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Title: Identification of a criteria for date of dry-seeded rice planting, paper presented at the 9th Annual Scientific Meeting of the Crop Science Society of
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Title: Identification of a criteria for date of dry-seeded rice planting, paper presented at the 9th Annual Scientific Meeting of the Crop Science Society of
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Creator: Furoc, R. E.
Magbanua, R. D.
Gines, H. C.
Morris, R. A.
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Table of Contents
    Abstract
        Abstract
    Introduction
        Page 1
    Materials and methods
        Page 1
        Page 2
        Page 3
    Results and discussions
        Page 4
        Page 5
        Page 6
        Page 7
        Page 8
        Page 9
    Reference
        Page 10
        Page 11
        Page 12
        Page 13
        Page 14
        Page 15
        Page 16
Full Text






IDENTIFICATION OF A CRITERIA FOR DATE OF
DRY-SEEDED RICE PLANTINGI/


R.E. Furoc, R.D. Magbanua, H.C. Gines and R.A. Morris 2/


ABSTRACT


IR36, an early maturing rice variety, was used as test material to
determine the effect of sequential seeding dates of dry-seeded rice (DSR)
under upland and lowland conditions.

The DSR experiment in Los Bafos, Laguna was established in an unbunded
upland rainfed field while the experiments in Manaoag, Pangasinan and Tigbauan,
Iloilo were conducted on rainfed bunded lowland fields.

Identification of patterns of crop emergence and differences in yield
responses as affected by rainfall over the seeding dates was the main objective
of the three experiments. The seeding dates in Pangasinan ran from April 20 to
May 27., 1977; in Iloilo from May 6 to June 10, 1977; and in Laguna, from April 20
to May 25, 1977. The inclusive seeding dates in the three experimental sites
were equally divided into eight planting dates spaced at five-day intervals.

In an increasing order, yield levels across planting dates were general-
ly lower in Laguna, Iloilo and Pangasinan. Grain yield from Laguna, Iloilo and
Pangasinan ranged from 1.6 to 2.5, 3.6 to 4.5, and 3.9 to 5.1 tons/ha, re-
spectively. In Pangasinan and Iloilo, the effect of seeding date on grain
yield was not statistically significant. The Laguna yields were found signifi-
cantly different but not in an explainable pattern. The differences in
observations were attributed to water sufficiency under the flooded conditions
in Pangasinan and Iloilo which effected more or less uniform growth and develop-
ment during the critical reproductive stage. In Laguna, .a water stress effect
was more evident as indicated by variations in flowering dates, despite similar
emergence dates.

The pattern and extent of crop emergence in relation to rainfall variation
did not vary much in the three locations. Ninety percent emergence was attained
when an average of approximately 50 mm rainfall accumulated at the onset of the
rainy season. Implications of empirical cumulative probabilities of rainfall
accumulation in relation to DSR seeding dates was discussed. For maximum benefit
from early rainfall onset, DSR planting should be completed by dates based on
rainfall onset probabilities.

Crop emergence and yield response data obtained from the staggered
planting dates of this study provides useful base information on DSR establish-
ment strategies under variable rainfall onsets.

Paper presented at the 9th Annual Scientific Meeting of the Crop Science
Society of the Philippines, Iloilo City, May 11-13, 1978.
2/
-Research Assistant, Site Coordinators in Iloilo and Pangasinan,
Agronomist/Philippine CS Outreach iCoordinator, respectively; Cropping Systems
Program, IRRI, Los Bafos, Philippines.












INTRODUCTION


Establishment of dry-seeded rice (DSR) under either upland or

lowland conditions must be in accord with the local rainfall pattern.

At the farm level, upland crop establishment usually takes place after

the regular rainy season has started to effect good crop germination

and to reduce the risk of losing crop stand. However, field observations

under lowland conditions have indicated that by seeding after rains

commence, seedling emergence is adversely affected and yields are low.

