Maize Home
Doubling yields?
Using the forgotten half of our grain crops
J. Gressel, A.
Zilberstein
With little
additional land for crop production, how will Africa’s expanding population
be fed? Half the biomass produced by row crops is grain—the forgotten half
is straw and stover. Grain straw is the largest tonnage and most pervasive
organic agricultural waste in the world; its efficient recycling through
ruminant animals could alleviate this wastage, with lower inputs of feed
grains into the farming system and thus enhance economic as well as
ecological sustainability of agriculture. Because the polymer lignin in
straw prevents ruminants from digesting the cellulose, straw is almost
useless as animal fodder. Technologies available from other systems can
slightly lower or modify lignin composition, releasing much of the
cellulose. Treating straw with urea or ammonia can release additional
material, as well as being a nitrogen supply for ruminant bacteria,
replacing the need for protein. If indeed very poorly digestible straw with
its very low nutritional value can be economically converted into
hay-quality material having highly enhanced caloric value as well as being a
nitrogen source, using transgenically modified grains mixed with physical
and chemical treatments, the straw and stover could fully feed 170 million
more goats per year in Africa (or 500 million goats per year if grain yields
were increased to match world averages), 80% more, to triple the present
number. This would free billions of tonnes of grain for human consumption or
for non-ruminant animals. The time has come to use accumulated knowledge
from model systems to simultaneously deal with straw pollution as well as
food security.