Rethinking Agriculture for New Opportunities 411production that cannot be explained simply by the inputs applied, an increase
reflecting synergy within the crops’ growing environments (Vandermeer, 1989).
Plant–animal intercropping yields comparable benefits. There are many situations,
determined more by economic than by agronomic considerations, where mono-
culture will be a preferable strategy. But its superiority should not be assumed
without proof, as happens now.
Mechanical conceptions of agriculture
Monocropping implicitly regards agriculture as a mechanical process, with inputs
being converted into outputs by some fixed formula, whereas polycropping recog-
nizes the inherently biological nature of agriculture. The relation posited between
inputs and outputs is different for mechanical and biological paradigms. In the
first, the ratio of outputs to inputs is predictable and proportional, fixed and usu-
ally linear. In the realm of nature, on the other hand, relationships are less predict-
able and seldom proportional. Large investments of inputs can come to nought,
while under favourable conditions and with good management, modest inputs
have many-times-larger effects.
Until something like the perpetual motion machine is invented, such dispro-
portionality is not possible with mechanical phenomena, which depend on con-
tinuous inputs for their operation. Biological processes, on the other hand, can be
self-sustaining and can adapt and evolve unassisted. Moreover, biological inputs
can reproduce themselves. How one regards and utilizes inputs thus differs in sub-
tle but important ways according to whether they are understood within a mechan-
ical framework or in a biological context.
One area where ‘modern’ agriculture has rediscovered the advantages of biol-
ogy is with so-called minimum tillage or no-till systems, now given the positive
appellation ‘conservation tillage’ (Avery and Avery, 1996). Twenty years ago this
was considered atavistic agriculture, harking back to the dibble stick in a modern
era when heavy tractors and field machinery should be used to plough, plant, weed
and harvest ‘clean’ fields. Yet no-till agriculture has now become state-of-the-art in
many areas of the US. Mechanical corn harvesters are designed to chop up plant
stalks, leaves, husks and cobs to return this biomass to the land in biodegradable
form to preserve soil fertility. In addition to recycling nutrients, conservation till-
age protects the soil’s surface and reduces wind and water erosion. The main limi-
tation with little or no tillage is that weeds can become more of a problem unless
farmers can afford chemical herbicides or use hand labour. (This new/old technol-
ogy has become popular with businesses that sell herbicides to control weeds when
there is no ploughing).
Innovative practices like the use of mulches, cover crops and green and animal
manures, which were until recently largely ignored in ‘modern’ agriculture, can
solve the problem of weeds. These techniques capitalize on the large dividends that
nutrient recycling can pay because of the multiplicative dynamics of biological
processes. Whereas mechanical advantage is a well-accepted principle in physics