Brian et al.,
The legume models include N in the plant even though the N in the soil is
turned off. This is because legumes fix N but when seeds are growing, the
plants may not fix N due to the demand for seed growth. During this time, N
is taken from other plant parts to provide the N required for the high
protein seeds, and thus N in leaf tissue, for example, can become low enough
to reduce photosynthesis and subsequent plant growth. Thus, the plants that
fix N can have N stress, even if the soil N balance is turned off, due to
low concentrations of N in the plant. This reflects the "self-destruct"
mechanism that Sinclair and others have published, which means that heavy
seed loads on soybean, for example, will demand a lot of N, which is
mobilized from other tissue at the detriment of future photosynthesis. When
N concentration in leaves drops below a certain level, they abort, and thus
lose their foliage and further ability to intercept light and produce
photosynthesis.
Hope this helps.
Best regards!!
Jim Jones
James W. Jones
Distinguished Professor
Agricultural and Biological Engineering Department
University of Florida
PO Box 110570
Gainesville, FL 32611
Tel: (352) 392-1864 ext. 289
Fax: (352) 392-4092
-----Original Message-----
From: Brian Baer [mailto:[log in to unmask]]
Sent: Monday, February 18, 2002 3:41 PM
To: [log in to unmask]
Subject: N-Stress in Legumes when stress is turned off
Hello Everyone,
I received a question from a fellow DSSAT user that I could not answer. In
short he was asking why when he runs a legume experiment with the N switch
turned off he still sees N stress.
I ran the first treatment (no H2O or N stress) of IUCA experiment that came
with DSSAT and confirmed that this phenomenon occurred.
Does anyone know the reason for this?
Thank you in advance.
Brian
*SIMULATION OVERVIEW FILE
*RUN 1 : 0.25m ROW, NO WATER STRES
MODEL : CRGRO980 - SOYBEAN
EXPERIMENT : IUCA7901 SB WAYNE, IRRIGATED &
NON-IRRIGATED
TREATMENT 1 : 0.25m ROW, NO WATER STRES
CROP : SOYBEAN CULTIVAR : WAYNE (3) - MATURITY
GROUP 3
STARTING DATE : MAY 15 1979
PLANTING DATE : MAY 15 1979 PLANTS/m2 : 16.0 ROW SPACING : 25.cm
WEATHER : IUCA 1979
SOIL : IBSB910026 TEXTURE : -99 - Ida Silt Loam
WATER BALANCE : NOT SIMULATED ; NO H2O-STRESS
IRRIGATION :
NITROGEN BAL. : NOT SIMULATED ; NO N-STRESS
N-FERTILIZER :
RESIDUE/MANURE :
ENVIRONM. OPT. : DAYL= .00 SRAD= .00 TMAX= .00 TMIN=
.00
RAIN= .00 CO2 = R330.00 DEW = .00 WIND=
.00
SIMULATION OPT : WATER :N NITROGEN:N N-FIX:N PESTS :N PHOTO :L ET
:R
MANAGEMENT OPT : PLANTING:R IRRIG :N FERT :N RESIDUE:N HARVEST:M
WTH:M
*SUMMARY OF SOIL AND GENETIC INPUT PARAMETERS
SOYBEAN CULTIVAR :IB0003-WAYNE (3) ECOTYPE :SB0301-MATURITY
GROUP 3
CSDVAR :13.45 PPSEN : .25 EMG-FLW:19.50 FLW-FSD:14.80 FSD-PHM :28.00
WTPSD : .180 SDPDVR : 2.20 SDFDUR :21.00 PODDUR :14.00 XFRUIT : 1.00
*SIMULATED CROP AND SOIL STATUS AT MAIN DEVELOPMENT STAGES
RUN NO. 1 0.25m ROW, NO WATER STRES
DATE CROP GROWTH BIOMASS LAI LEAF ET RAIN IRRIG SWATER
CROP N STRESS
AGE STAGE kg/ha NUM. mm mm mm mm kg/ha
% H2O N
----------------------------------------------------------------------------
----
15 MAY 0 Start Sim 0 .00 .0 0 0 0 0 0 .0
.00 .00
15 MAY 0 Sowing 0 .00 .0 0 0 0 0 0 .0
.00 .00
28 MAY 13 Emergence 8 .01 .0 0 0 0 0 0 5.1
.00 .08
28 MAY 13 End Juven. 8 .01 .0 0 0 0 0 0 5.1
.00 .08
7 JUN 23 Unifoliate 16 .03 1.2 0 0 0 0 1 4.8
.00 .47
10 JUN 26 Flower Ind 21 .04 1.6 0 0 0 0 1 4.8
.00 .03
13 JUL 59 First Flwr 1301 2.22 9.3 0 0 0 0 52 4.0
.00 .00
28 JUL 74 First Pod 3652 4.62 13.0 0 0 0 0 133 3.6
.00 .00
9 AUG 86 First Seed 5665 5.46 16.2 0 0 0 0 194 3.4
.00 .00
21 AUG 98 End Pod 6807 4.80 18.6 0 0 0 0 226 3.3
.00 .00
26 AUG 103 End Msnode 7373 4.46 19.4 0 0 0 0 241 3.3
.00 .00
26 AUG 103 End Leaf 7373 4.46 19.4 0 0 0 0 241 3.3
.00 .00
10 SEP 118 Phys. Mat 8814 3.42 19.4 0 0 0 0 300 3.4
.00 .00
22 SEP 130 Harv. Mat 7115 .22 19.4 0 0 0 0 265 3.7
.00 .00
22 SEP 130 Harvest 7115 .22 19.4 0 0 0 0 265 3.7
.00 .00
|
