• TABLE OF CONTENTS
HIDE
 Introduction
 Pangasinan
 Iloilo
 Conclusion
 Tables






Title: Dynamics of water regimes in Iloilo and Pangasinan land systems (IRRI Saturday Seminar, March 18, 1978)
CITATION PAGE IMAGE ZOOMABLE PAGE TEXT
Full Citation
STANDARD VIEW MARC VIEW
Permanent Link: http://ufdc.ufl.edu/UF00055434/00001
 Material Information
Title: Dynamics of water regimes in Iloilo and Pangasinan land systems (IRRI Saturday Seminar, March 18, 1978)
Physical Description: Book
Language: English
Creator: Morris, R. A.
Magbanua, R. D.
Gines, H. C.
Tinsley, R. L.
Publication Date: 1978
 Subjects
Subject: Farming   ( lcsh )
Agriculture   ( lcsh )
Farm life   ( lcsh )
 Notes
Funding: Electronic resources created as part of a prototype UF Institutional Repository and Faculty Papers project by the University of Florida.
 Record Information
Bibliographic ID: UF00055434
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.

Table of Contents
    Introduction
        Page 1
    Pangasinan
        Page 1
        Page 2
        Page 3
        Page 4
        Page 5
        Page 6
    Iloilo
        Page 7
        Page 8
        Page 9
    Conclusion
        Page 10
        Page 11
    Tables
        Page 12
        Page 13
        Page 14
        Page 15
        Page 16
        Page 17
        Page 18
        Page 19
        Page 20
Full Text




IRRI Saturday Seminar
March 18, 1978

The Dynamics of Water Regimes in Iloilo and
Pangasinan Land Systems


R.A. Morris, R.D. Magbanua, H.C. Gines, and RL. Tinsley*


INTRODUCTION


Cropping systems research methods prescribe a describe-design-
test sequence to be used in site-related studies to develop improved
rice-based cropping patterns for defined environments (Zandstra, 1976).
The method assumes a set of agronomic and economic performance cri-
teria established prior to the testing phase. At different research
steps, agronomic and economic criteria can be used separately, but in
the final evaluation of a pattern, both economic and agronomic per-
formance should be considered. The cropping pattern's domain of
adaptation should be specified simultaneously for obvious reasons.

In application, however, it is futile to carry pattern evalua-
tion beyond gross agronomic considerations if it is apparent that an
attempt has been made to grow a pattern outside its domain of adapta-
tion. However, the domain of adaptation is generally not fully
recognized and must be investigated. Thus, studies to determine
pattern performance and to specify pattern adaptation domains will
usually proceed concurrently, as they have in the IRRI-BPI Outreach
sites in Pangasinan and Iloilo. In the first year of research at
these sites, researchers began to hypothesize differences in land-
related factors which affected pattern performance (IRRI, 1975; IRRI,
1976). This seminar paper examines the hypotheses implicit in the
early division of the Pangasinan and Iloilo sites into complexes based
on land-related factors. To examine the hypotheses, the behavior of
flooding regimes and the performance of cropping patterns are exa-
mined as logical deductions from the implied hypotheses.


PANGASINAN


Taxonomically, most soils at the Pangasinan site fall within
the Eutropept Great Group. The soil pH ranges between 6.7 and 7.9,
with a raw mean of 7.4, Clay loam is the modal surface soil texture.
Using a landform classification proposed by Desaunettes (1977), the
-------1--------1------


Agronomist; Site Coordinator, Iloilo Outreach Site; Site Coor-
dinator, Pangasinan Outreach Site; former Visiting Scientist, Cropping
Systems-Program, -The-International Rice Research Institute, P.O. Box
933, Manila, Philippines.








IRRI Saturday Seminar
March 18, 1978

The Dynamics of Water Regimes in Iloilo and
Pangasinan Land Systems


R.A. Morris, R.D. Magbanua, H.C. Gines, and RL. Tinsley*


INTRODUCTION


Cropping systems research methods prescribe a describe-design-
test sequence to be used in site-related studies to develop improved
rice-based cropping patterns for defined environments (Zandstra, 1976).
The method assumes a set of agronomic and economic performance cri-
teria established prior to the testing phase. At different research
steps, agronomic and economic criteria can be used separately, but in
the final evaluation of a pattern, both economic and agronomic per-
formance should be considered. The cropping pattern's domain of
adaptation should be specified simultaneously for obvious reasons.

In application, however, it is futile to carry pattern evalua-
tion beyond gross agronomic considerations if it is apparent that an
attempt has been made to grow a pattern outside its domain of adapta-
tion. However, the domain of adaptation is generally not fully
recognized and must be investigated. Thus, studies to determine
pattern performance and to specify pattern adaptation domains will
usually proceed concurrently, as they have in the IRRI-BPI Outreach
sites in Pangasinan and Iloilo. In the first year of research at
these sites, researchers began to hypothesize differences in land-
related factors which affected pattern performance (IRRI, 1975; IRRI,
1976). This seminar paper examines the hypotheses implicit in the
early division of the Pangasinan and Iloilo sites into complexes based
on land-related factors. To examine the hypotheses, the behavior of
flooding regimes and the performance of cropping patterns are exa-
mined as logical deductions from the implied hypotheses.


