Yield Variability

Chuck Benbrook (benbrook@hillnet.com)
Tue, 27 Oct 1998 21:46:40 -0800

Sorry I have had so little time to contribute of late. The posts re
yield variability and traditional varieties are important. I just attended
the Tri-Society meeting at Baltimore, and the World Bank Sustainable
Transitions symposium. In three different sessions with recognized leaders
in plant physiology and breeding, I heard people say very clearly that most
breeding advances have been designed to overcome sources of stress to the
plant that limit the expression of the genetic potential in the plant, and
in many cases, traditional varieties. In a session discussing corn, among
other crops, one of the speakers clarified his remarks, in a response to a
question, and said that his data show that there would be very little
difference in yields harvested today from the good open pollinated corn
varieties of the 1970s in contrast to the best hybrids, when both are grown
in soil, climate where there are ample nutrients, water, sun, and little
pest pressure.

The same point was made by many other people. This realization
triggered a recurrent theme that arose in several meeting sessions,
especially those asking the question how will global agriculture
double/triple production to meet demand over the next half century --
management of soil and farming systems, long term soil quality and
biodiversity may be having impacts on yields, and the attainment of genetic
potential, that far exceeds what breeders have been able to accomplish, or
which biotech will deliver. Many said that yield suppression in poorer
soils, saline soils, etc is well understood, but that even in what we think
of as prime soils, with more than ample N,P,K and water, all is not well in
root zones, and that plants may be suffering from a variety of disease and
pest pressures that undercut yields.

I left the meeting reminded that much of the focus of breeding has
been overcoming problems created by other changes in management practices
and systems. This is the point Ann Clark has made many times on this list.
What struck me at the meeting was the diversity of people, from England, CG
centers, U.S. universities, all reporting the same finding and drawing
similar conclusions from very different sorts of work, different crops,
different systems. Perhaps there are some first principles at work here.

chuck

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