AGROCLIMATIC FACTORS AFFECTING RICE CULTURE IN COMMUNIST CHINA

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP79-01009A002300120003-1
• Release Decision: RIFPUB
• Original Classification: U
• Document Page Count: 26
• Document Creation Date: November 9, 2016
• Document Release Date: April 20, 1999
• Sequence Number: 3
• Publication Date: July 1, 1959
• Content Type: IR

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AGROCLIMATIC FACTORS AF1M TING
RICE CULTURE IN CO1MMtJNIST CHINA
(Preliminary Draft)
CIA/RR GR 59-13
July 1959
Office of Research and Reports
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CONTENFS
Page
I. Objectives and Methodology . . . . . . . . . . . . . . . 1
II. General Background . . . . . . . . . . . . . . . . . . 1
1. Ecological Development . . . . . . . . . . . . . . 1
2. Interrelation of Basic Vegetative Growth,
Photoperiod, and Temperature . . . . . . . . . . . 3
3. Characteristics of Rice Grown in China . . . . . . ci
III. Temperature Requirements . . . . . . . . . . . . . . . . d
1. Germination . . . . . . . . . . . . . . . . . t3
2. Vegetative Growth . . ? . ? ? ? ? ? ? ? ? ? ? ? ? ? 9
3. Heat Summation . . . . . . . . . . . . . . . . . . . 10
IV. Water Requirements . . . . . . . . . . . . . . . . . . . 12
1. Supply . . . . . . . . . . . . . . . . . . . . . . 12
2. Control . . . . . . . . . . . . . . . . . . . . . . 14
3. Quality . . . . . . . . . . . . . . . . . . . . . . 15
V. Phenological Aspects of Rice Culture in China . . . . . 17
1. Phenologicai Charts . . . . . . ? . . . . . . . 17
2. Kwangtung and South China (Hong Kong) . . . . . . . 17
3. Upper Yangtze Valley (Szechwan) . . . . . . . . . . lt3
4. Middle Yangtze Valley (Hankow) . . . . . . . . . . . id
5. Lower Yangtze Valley (Shanghai) . . . . . . . . . . 19
t,. Han River Valley (Nancheng) . . . . . . . . . . . . 20
VI. Application of Agroclimatic Analysis to Crop
Estimating . . . . . . . . . . . . . . . ? . . . . . . 20
Appendix
Source References . . . . . . . ? . . . . 22
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AGROCI TIC FACTORS AFFECTING RICE CULTURE IN COMMMIST C'RIM
I. Ob ectives and Methodology
The purpose of this study is (1) to analyze agroclimatic factors
that influence the potential distribution of rice cultivation in Communist
China and (2) to provide the climatic bases for determining the possibility
of extending the areas in which rice can be grown. This report constitutes
a pilot study to test both the adequacy of available climatic and agronomic
data and the agroclimatic methodology used. In general, the data on
the critical climatic requirements for the germination, growth, and
ripening of rice are derived from the published results of crop research
in parts of China and in analogous areas. These data are then correlated
with climatic data available for the China mainland.
II. General Background,
1. Ecological Development
The agroclirzatic evaluation of current rice production in Communist
China and of possible future production is complicated by (1) the
ecological adaptability of the rice plant (Orryza sativa) to nearly all
environmental conditions encountered between 4O?N and 400S latitude; (2) the
resultant development of thousands of native varieties of rice, generally
related to two main types (0. sativa indica and 0. sativa japonica); and
particularly by (3) a lack of information on the distribution and
characteristics of local varieties of rice throughout China. Commercially
grown rice in the Far East consists primarily of various strains of
0. sativd Japonica. which is cultivated chiefly in Japan, Korea, Taiwan,
and Northern China; and of 0.
indica, to which most native types
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in South China belong. Both types are found in Central China. Japonica
rites are generally characterized by high yields, good response to
intensive manuring, a short nonlodging* straw, a coarse round grain,
and a higher ratio of husked rice to unhulled grain than is found in
Indica strains. Indica rices have a longer grain, generally have lower
yields, and are more susceptible to lodging because of the heavy vegetative
growth they develop when manured. They are hardier, however, and more
resistant to unfavorable environmental conditions.
Figure 1 shows the growth of one variety of rice (Norio Ito. 8),
which was planted at the Konosu Agricultural Experiment Station in Japan.