Direct seeding ahead of the rainy season, under either lowland and

upland conditions, requires consideration of rainfall patterns and the

effects of early rainfall on crop performance. Once it begins, rainfall

should be adequate to promote fast seed emergence and rapid early vege-

tative growth, which are prerequisites to high yields.

The experiments reported here are part of a research effort to

identify rainfall pattern characteristics useful to select dates before

which rice can be planted in dry soil with an expectation of uniform

and successful emergence and satisfactory crop performance.


MATERIALS AND METHODS


The three experiments were laid out in three locations: Los

Bafos, Laguna; Manaoag, Pangasinan; Tigbauan, Iloilo. The treatment

design consisted of eight seeding dates spaced at 5-day intervals,

with the starting date chosen so that monsoon rains would usually

begin sometime before final plantings were made, i.e., so that some

planting would be made in wet but unpuddled soil.












INTRODUCTION


Establishment of dry-seeded rice (DSR) under either upland or

lowland conditions must be in accord with the local rainfall pattern.

At the farm level, upland crop establishment usually takes place after

the regular rainy season has started to effect good crop germination

and to reduce the risk of losing crop stand. However, field observations

under lowland conditions have indicated that by seeding after rains

commence, seedling emergence is adversely affected and yields are low.

Direct seeding ahead of the rainy season, under either lowland and

upland conditions, requires consideration of rainfall patterns and the

effects of early rainfall on crop performance. Once it begins, rainfall

should be adequate to promote fast seed emergence and rapid early vege-

tative growth, which are prerequisites to high yields.

The experiments reported here are part of a research effort to

identify rainfall pattern characteristics useful to select dates before

which rice can be planted in dry soil with an expectation of uniform

and successful emergence and satisfactory crop performance.


MATERIALS AND METHODS


The three experiments were laid out in three locations: Los

Bafos, Laguna; Manaoag, Pangasinan; Tigbauan, Iloilo. The treatment

design consisted of eight seeding dates spaced at 5-day intervals,

with the starting date chosen so that monsoon rains would usually

begin sometime before final plantings were made, i.e., so that some

planting would be made in wet but unpuddled soil.











2


Los Baios, Laguna. The experiment in Laguna was located in the IRRI

farm in an unbunded upland rainfed field on silty clay loam soil. For

initial land preparation, the field was rotovated with a large tractor

shortly after harvesting the preceding crop. The final rotovation to

further pulverize and level the soil was made by a small power tiller.

Furrows were set 25 cm apart by a "lithao"; seeds of IR36 were

then hand-drilled at 120 kg/ha. An application of 40 kg/ha each for N,

P205 and K20 was given as basal fertilization in rows. A topdressing

of 30 kg N/ha was given at 30 days after emergence; the same amount was

again topdressed at panicle initiation. Butachlor EC was sprayed at

1.2 kg a.i./ha on the furrows after a soaking rain or after seeding if

on moist soil; handweeding was done after weed sampling five weeks after

crop emergence. To control insects, Furadan 3G was applied at 1 kg

a.i./ha at planting directly in the furrows with the seed. Other

chemicals were applied at recommended dosages as needed to control

other pests.

The eight planting dates were April 20, 25, 30, May 5, 10, 15,

20 and 25. The five-day planting interval was chosen to provide a

better assessment of possible abrupt rainfall onset on seedling emergence

and early growth. The treatments were replicated four times in an RCBD.

Plot dimensions were 2m x 7m for three replications and 2m x 8m for the

fourth replication. The last replication was slightly larger, providing

an allowance for destructive root sampling at various growth stages of

the crop.










Tigbauan, Iloilo. The DSR experiment in Iloilo was conducted on a

bunded silty clay loam soil located in a rainfed lowland field. Plowing

was done with a carabao-drawn native plow shortly after harvesting

previous crop. A landmaster rotovator was employed for final levelling

and pulverization. Furrows at 25 cm intervals were made with a native

plow and IR36 was hand-drilled in these furrows at the rate of 120 kg/ha.

