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III. Division of Rice Belts

III. Division of Rice Belts

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346



GUO YI XIAN AND FEI HUAI LIN



A. SOUTHCHINADOUBLE-CROPPING

RICEBELT

The South China double-cropping rice belt consists of areas south of the

Nanling Mountains, including Taiwan, Fujian, and Guangdong Provinces

and the Guangxi Autonomous Region. This belt has the highest annual

accumulated temperature and the longest crop-growing period in China. The

total cropping area of rice is about 27% of the national rice areas (Taiwan

excluded).

The mean temperature, except in the moutainous areas in the northern

parts, is about 10°C which allows thermophilic plants to overwinter safely.

The annual accumulated “active” temperature (diurnal average temperature

higher than l 0 T ) amounted to 6000-9000°C. During the growing period of

rice (March-September), the average temperature is about 22-26“C, the

relative humidity is 80%, and the annual precipitation is 1500-2000 mm. In

most areas of this belt, the growing period of rice is longer than 290 days a

year. The cropping systems are chiefly double cropping of rice. And, in

localities where the water resources are scarce, upland crops such as sweet

potatos, peanuts, and soybeans are grown in combination with rice to make

up double-crossing systems. In the districts of Hai-nan Island and Zhan-jiang

of Guangdong, there is also a limited area of triple cropping of rice (Fig. 6).

The soils of most of the paddy fields in this belt have developed from alluvial,

lateritic, and yellow soil material after long periods of cultivation. Generally

they have an acid reaction, but there are also saline-alkali soil in the Pearl

River Delta and in the coastal areas.

B. CENTRAL CHINA SINGLE-



AND



DOUBLE-CROPPING

RICEBELT



The Central China single- and double-cropping rice belt consists of areas

north of the Nanling Mountains and south of Huaihe River and the Chinling

Mountains. Included are provinces along the Yangtze River, the Han-zhong

Basin of Shanxi Province, and the Xin-yang Prefecture of Henan Province.

The rice-cropping area of this belt, China’s most important rice belt, accounts

for more than 63% of the national area.

The mean temperature in January is 2-8°C; that in July is about 26-30°C.

During the rice-growing period (late March to October), the average

temperature is about 22-26°C and the annual accumulated “active” temperature is 4500-6000°C and higher. The relative humidity is about 80% and the

annual precipitation is generally more than 1000 mm. There is more rainfall

on the upper reaches of the Yangtze River in autumn and more on the lower

reaches in spring. The intermittent drizzles during late spring and early

summer, characteristic of the rainfall in this belt, are very favorable for rice

production.



347



RICE-BASED CROPPING SYSTEMS



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Late rice



Early rice



Late rice



Early rice



Late rice



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FIG.6. Major rice-based cropping patterns in Guangdong Province.



Areas to the south of Najiang in Jiangsu, Hefei in Anhui, Xinyang in

Henan, Gucheng in Hubei and Nanzhong in Shanxi Provinces (about

32-33"N) are suitable for double-cropping of rice (Fig. 7). However, in the

past fallow-rice, green manure-rice, wheat-rice, rapeseed-rice, and faba

bean-rice have been the major cropping systems in this belt. The soils of

paddy fields have developed from alluvial, illuvial, lateritic, yellow, brown,

and purple soil materials. Generally, the soils are quite clayey with strong

acid reactions, are not very rich in organic matter, and are moderate in

fertility levels. However, the soils in the eastern part of Jiangsu, in the

southern part of Hunan, and in the Sichuan Provinces have developed from

purple soil parent materials and are higher in fertility.



Green manure



Early rice



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Late rice

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FIG.7. Major rice-based cropping patterns in Suzhou District, Jiangsu.



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348



GUO YI XIAN AND FEI HUAI LIN



C. NORTHCHINASINGLE-CROPPING

RICEBELT

The North China single-cropping rice belt consists of the area north of the

Huaihe River and the Chinling Mountains and south of the Great Wall,

included the Beijing and Tianjin Municipalities, the Hebei, Shandong, and

Shanxi Provinces, the areas north of Huaihe River in Anhui and Henan

Provinces, the central and northern parts of Shanxi, and the areas east of

Lanzhou in Gansu Province. The rice-cropping area in this belt is only about

1.5% of that in the country.