Varieties of rice from all areas of the world have been studied by
Japanese agronomists and classified into three broadly inclusive types,
or ecotypes**, whose geographical distribution was found to be closely
related to their hypothetical centers of origin. The major ecotypes --
"A", "B", and "C" -- are most widespread in Japan, Java, and India,
respectively. For the purpose of establishing general agroclimatic
requirements of rites groom in China according to their regional
Under various adverse conditions of drainage or too rapid growth
prior to heading, the rice plant develops a weak stem and the panicles
bend over. Such plants are particularly vulnerable to storm damage because
the stems and heads pack, or lodge, together; this phenomenon is known as
"lodging". Some varieties of 00. sativa are more susceptible to lodging
than others.
** An "ecotype" represents a group of botanical types belonging to one
species that are unified by certain common genetical characteristics,
particularly those adapted to the ecological environments of a given area.
The well known Japanese, Javanese, and Indian ecotypes are generally
referred to as types.
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distribution, the three ecotypes of 00. sativa that were developed
through agronomical research in Japan are assumed to be representative
of native Chinese types. In China, however, the rice plants related
to A, B, and C ecotypes have been modified through their adaptability
to different regional environments. Table 1 shows the distribution by
percentage of the three major rice ecotypes in various parts of China.
Their distribution, however, is no indication of the acreage sown to
each or of the volume of rice production from each type grown.
Table 1
Distribution of Selected Ecotypes of Oryza sativa in China a/
Percent (in rounded figures)
Area
Type A
(Japanese, Japonica)
Type B
Javanese
Type C
(Indian, Indica)
Manchuria
22
11
North China
29
21
50
Middle China
39
1
60
South China
9
87
West China
Taiwan
27
72
a. All data were taken from source ~/.
Inferences about rice production t ;at may be drawn from the distribution
of the three main types throughout China must of necessity be confined to
generalizations on the kind of problems that are likely to occur in the
areas listed, since information on the extent of planting is lacking.
2. Interrelation of Basic Vegetative Growth Photo eriod and Temperature
Rice is normally considered to be a short-day plant because heading
and ripening are usually accelerated as the days become shorter. Since
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late varieties are usually sensitive to day length, they must be grown
only during a specific season of the year. Early varieties, however,
are normally not sensitive to the length of days and can be grown
during any part of the summer and autumn. 1/
In Japan, studies of Japanese varieties of rice grown under
experimental conditions simulating periods of short days and periods of
high temperatures indicate a close interrelation of basic vegetative
growth,,photoperiod response, and temperature response.* Rice varieties
with low photoperiod responses are usually grown in northern latitudes
and exhibit an increasing sensitivity to temperature as the latitude
becomes higher. With northern varieties, heading occurs upon completion
of the basic vegetative growth of the plant, irrespective of the length
of days. The time required for heading may be shortened, however, by
high temperatures in the summer.
Japanese varieties with a high photoperiod response are usually
planted in double-crapping areas where the shortening of the days after
the lst of August induces early heading in the second crop. In such
areas in Japan, early-maturing varieties with low photoperiod responses
are usually planted as the first crop and medium-maturing varieties
* For purposes of this report, the basic vegetative growth of a rice
plant is considered to be that which is made during a period that is
affected neither by short days nor high temperatures. In recording the
results of the Japanese controlled treatment of selected rice varieties,
the factor used for "basic vegetative growth" is the number of days in
such a growing period. The factor of "photoperiod response" is the
number of days that the period from seeding to heading can be shortened
by planting rice during a short-day (10 hours) season under normal
temperature conditions. Conversely, the "temperature response" factor
is the number of days that this period from seeding to heading can be
shortened by planting during a season of high temperatures if the days
are of medium length.
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with high photoperiod response as the second crop. J Day lengths at
latitudes between 200 and 5001 are shown in the following tabulation:
Hours and Minutes
Spring
birch 21)
Summer
(June 22)
Fall
September 23)
200N
12h0m
13h12m
12h0m
30ON
12h0m
13h56m
12h0m
400H
12h0m
14h52m
12h0m
5001
12 h 0 m
16 h 18 m
12 h 0 m
Studies of rice varieties in Fukien,, for example, using day lengths
of 5,, 7, 9, and 11 hours, showed that vegetative growth and the development
of tillers* were greatest in an 11-hour day, and were noticeably less
during a shorter photoperiod. The studies included 1 early,, 1 medium,
and 1 late variety. The time of heading was not influenced by day length
in the early variety, but heading in the medium variety occurred 11 to
16 days earlier in short-day treatments. In the late variety, the time
of heading occurred 63 to 74 days earlier, or half the total vegetative
period, in the short-day experiments. y.T'hus, the relationships between
vegetative growth and length of days observed in Japanese studies of
Chinese varieties appear to hold true in at least one area of China.