PANGASINAN


Taxonomically, most soils at the Pangasinan site fall within
the Eutropept Great Group. The soil pH ranges between 6.7 and 7.9,
with a raw mean of 7.4, Clay loam is the modal surface soil texture.
Using a landform classification proposed by Desaunettes (1977), the
-------1--------1------


Agronomist; Site Coordinator, Iloilo Outreach Site; Site Coor-
dinator, Pangasinan Outreach Site; former Visiting Scientist, Cropping
Systems-Program, -The-International Rice Research Institute, P.O. Box
933, Manila, Philippines.










- 2-


Pangsinan land system- is composed of flat plains of a river terrace
sub-system (P.3.1) and levees (A.2.6) of an alluvial sub-system.
The rainfall distribution at the site normally contains 3-4 months
with total rainfall exceeding 200 mm (including one month during which
rainfall exceeds 500 mm) and 5-6 months with less than 100 mm total
rainfall.

Cropping systems researchers have divided the Pangasinan site
area into several complexes (IRRI, 1976; Herrera et al., 1975; Gines
et al., 1977). A major division between complexes has been based on
deep versus shallow water table depth. Further divisions have been
based on differences in soil texture, water source and relative eleva-
tion. Relative elevation simply refers to difference between fields
located in waterways (i.e., broad natural occurring drainage ways)
and in non-water ways. To a casual observer, the landscape appears
rather level, grading away slightly from river levees to occasional
deeply dissected creeks into which waterways drain.

Although a hypothesis that the complexes affect cropping pattern
performance has not been formally stated previously, it is apparent
that the complexes have been perceived to constitute different domains
of pattern adaptation, as indicated by the.distribution of designed
patterns. As logical deductions from this implied hypothesis, dif-
ferences in complex characteristics such as flooding regimes, changes
from designed to implemented patterns and differences in pattern crop
performance would be expected to vary according to complex. If the
characteristics are found to behave in accordance with the deductions,
the implied hypothesis would be supported. For the evaluation, daily
flooded status (FS), crop yields, and changes from designed to imple-
mented patterns, were examined, using data collected in CY 76/77.
Alos, the effect of water table depth (deep and shallow), relative
elevation (waterway and non-waterway) and water source class
(rainfed, partially irrigated, free-flowing well) have been examined
over the season to better understand the role of each factor.


Flooding regimes. As an indication of water availability for
lowland rice, a stress day (SD) concept has been effectively used by
IRRI scientists in the past (IRRI, 1976; IRRI, 1972), In the analy-
sis presented here, a flooded status (FS) concept has been used which
is basically the reverse of the-SDceoncept, but with two important
differences. An FS is taken as any day on which there is standing



Although used rather loosely here, the term land system is
meant to denote a naturally recurring pattern of land units, A land
unit is an area which is homogenous with respect to land form, soil
characteristics and hydrological features, Land use, agronomic prac-
tices and crop performance would be relatively uniform with a land
unit.









-3-


water on the field, whereas SD is taken as any day beyond three
successive days during which there is no standing water on the field.
The other difference lies in the application of the two concepts.
For this analysis, FS have been counted over approximately a seven-
month period, whether or not a crop was in the field, while SD have
been counted over a period when a crop was actually grown. Thus in
this analysis, the FS concept has been used to indicate the duration
over which standing water has been kept on the field. Such charac-
teristics as the rapidity of FS increase at the beginning of the sea-
son, the reliability of FS over the season and the rate of FS decline
at the end of the season are important factors which affect pattern
performance and thereby influence the domain of pattern adaptation.

In the analysis, 13 separate models were computed, using the
number of FS in a 3-week interval as dependent variables and the same
set of land-related classification facrors ad independent variables.
The dependent variables were obtained summing the number of observed
FS in weeks 1 to 3, in weeks 3 to 5, in weeks 5 to 7, and so forth
starting with May 26, 1976. The one-week overlap was incorporated
to reduce the effect of farmer's field operations, such as drainage
prior to harvesting, on the number of FS observed,

The land-related factors which have been found to influence FS
regimes are water table depth class, water source class within water
table depth class, and relative elevation within the water table
depth and water source classes. Figure 1 presents estimated FS fre-
quencies for 9 land units for a 27-week period. Smooth curves have
been drawn through the 13 estimates. An inspection of Figure 1 indi-
cates water table depth was the major factor differentiating land
units; the factor divides the area into two sectors: deep water table
(Lipit Pao) and shallow water table (Caaringayan).

The major differences .between shallow and deep water table
land units, as characterized by the FS regimes, were (1) an early
increase in FS, and (2) a broader interval of peak FS frequencies in
the shallow compared to deep units. Much less rainfall is required
to recharge the subsoil and the saturated soil sub-strata retards
deep percolation losses in the shallow units. By comparison, it is
apparent that substantial early rainfall was used to recharge the deep
water table units. The soils in the deep water table sector are very
permeable, and rainfall rapidly infiltrates and percolates to deep
soil layers. It is also apparent that the local irrigation system
had no significant impact on FS regimes, either early or late in the
wet season. Moreover, the main irrigation canal runs along a river
levee before its water enters the fields. Therefore, fields close
the irrigation canal which are generally partially irrigated, tend to
have deeper water tables and to be faster percolating than the lower-
lying fields further from the canal. Furthermore, the lower fields
also receive run-on from higher fields, These two factors help to
explain the slightly higher FS frequencies on rainfed fields in compa-
rison to partially irrigated fields,









-4-


Fields located within relative depressions or waterways did
not have greatly modified FS regimes as had been postulated, al-
though lower units under rainfed conditions had slightly prolonged
FS regimes as rainfall declined.

By contrast, within the shallow water table sector, water
source differences were clearly expressed. The major irrigation
difference arose between land units near free-flowing well and rainfed
or partially irrigated units. However, the partially irrigated units,
in comparison to rainfed units, had higher FS frequencies toward the
end of the wet season. A comparison between the non-waterway land
unit FS regimes indicates that the lower positions had higher FS
frequencies, especially under rainfed conditions situations as was
noted in deep water table fields. In partially irrigated fields the
FS regimes were more favorable as the dry season was entered, although
the frequencies were far from ideal.

Soil texture has also been postulated as a factor modifying FS
regimes. However, eatly models indicated that texture was less
important overall than relative elevation differences. Therefore,
soil texture was abandoned as an explanatory variable so that model
degrees of freedom would be reduced. However, composite FS estimates
from an early model which did include the textural class of the se-
cond soil horizon as an independent variable, are presented in Figures 2
and 3 for the two land units having the greatest number of observations.
The estimates in Figure 2 are from rainfed, non-waterway deep water
table land units, and in Figure 3, from partially irrigated, non-water-
way shallow water table land units. In both figures, lighter tex-
tared classes were combined to form Set II, whereas the heavier
textured classes made up Set I. A comparison of the estimates indi-
cates that soil texture did alter the regimes as expected, ie.,
greater average FS frequencies over the season for the heavier soils.
However, the major difference between heavy and light texture in the
deep water table units occurred during the rise to maximum FS frequen-
cy, whereas the effect in the shallow land units was more general
over the period analyzed.

Several model statistics are presented in Table 1 for the 13
Pangasinan models. R2 started at a high level and decreased with
minor variation through Models 4 to 8, which correspond to the
period of maximum FS frequencies. R2 again increased over the last
6 models. Except in Model 4, intercept values steadily increased
to a maximum in Model 8. Total SS decreased to Model 8, than in-
creased. Model 4, which has a lower than expected R2, corresponds
to the reduction of FS frequencies at week 8 which was preceded by
an interval of low rainfall. The general behavior of Total SS,
Model SS and intercept values reflect the influence of rainfall
distribution on FS, especially after land units have been recharged,
The extra SS suggest that water table depth was the dominant factor
explaining the differences between land units, although its importance









-5-


was greatest during the first three-quarters of the period examined.
Water source class played a moderate role in the early weeks, minor
in the middle weeks and major in the last weeks, as indicated by
Models 1-4, Models 5-6 and Models 9-13, respectively. However, the
impact of water source was important only in the shallow water table
sector. Relative elevation played a moderate role as rainfall de-
clined, as indicated by Models 7 to 10. Because of the model struc-
ture and the distribution of the data points, conclusions about the
dynamic aspects over the season as suggested by the extra SS must be
considered tentative although they behave as expected.

Changes in patterns. Table 2 shows pattern group distribution
according to water table depth and water source (rainfed vs. partial
irrigation). The distributions are for cropping pattern groups as
designed and as implemented. As the CY 76/77 season commenced and
the factors which control pattern adaptation became more obvious,
there was a shift to more R-UC and less GC-R-UC and R-R-UC patterns
in the deep water table sector; in the shallow water table sector,
the shift was towards more intensive patterns. These pattern.shifts
reflect realizations that water would be a less limiting factor in
the shallow water table sector. Under rainfed conditions, across
both water table classes, fields were shifted out of R-R-UC and into
R-UC patterns. Initially, 46% of the R-R-UC patterns were designated
for rainfed fields, but upon implementation only 24% were grown under
rainfed conditions. For the R-UC group the shift was reversed; 41%
were designed for rainfed conditions whereas 52% were implemented.
Although the changes in pattern distribution are not overwhelming,
they are in agreement with expectations. There was a shift toward
more intensive patterns in the shallow water table sector and in
partially irrigated units. An evaluation of the performance of the
implemented pattern groups is presented in the next session,

Pattern performance. Because soil texture and relative elevation
effects were of minor importance, pattern performance has been summa-
rized only by water table depth and water source factors (Table 3).
A comparison of average rice yields in the different rainfed and
partially irrigated land units showed that yields of patterns contain-
ing single rice crops (R-UC and GC-R-UC) were not greatly different
between land units. The rice component of both these patterns co-
incides with maximum FS intervals as depicted in FS frequency diagrams
for Pangasinan. The rice yields for single rice pattern groups grown
in the deep water table units averaged 3.6 and 3,2 t/ha for rainfed
and partially irrigated units, respectively, In the shallow water
table sector, yield averages for the same crops were 3.1 and 3.4 t/ha
for the rainfed and partially irrigated units, respectively,

Between the deep and shallow sectors, there were no distinct
differences in the yields of first rice crops in R-R-UC patterns,
Within the deep water table sector, however, there was an advantage
for partially irrigated over rainfed units, but there were limited
observations in both cases. The first rice crop yield from R-R-UC
patterns averaged 1.4 t/ha higher than rice yields of the later









-6-


planted single rice patterns, reflecting in part, a greater build-up
of rice pests and late drought stress. The second rice crop in
R-R-UC patterns was affected by late stress, yielding an average of
3.0 t/ha in rainfed and partially irrigated units of the deep water
table sector and 3.6 t/ha in the partially irrigated shallow water
table units. No R-R-UC were attempted on rainfed shallow water table
land units.

In fields near free-flowing wells, the average yields for
the first and second crops were 4.7 and 4.0 t/ha, respectively. One
cooperator failed to complete the two crops in time to start the third
crop so it would be completed prior to the following wet season, and
three farmers planted the third crop but experienced failures because
wells ran dry towards the end of the dry season. The -average third
crop yield of the three farmers who grew the full R-R-R pattern was
4.4 t/ha,

Green corn failures were common because of the early typhoon.
All but one of the green corn crops in the shallow water table area
were total failures. Only on the partially irrigated units near the
canal, where internal and surface drainage is adequate, did the GC
component approach satisfactory performance on more than half of the
units tested. On this land unit, four of seven cooperators grew
crops averaging 19,600 marketable ears and the remaining three coope-
rators experienced total failures. Five of six cooperators on the
rainfed units experienced failures.

There appeared to be a slight UC yield advantage for deep water
table land units over pattern group as indicated by average relative
yields in Table 3. However, 9 of the 20 farmer-cooperators growing
two rice crops, did not attempt the UC crop because of dry conditions
prevailing at the harvest of the second rice crop, whereas all farmer-
cooperators did plant UC after single rice crops,

In support of the division of the site into different units,
pattern performance data from implemented patterns indicate that
early season drainage characteristics influence the suitability of
land units for green corn cultivation and the presence of partial
irrigation leads to higher second rice crop yields. However, there
appears to be no advantage of a shallow table over a deep water
table relative to the performance of rice as a first crop in a double
rice pattern or in a single rice pattern, disregarding performance
in free-flowing well areas, and there appears to be lower UC yield
performance in the shallow water table sector.








-7-


IILOI


Taxonomically, the predominant soils in the Iloilo site fall
within the Pelludert, Eutropept, and Tropfluvent Great Groups. Soil
surface materials are generally moderately to slightly acid clay or
silty clay materials. Although the site area is primarily rainfed,
in CY 76/77 an increased number of land units received partial irri-
gation of varying durations beyond the normal end of the wet season.
In the upper section of the site, the land system is composed pri-
marily of ramified inter-hill miniplains and lower colluvial slopes
of a alluvio-colluvial sub-system (A.3.3 and A.3.7) using Desaunettes'
classification (1977). The land system in the lower section of the
site consists primarily of flat plains in a river terrace subsystem
(P.3.1). The rainfall distribution at the site normally consists of
5-6 months with total rainfall exceeding 200 mm and 3-4 months with
less than 100 mm total rainfall.

A statement of the expected effect of landscape and soil factors
on pattern adaptation have been clearly expressed for the Iloilo site
(IRRI, 1976; Magbanua et al., 1977). The effects of landscape, soil
texture, and water sources on flooding regimes, and the logical ex-
tensions of differences in water regimes on pattern performance are
examined in the following sections, The procedures used are the same
as those applied to the Pangasinan data, but the period of Iloilo
data collection was slightly longer and the factors examined are,
of course, appropriate to the Iloilo land system,

uAlthough rainfall must have a major influence on FS regimes,
Figures 4 and 5 show that regimes were modified by landscape, soil
texture2/ and water source class within landscape. Bund position
or relative elevation within a landscape class has been found to be
important only for sideslopes, Estimated FS frequencies per week
have been plotted in Figure 4 for six landscape positions, which
have heavy-textured soils and are rainfed and for plateau units
which have heavy-textured soils but are under different irrigation
durations. Smooth curves have been drawn through the 15 estimates.
For the rainfed land units, a trend towards decreased FS frequency,
when progressing from waterways to high sideslopes is apparent.
The major differences between units occurs after the thirty-seventh
week, reflecting the greater decline in frequency for the higher
landscape positions. There is little difference between the medium




/ In this analysis, soil texture refers to the texture of the
second horizon, usually between 12 to 30 cm deep, This horizon was
used rather than the surface because it was thought to have more of
an effect on the establishment of a perched watertable, Texture
classes were heavy (c, sic, sc), medium (cl, sicl), and light (scl,
1, sil, Is, sl).









8 -
and high sideslope FS regimes, and between the plateau and low side-
slopes FS regimes.

For the Iloilo rainfed units, all FS estimates began at high
frequencies because of the heavy rainfall which preceded the start
of FS data recording. In the lower landscape positions, the exten-
sion of FS beyond the end of the peak rainy periods results from
late surface and base flow from higher elevations.

The influence of irrigation on FS frequencies for heavy-textured
plateau units is also apparent in Figure 4. Irrigation greatly
increased the frequency of FS after the thirty-eight week as is evi-
dent by a comparison between rainfed and irrigated heavy-textured
plateau units. In Figure 4, Irrigation I refers to units receiving
partial irrigation two months or less beyond the end of the wet sea-
son, whereas Irrigation II refers to units receiving partial irrigation
more than two months beyond the end of the wet season. Differences
between irrigation classes would become more distinct if data from
a longer period had been analyzed.

Composite FS frequency estimates from four rainfed fields
located on plateaus having medium or light-textured soils and four
fields having light-textured soils plus coarse (sl or Is) sub-soil
strata of at least 10 cm thickness are presented in Figure 5.
Figure 5 is interpreted as follows: (1) A medium- or light-textured
second soil horizon hampers the formation of a perched water table,
which by contrast causes a rapid and early increase in FS on land
units with heavy-textured second horizons; (2) For a land unit with
a coarse substrata, rapid and deep percolation is a major factor
causing lower-than-average FS frequencies, even when sufficient rain-
fall to recharge coarse substrata has accumulated and has continued
to fall frequently enough to maintain near maximum FS frequencies on
land units with medium- and light-textured soils over heavy material;
(3) Although irrigation water increases the FS frequency on a coarse
substrata land unit, irrigation water is also subject to high seepage
and percolation losses.

Several model statistics are presented for the 15 Iloilo FS
models in Table 4. Inspection of the table indicates the dynamic
role of factors over the period analyzed. A decreasing trend in
total SS occurred up to the sixth model; following the7.eight model,
it increased rapidly. As indicated by the R2, less variation has
generally been explained by the first ten models, than by the remain-
ing four models. The model intercept values started at moderate va-
lues, increased to high values towards the middle of the series, and
then rapidly dropped to negative values. The changes in Total SS,
R2, and intercept values are a reflection of the dominance of rain-
fall at the peak of the wet season.

The extra SS for model variables suggest that the role of
landscape position was moderate over all intervals, The relative
elevation of sideslope positions were moderately important during









-9-


a few dry intervals toward the middle of the wet season and again at
the end of the wet season. Water source played a moderate role up
to the eighth model and from then onward played the dominant role in
explaining the differences in FS observations among the land units.
The influence of a landscape X texture interaction was moderate in
a few models but is notthought to be important. The same cautions
applied to the interpretation of extra SS in the Pangasinan models
apply to the Iloilo models also.

Changes in patterns. Changes between implemented patterns
versus designed patterns occurred in Iloilo as in Pangasinan. Early
and heavy rainfall from a typhoon triggered the bulk of the changes.
Many green corn crops proposed to precede lowland rice were eliminated
because of the early wet conditions, the method of establishment
shifted heavily to WSR because seedlings were not available for trans-
planting or soils were too wet for DSR, and there was a shift towards
double rice crops, mainly in rainfed and partially irrigated plateau
and plain units. These observed changes although strongly induced by
very early rainfall, are in agreement with results obtained from
flooding regime analysis.

Pattern performance. Because of the similarities found in FS
regimes and in yields, cropping pattern performance data were ave-
raged by pattern group within the following heavy-textured land units:

1. High and medium sideslopes, rainfed
2. Low sideslopes and plateaus, rainfed
3. Plains and waterways, rainfed
4. Plateau and plains, irrigation I
5. Plateau, irrigation II and III.

Mean crop yields by pattern groups grown only on these heavy-textured
units are presented in Table 5. Yield data from a group of medium-
and light-textured soils, some with coarse-textured substrata and par-
tial irrigation, have been interpreted separately.

Between land units there was very little difference in the yield
of the first rice crop, regardless of landscape position, water source,
or pattern group. However, yields of the second rice crop were much
more influenced by water availability, as governed either by landscape
position or water source. Upland crops generally suffered drought
stress following two rice crops, although in areas covered by irriga-
tion II and III systems, lateral seepage caused poor performance of
many upland crops planted at a time when adjacent fields were maintained
in a flooded state for the rice crop.

Within heavy-textured, rainfed low sideslopes and plateau units,
most farmers were not able torsuccessfully grow the full R-R-UC pat-
tern, i.e., 39% did not grow the UC portion and of the 14 that did
attempt to grow an UC crop, six experienced complete crop failures,
resulting in a relative yield average of only 13% for the pattern
group. Furthermore, the second rice crop in these units was very










- 10 -


sensitive to moisture regimes as affected by planting date and slight
positional differences within land units. Of the 23 second rice crops
attempted, five were total failures, whereas the top five yielders
averaged 4.0 t/ha. The nine cooperators who grew only R-R patterns
were eighter delayed in their crop plantings or located on less favor-
able fields within the land units, and therefore the second rice crop
yields were only 0.8 t/ha) compared to the 2.8 t/ha of the 14 farmers
who attempted the UC crop.

In the plain and waterway land units, only R-R-UC patterns were
attempted. However, one farmer-cooperator did not grow the UC por-
tion while of the five who did, four experienced total UC failure be-
cause of drought and the remaining individual harvested a mungbean
crop of only 79 kg/ha.

In heavy-textured plateau and plain units receiving irrigation
for a duration of less than two months beyond the end of the normal
end of the wet season (Irrigation I), farmers easily grew the R-R
portion of a R-R-UC pattern. However, four of the eleven farmer-
cooperators did not plant a UC crop and furthermore, performance of
the UC crop was generally poor for the seven cooperators who did.
For heavy-textured plateau positions receiving irrigation for more
than two months beyond the normal end of the wet season (Irrigation
II and III), farmers easily grew at least two rice crops, Where
attempted, yields were reduced on the third rice crop of R-R-R
patterns, but they were still substantial at 3.3 t/ha. The R-R-R
patterns were located primarily in Irrigation III units. Upland
crops performed poorly in Irrigation II units, partly because of see-
page from adjacent fields which farmers were trying to keep flooded
to finish late rice crops,

Land units with medium- and light-textured soils, as expected
were generally poorer performers than the heavy textured units,
especially with regards to either the second rice crop or upland
crops. The average yield of the first rice crop over all medium-
and light-textured units was 4,9 t/ha, which is 0,5 t/ha less than
the weighted average over all heavy-textured rainfed units. Further-
more, UC yields were very much lower, after either one or two rice
crops. Where partial irrigation existed, farmers were capable of
producing an adequate second rice crop with yields sufficient to
make a R-R pattern more profitable than a R-UC pattern.


CONCLUSIONS


Based on Pangasinan CY 76/77 cropping pattern monitoring data,
water table depth and water source factors were found to be important
factors altering FS regimes whereas relative elevation and soil tex-
ture differences induced only minor modifications on FS regimes.
Observed changes in the distribution of patterns over the land units










11 -

and the performance of the crops in the pattern groups were in general
agreement with a division of the site into complexes based on water
table depth and water source class, especially considering the start
and end of the wet season. Using Iloilo CY 76/77 pattern monitoring
data, landscape, water source and soil texture were found to be impor-
tant factors altering FS regimes. Differences found in the perfor-
mance crops within pattern groups over the land units were in general
agreement with the division of the site into land units based on
landscape position and water source class; However, differences
between the high and medium sideslopes and between low sideslopes
and plateaus were not major, as indicated by FS regimes analysis and
crop performance.

Similar analyses of cropping pattern monitoring data which is
being collected for CY 77/78 and is to be collected in CY 78/79, should
lead to a clearer understanding of the dynamics of water regimes,
especially under different rainfall patterns, and thereby aid in
designing and testing improved patterns for other locations.

It is apparent that there are identifiable land unit differences
within both the Pangasinan and Iloilo sites, and these differences
influence at least the agronomicS/ domain of pattern adaptation.
The analyses show that the landscape, soil texture, water source and
water table depth factors play roles in modifying FS regimes, and
that the roles change as the season progresses. A classification of
land units, employing a land system concept, should aid in the extra-
polation of information from the immediate site area to a more general
region. A better understanding of the factors involved in FS regime
dynamics within a land system is important because it provides an
improved basis for defining the domain of rice-based cropping patterns.
Furthermore, documentation of the regimes on different land units,
and the roles played by factors at different stages of the season,
form an important basis for convincintly communicating site-related
research results to others.

Undoubtedly however, there are land-related and other factors
that modify FS regimes and which are important but which have been
either ignored or incorrectly characterized in the FS regime analysis
presented in this seminar paper. The impact of the watershed above
the land units and the effect ofifield level water management on FS
regimes are undoubtedly important consideration.




By involving the farmer in cropping pattern research, a farmer-
resource factor has a bearing on pattern performance. This factor
is operating to an unknown degree in these evaluations, and therefore
the agronomic potentials as discussed here are not the same agronomic
potentials which would arise if all farmer-resource constraints were
removed,







Table 1. Pangasinan FS model statistics, Models 1 to 13, CY 76/77.