No weed control measures were employed nor was a prophylactic application

of insecticide used. Lannate and Azodrin, however, were sprayed after

flowering at recommended dosages and frequencies. Urea at a rate of

90 kg N/ha was applied in split doses. A basal application of 20 kg N/ha

was given by drilling the fertilizer material in the furrows prior to

seeding, 40 kg N/ha was topdressed at 26 days after crop emergence,

and 30 kg N/ha was topdressed at 57 days after emergence. Phosphorus

and potassium were not applied to the crop.

The eight planting dates were May 6, 11, 16, 21, 26, 31, June 5

and 10. These treatments were replicated four times in an RCBD, with

plots measuring 3m x 5m.


Manaoag, Pangasinan. The DSR experiment in Pangasinan was established

in a rainfed bunded lowland field. The field was plowed once, followed

by three passing of a landmaster rotovator. After the last rotovation

furrows were set at 25 cm apart by a lithao.

Nitrogen was applied at 20 kg N/ha applied as basal in the

furrows 30 kg N/ha as topdressing at 30 days after emergence and

20 kg N/ha at panicle initiation. To control weeds, Butachlor at

2.0 kg a.i./ha was applied after a germinating rain and handweeding

was done as needed three weeks after emergence. For insect control,

Thiodan was applied at 0.5 and 0.75 kg a.i./ha respectively on July 15

and August 19, 1977.












The eight planting dates were April 22, 27, May 2, 7, 12, 17,

22 and 27. These treatments were replicated four times in an RCBD.


RESULTS AND DISCUSSIONS


Grain yield

Yield data, emergence dates and rainfall distributions for the

three experiments are summarized in Figure 1. Maximum yields in all

experiments were obtained from seedings made just prior to heavy

rainfall. Highest grain yields from Pangasinan, Iloilo and Laguna were

obtained from plantings on May 12, June 5 and May 5, respectively.

However, yields were not significantly reduced by seeding earlier.

The treatment mean squares, s- and coefficients of variation
x

for the three experiments are shown in Table 1. Grain yield was not

significantly affected by seeding time in Pangasinan and Iloilo but

was found significant in Laguna. The experimental results appear

relatively reliable based on CV levels and are consistent among the

locations. Similar observations were found by Craufurd (1964) and

Dore (1960). The factors which caused the statistically significant

yield variation in Laguna are uncertain. A possible explanation of

the variance may be found in studies related to drought tolerance which

have shown that yield reductions are more substantial when moisture

stress is imposed during the reproductive stage than during the vege-

tative stage (IRRI Annual Reports, 1973, 1974, 1975). Note that

compared to Laguna, there was no significant yield variation across

planting dates in Iloilo and Pangasinan. Although the differences

in variability between locations may also be a reflection of the

distinctly different conditions under which the DSR crops were grown.











During the critical reproductive stage sufficient water was available

under flooded conditions in Pangasinan and Iloilo. In Laguna, water

stress effect was more evident as indicated by the variations on

flowering date (Table 4) despite similar emergence dates. A short

drought period occurred in August during flower initiation which could

have led to reduce yields on a few plots which had less available soil

moisture under the upland conditions.


Agronomic components


Data for several agronomic attributes are presented in Table 2

for Laguna and Iloilo. The number of productive tillers did not vary

significantly at different seeding dates in Laguna. Productive tillers

per meter of row ranged from 146 to 158 and the number of plants at 90

percent emergence ranged from 60 to 111 in Laguna. These attributes,

however, were not directly related to differences in grain yields.

In Iloilo, tiller count at harvest did vary significantly across planting

dates. Also yield levels were generally lower when tiller counts were

low, suggesting some degree of relationship. The correlation between

yield and tiller counts approached the 5% significance level.

