Dear Sir,

Thanks for your valuable comments. However, I have some clarification for
your doubts

> First, the DSSAT models do not respond to P or K.

This may be the reason since literature also shows that Peanut crop responds
for P & K positively. Hence the treatment with fertilizer does not predict
higher yeild compared to the one without fertilizer.

> As for N, it is possible that the non-fertilized (no N) peanut crop can
> yield more because N-fixation is greater than when fertilized with 40 kg
of
> N which would inhibit nodule growth and N-fixation just long enough, so
> that you would have poor nodulation at crtical time of pod growth.

I am not sure whether all crop N requirement  can be met by fixing N through
atmosphere. It seems some N input by way of fertilizers is necessary. The N
appication was decided after all these calculations(considering soil N
before sowing) and the fertlizer we applied is the regular recommonded dose
for Peanut in our soils. Hence I may expect slightly higher values of all
yield parameters in the teatment with N.

May I get some details of N balance calculations which DSSAT does during
simulation.

> Lastly, it is not good to run the model with water balance turned off, yet
> N balance turned on.  Or was it done to specify optimum irrigation to
> create "no water stress."
>

I compared the Pod, Bomass and  Seed yield and max leaf area under N and
No-N treatments
at same conditions of soil moisture. Both the treatments were irrigated at
15% depletion of available soil moisture throughout the growth period. So
there was no water stress under both these treatments. Hence, water balance
was not turned off during the simulation.

Thanks.

Uday Khodke

> Ken Boote
>
> At 08:18 PM 9/12/01 +0530, you wrote:
> >Dear Members,
> >
> >I am using DSSAT 3.5 for peanut crop growth simulation. I have calibrated
> >the model with one of my treatments which is without water stress and
> >recommonded (N P K as 40:60:30) fertilizer input. The observed and
> >simulated data for this perticular treatment are matching.
> >
> >I simulated another treatment keeping all the inputs same as above
except,
> >there was no fertilizer.
> >
> >I observed tnat the simualated Pod yield, total biomass and max leaf area
> >and seed yield in case of treatment without fertilizer are higher
compared
> >to the treatment with fertilizer. In my opinion the treatment with
> >fertilizer should show higher values.
> >
> >I will appreciate your comments on this please.
> >
> >Thanks.
> >
> >Uday