Alternative Paths to Food Security - The Oxford Topic of Food, Politics, and Society - page 207

chemical fertilizer), paddy yield was 3.0 tons per hectare (ha), somewhat better than the
2.0 ton national average yield. With contrasting SRI practices (8-day-old seedlings, 1
plant per hill, intermittent irrigation, and compost application), average yield achieved
was 10.35 tons per hectare.
How could there be more than a three-fold increase on the same soil with the same
rice variety and the same climate? The research design included an evaluation of the
populations of Azospirillum , a nitrogen-fixing bacterium, counted in tissue samples
taken from the roots of the rice plants growing in the plots receiving different treat-
ments. There turned out to be a very strong correlation between crop performance and
the concentrations of this microorganism, considered as a proxy for the many commu-
nities of beneficial soil organisms. When there were no nutrient additions to the soil,
Azospirillum populations were more than ten times greater with SRI practices than with
conventional management. When compost was used with SRI practices, their numbers
were three times higher than when chemical (NPK) fertilizer was applied (Uphoff et al.
2012).
Subsequent studies in India and Indonesia examined the populations and activity of
beneficial soil organisms in the root zones (rhizospheres) of rice plants, using the same
variety on the same soil but grown with either conventional or SRI practices. These eval-
uations showed that the number and the biochemical activity of beneficial microbes in
rice plant root zones were usually increased with SRI methods (Uphoff et al. 2009; Anas
et al. 2011). It remains to be determined why beneficial organisms should be more abun-
dant in the rhizospheres around roots, and also in the roots themselves as endophytes,
when rice plants are grown with SRI practices. That changes in microbiological den-
sity and activity would accompany these practices should not be surprising, however,
because SRI management makes the soil better aerated and more endowed with organic
matter.
Beneficial Effects of Microbes in Plant Leaves and Seeds
Symbiotic relationships in the root zone are reasonably well known to soil biologists and
plant physiologists (Pinton et al. 2007; Waisel et al. 2002). However, recent research on
the phyllosphere (the leaf zone, where microorganisms live in, on and around the leaves)
has produced some unexpected findings. These indicate that associations between
plants and microorganisms, like those between microoganisms and animals, are more
significant, intimate, and beneficial than previously understood. This adds another eco-
logical dimension to the concept of agroecology as we look more closely at the interac-
tions between and among species, rather than focusing on just one species at a time.
The positive relationships between plants and microorganisms now being discovered
parallel those that medical researchers are identifying between human bodies and what
is called the “human microbiome” (Turnbaugh et al. 2007).
Research on rice plants by Chi and associates (2005) found that certain soil microor-
ganisms (rhizobia) migrated up from the soil through plants' roots and stems and into