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.


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Farming ( LCSH )
Agriculture ( LCSH )
Farm life ( LCSH )


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R.D. Magbanua, R.A. Morris and H.G. Zandstra7ABSTRACT
For the past three years of cropping systems research activities in a rainfed lowland rice area Qf 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 productive 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 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 function of cropping systems outreach sites are to develop economically sound rice-based cropping patterns for defined environments. Based on information 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 variables.
Results of cropping pattern trials conducted under both experimental 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 performance.
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 determinants.
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 croppi~ig 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 performance 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 henef its 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 landscape position. Productivity increased in the lower landscape positions. The differences were not pr onounced 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 1976-7,7 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 1and 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 mediumand light-textured soils were generally poorer performers than heavytextured units, especially with regards to second rice crops. The average yield of the first rice crop over all meditum- 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 crops.

6. Where short-duration partial irrigation exists, fazmercooperators 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 turnaround 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 Bafios, Laguna, Philippines.
International Rice Research Institute. 1974.
An Agro-Climatic Classification for Evaluating Cropping 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.
Class D e s c r i p t i o n
Rainfed Strictly rainfed. No supplemental irrigation.
Depends entirely on rainfall for water accumulation.
Partially irrigated. With supplemental irrigation at least one month after the end of the rainy season.
II Partially irrigated. With supplemental irrigation 1 to 2 months after the end of the rainy season.
III 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
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
Bottomland Plain Plateau Sideslope
Rice -Rice 2-UC 6245(10) 5187(13) 4871(4) 5088(5)
Rice -UC 5100(11) 5189(16) 4883(17)
GCa-Rice1-UC 6356(4) 5128(10) 5039(6)
Mean 6245 5545 5063 5003
/ 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(1)a
Mean 2265 1818 1012
aExcluding 1 failure
bExcluding 6 failures
Note: Number in the parentheses represent the number of fields.

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
High & medium side- R-R-UC (5) 5.2 1.3 21%/1b
slopes, rainfed
R-UC (6) 5.4 64%
Low sideslopes & R-R-UC (23) 5.3 2.0 13%/9
plateaus, rainfed
R-UC (2) 5.2 57%
Plain & waterway, R-R-UC (6) 6.1 4.7 1%/1
Plateau & plain, R-R-UC (11) 5.7 4.6 13%/4
irrigation I
R-UC (2) 4.5 64%
Plateau, irrigation R-R-R (7) 5.4 4.7 3.3
R-R-UC (9) 5.1 4.6 2%/1
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.
b/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
First 4819 (48) 5532 (27) 4887 (22) 5559 (10)
Second 2003 a(41) 3476 (20) 4603c(21) 4193 (11)
Third (0)b 3375 (1) 3464 (4) 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)
.J (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.
Landscape Number of Non-flooded days1position First crop Second crop
Plain 5.5 16.8
Plateau 3.2 23.4
Sideslope 19.7 26.5
1 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.

I j I I IP aiI
Sid- Pateu ISide- Plain
Landscape position Summit Side- Plateau Sideslope slope
II IIsop ,,
" I II I I r
~ 4 Expadingacla
teter I I
(3) (3) River
"---- .. I (2) ( 3)
Soil texture: (4) (5)
Expanding clay
:.'' Loamy texture or
non-expanding clay
( I ) Pluvic, ( 2) Fluxic, ( 3) Fluxi-cumulic, (4) Cumulic, (5) Cumulo-delugic.
Figure 1. Schematic presentation of geomorphic and pedologic conditions
in Iloilo outreach site. (Source: M.E. Raymundo, 1976)

Rainfall (mm) 900
800S1950-75 Y/ 1975-76 700- if 1976-77
S1977-78 600500
300- %
Apr May June July Aug Sept Oct Nov Dec Jan Feb Mar
Figure 2. Comparison of the 1975-1978 monthly rainfall with the 25-year average. Oton and Tigbauan, Iloilo.

S4000 y= 4949.0 35x
r= -0.6001**
n = 7 '7
30 50 70 90
Number of Non-flooded days Figure 3. The relationship between the number nonflooded days and grain yield of the second
rice crop. Iloilo 1976-77 crop year.
a/Observations taken across landscape positions
and water source classes.

FS per week
~ Rn W~I K500
S I trreano I 200
0 ulLll i l
19 23 27 31 35 39 43 47 51 1 23 27 31 35 39 43 47 5 Week
4 Figure 4 Weekly total rainfall and estimated FS
regimes for 8 heavy-textured rainfed and
2 irrigated Iloilo land units, weeks 19 to
51, 1976.
19 23 27 31 35 39 43 47 51 Week