Dear Subash,

Indeed, resetting simulation models is a necessity if they are to be used
effectively in operational decision making. For closed horticultural systems
we are working on an integrated set of soft- and hardware that enable such.
As the season proceeds, past growth is simulated on the basis of observed
climate observations (up to the current day) and future growth for average
or representative climate data (for a limited number of days only). The
latter is done for a number of fertigation regimes (implying variation in
nutrient and water availability). An optimization programme then decides on
the basis of certain rules what fertigation regime should be implemented.
These rules typically include minimization of water and nutrient loss, and
yield optimization. A real-time controller translates the selected
fertigation regime into actions (e.g., what nutrient solutions to mix, when
and for how long to open valves). This procedure is repeated daily.

This only makes sense if simulated and actual growth correspond, as
otherwise for instance simulated nutrient demand is incorrect. Therefore,
with sensors we determine essential growth variables that are used to
calibrate the model. For example, LAI is always important, but it can only
be re-set if also weights are also re-set, as physiological imbalances must
be avoided. So we track both. A separate calibration procedure enables us to
modify for instance minimum and maximum values of SLA in such a manner that
the desired LAI and weight are maintained. This calibration routine is run
for a number of past days, so that the simulated variables of the current
day match reality. Of course, there are many other variables in the model
that are linked to weights and LAI but are very hard to re-set. We simply
assume that their new values are correctly estimated with the calibration
routine.

We are only beginning, but are hopeful to implement such a system in the
near future in commercial horticulture.


================================
Anne Elings
Crop Modeller / Physiologist
Cropping Systems
Plant Research International
P.O. Box 16, 6700 AA Wageningen
tel.: +31 - (0)317 - 475826
fax: +31 - (0)317 - 423110
email:  <mailto:[log in to unmask]> [log in to unmask]

This message is for informal purposes only.
================================