Weed weights did not confer any consistent effects on yield. A

simple regression of yields on weed counts or weed weights in the three

sites produced significant negative and positive correlations for Iloilo

and Pangasinan data respectively, whereas no significant association

was found in the Laguna data, indicating that weeds are not a universal

problem with the suggested DSR method. Significant differences in weed

weights were observed in Iloilo and Laguna but weed counts did not

markedly vary in Pangasinan. Weed data was highly variable, as

indicated by the CVs.









6


Emergence and harvest data are summarized in Tables 4 and 5

for Laguna and Pangasinan, respectively. Isolated early showers

appeared to have little effect on germination and emergence. For

pre-rainfall plantings ninety percent emergence was attained within

a three-to four-day period (Figure 1). A ten-day difference to 50

percent flowering period was observed in Laguna which to some extent

caused variation in effective grain filling period and yields obtained.

For pre-rainfall plantings, maturity dates were more or less uniform

both in Pangasinan and Laguna.

No clear pattern was found between root weight and planting

date (Table 6). However, a significant positive correlation of 0.77

between root weight sampled three weeks after emergence and grain yield

was found. This relationship disappeared when root weight sampled at

six weeks after emergence were correlated with yields.

Although the root weight-yield relationship was lost by the

sixth week, perhaps because of problems associated with sampling a much

larger root volume, it appears that some of the yield variability was

due to differences in root development. Under upland conditions, root

volume differences may be more closely associated with slight soil

surface depressions which permit water accumulation and prolonged in-

filtration. The association between root growth, water enrichment,

and perhaps nutrient uptake, may explain some of the yield variation

found between planting dates.


Implications

The results of these experiments indicate that rice can be dry-

seeded in soil in advance of expected rainfall onset without substantial











yield reductions. The experimental results indicate that an accumulation

of 50 to 125 mm of rainfall, depending on the actual distribution, is

sufficient to trigger emergence and early growth. The empirical cumu-

lative probability curves in Figure 2 show that there are important

differences between locations, both in the rate of rainfall accumulation

and in the interval over which the rainfall onset is expected to begin.

In comparison to Iloilo, rainfall onset is more gradual and the interval

of onset dates is shorter under the Pangasinan climatic regime. Exami-

nation of rainfall onset data can aid in selecting dates by which DSR

planting should be completed. The distributions also suggest that

greatest advantage for DSR may be under climatic regimes similar to

that of Pangasinan. Once it starts, rainfall accumulation in Iloilo

occurs at a faster rate and therefore less time advantage is gained

between initial onset and the date by which soils could be puddled for

a transplanted crop.

There are several advantages to dry seeding early, namely,

(1) labor and power use can be spread out over longer period avoiding

the labor-power constraint associated with traditional transplanting

methods under rainfed rice culture, (2) more effective use can be made

of early season rainfall and (3) a better opportunity exists for

producing a second rice crop if the wet season rainfall pattern is

sufficiently long or an upland crop if it is short. The major dis-

advantage to early dry-seeding are the draft requirements necessary

for dry soil tillage and weed control problems. Selection of

appropriate conditions under which the DSR method should be tried

is important. Additional experiments are needed to substantiate the

results presented here relative to rainfall characteristics. Further













studies are needed on soil and tillage requirements, and other crop

management aspects which should make DSR a viable alternative to

transplanting.


CONCLUSIONS


This study was conducted to obtain information on rice yields

and rainfall characteristics associated with successful DSR establishment.

Results from experiments conducted at three locations suggest that DSR

planting can be completed late in the dry season but prior to rainfall

onset without significantly reducing yields. In all cases were plantings

occurred prior to rainfall onset, 90% emergence was reached within 3-4 days

after 50 mm of rainfall had accumulated. Tiller counts at harvest,

root weights three weeks after emergence, and weed counts were some of

the agronomic yield components associated with changes in yield level

for Iloilo, Laguna and Pangasinan, respectively, but none of these

factors appeared to be associated with rainfall characteristics.