PANGASINAN



Total SS
Model SS
Extra SS
WT
WS/WT
RELEV/WS/WT
Error SS


MODEL NUMBER
DF 1 2 3 4 5 6


2503
1917


1207
579
131
587


R2
Probability level*
Intercept


(63.0)
(30.2)
(6.8)


0.77
0.0001
0.9


3624
2466


2121
337
8
158


(86.0)
(13.7)
(0.3)


0.68
0.0001
0.9


1961
934


546
366
21
1027


(58.5)
(39.2)
(2.2)


0.48
0.0001
3.6


1685
563


227
308
28
1122


(40.3)
(54.7)
(5.0)


0.33
0.0009
2.3


2442
1371


1133
104
134
1071


(82.6)
(7.6)
(9.8)


0.56
0.0001
4.6


2297
834


563
130
142
1462


0.36
0.0003
9.8


7 8 9 10 11 12 13


Total SS
Model SS
Extra SS
WT
WS/WT
RELEV/WS/WT
Error SS

R2

Probability level
Intercept


1503
630


425
60
145
873


(67.5)
(9.5)
(23.0)


0.42
0.0001
12.4


136
54
126
598


(43.0)
(17.1)
(40.0)


0.35
0.0006
20.6


2609
1165


451
378
336
1444


(38.7)
(32.4)
(28.8)


0.45
0.0001
17.8


4343
1781


470
838
474
2562


(26.4)
(47.0)
(26.6)


0.41
0.0001
11.9


3455
1589


58
1339
192
1866


(3.7)
(84.3)
(12.1)


0.46
0.00oo
2.4


2995
1656


482
1084
89
1339


(29.1)
(65.5)
(5.4)


0.55
0.0001
0.0


( ) % of Model SS explained by the extra
* Probability for the F value from the


SS due to inclusion of the
test of Model SS


variable in the model.


(67.5)
(15.6)
(17.0)


2310
1256


357
763
135
1054


(28.4)
(60.7)
(10.7)


0.54
0.0001
0.0










Table 2. Distribution of designed and implemented patterns, by pattern group, water
source class and water table depth. Pangasinan CY 76-77.




PATTERN GROUP /- Designed Implemented
Water source class Water source class


Total RF PI Total RF PI

1. GC-R-UC
Deep water table 15 8 7 11 6 5
Shallow water table 8 5 3 9 7 2
Total 23 13 10 20 13 7

2. R-UC
Deep water table 7 4 3 17 10 7
Shallow water table 15 5 10 12 5 7
Total 22 9 13 29 15 14

3. R-R-UC
Deep water table 12 9 3 6 5 1
Shallow water table 12 2 10 15 0 15
Total 24 11 13 21 5 16


1/
A fourth group, R-R-R, was designed also. Seven
Caaringayan (all near free-flowing wells) and none for
were implemented.


R-R-R plots were designed for
Lipit-Pao. Six of the seven













Table 3. Mean yields of crops in the three pattern groups according to land units, Pangasinan, CY 76/77.


Land unit

Deep:
Rainfed

Partially
irrigated

Shallow:
Rainfed

Partially
irrigated


No.a/
Obsn.


Yieldb/
GC R UC


No. not-/


plant


6 2.1 3.4 47%


7 11.2 3.6 41%


9 0.3 3.1 34%


2 0 4.6 -


:ing UC Ob


0 5


0 2


0


0 13


o. Yield
sn. R R UC


4.7 2.8


5.2 3.5


No. not No.
planting UC Obsn.


54%


38%


None


4.7 3.6 40%


Yield
R UC


11 3.7


39%


No. not
planting UC


0


8 2.8 56%


4 3.0 26%


7 3.0 46%


a/
- Number of observations in pattern group.

-As t/ha for rice; thousand green ears for corn; and relative yield
for UC, where yields of 1.53, 1.29 and 4.50 t/ha mungbeans, cowpeas,
sorghum were used as the basis for the relative yield computation.
These were the maximum yields obtained by farmer-cooperators.
C/
SNumber of cooperators not planting UC

GC = green corn
R = rice


UC = upland crops


Nc





Table 4. Iloilo FS model statistics, Models 1 to 15, CY 76/77


ILOILO


Total SS
Model SS
Extra SS
LNDSCP
BNDPOS/LNDSCP
WS/BNDPOS/LNDSCP
TEXT2
LNDSCP X TEXT2
Error SS
R2

Probability level*
Intercept


MODEL NUMBER
DF 1 2 3 4 5 6 7


4012
1625

109 (7.0)
12 (0.7)
280(17.2)
485(29.8)
25 (1.5)
2387
0.41
0.005
13.1


2364
1097


125 (11.4)
36 (3.3)
297 (27.1)
294 (26.8)
47 (4.3)
1267
0.46
0.0004
13.7


1793
723

133
151
131
118
164
1070
0.40
0.005
11.3


(18.4)
(20.8)
(18.1)
(16.3)
(22.7)


