Albert .... you hit on a really 'fuzzy' problem! The Zadoks conversion is based
on developmental (ie. reproductive) progress throughout whereas Zadoks itself
is a growth+development scale ... in the early stages there is no way to relate
developmental progress to things like tillering (especially beginning of
tillering), and later the associations can only be made 'fuzzily'. In fact, the
only really hard point of contact is at last leaf (Zadoks 29,Istage 3 just
reached) ... and possibly also, physiological maturity (although this is not
nailed down as such in Zadoks). I've been trying to develop a somewhat better
conversion, and attach my current attempts for your perusal and comments.
       As to the critical N curves. They also are 'fuzzy' .. even without the
Zadoks problem, and really need some simplification ... and perhaps linking to
something that accounts for current leaf sizes (big leaves have more structural
material!), and leaf to stem ratio.
       Hope this is of some use .... Tony Hunt

Albert Weiss wrote:

> Colleagues: In the subroutine NFACTO of CERES-Wheat, there is an algorithm
> for the calculation of a modified Zadoks scale (ZSTAGE) based on the 1-5
> development scale (XSTAGE) used in CERES Wheat. (By modified, I mean that
> values are calculated in 0-9 range rather than in the 0-99 range, as in the
> original Zadoks scale.) The value of the ZSTAGE is used to calculate TCNP,
> the critical N concentration. My concern is about the values of the Zadoks
> scale used to develop this algorithm. For example, an  XSTAGE of 1 goes
> from emergence to terminal spikelet initiation. What are the corresponding
> values of the Zadoks scale? Emergence is at 1 (10). The value for terminal
> spikelet initiation from the algorithm is 2 (20) which corresponds to the
> beginning of tillering from the Zadoks scale. Does terminal spikelet
> initiation occur at the beginning of tillering or later on just before stem
> elongation (jointing, at a Zadoks scale of 3(30))? Similar comments can be
> made about the other beginning and ending values of the other Zadoks scale.
> Thanks for your help.
>         Albert Weiss



                                                                              !S
            ! Istage Stage                                                    !S
            !   0    Germination                                              !S
            !   1    End Juvenile                                             !S
            !   2    Maximum spikelet number                                  !S
            !   3    End leaf growth                                          !S
            !   4    End spike/panicle growth                                 !S
            !   5    Start linear grain fill                                  !S
            !   6    Maturity                                                 !S
                                                                              !S
            ! Stages - ZADOKS                                                 !S
            !  Estage = Emergence stage (Estages=secondary estage)            !S
            !  Xstage = Istage with intermediate values                       !S
            IF (ESTAGE .LT. 2) THEN                                           !S
              IF (ESTAGE .LT. 1) THEN                                         !S
                ZSTAGE = ESTAGES/2.0                           ! 0->0.5 Germ  !S
              ELSE                                                            !S
                ZSTAGE = 0.5 + ESTAGES/2.0                     ! 0.5->1.0 Emr !S
              ENDIF                                                           !S
            ELSE                                                              !S
              IF (XSTAGE .LE. 2.0) THEN                                       !S
                ZSTAGE = 1.0 + TDU/PCUM(1)                       ! 1->2 Max sp!S
                ! TDU=total developmental units accumulated                   !S
                ! PCUM=Photo-vernal-thermal units needed to reach end phase 1 !S
              ELSEIF (XSTAGE .GT. 2.0 .AND. XSTAGE .LE. 3.0) THEN             !S
                ZSTAGE = 2.00 + 2.0*(XSTAGE-2.0)                 ! 2->4 Last l!S
              ELSEIF (XSTAGE .GT. 3.0 .AND. XSTAGE .LE. 4.0) THEN             !S
                ZSTAGE = 4.00 + (XSTAGE-3.0)                     ! 4->5 End sp!S
              ELSEIF (XSTAGE .GT. 4.0 .AND. XSTAGE .LE. 5.0) THEN             !S
                ZSTAGE = 5.00 + 3.0*(XSTAGE-4.0)                 ! 5->8 EndLag!S
              ELSEIF (XSTAGE .GT. 5.0) THEN                                   !S
                ZSTAGE = 8.0  + (XSTAGE-5.0)                     ! 8->9 PM    !S
              ENDIF                                                           !S
            ENDIF                                                             !S