A very, very interesting post.
In regard to soil types and crop production, the people working with
yield monitors seem to be finding that it is very difficult to equate
yield with the traditional ways of looking at inputs. In some cases,
there are more yield differences within soil types in the same field as
there are across soil types. For people like me who usually have 3 - 5
soil types in one cropping unit, this is very interesting. It's also a
little unsettling, because some of the old notions about management are
being challanged.
Initial discussions I've heard, indicate that drainage has a large
function in yield. Fertilizer does, but only to a point and not directly
related to input quantity. Variety can make a difference, but it is not
the major factor. Therefore, all the variable rate technology (VRT)
needs to be investigated very carefully before buying into that. Some
farmers are saying that temporal factors are more important than spatial
factors.
Can you offer any comments on the above, both in the impact on farming
and the science of determining sustainability indicators?
Jim - Farmer - Iowa City, IA,
jnmeade@blue.weeg.uiowa.edu