No information is available on such relationships for other rice-growing
areas on the mainland.
A tiller is a sprout, shoot, or stalk of any grain, especially one
that comes from the root of the plant or from the axils of its lower
leaves. "Tiller" and "tillering" are also used in verb form to indicate
the putting forth of-new stalks,, or tillers.
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Despite the lack of information on the growth characteristics of
specific Chinese varieties, it can be assumed that relationships between
photoperiod, temperature response, and vegetative growth developed by
Japanese research on Chinese varieties will provide a base for measuring
the effects of the same factors for rice grown on the mainland. Distri-
butions of such relationships for varieties of rice grown in Manchuria,
North China, Central China, South China, and West China are shown in
Figures 2, 3, and 4.
3. Characteristics of Rice Grown in China
Most varieties grown in northern latitudes such as Manchuria and
North China (chiefly Japonica types) have moderate-to-high sensitivity
to temperature and low sensitivity to day length as well as a moderately
low basic vegetative growth (see Figure 2). Climatic characteristics of
the higher latitudes include relatively low temperatures during the
initial period of growth and days that become progressively longer as
the time for heading approaches. The phenological chart (Figure 11) for
Shensi (Nancheng), which is selected as representative of high latitude
locations, shows that the northern varieties are able to accomplish the
minimum vegetative growth required to support their flowering and heading
within a shorter-than-average growing period. Since northern rice is not
highly sensitive to day length, flowering and heading can occur without
the periods of short days that are generally necessary to induce generative
rather than vegetative growth. Furthermore the low temperatures in the
latter part of the growing period reduce the danger of heading before
the basic vegetative growth of the plant has been completed.
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Mid-latitudinal varieties of rice such as those grown in Central,
South, and West China have varying responses to temperature and day
length, depending upon whether they are early- or late-maturing varieties
(Figures 6 and 7). Early varieties are often the first crop in a
double-cropping combination, or they may be the only crop in other types
of rotation. In South China, early varieties exhibit a low sensitivity
to day length and a high sensitivity to temperature (Figures 3 and 4).
In the latitudes of Central China, temperatures during the initial period
of growth are low and days are short (12 hours). As the growing period
progresses and the date of flowering and heading approaches, the days
become longer (14+ to 15 hours) and temperatures increase. Since the
early varieties are not sensitive to day length, they can grow to the
flowering and heading stage in spite of the fact that they experience
no period of short days. Late varieties grown in mid-latitudes, however,
have the opposite characteristics: high sensitivity to day length and
relatively low sensitivity to temperature. Temperatures during the
initial growth period of late varieties in Central China, for example,
are high and the days are long. In subsequent periods of growth leading
to flowering and heading, mid-latitude temperatures fall and days become
shorter. Being highly insensitive to temperature, the late varieties
are not affected by the high temperatures at sowing time. These varieties,
however, are sensitive to length of day, and consequently the shorter
autumnal days accelerate the progress toward flowering and heading. The
plants are thus able to complete their growth cycle before fall frosts
occur. Late varieties are therefore used as a fall crop or as the second
crop in double cropping.
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III. Temperature Requirements
1. Germination
Rice appears to require higher temperatures for germination than
other major grains. Within limits, the speed of seed germination
increases with the increase of temperature, but optimum temperatures
for the germination of rice are between 86?F and 95?F (30?C and 35?C).
Most northern varieties of rice, however, can germinate at temperatures
as low as 50?F to 55?F (10?C to 13?C), whereas varieties grown near the
Equator may require from 59?F to 68?F (15?C to 200C). The maximum
temperature for rice germination in Japan is 104?F (40?C), the optimum
being the normal &6?F to 95?F and the minimum between 50?F and 540F.
Optimum temperatures for early varieties generally tend to be lower than
those of the later varieties.
