I work mostly with the legume part of the model but will help as much as I can.

First, you can find the definitions of the various codes in the file "DATA.CDE" in the DSSAT4 or DSSAT35 subdirectories.

GWAD is the amount of grain or seed dry matter (DM) (kg DM/ha) present on the current day of the simulation and is calculated daily.

HWAM is defined as the amount of grain or seed dry matter (DM) (kg DM/ha) present on the day the crop reaches physiological maturity and represents the state of the crop on that day only.  This is true for crops using the CROPGRO code within DSCSM040 (legumes tomato, and bahiagrass).  For crops using the CERES routines in DSCSM040 (maize, wheat, sorghum. millet, etc.), HWAM is calculated on the final day of the simulation, not on the day that physiological maturity occurs.  This is the same day that HWAH is calculated.

HWAH is the amount of grain or seed dry matter (DM) (kg DM/ha) harvested on the last day of the simulation.

HWAH may be different from GWAD or HWAM as it is adjusted for the percent of the crop harvested (HPC) entered in the "X" or experiment file located under the "Harvest Details" header (applies to all species)  Another place that this adjustment might be listed is under the "Automatic Management" header in the species file (variable name HPCNP).

I suppose that for legumes (but not cereals), this could differ from HWAM if there was a delay between maturity and harvest and something like pest damage occurred that resulted in the loss of some seed.

Looking at outputs from Maize simulations in DSSAT v4, there may be something else going on there and I'm looking into that.

For all other cereals, the final GWAD value in PLANTGRO.OUT should be the same as HWAM in SUMMARY.OUT.

If you are seeing differences between HWAM and HWAH, then HPC is not 100.

Stu Rymph
Post Doctoral Assistant
University of Florida
University of Wisconsin
Madison, WI

----- Original Message -----
From: "Srinivas, K (NRMP) (ICRISAT-IN)" <[log in to unmask]>
To: [log in to unmask]
Sent: Tue, 7 Dec 2004 21:33:27 -0800
Subject: Small clarification required

> Dear List server members
>
> I request small clarification from members. In DSSAT version 3.5 and 4.0
> cereal models the output yield parameter at harvest/maturity in growth.out
> (GWAD) and summary.out(HWAM and HWAH) are different. Where as these values
> in legume output files are same. Can anybody explain why is this. Thanks
>
> K.Srinivas
> ICRISAT, India
>
>