunity.