Influence of site variables on performance of croppig pattern groups in Iloilo, paper presented at the 9th Annual Scientific Meeting of the Crop Scien

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Influence of site variables on performance of croppig pattern groups in Iloilo, paper presented at the 9th Annual Scientific Meeting of the Crop Scien
Magbanua, R. D.


Subjects / Keywords:
Farming ( LCSH )
Agriculture ( LCSH )
Farm life ( LCSH )


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Full Text


R.D. Magbanua, R.A. Morris and H.G. Zandstra-


For the past three years of cropping systems research activities
in a rainfed lowland rice area of Iloilo, it has been observed that the
performance of cropping patterns has been dependent on the combined
influences of landscape, water source class, soil texture and rainfall.
Cropping pattern groups consisting of two rice crops (rice-rice-upland
crop) have been found to fit in lower landscapes such as plains and
waterways. The rice-upland crop pattern group fits upper landscapes
(sideslopes and plateaus).

Cropping pattern productivity and intensity generally increase
with higher water source classes. Heavy-textured soils are more pro-
ductive than lighter-textured ones. The rainfall regime during the
crop year influences the establishment date and method of the first
crop, turnaround time between crops, productivity of the separate crops,
and the whole pattern groups. Modifications of crop management within
pattern groups, such as alternative establishment and tillage techniques,
can modify pattern group performance but are often restricted by the
ci resource capability of the farmers.

Paper presented at the 9th Annual Scientific Meeting of the
Crop Science Society of the Philippines, Iloilo City, May 11-13, 1978.

Iloilo Site Coordinator; Philippine Outreach Coordinator and
Agronomist; Head, respectively, Multiple Cropping Department, The
International Rice Research Institute, P.O. Box 933, Manila, Philippines.


The IRRI-BPI Cropping Systems Research in Iloilo was initiated

in early 1975, with the main objective of identifying and developing

possible alternative technologies with which crop production in rainfed

and partially irrigated areas could be intensified. The research area

falls in a 2.3 climate pattern characterized by 5 to 6 consecutive

wet months of more than 200 mm per month and 2-4 dry months with less

than 100 mm per months (IRRI, 1976). The land units and soils are

common in the rice growing areas of the region. The research area is

essentially rainfed; however, an increasing portion of the area is

receiving partial irrigation of varying durations beyond the normal end

of the wet season.

Cropping Systems Research methods consisting of (1) site selection,

(2) site description, (3) designing, testing and evaluation of improved

cropping patterns, (4) agricultural economic studies, and (5) component

technology trials have been discussed previously (IRRI, 1976; Palada et

al, 1975; Magbanua, et al, 1976; Zandstra, 1976). The main functions

of cropping systems outreach sites are to develop economically sound

rice-based cropping patterns for defined environments. Based on infor-

mation collected through the describe-design-test sequence during the

past three years, the performance of the different groups of cropping

patterns have been observed to vary within the site according to several


Results of cropping pattern trials conducted under both experi-

mental and farmer's management conditions, indicate that for a given

rainfall regime, the performance of pattern groups or component crops

of patterns, varies according to influences of within site variables.

The important within-site variables are landscape, soil textural

types, and water source class. The results of the first year (1975-76)

of cropping pattern trials prompted the cropping systems researchers

(Moorman and Tinsley, 1976 and Raymundo, 1977) to classify landscape

and soil-related factors as important modifiers to water regimes.

Hypotheses and concepts were formulated as to the differences in the

land-related factors that affect water regimes and therefore pattern


The landscape of Iloilo test site has been broken into five

classifications, namely: knoll (or summit), plateau, sideslopes, plains

and waterways (or bottomlands) (Figure 1). The detailed description

of these landscape positions have been outlined elsewhere (Moorman,et.

al, 1976; Tinsley, 1976; Raymundo, 1977). The soil textural classes

were placed into heavy, medium and light groups. The four water source

classes were based on the duration and availability of irrigation water

after the end of the wet season (Table 1). Water availability is mainly

a function of the field's relative elevation and proximity to principal

irrigation systems.

Aside from these physical determinants, variability of rainfall

greatly influences the performance of the cropping patterns. Rainfall

variability may arise from variation in the time of onset, variation

in total rainfall over selected intervals,and variation in rainfall

during the transition from wet to dry season. Figure 2 shows the

deviation of the 1975-78 rainfall from the long term average.