The effect of weeds on yield was not consistent for the three

experimental sites. Significant negative and positive correlations for

Iloilo and Pangasinan, respectively, were obtained whereas no significant

relationship was found in the Laguna data. The conflicting relationships

imply that weeds are not a universal problem with the DSR technique.

Neither productive tillers nor number of plants per meter-row were

directly related to yields obtained in Laguna. In the Iloilo data,

there was a positive trend between productive tiller number and yield.

Emergence dates were not as variable as maturity days, especially

with reference to the last planting dates in Pangasinan and Iloilo.

Apparently, there was a shorter vegetative phase development in the













last Laguna planting but comparable grain filling period for the

other seeding dates.

The use of cumulative probabilities of rainfall accumulations

was discussed. The rate of rainfall accumulations and the interval

over which the rainfall onset is expected suggests dates after which

DSR seeding should be initiated and before which it should be completed.

The results reported are relevant considerations to make before

undertaking further experiments on DSR establishment techniques.

Additional studies on soil condition factors, tillage requirements,

methods of establishment and other cultural management practices as

well as further experiments to substantiate the results presented in

this paper, are needed to further assess the practicality of DSR in

cropping intensification.













LITERATURE CITED


Craufurd, R.Q. 1964. The relationship between sowing date, latitude,
yield and duration for rice (Oryza sativa L.) Trop. Agric.
(Trinidad) 41:213-224.

Dore, J. 1960. The relation of flowering and maturation period in
some Malayan rice to sowing date and latitude. Malayan Agric.
J. 43: 28-48.

International Rice Research Institute. 1974. IRRI Annual Report for
1973. Screening varieties for drought tolerance, p. 85-87.
IRRI, Los Bafos, Philippines.

International Rice Research Institute. 1975. IRRI Annual Report for
1974. Response of yield to soil moisture deficits at different
growth stages-field studies, p. 177-178. IRRI, Los Bafos,
Philippines.

International Rice Research Institute. 1976. IRRI Annual Report for
1975. Field performance of rices under upland culture-field
studies, p. 136 and 146. IRRI, Los Baios, Philippines.












Table 1. Significant comparison between yield data for Pangasinan,
Iloilo and Laguna.



Treatment MS s- CV
x


Pangasinan 652899ns 300 12.8

Iloilo 537695ns 371 18.5

Laguna 301041 159 15.1


Table 2. Average productive tillers and plant counts at harvest,
wet season, 1977.



Laguna Iloilo
Planting Ave. No. of No. of Seeding Tiller count
D a t e prod. tillers plants Date at harvest
per m- row per m-rowa/


April 20 157 60 May 6 110
25 146 70 11 112
30 157 66 16 103
May 5 153 72 21 100
10 153 83 26 92
15 150 82 31 91
20 158 69 June 5 108
25 157 111 10 131


Me a n 154 77 106
Trmt MS ns **
CV 11.9 12.3


a/No


statistical analysis.












Table 3. Weed weights/counts across planting
Iloilo and Laguna, Wet season 1977.


dates on DSR experiments for Pangasinan,


Pangasinan Iloilo Laguna
(counts/0.25m2) (Dry wt/0.25m2) (Dry wt/0.25m2)
Seeding (3 W A E) Seeding (30 DAE) eedng (2 W A E)
date (date date
Ga Sb Bc G B


April 22 7 2 4 May 6 33 April 20 10 5
27 9 0 6 11 30 25 7 1
May 2 6 1 3 16 29 30 21 5
7 9 1 5 21 41 May 5 9 1
12 8 8 3 26 24 10 29 4
17 9 9 2 31 40 15 12 2
22 11 5 1 June 5 15 20 50 4
27 1 0 0 10 25 25 66 11



Treatment MS ns ns ns ** *

s- 2,5 2.5 1.1 5.1 3.9 1.7
x
C V 67 154 72 35 31 81


a/Grass /Sedges


/Broadleaf
- Broadleaf














Table 4. Dates to 50 percent flowering, emergence and harvest dates of DSR,
Los Bafos, Laguna, wet season 1977.