Indira rice -- the type most widely grown in China as a whole --
generally has the best germination rate at low temperatures. Although
a few varieties require 60?F to 63?F (16?C to 17?C) for germination,
most varieties have a minimal germination temperature requirement of
59?F (15?C); a few can germinate at 55?F or 57?F (13?C or 140C); but
none will germinate in temperatures below 55?F (13?C). Most of the
rites planted in North China, however, are of the Japonica type. They
require at least 55?F (13?C) for germination, but a few will germinate
in temperatures as low as 52?F to 54?F (11?C to 12?C). Only one variety
requires a temperature of 57?F (140C) for germination. 2/ Maps 1 and
2 show the average dates of the first and last occurrence of 50?F daily
mean temperature in China.
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2. Vegetative Growth
The maximum temperature for seed-ling growth in Japan is 86?F (300C)
and the minimum temperature is 45?F to 46?F (7?C to 8?C). The generally
accepted optimum temperature for the healthiest growth of seedlings in
Japan is 73?F (23?C). 10
During its growing season, rice usually requires temperatures of
about 68?F (20?C) for at least 2 or preferably 3 months. 11 The generally
accepted optimum temperatures for the stages of tillering and formation
of young ears (see Figure 1) are 90?F to 93?F (32?C to 34?C) and 86?F to
90?F (30?C to 32?C), respectively. The actual optimum temperature varies,
however, with the variety and with the stage of plant growth. Temperatures
below the optimum during the early period of seedling growth retard their
growth and delay the transplanting date. Low temperatures during the
tillering stage of vegetative growth inhibit the development of tillers.
The flowering and heading of rice may be delayed by temperatures
below the optimum. Optimum temperatures for flowering are between 80?F
and 90?F. / High nighttime temperatures, however, are undesirable
during flowering, whereas experiments show that a marked difference
between day and night temperatures has a beneficial effect on the
maturing rice heads. 13 Low daytime temperatures tend to retard the
initiation of the flowering stage and high temperatures (near the
optimum) accelerate it. The average number of days in a year having
daily mean temperatures higher than 50?F (for China) are shown on
Map 3.
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3. Heat Summation
Temperature requirements for the growth of rice plants can be
expressed in terms of heat summations as well as in terms of the
permissible temperature ranges for germination, vegetative growth,
flowering, heading and maturation discussed above. By using as a base
the minimum temperatures at which growth occurs, the additional heat
required to mature a crop may be used as an index to the feasibility
of rice cultivation in a particular area. Such heat summations are
computed by totaling the number of degree-days* that can be accumulated
in a specific area between germination and harvest. For the same
variety of rice, temperature summations may vary considerably under
different growing conditions. Temperature summations in the higher
latitudes tend to be lower than in the tropics, possibly because the
growth of temperate varieties may be reduced rather than increased by
excessively high temperatures. The longer duration of sunlight in
higher latitudes during the summer may also compensate in part for
the lower summations of heat. 14
A comparison of'heat summations for Japanese varieties grown as
far north as Hokkaido (440N) and as far south as Shikoku (about 349N)
suggest that there is little difference in the summation of heat required
to grow specific varieties in different latitudes. 15 The earliest
* A degree-day, the heat unit generally used in computing heat summations,
is expressed as one degree of temperature above the base for one day, the
total degree-days for one day being the difference between the mean
temperature for that day and the base. Japanese heat summations are
computed on a base of 32OF (O?C), and represent the accumulated degrees
of temperature higher than 32OF for all the days of a growing season.
For approximations of probable heat summations in China, 50OF (10?C)
seems a more realistic base.
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varieties require only about 4352?F (24000C) heat summation to complete
their growth cycle from seeding to harvest. Most early varieties,
however, require from 4712?F to 5432?F (2600?C to 3000?C) heat summation
during their growing seasons, and late varieties require only slightly
more (5581?F or 3083?C). Conclusions drawn from Japanese experience
indicate that the rice varieties tested require the ranges of heat
summations indicated above regardless of the latitude or the length of
growing season. Thus two successive crops a year can be raised where
the annual heat summation exceeds 7952?F (4400?C) if a very early
variety is selected for the first crop and if the last 752?F (400?C) of
this amount of heat can also be devoted to raising the seedlings for
the second crop in nursery beds. For normally early varieties requiring
as much as 5432?F (3000?C), double cropping will require a total of
8672?F (4800?C). L31
Information on optimum or minimum heat summations required to
mature Chinese rice crops is not available. Tentative approximations
of optimum heat summations for early and late Chinese varieties can be
derived from the Japanese summations indicated above together with an
analysis of heat summations in the phenological charts (see Figures
5-11). 17 Thus it is assumed that early varieties of rice, regardless
of the latitude in which they are grown, will require from 2600?F to
3200?F of heat above 50?F. Late varieties will require from 3200?F to
3400?F, and double cropping will require a total of 5t300?F to 6600?F of
heat above 50?F. 18 Figure 5 gives heat summations over 50?F for all
of China (from 85?E to 130?E) by intervals of 5 degrees of latitude
between 25?N and 50?N and also for "agricultural China" (from 110?E to
130?E).
