Draining Rice by Growth Stages A computer program

1
Draining Rice by Growth StagesA computer
program Paul Counce, Earl Vories, Terry
Siebenmorgen, Mike Popp, Vetress Thompson and
Brad Watkins
Introduction The current recommendations for
terminating rice irrigation in Arkansas and
Mississippi were developed from our research
(Counce et al., 1990 1993). Subsequent
research results by other scientists have
confirmed our findings (Grigg et al., 2000
McCauley and Way, 2002). Due to the large number
of soil types for which the rice crop may have
different responses to draining, however,
potential water savings have only been partially
realized. Farmers are wasting water by
maintaining a flood for too long in many
situations. This costs the aquifers water and
the farmers money. Despite convincing evidence
cited above that rice can be drained for harvest
2 weeks after 50 heading (when panicles emerge)
farmers have been reluctant to practice this.
Part of the reluctance lies with an inadequate
frame of reference for understanding, in a
practical way, how the rice crop uses water and
how the soils supply that need after draining the
rice field. Also, farmers need to know when to
drain for harvest whereas current extension
recommendations relate to time to cease
irrigation. To reduce labor costs, farmers want
to know when they can safely drain their rice
fields since levee gates must be removed at
draining to reduce labor. Also, for no-till rice
production, appropriate draining of rice fields
is critical since rutting leads to termination of
the no-till practice to repair ruts and reform
land. Consequently, appropriate rice draining is
a linchpin for no-till rice production. Mr.
Terry Gray said the key to no-till is no red,
the key to no red rice is no ruts, and the key to
no ruts is early draining.
Grain Dry Down
End of Grain Filling
Anthesis
Grain Filling
Caryopsis expansion
Rationale A simple, field-specific computer
program has been developed which utilizes four
different information systems and data sets. The
information system is the rice growth staging
system (Counce et al., 2000). The rice growth
staging system was developed to allow meaningful
communication about rice farming practices and
research results. The growth staging system also
improves timing of management practices. The use
of the rice growth staging system allows
reproductive development of the rice crop to be
timed with DD50 rather than simply days after 50
heading as is presently done (Keisling et al.,
1984). The data sets are (1) a database for
timing between the reproductive growth stages
(Clements et al., 2003, Watson et al., 2005) (2)
water availability dataset consisting of (a) the
NRCS soil information for available water in
soils and (b) further published data for water
held between field capacity and saturation (which
is available to rice crop but not to most other
crop plants) (3) a historical weather dataset
to allow computation of timing in combination
with the database for timing between reproductive
stages of development (see graph for example with
Drew rice) and (4) a water use database for the
rice crop at different reproductive stages of
development (Lage et al., 2003 Renaud et al.,
2000). These calculations are combined in a cell
within a spreadsheet with four site-specific
inputs. The simple program provides the frame of
reference.
R9 occurs when all grains which reached the R6
stage reach R8 all filled grains are brown
R-Stage Progression For Drew Rice
s
The Program See the spreadsheet below for one
example of Wells rice on a Stuttgart silt loam.
The program works by putting together four
information sets (described in the Rationale)
inside of an Excel spreadsheet. Available water
at draining is calculated for a particular soil
(yellow highlight) , the projected water use from
maturity to each reproductive growth stage is
calculated (Orange highlight) and the growth
stage at which draining will be safe (blue
highlight).
Significance Rice requires large amounts of
water and, in turn, rice production and
processing contribute greatly to many communities
in the rice producing states. Furthermore,
competing water demands conflict with other water
users. Improved utilization of water for rice
production could thereby increase the water
available for other uses. Implementation of this
research in Arkansas alone could result in
savings of 3 million acre inches of water per
year. This, in turn, could reduce depletion of
aquifers, lower pumping costs to farmers, and
reduce tillage costs associated with rutted soil
conditions. The water use savings available to
farmers in each situation have been substantial
(23/acre in some cases) and other ramifications
of this work such as increased soybean yields
make earlier draining of rice an attractive
option for many growers (Popp et al., 2004).
