Laura:

I have never been certain if I should consider DSSAT simulations as tilled
or no-tilled systems.  In our paper published in Agronomy J, we averaged
across the tilled and no-till treatments because we could not rationalize in
our own minds which the current system is closer to for the following
reasons.

1. Since there are not tillage affects on the soil when a tillage is entered
in the input file, the change in bulk density and subsequent loss of soil
moisture does not occur.  Therefore this part is more like a no-till system
here on the Great Plains in that no soil moisture is lost prior to crop
establishment.

2. However, I am certain that the water use calculations do not take into
account the impacts of residue on the soil surface.  Again, here in the
Great Plains, this can result in savings of 50 to 100 mm of growing season
moisture according to research conducted in Nebraska.  Now, it would seem
very easy to mimic this by increasing the soil water holding capacity to
reflect this and simply have a "Tilled" soil and a "No-tilled" soil.  For us
here in the Great Plains, it is easy to justify this as we believe that
no-till systems will be the only sustainable method for us and that is the
focus of most of our research, both in the field and in our simulations.

I could be way off base on some of this thinking, but thought I would share
my thoughts on this since I had to reconcile this exact issue a couple of
years ago when looking at carbon modeling and DSSAT cropping systems.

Sincerely
Scott Staggenborg

===================================
Scott Staggenborg
Department of Agronomy
2004 Throckmorton Plant Science Ctr.
Manhattan, KS 66506
785-532-7214 (phone)
785-532-7039 (fax)
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=================================

----- Original Message -----
From: "Laura Olivera" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Monday, August 14, 2006 8:42 AM
Subject: tillage and no tillage


> Dear all:
>
> I want to simulate, tillage and no tillage effect in differents soils, so
> the question is.... if I don't put anything in the XBuild file
> managment/tillage/tillage implement, the simulation model assume that this
> is ''no tillage''?
>
> Thanks!!
>
>
> Laura Olivera McAlister
> Agronomist Engineer
> Agro climatic and Information Systems (GRAS)
> INIA La Estanzuela
> Colonia, Uruguay
> Phone: (00598) 574 8000 ext. 1439
> Visit our web site: www.inia.org.uy/gras/
>
>