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IV. Water Requirements
1. Supply
The consensus of experts on the problems of rice cultivation in
the Far East.and Southeast Asia appears to be that the chief limiting
factor to the growth of rice is water supply. Grist contends that,
compared with water supply, the suitability of the soil for rice growing
is relatively unimportant. / In Asia alone there are many varieties
of paddy rice. Some are drought-resistant and others flood-resistant;
some can be grown in brackish water and others require fresh water;
collectively they exhibit a wide variety of tolerances to sunshine,
temperature, and other climatic factors. It is generally agreed, however,
that some variety of paddy can be grown under almost any climatic
condition within 40 degrees north or south of the equator and on
nearly every kind of soil, if given an adequate supply of water. 20/
The definition of "an adequate supply of water", however, has no
such consensus. The optimum amount of water required for adequate
tillering of a growing rice crop varies among the various producing
areas in the world and even among rice-growing areas of the Far East
that have nearly analogous climatic and cultural conditions. Contrary
to general opinion, the most favorable climatic regions for the growth
of rice are those characterized by a seasonal cycle of precipitation
rather than the tropical rainforest regions -- which have heavy rainfall
and little or no dry season. If no provision is made for timely
irrigation, regions that have a yearly average of at least 40 inches
of rainfall (mainly concentrated in the growing season) appear to be
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optimum. Also important is a relatively dry season during the time
when the rice matures. 21 Since most rice in Communist China is
irrigated paddy, the availability of water for irrigation is of greater
relevance to the problems of rice culture than are climatic conditions.
The regional patterns of moisture deficiency and surplus in mainland
China, however, considered in relation to water requirements of rice,
may afford a measure of regional water needs for rice culture. The
average annual water deficiency and surplus for China is shown on
Maps 5 and 6. A tentative assessment of the probability of success or
failure of the rice crop in any particular year should be possible if
the water requirements are considered in connection with the availability
of irrigation water.
The principal factors determining the effect of water on the growth
of rice are quantity, quality, and control. The total annual water
requirement varies with the varieties grown and with the region of
cultivation, but the principal factors that influence the consumption
of water are field evaporation, seepage, differences in soil preparation,
and the amount and method of initial flooding. The minimum water
requirement for paddy is estimated at about 3.2 acre-feet 22 but,
except in Japan -- where the total requirement amounts to only 2.3 to
4.3 acre-feet -- the most common total water requirement for irrigated
paddy is 6 acre-feet. 23 The degree of variation in total water
requirements that may be expected even within the same general growing
area, however, is exemplified by the contrast between northern and
southern Tatman, where the amounts of water required for the 135-day
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irrigation season are reported as 3.75 and 5.63 acre-feet, respectively. 24+
For purposes of a climatic evaluation of rice irrigation in mainland
China a total annual water requirement of 5 to 6 acre-feet-is assumed.
2. Control
One of the most critical factors affecting the germination, growth,
and maturation of rice is the control of the water supply during the
growing season., which includes the timely application of water at depths
that will insure the optimum growth of the crop and also the provision
for adequate drainage of the fields at certain periods of plant growth.
It is. generally agreed that paddy should be grown in a well-soaked field,
but with little standing water since it suppresses the production of
tillers in the vegetative growth stage. 25/
A large supply of water is required for the preparation of a field
by wet tillage before planting. In areas of heavy paddy soils, this
preliminary requirement may amount to 30 percent or more of the total
water requirement for the crop. 26 The chief purpose of irrigation
before planting is to facilitate the intensive soil tillage necessary
to create the so-called puddled soil condition in which a 6- to 8-inch
layer of soil is worked into a consistency of fine soft mud. Although
practices vary from place to place, the depth of water is generally
increased gradually as the newly transplanted rice plants grow until a
depth of 6 to 12 inches is reached. 27/ A rice plant uses a comparatively
small amount of water immediately after it has been transplanted, and
the depth of water at this time is usually kept at'about the 2 inches
necessary to check weed growth. As the plant grows, however, the quantity
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of moisture transpired increases and the depth of the water on the
field must be gradually increased first to 4 inches and later to t3
to 12 inches. 28 2 Although water promotes and maintains the soil
texture and temperature necessary for the growth of young seedlings,
the drainage of soils is necessary for aeration in later stages of
growth. 30
As a result of experiments conducted in India, the total amount of
water required for each acre during the different stages of plant growth
was determined to be as follows: (1) seedbed, 1 acre-inch; (2) after
transplanting and during vegetative growth, 22 acre-inches; and (3) matu-
ration period, 37 acre-inches. The application of water to a depth of
2 inches at intervals of 3 to 4 days was found to give best yields,
and on the average the rice crop in India requires the application
about a half inch of water per day. ,d_? Other Indian experiments
indicate that the chief periods of high water requirement during the
growth cycle of the rice plant come during the initial seedling period
(about 10 days), the preflowering and flowering period (about 25 days),
and the grain formation period of about 5 to 7 days. Yields are adversely
affected if there is a deficiency of water during these periods. Probable
periods of water deficiency in China can be derived from the climatic
graphs shown in Figures 6 through 9.
3. Quality
In addition to the quantity and control of the water supply required
for a growing rice crop, certain characteristics of the water itself
may adversely affect rice yields. During the seedling and tillering
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phases of vegetative growth, temperatures of irrigation water can delay
plant growth, causing rudimentary plant growth, retarded flowering and
heading, or even sterility. / Japanese studies indicate that 90?F
(32?C) is the optimum water temperature and that the use of water at
other temperatures results in retarded growth and decreased yields. 33
The lethal maximum temperature is 122?F (50?C). For normal growth of
the rice plant, the minimum water temperature is 55?F (13?C) and the
maximum something between 102?F and 108?F (39?C and 13.5?C). AL-3-5/
Studies on the effect of water temperature have usually included the
effects of water stagnation and turbidity. In general, it was found
that rice plants covered with turbid water for 10 days or more during
flood were killed, whereas plants in fields flooded with clear water
usually recovered after the water had receded. i Stagnant water had a
similar effect on plants in flooded fields. In irrigated fields of
semiarid or temperate areas, however, salt damage is the most serious
problem. Considerable difficulty is experienced in preventing salt
damage resulting from the rapid evaporation of water on the fields
during periods of drying winds. Water shortages also complicate the
problem of providing fresh water to flush out increasing salt deposits
since "new" irrigation water during droughts may prove to have nearly
the same or often a higher salt content than the "used" drainage water
from the fields. Climatic conditions that exacerbate drought conditions
include strong, dry spring winds together with high temperatures.
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V. Phenological.Aspects of Rice Culture in China
1. Phenological Charts
The approximate dates of sowing, transplanting, and harvesting rice
as well as the date of heading and the periods of seedling growth,
vegetative growth, and ripening are shown in Figures 6 through 11 for
single, double, or interplanted crops in representative areas of North,
Central, and South China. The charts also include the mean monthly
temperatures during the growing period, a summation of degree-days of
heat during the growing period of each crop, and a graph showing the
relation between the precipitation-potential and evapo-transpiration
at a representative station in the area. A synthesis of the critical
climatic requirements for rice growing in each area is indicated by
the phenological chart for the area. When correlated with maps showing
the distribution of the critical climatic elements in China, the charts
provide the basis for a tentative evaluation of the composite optimum
for rice growing in each area and a rough approximation of the geographical
limits for rice cultivation.
2. Miangtun, and South China (Hong Kong)
The phenological aspects of rice cultivation in Kwangtung and South
China are represented by the phenological chart for Hong Kong (Figure 6).
Almost 90 percent of the varieties raised are Indica rices with basic
vegetative growth, photoperiodic, and temperature characteristics similar
to those indicated in Figure 6. The early crop is relatively insensitive
to day length and can progress to flowering and heading, and can mature
without requiring periods of short days. The late crop is relatively
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insensitive to temperature and can be planted during periods of high
summer temperatures. Its flowering and heading, however, is accelerated
by the shorter days in the fall. The growing period is long enough for
the crop to mature before danger of frost damage. The most critical
climatic problem is a possible shortage of precipitation during the
seedling and early growing period of a nonirrigated early crop in dry
years, and the lack of periods dry enough to mature and ripen the early
crop in June and July. Rainy and dry spells coincide advantageously with
the growth characteristics of the late crop.