Research in 2005 To calculate the safe stage of
growth for draining a rice field using the
program, several inputs are needed. Two field
experiments are being conducted this year. The
rooting depth for the soil at the Stuttgart site
is 4 inches. The program inputs include soil
type, rooting depth, 50 heading date (for
historical weather data) and cultivar. One
assumption embedded within the model is that
water use will be maximum based on published
water use data for rice. This assumption is made
to assure adequate water to meet the crops needs
after draining. One field experiment was
established at Stuttgart at the Rice Research and
Extension Center and another experiment was
established at Gillett. The rice cultivar at
Stuttgart is Wells. There are two treatments in
the experiment at Stuttgart (1) Draining at 28
days after heading and (2) Draining by the growth
stage as determined by the program. The program
projected the safe stage of growth for draining
the rice at Stuttgart was R8 (one brown seed on
the main stem panicle). The rice at present is
not quite at R3 and 50 heading. The rice
cultivar at the Gillett experiment is Francis.
We utilize metal frames to create a drained rice
field within a flooded rice field. There are
three treatments (1) Drain as the field would
normally be drained (approximately 30 days after
heading), (2) Drain by growth stage as determined
by the growth stage program, and (3) A second
control with the frame around the rice as in
Treatment 2 without draining prior to draining
the entire field. The rooting depth at the
Gillett field is 8 inches compared to 4 inches at
the Stuttgart field. At the Gillett field the
predicted safe stage of growth for draining rice
is R6. The rice at was at 50 heading on July
23. The present stage of development is R4.
We continue to discuss ways to improve the
program with a number of cooperating farmers.
The program provides a comprehensive way to
consider decisions on rice draining. Our goal is
to allow rice producers to save money without
reducing rice yield or quality.  
References Clements, J., T. Siebenmorgen and P.A.
Counce. 2003. Relationship of thermal units
during grain filling to rice kernel development.
pp. 373-381. In R.J. Norman and J.-F. Meullenet,
Eds., Rice Research Studies 2002. University of
Arkansas Agricultural Experiment Station Research
Series 504. Counce, P.A., T.C. Keisling and A.J.
Mitchell. 2000. A uniform, objective and
adaptive system for expressing rice development.
Crop Science 40436-443. Counce, P.A., T.J.
Siebenmorgen, E.D. Vories and D.J. Pitt. 1990.
Time of draining and harvest effects on rice
grain yield and quality. Journal of Production
Agriculture 3 436-445. Counce, P.A., T.J.
Siebenmorgen and E.D. Vories. 1993. Post-heading
irrigation management effects on rice grain yield
and milling quality. University of Arkansas,
Agricultural Experiment Station, Fayetteville,
Arkansas. Bulletin 940. Grigg, B.C., C.A.
Beyrouty, R.J. Norman, E.E. Gbur, M.G. Hanson and
B.R. Wells. 2000. Rice responses to changes in
floodwater and N timing in southern USA. Field
Crops Research 6673-79. Keisling, T. C., Wells,
B. R. and Davis, G. L., 1984. Rice management
decision aids based upon thermal time base 500F.
Arkansas Cooperative Extension Service Technical
Bulletin No. 1. Lage, M., A. Bamouh, M. Karrou
and M. El Mourid. 2003. Estimation of rice
evapotranspiraton using a rice microlysimeter
technique and comparison with FAO Penman-Monteith
and Pan evaporation methods under Moroccan
conditions. Agronomie 23625-631.  McCauley,
G.N. and M.O. Way. 2002. Drain and harvest
timing affects on rice grain drying and
whole-milled grain. Field Crops Research
74163-172. Popp, M., P. Manning, P. Counce and
T. Keisling. 2004. Rice soybean rotations
opportunities for enhancing whole farm profits or
water savings. Agricultural Systems (In
review) Renaud, F., J.A. Ferguson, H.D. Scott and
D.M. Miller. 2000. Estimation of seasonal rice
evapotranspiration. pp. 283-293. In R.J. Norman
and C.A. Beyrouty, Eds., Rice Research Studies
1999. University of Arkansas Agricultural
Experiment Station Research Series 476. Watson,
N.T, P.A. Counce and T.J. Siebenmorgen. 2005.
Growth Stages of 12 Rice Cultivars (Oryza sativa
L.) Expressed in DD50 Thermal Heat Units. pp
56-62. In R.J. Norman, J.-F. Meullenet, and K.A.K
Moldenhauer, Eds., Rice Research Studies 2005.
University of Arkansas Agricultural Experiment
Station Research Series 529.