The purpose of this paper is to summarize the performance of

dominant pattern groups introduced and tested in Iloilo outreach over

the past three crop years, as influenced by the dominant within-site



Available data and other relevant information from the 1975-78

cropping pattern trials were examined. The agronomic performance of

the different pattern groups expressed in terms of crop yields, crop

failures and farmers' reactions were evaluated in relation to the land

units and other variables in the test sites. The pattern performance

data was obtained from fields of approximately 0.1 ha in area managed

by farmer-cooperators' who have agreed to grow the patterns as designed.

All power and labor inputs were supplied by the farmer but material

inputs were supplied by the cropping systems project.


Groups of Cropping Patterns Studied

Table 2 presents the breakdown of the cropping patterns tested

during the 1975-.78 crop years. There were three groups of cropping

patterns initially designed during the first years. These were mainly

modifications and improvements of the farmer's traditional patterns

of the area. On the bases of the results of the 1975-76 cropping studies,

variables such as landscape, soil texture, and position of the paddies

within the landscape were considered in the refinement of the 1976-77

pattern groups. Generally, the cropping patterns designed for the


second year were intensified over the first year's patterns. The

proposed cropping pattern groups were further refined in the third

year by dropping crops and cropping patterns that were found to be

unadapted thereby concentrating only on promising pattern groups.

Performance of the pattern groups

Based on results obtained during the past three years, pattern

group performance as influenced by site variables, is summarized in

this section.

Influence of the rainfall. Over the 1975-78 period, the

establishment of the crops in different pattern groups has been

influenced by rainfall distribution for the crop year. As an example,

the adaptability of green corn before rice in lowland fields has been

a function of the behavior of rainfall during the early wet monsoon

period. This crop has not been feasible when rains start abruptly

during April and May (i.e. 1975-76 and 1976-77) or when rains are

delayed (1977-78).

The choice of the establishment technique for rice has also

shown a dependence on rainfall. Farmers opted to wet-seed rather than

dry-seed when water rapidly accumulated in paddies as a result of

abrupt rainfall. The behavior of rainfall during the tail end of the

rainy season has a pronounced influence on the performance of the

second rice crop and the establishment of upland crops. Because of

the early onset of dry season in all three crop years, yield per-

formance of the second rice crop or upland crop has often been poor.

The timing of establishment of the second rice crop in the rice-rice

pattern depends on rainfall during the turn-around time. When rainfall

during the turn-around period is high, farmers are able to puddle their

fields rapidly to establish second rice crops quickly. On the other

hand, upland crop establishment benefits from low rainfall during this

turn-around period because fields can be drained so that land preparation

and upland crop planting can proceed under aerated conditions.

Influence of landscape and soil-related factors. The successful

green corn production before rice depends on selection of paddies

situated at higher elevations (upper paddies and sideslopes and plateaus)

and with lighter-textured soils, hence, with good surface and internal

drainage. All the corn plots successfully grown during two crop years

were located in this condition. Water was found to accumulate rapidly

on lower landscape positions (low bunds of plateaus and plains, and

waterways), especially on fields with heavy-textured soils. The early

accumulation of water on low landscapes having heavy-textured soils,

prohibited green corn successful production.

The choice of establishment technique for rice also depends on

the position of the paddy in the landscape. In any crop year, farmers

were found to wet-seed the earliest rice crops on lower positions (plains,

low plateau and waterways) with heavy-textured soils. Since water

accumulated rapidly in these paddies, a loss of the stand would be

incurred if the DSR establishment were used. During the crop year

1976-77, 33 out of 36 DSR fields were shifted to WSR (Table 3). During

crop year 1977-78, six of the seven DSR crops were those grown on

plateau and sideslope positions where water took longer to accumulate

(Table 4).

The timing of the first crop also varied across the different

landscape positions (Table 5). During the crop year 1977-78, fields

situated in the bottomlands were established the earliest, about third

week of June (Week 25-26), while latest establishment occurred on the

sideslopes. The timing of first crop establishment has important

implications on the possibility of planting two rice crops. In general,

it has been possible to successfully grow two rice crops in low and

flat areas such as bottomland or plains where the establishment of the

first crop is early, while it is risky to grow the patterns containing

two rice crops on higher and rolling landscape positions where the

establishment of the first crop is expected to be delayed.

The productivity of the rice crops in patterns varied with land-

scape position. Productivity increased in the lower landscape positions.

The differences were not pronounced during the first rice crop (Table 6);

however, during the second crop the differences varied greatly (Table 7).

Furthermore, the failure rate increased as elevation increased. Yields

were also reduced using WSR establishment because the crop was exposed

to great stress late in the season. Similar results were found during

the 1976-77 crop year but the effects were not as pronounced because

early rainfall allowed the first 1976-77 crop to be planted a month

sooner (Table 8).

Influence of water source classes. The duration of water supply

in the plots after the end of the wet season also affected the performance

of rice crops as shown in Tables 9 and 10 for 1976-77 and 1977-78. Rice

yields as well as the possibility of additional crop increased in the

higher water source classes. Many failures occur in the lower classes.

Differences in cropping pattern performance are an expected

effect of the paddy hydrologic condition or water regime. During the

crop year 1976-77, an attempt was made to reflect this condition as

the number of non-flooded or stress days. As shown in Table 11 the

number of non-flooded days varied with the different landscape positions.

The differences between positions and crops were pronounced. Yield

significantly decreased with an increasing number of non-flooded days

(Figure 3).

Recently a flooded status (FS) concept has been used, which is

basically the reverse of the non-flooded concept, to indicate water

availability for lowland rice. In an analysis by Morris et al (1978),

FS were counted over approximately a seven-month period whether or not

a crop was in the field. As illustrated in Figure 3, water regimes were

modified by landscape, soil texture, and water source class within the

landscape. Bund position or relative elevation within the landscape

class has been found to be important only on the sideslopes. Because of

similarities between FS regimes in several landscapes, cropping pattern

yields were averaged over these landscapes and are presented in Table 8

for units with heavy-textured soils. The rice-rice-upland crop pattern

group performed better on lower rainfed landscape positions such as plains

or waterways, and on irrigated plateaus, than on rainfed sideslopes and

plateaus. Upland crops were found to perform well on upper landscapes

(sideslopes, upper plateaus). Production of the pattern group containing

three rice crops was possible only in plateaus and plains with water source

classes II and III. The rice-upland crop pattern was found to perform

well on all land units except those with partial irrigation one or more

months beyond the normal end of the wet season. Land units with medium-

and light-textured soils were generally poorer performers than heavy-

textured units, especially with regards to second rice crops. The

average yield of the first rice crop over all medium- and light-textured

soils was 4.9 t/ha which is 0.5 tons less than yields obtained on

heavy-textured land units.


Based on the preceding discussions, relevant conclusions can

be outlined as follows:

1. Landscape, water source and texture have been found to be

important factors that influence both agronomic and economic performance

of the cropping patterns.

2. Aside from these fixed determinants, cropping pattern

performance as well as cropping strategies of the farmers radically

change from year to year in reaction to variability in the distribution

of rainfall.

3. In rainfed areas, two rice crops can be successfully grown

on lower landscape positions such as plains and waterways, especially

on heavy-textured soils.

4. Rice-upland crop patterns fit best in the upper landscape

position (sideslopes and plateau).

5. Upland crops have generally not performed well following either

one or two rice crops, under farmer-cooperators management. This may

be due to the early cessation of rains experienced in the past three

years and to the effect of a previously puddled soil which dries to a

very unfavorable physical environment for the root systems of upland


6. Where short-duration partial irrigation exists, farmer-

cooperators have been able to produce additional rice crops with

yields sufficient to make rice-rice and rice-rice-upland crop patterns

more promising than rice-upland crop patterns.

7. Early establishment techniques for the first crop and turn-

around time reductions between crops are important factors which can

modify the influence of land-related variables on pattern performance.

8. Flexibility in the design of the cropping patterns to allow

the farmers to react to unpredictable conditions, is important in

cropping pattern introduction.


International Rice Research Institute. 1973. Annual Report for 1972,
IRRI, Los Bafos, Laguna, Philippines.
International Rice Research Institute. 1974.
An Agro-Climatic Classification for Evaluating Croping Systems
Potentials in Southeast Asian Rice Growing Regions, Los Baios,
Laguna, Philippines.
International Rice Research Institute. 1976. Annual Report for 1975,
IRRI, Los Baios, Laguna, Philippines.

