However, little is known about how the leaf extracts might
affect plant growth and soil processes. Gopal et al. (2007)
studied the effect of 10% azadirachtin granules, i.e. alcoholic
extract of neem seed kernel mixed with China clay, on the population
of bacteria, actinomycetes, fungi, azotobacter and nitrifying
bacteria. They found that azadirachtin exerted a negative
effect on the microbial communities in the initial 15-day
period, but not on Azotobacter sp. It has been shown that the
production of N2O through nitrification is affected, i.e. neem
extracts can be used as a nitrification inhibitor (Majundar et al.,
2000), so other soil processes, such as C and N mineralization
or N2 fixation, might be affected. Additionally, neem is not
a native plant of Mexico and A. indica originates from India
(Koul et al., 1990). Its possible effects on the ecosystems of
South Mexico are difficult to foresee, but neem grows abundantly
and could easily replace native plant species. Additionally,
leaves of neem accumulate under its canopy and it remains
unknown how that organic material would affect fauna
and flora. Mexico has an extremely rich flora and a lot of plants
are used by the local population to control pests. Gliricidia
sepium (Jacquin), locally called ‘mata-raton’, is a leguminous
tree and belongs to the family of the Fabaceae. G. sepium originates
from Central America, but can now be found throughout
the world. It is used in many tropical and sub-tropical countries
as live fences and sometimes as fodder. It is also used
in Mexico to repel insects, so it has potential as a botanical
insecticide.
Bean, Phaseolus