Dear Dr. Roger,

Thanks for the detailed inforamtion.

Sincerely,

Dr. Srinivasa Rao Gattineni
(040) 55791128 / 9848127159

----- Original Message -----
From: "Roger E. Rivero" <[log in to unmask]>
Date: Sunday, March 20, 2005 2:39 am
Subject: Re: Request for Ky values

> Dear Dr. Rao:
>
> I am assuming that in your question you are talking about the Ky
> factor in
> the Kassam's equation displayed in FAO 33 which relates relative
> yield to
> the quotient real evapotranspiration / potential crop
> evapotranspiration.It's true that in FAO 33 there is no millet nor
> vigna or paddy. But it
> doesn't means that there is no such data at FAO now, maybe there is.
>
> For anyone to have such coefficients he would have had to use that
> approachto derive it. To find such a coincidence may not be easy.
> That kind of data
> is the hardest to find in the crop modeling field.
>
> I call your attention to the book "Bilan hydrique agricole et
> secheresse en
> Afrique Tropicale" (1994) John Libbey Eurotext, 415 pp. There we
> have at
> least 6 papers on water balance and millet yields with a lot of
> Tables and
> Figures. I think that a a careful analysis of that data could
> allows you to
> derive such Ky values by yourself. As some of those papers are
> from very
> well recognized specialists as G. Maracchi, G. Popov and others,
> maybe they
> could assist you in the reanalysis process of their own experiments.
>
> Additionally, if you take some crop models as Generic CERES from
> DSSAT or
> WOFOST 7.1.2, which give at the output potential yield, real water
> stressedyield, and total evapotranspiration during different
> phenological phases and
> for the whole crop cycle, you could also obtain a set of "model
> derived" Ky
> coefficients for every crop that have a biophysical model available.
>
> Then you could substitute that in the equation,
>
>  (1 - (yield/potential yield)) = Ky (1 - (Real evapot./Max. pot.
> crop.evap))
>
> Of course, to calculate Max. pot. crop. evap you'll have to use the
> Doorenbos and Pruitt Kc coefficients available in the literature
> or obtain
> that data from biophysical potential yields crop model simulations.
>
> Sincerely yours,
>
> Roger E. Rivero Vega
>
>
> ----- Original Message -----
> From: "Dr. Srinivasa Rao Gattineni" <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Saturday, March 19, 2005 12:46 AM
> Subject: Request for Ky values
>
>
> > Dear List,
> >
> > Sorry for repeated mail.
> >
> > Can some body provide me "YIELD RESPONSE FACTOR (Ky)" values for
> paddy,> pearl millet and green gram (VIGNA RADIATA), please.
> >
> > Thanks in advance.
> >
> > Srinivasa Rao Gattineni
> > Research Associate
> > Databank
> > Central Research Institute for Dryland Agriculture (CRIDA)
> > Santoshnagar, Hyderabad
> > India.
> >
> >
> >
> > Dr. Srinivasa Rao Gattineni
> > (040) 55791128 / 9848127159
> >
> >
>