International Rice Research Institute. 1977. Annual Report for 1976,
IRRI, Los Baios, Laguna, Philippines.

Magbanua, R.D., N.M. Roxas and H.G. Zandstra. 1977. Comparison of the
turn-around period of the different groups of patterns in Iloilo.
A paper presented at the 8th CSSP Scientific Meeting, MSAC,
La Trinidad, Benguet, May 5-7, 1977.

Magbanua, R.D., N.M. Roxas, M.E. Raymundo and H.G. Zandstra. 1977.
Testing of Rainfed Lowland Rice Cropping Patterns in Iloilo,
Crop Year 1976-77. IRRI Saturday Seminar, June 18, 1977.

Moorman, F.R., R.L. Tinsley and N. van Breemen. 1976. Notes on a Visit
to Multiple Cropping Project Area in Iloilo. (Mimeographed).

Morris, R.A., R.D. Magbanua, H.C. Gines and R.L. Tinsley. 1978. The
Dynamics of Water Regimes in Iloilo and Pangasinan Land Systems.
IRRI Saturday Seminar, March 18, 1978.

Palada, M.C., R.L. Tinsley and R. R. Harwood. 1976. Cropping Systems
Agronomy Program for Rainfed Lowland Rice Ares in Iloilo. IRRI
Saturday Seminar, April 24, 1976.

Raymundo, M.E. 1977. An Approximation of the Soils and Immediately
Associated Physical Determinants for Rice Based Cropping Systems
in the Tropics. (Mimeographed).

Tinsley, R.L. 1976. Geomorphic Classification of Iloilo Cropping Systems
Research Area. (Mimeographed).

Zandstra, H.G. 1977. Cropping Systems Research for the Asian Rice Farmers.
Paper presented at the Soils and Rice Symposium, September 21-25,
1976, IRRI, Los Baios, Laguna, Philippines.

Table 1. Description of the different water source classes
occurring in Iloilo test site.



Strictly rainfed. No supplemental irrigation.
Depends entirely on rainfall for water

Partially irrigated. With supplemental irri-
gation at least one month after the end of the
rainy season.

Partially irrigated. With supplemental irri-
gation 1 to 2 months after the end of the rainy

Fully irrigated. Has available water 11 or more
months of the year.

Table 2. Summary of the pattern groups tested in Iloilo test sites.
1975-1978 crop years.

Number of Plots
Pattern Groups 1975-76 1976-77 1977-78

1. Corn-Rice 10 -

2. Corn-Rice-UC 10 20

3. Rice-Rice 13 -

4. Rice-Rice-Rice 13 -

5. Rice-Rice-UC 60 28

6. Rice-UC 84 24 48

7. Corn + Rice-UC 4 -

8. Corn-UC-UC 6 -

Total 107 116 96


Table 3. Summary of the cropping pattern components distributed
to proposed, shifted, actual, cancelled and failures
during the first crop. Iloilo 1976-77 crop year.

Pattern Number of fields
Component Proposed Shifted Actual Cancelled Failed

DSR 37 33 WSR .4 2

WSR 34 1 TPR 89 -

TPR 26 17 WSR 8 1 -

Corn 16 6 WSR 9 1 2

Corn + Rice 4 0 4 1 Corn
1 Rice

Table 4. Summary of the cropping pattern actually grown during the
first crop. Iloilo 1977-78 crop year.

Pattern Landscape Position
Component Bottomland Plain Plateau Sideslope

GC -

DSR 1 4 2

WSR 10 25 22 12

TPR 2 4 14

Total 20 28 30 28 (96)

Table 5. Timing of first crop establishment in the different
landscape positions. Iloilo 1977-78 crop year.

Landscape Time range Average time
position (Week No.) (Week No.)

Bottomland 24 28 25.5

Plain 25 31 27

Plateau 25 31 27

Sideslope 25 32 28.5

Table 6. Yield performance of the first rice crop (R1) in the
different landscape positions. Iloilo 1977-78 crop year.