Planting Date of 90% Date of 50% Harvest No. of days Maturity
Date emergence flowering date from 50% flower- date
ing to harvesting


April 20 May 26 August 14 Sept. 10 27 115

25 27 16 12 28 116

30 26 17 12 26 117

May 5 26 7 10 34 115

10 27 13 12 30 116

15 28 16 13 28 116

20 28 10 11 32 114

25 June 14 12 13 32 90











Table 5. Emergence and harvest dates and maturity days of lowland
DSR, Manaoag, Pangasinan, wet season, 1977.



Planting Date at 90% Harvest No. of days
Date emergence d a t e to maturity



April 22 May 25 September 19 118

27 25 19 118

May 2 25 19 118

7 27 20 117

12 27 20 117

17 27 20 117

22 29 21 116

27 June 4 21 110




a/
Table 6. Mean root weight and yield of upland DSR, Los Bafos, Laguna


Root Weight
Planting (gms/plant) Yield
Date
3 WAE 6 WAE t/ha


April 20 3.9 3.3 2.52

25 2.2 2.1 1.98

30 2.9 6.4 2.15

May 5 3.4 8.6 2.53

10 3.0 6.8 2.25

15 3.3 13.4 2.27

20 2.5 5.3 2.63

25 1.2 3.5 1.64


a/taken in replication 4 only.
taken in replication 4 only.








Pangasinan


Iloilo


Laguna


Yeld Yteld
..,,,., 8r"eece Si-l\ r Eme .gence Se.,ng Efr'l Qn c,
D.3.; :, D!e .>' Aci.al fRe:jtve Do (j l D:te t*(2 Acltua Relatuve Dat. Ix) Oat* ( '
(t Ij) I (-J (t.ha ) t l

A;,, 2- 4 5 L8 May 6 x 3.6 80 Apr 20 0


A, a0 50 97 My 11 x 4.2 92 Apr 25 x 0


Fv 2 a 0 49 95 May 16 x 4.0 88 Apt 30 x


., 7 0 16 90 May 21 x 0 3.7 81 May 5 x


r,,V 12 1 100 May26 .x 38 84 May 10 x 4


May 17 x 6 89 M.y 31 x 0 3.7 82 May 15


2,2 02 53 97 June S x 4.5 100 May 20 x


t:., 27 x 3) 75 June 10 x 4.5 99 May 25 x



7 -.--------- 70 70
S60oL 60
3- 50- 50 -
Io40 F 40 -
i-- 30 30
S20- 20


0 _- T-r-r T -- t- Id I- 0
22 2 12 22 11 6 16 26 5 1 55 1 25 4 14
URE L MAY Y JUNE MAY JUNEUNE

Figure 1 -frct of dcae of seedig and rainfall on emergence and yield of dry-seeded rice in Pangasinan (lowland),
il. .io (!:.'v: d) and agaua (upland). 1977 wet season.

1/ Date by wthc C0% of rr.ximum stcd had emerged ,determined by plant counts.
2/ Date by which full stands were ochiad, determined visually.


Y..Ih

It ha) h\,)

2.2 94


1.7 72


2.0 87


2.3 100


19 81


1.6 GO






1.9 81


II











075 1-- o,<'- -.'

75mm ,. ./ >
050 100 mm
50mm / / mm
/125 m



0.00 ,_ .,_ I \ I 1I111 I--
// ..





0.,25 4.0
110 .......... ...


50 mm ,. .

0 50 -100 mm
125 mm



.^*'^^ **^ <.
00ooo :-r-:^:-, i^" r L I I I I -- I I i- I I
15 20 25 30 5 10 15 20 25 30 5 10 15 20 25 30
Ai May I June ---

FirG 2 E-rr.,:'ic CL .i-."'.live probabilites of rainfall accumulations (50,75, 100 and 125 mm) using April 15 as the starting
cdal, for tv;o CS outreach sites.


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