3. Upper Yangtze Valley (Szechwan)
In the Upper Yangtze Valley, photoperiodic, temperature, and growing
period conditions are about the same as those for Hong Kong. In some
areas, however, a water deficiency is indicated for the midsummer,
coinciding with the late crop seedling and transplanting period (see
Figure 7). Pap 3 shows that the area has a range of only 0 to 12 inches
in the average annual water surplus, suggesting that irrigation requirements
may be critical in dry years.
1#. middle Yangtze Valley (Hankow
Critical climatic conditions for double cropping in the Middle
Yangtze Valley (Figure 8) include the possibility of frost during the
seedling period of the early crop, excessive rainfall during the harvest
of the early crop, and a possibility of water deficiency during the
late summer and early fall. Shortage of water during the critical
preflowering, flowering, and grain formation periods of the late crop
would adversely affect yields.
18
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5. Lower Yangtze Valley (Shanghai)
Phenological conditions for both interplanting and double cropping
systems of cultivation are given for the Lower Yangtze Valley (Shanghai)
and the southern Huai River plain in Figures 9 and 10. Figure 9 shows
the differences between a short-season, early-maturing crop and a
long-season, late-maturing crop that is interplanted simultaneously
with or shortly after the planting of the early crop. In this area the
high temperatures and long days of midsummer indicate the desirability
of selecting early varieties that do not require short days to accelerate
heading and ripening but which instead are induced to mature by high
temperatures. On the other hand, varieties chosen for the late crop,
1
although planted at about the same time as the early crop, are relatively
insensitive to temperature but have a fairly high sensitivity to the
shorter days of September and October. High summer temperatures may
serve to accelerate vegetative growth of the late crop, but may also affect
it adversely if the high temperatures occur during the period of rainfall
deficiency in July and August.
A possible double-cropping schedule in the Lower Yangtze intertilled
crop area is indicated in Figure 10. In order to accommodate two
successive crops during the growing season, early and late short-season
rice varieties are necessary, with the seedling period of the second
crop overlapping the late maturation period of the first crop. Growth,
temperature, and photoperiod characteristics of the varieties used for
the two crops should be similar to those of varieties planted in other
double-cropping areas. Moisture distribution, however, favors the water
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requirements of the first crop; the seedling period of the late crop
coincides with a period of water deficiency in July and August.
6. Han River Valley (Naneheng)
A single cropping system in the Han. River Valley of Shensi is
shown in Figure 11, together with a tentative double-cropping system
proposed by the Chinese Communists. The single-crop schedule is
probably representative of growth, temperature, and photoperiod
responses similar to those discussed on page 6. Flowering and heading
occur during the long days of August and, therefore, varieties that do
not require short days to mature are used. In order to advance the
growing period, seedlings for the early crop in a double-cropping
system would probably have to be raised in hotbeds to escape damage by
early frost. The harvest date of the late crop would approach dangerously
the average date of the first frost.
VI. Application of A oclinatic Analysis to Crop Estimating
The tentative nature of some of the climatic requirements developed
in this study is necessitated by lack of information on their applicability
to Chinese varieties of rice. Unless further details on the growth factors
of Chinese rices are developed through more intensive study of available
sources or unless additional information can be obtained from Chinese
Communist sources, the value of further refinement of critical climatic
factors through analogous-area study is doubtful. The validity and value
of the agroclimatic factors developed in this study, moreover, can be
determined only by a trial application of the factors to an actual
growing-season situation in China. It should be possible for analysts
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in the United States to maintain a trial accounting of accumulated
degree days for representative rice growing areas in China, and to
relate these heat summations to critical germination, growth, flowering,
and ai-ierllug it would Vihezi be possthie to coi'b'elate ssuei
data with the balance between evapotranspiration and the precipitation
potential for the area. Using the average conditions and optimum
requirements that are indicated in this report together with the monthly
mean temperature and precipitation readings already being supplied by
Air Weather Service, it should be possible to keep a running account of
agroclimatic conditions for a current year's rice crop. Such bookkeeping
procedure should provide at least an approximation of the chances for
success or failure of the rice crop in various parts of China, especially
when related to the availability of irrigation water. By checking the
results of the accounting procedure against Chinese Communist reports of
crop successes or failures, in time it may be possible to build up an
evaluation of the validity and reliability of the procedure and of the
agroclimatic parameters. Should studies of yields, areas sown, and the
extent of double cropping be possible at a later time, the results of
the accounting procedure for agroelimatic data could be incorporated in
them.