Cropping Landscape Position
Cropping Bottomland Plain Plateau Sideslope

Rice -Rice2-UC


GCa-Rice -UC


6245(10) 5187(13) 4871(4)


5100(11) 5189(16) 4883(17)

6356(4) 5128(10) 5039(6)





a/All of the green corn plots were not actually planted.

( ) Number of fields.


Table 7. Average productivity of the second rice crop (WSR/TPR)
in different landscape positions (kg/ha). Iloilo Crop
Year 1977-78.

Method of Landscape Position
Establishment Bottomland Plain Plateau Sideslope

WSR 2239(4)a 1213(9)b 1012(2)a

TPR 2291(5)a 2423(9)a 0()a

Mean 2265 1818 1012

aExcluding 1 failure

Excluding 6 failures

Note: Number in the parentheses represent the number of

Table 8. Summary of cropping pattern performance in heavy-textured
land units, by pattern groups. Iloilo CY 76/77.

Yield (t/ha)a
Land units Pattern Group 1 2 3
1 2 3

High & medium side-
slopes, rainfed

Low sideslopes &
plateaus, rainfed

Plain & ~aterway,

Plateau & plain,
irrigation I

Plateau, irrigation

R-R-UC (5)

R-UC (6)

R-R-UC (23)

R-UC (2)

R-R-UC (6)

R-R-UC (11)

R-UC (2)

R-R-R (7)

R-R-UC (9)











a/Yield of upland crops is on a relative yield basis, with
CP = 1.72 t/ha = 100; S = 8.33 t/ha = 100; M = 1.20 t/ha = 100. These
were the highest yields obtained in any of the cropping pattern trials,
and are believed to reflect the maximum performance obtainable by
farmer-cooperators. Data from patterns which included SB were not
included in the relative yield computation because SB is not locally
adapted due to the high qnd uncontrollable levels of insects which causes
low yields.

/ The integer after the slash is number of patterns in which
a UC was not attempted.

( ) Number of observations per pattern group.

Table 9. Difference in average productivity of the rice crops as
affected by water source classes (kg/ha). Iloilo 1976-77
crop year.

Rice Crop




Water Source Classes

4819 (48)









4887 (22)


3464 (4)

5559 (10)

4193 (11)

3543 (10)

aExcluding 8 failures


CExcluding 1 failure

Table 10. Productivity of first rice crop in the different water
source classes. Iloilo 1977-78 crop year.

Water Management Number of Yield
Classes Field (kg/ha)

.I (Strictly rainfed) 91 5140

II (Partially irrigated) 5 7223

Difference 2083**

** Highly significant difference based on "t" test.

a Description of the different water source classes is
outlined in Table 1.

Table 11.


Number of non-flooded days on first and second rice
crop in the different landscape positions. Iloilo
1976-77 crop year.

Number of Non-flooded days1
First crop Second crop

Plain 5.5 16.8

Plateau 3.2 23.4

Sideslope 19.7 26.5

In rice it is considered a day in which there is zero
reading in water level. It is reckoned three days after the
consecutive zero reading.

.";.;::"~; Loamy texture or
: non-expanding clay

( I) Pluvic, (2) Fluxic,

Figure 1.

(3) Fluxi-cumulic, (4) Cumulic, (5) Cumulo-delugic.

Schematic presentation of geomorphic and pedologic conditions
in Iloilo outreach site. (Source: M.E. Raymundo, 1976)


Rainfall (mm)

Figure 2.

Comparison of the 1975-1978 monthly rainfall with the
25-year average. Oton and Tigbauan, Iloilo.

y= 4949.0 35x
r= -0.6001**
n = 73-/

Number of Non-flooded days

The relationship between the number non-
flooded days and grain yield of the second
rice crop. Iloilo 1976-77 crop year.

/Observations taken across landscape positions
and water source classes.

8000 -

6000 -

4000 -


Figure 3.

FS per week


b I^i l Mx~

Rtonfll (mrn/gk)

19 23 27 31 35 39 43 47

Figure 4

51 19 23 27 31 35 39 43 47 5

Weekly total rainfall and estimated FS
regimes for 8 heavy-textured rainfed and
irrigated Iloilo land units, weeks 19 to
51, 1976.

nP/ohon I
hrI I t j


rkf j
.J~~~~p jrl ^{ In~z~



9 23 27 31 35 39 43 47 51