1628
569

83
93
65
181
140
1059
0.35
0.03
10.2


(14.6)
(16.3)
(11.4)
(31.8)
(24.6)


1235
458

104
38
77
54
46
777
0.37
0.02
15.1


358
156


(22.7)
(8.3)
(16.8)
(11.8)
(10.0)


919
640


24 (15.3)
4 (2.5)
27 (17.3)
7 (4.5)
24 (15.3)
202
0.44
0.001
18.7


8 9 10 11 12 13 14 15


Total SS
Model SS
Extra SS
LNDSCP
BNDPOS/LNDSCP
WS/BNDPOS/LNDSCP
TEXT2
LNDSCPXTEXT2
Error SS
R2

Probability level
Intercept


552
235


2016
470


7 (3.0)
3 (1.3)
60 (25.5)
2 (0.8)
3 (1.3)
316
0.43
0.002
20.7


5156
2667


10 (2.1) 228 (8.5)


57
298
25
67
1546
0.23
0.4
17.1


(12.1)
(63.4)
(5.3)
(14.3)


205 (7.7)
1895(71.1)
33 (1.2)
141 (5.3)
2490
0.52
0.0001
4.2


6588
3963

261 (6.6)
329 (8.3)
3114(78.6)
86 (2.2)
6 (0.1)
2624
0.60
0.0001
-1.5


7558
5793

281 (4.8)
195 (3.4)
4944(85.3)
92 (1.6)
4 (0.1)
1765
0.77
0.0001
-3.9


8805
6833

692(10.1)
88 (1.3)
5753(84.2)
86 (1.3)
35 (0.5)
1973
0.78
0.0001
-4.6


7085
4983

298 (5.9)
108 (2.2)
4278 (85.8)
29 (0.6)
190 (3.8)
2102
0.70
0.0001
-4.3


4894
2914

40 (1.4)
3 (0.0)
2683(92.1)
37 (1.3)
25 (0.9)
1980
0.60
0.0001
-3.2


( ) The % of model SS explained by the extra SS due to inclusion of the variable in the model.
* Probability for the F-value from the text of Model SS.


61 (9.5)
11 (1.7)
114(17.8)
23 (3.6)
20 (3.1)
279
0.70
0.0001
19.7








Table 5. Mean yields of crops in three pattern groups according to land units, Iloilo CY 76/77.



a/ b/ c/
No. Yield- No. not- No. Yield No. not No. Yield
Land unit Obsn. R UC planting UC Obsn. R R UC planting UC Obsn. R R R


High & medium
sideslopes,
rainfed 6 5.4 64% 0 5 5.2 1.3 21% 1 No ne

Low sideslopes
plateaus,
rainfed 2 5.2 57% 0 23 5.3 2.0 13% 9 None

Plain & water-
ways,
rainfed No n e 6 6.1 4.7 1% 1 NNone

Plateau &
plain
irrigation I 2 4.5 64% 0 11 5.7 4.6 13% 4 N o n e

Plateau, irri-
gation II &
III N o n e 9 5.1 4.6 2% 1 7 5.4 4.7 3.3


a/
- Number


of observations in pattern group.


-/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 yield 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 and uncontrollable levels of insects which causes low yields.
c/
Number of cooperators not planting UC.








FS per week


02 1rI I I I




6 Romfea, waterway APrta /r tron,
( eepwer tble) ^ waterwwy
S(DeeNWter ta) /






Rainfall (mm/week

6 Rairfed, mn'-wa rm P Rainfall 50
(VShaekw Mr tf /ot) w*a 40





(Shlloy Is9oO *VAV)Y \ (7fatable 4
4 NSD )- 30










6-



2eWk 4/47/







4 1 .1, I I (s w \ atIa,
23 27 31 35 39 43 4747
WeeWeek
wellarea






Figure 1. Weekly total rainfall and estimated FS regimes
for 9 Pangasinan land units, weeks 19 to 47, 1976.

















FS/week


0 I I -W
23 27 31 35 39
Week


Figure 2.


Estimated FS regimes for heavy-textured and
light-textured rainfed non-waterway deep water
table land units, Pangasinan, weeks 23 to 39,
1976.


















FS/week


25 29 33 37 41 45
Week


Figure 3.


Estimated FS regimes for heavy-textured and
light-textured partially irrigated non-waterway
shallow water table land units, Pangasinan,
weeks 23-45, 1976.













FS per week


9 23 27 31 35 39 43 47 51
Week


1 1 1 1 1 1 1 11
9 23 27 31 35 39 43 47 51
Week


Ronfoll ( mm/w~ )


Figure 4. Weekly total rainfall and estimated FS
regimes for 8 heavy-textured rainfed and
irrigated Iloilo land units, weeks 19 to
51, 1976.


F~tv




University of Florida Home Page
© 2004 - 2010 University of Florida George A. Smathers Libraries.
All rights reserved.

Acceptable Use, Copyright, and Disclaimer Statement
Last updated October 10, 2010 - - mvs