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SOURCE REFERENCES
1. Ghose, R.L.M., M.B. Ghatge, and V. Subrahmanyan. Rice in India
Indian Council of Agriculture Research, New Delhi, 195
2. Matsuo, Takane. Rice Culture in Japan, Yokendo, Ltd., Tokyo, 1955
3. Ibid.
4. Liu Cheng-yao and Chen Shih-Kai. Fukien Agricultural Journal,
vol 3, 1941, pp. 162-167
5. Natsuo, Takane9"Differentiation of Ecotypes in the Cultivated Rice
and the Variation of Characters Resulting Therefrom," Reports for
the Fifth Meeting of the Working Party on Rice Breeding, Ministry
of Agriculture and Forestry, Japanese Government, Tokyo, Oct 54
6. Wickizer, V.D. and M.K. Bennett. The Rice Economy of Monsoon Asia,
Food Research Institute, Stanford University, California, 1941
7. Ibid.
8. Matsuo, p2. Sit., (2, above)
9. Ibid.
10. Ibid.
U. Wickizer, off?. cit., (u, above)
12. Ibid. --
13. Kondo, Yorimi. "Studies on Cool Tolerances of Paddy Rice Varieties,"
Reports for the Fifth Meeting of the Working Part on Rice Breeding,
Ministry of Agriculture and Forestry, Japanese Government, Tokyo,
Oct 54
14. U.S. Dept. of Agriculture. Climate and Man, Yearbook of Agriculture,
U.S. Govt. Printing Office, 19-41
15. Komoda, Yoshio.."Tne Theory and Practice of Two Successive Rice Crops
in Temperate Japan," Rort for the Fifth Meeting of the Worki
Party on Mice B.~eeding, Ministry of Agriculture and Forestry,
Japanese Government, Tokyo, Oct 54
15. Ibid.
17. Yao, C.S. "Optimum Agricultural Temperatures and Heat Summations,"
Acta Geo a hia Sinica, vol 23, no 2, pp. 183-203 (Summary in
English, p. 202
13. Matsuo, ,off. cit., (2, above)
19. Grist, D.B. Rice, Longmans, Green and Co., London, New York,
Toronto, 1955
20. Ibid.
21. Wickizer, pp. Sit., (6, above)
22. De Gens, J.G. Means of Increasing Rice Production, Centre D'Etude
de L'Azote, Geneva, Jun 54
23. Grist, off.. cf.t., (19, above)
24. Iso, Eikiehi. Rice and'Crops'in Its Rotation in Subtropical Zones,
Japan FAO Association, Tokyo, 19
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25. Grist, op. cit., (19, above)
26. De Gens, op. cit., (22, above)
27. Grist, off. cit., (19, above)
23. Ibid.
29. be Gens, og. cit., (22, above)
30. Sen, P.K. "Effect of Watering on the Growth and Yield of Four
Varieties of Rice," Studies on the Water Relations of Rice,
Indian Journal of Agricultural Science, 1937, 7:89-117
31. Ghose, op. cit., (1, above)
32. Wickizer, c2. cit., (6, above)
33. Kikkawa, S. "The Influence of Temperature of Irrigation Water
on the Growth and Yield of Rice," Imperial Academy (Japan)
Proceedings, vol 5, 1929, pp. 303-305
34. Matsuo, M. cit., (2, above)
35. Kondo, M. and T. Okamura. "Beziehung zwischen der Wassertemperatur
and dem Wachstum der Reispflanzen" (Relationship Between Water
Temperature and the Growth of the Rice Plant), Berichte Ohara
Institut fur Iandwirtschaftliche Forschungen, vol 1, 1930, pp. 395-411
36. Kondo, M. and T. OkamurBeziehung zwischen der Wassertemperatur
and dem Wachstum der Reispflanzen. V. Uber den graduellen Unterschied
der Schadigung, der die Reispflanzen bei Uberschwemmung mit klaren
oder mit triubem Wasser ausgesetzt send" (Relationship Between Water
Temperature and Growth of the Rice Plant. V. The Gradual Distinction
of the Damage to which Rice Plants are Exposed by Flooding with Clear
or with Turbid Water), Berichte Ohara Institut fur Landwirtschaftliche
Forschungen, vol 6, 193V,.. pp. 205-209
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