The mean temperature in this belt varies from - 6 to - 2°C in January and

from 26 to 28°C in July; the annual accumulated active temperature is

3000-450o"C, and the yearly sunshine hours are usually 2000-2800 hours or

more.

During the rice-growing season (April to October), the comparatively

large difference between day and night temperature (1 1.3-14.5"C) is most

favorable for rice growth. Hence, the per-unit-area yield is comparatively

high. The annual precipitation, however, is low, about 600-700 mm in the

east and less than 400mm in the west. The relative humidity is 60% in

summer and 75% in autumn. However, the climate of the northwest part of

this belt is especially arid, the relative humidity in the summer and autumn

being only about 50%. The original cropping system was a single crop of rice

in a year. After harvest, the field was left idle for more than 7 months and the

cropping intensity was low. In recent years, double-cropping systems such as

green manure (rape)-rice, wheat-rice, silage barley-rice, and rape seed-rice

have been tested and found to be successful (Fig. 8). The paddy soils

developed mostly from soils classified as chestnut, brown, meadow, and

saline-alkali soils.

D. NORTHEAST

CHINAEARLYRICE BELT



The Northeast China early rice belt consists of areas north of the Great

Wall and east of the Da-Xing-an-lin Mountains, including the Liaoning, Jilin,

and Hei-long-jiang Provinces and the eastern part of Inner Mongolia

Autonomous Prefecture. The rice-cropping area occupies 2.6% of the national rice area. It has a humid to semihumid climate and monsoon temperate

and subtemperate zones. The annual precipitation is 750 mm in the east and

about 500 mm in the west. The relative humidity is about 65 % in the summer

and 75% in the autumn in the central and southern parts. However, it is quite

arid in the northern part. The rice-growing period is comparatively short,

from May to September. The average temperature during this period is

16.6-19.o"C. Rice varieties with growing durations of 120 to 160 days are



349



RICE-BASED CROPPING SYSTEMS



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Rice



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FIG.8. Major rice-based cropping patterns in Beijing Municipality.



suitable for this belt. The cropping system is one crop a year. The paddy soils

mostly developed from alluvial meadow, swamp, and saline-alkali soils.

E. NORTHWEST

DRYREGION RICEBELT



The Northwest Dry Region rice belt consists of areas west of the He-xi

Corridor of Gansu Province and north of the Chinling Mountains, including

the western parts of Gansu Province and the Inner Mongolia Prefecture and

the Xinjiang Autonomous Region. The rice-cropping area occupys 0.3% of

the total rice area in China. It has an arid climate. The rice-growing period is

from May to September in the north and from April to October in the south.

During the said period, the average temperature is about 18.3 to 21.8"Cand

the relative humidity is 4569%. Annual precipitation usually is less than

200 mm. Generally, only one crop of an early maturing variety of rice can be

grown. The paddy soils are mainly developed from saline-alkali, meadow,

and swamp soils,

F. SOUTHWEST

CHINAPLATEAUS

RICEBELT



The Southwest China Plateaus rice belt consists of the Guaizhou, Yunnan,

and Qinhai Provinces, the Tibet Autonomous Region, and the Kantze

Autonomous Prefecture of Sichuan Province. The rice cropping area occupies about 6% of that in the country.



3 50



GUO YI XIAN AND FEI HUAI LIN



This belt has a humid to semihumid climate of the monsoon tropical,

subtropical, and temperate zones. The differences in climate of different areas

(vertically distributed) are very striking on account of the marked variance in

altitude and complex topography of this region. Paddy fields are mainly

distributed in Guaizhou and Yunnan Provinces from 100 to 2600 m above

sea level. The annual precipitation is over 1000 mm. The rice-growing period

is from March to October, in general. However, in the southern part rice can

be sown in late February and early March, and the climate is favorable for

double cropping of rice. Major cropping systems in this belt are board

bean-rice, wheat-rice, barley-rice, rapeseed-rice, and green manure-rice, or

the fields are left flooded for storing water after harvest of rice. The paddy

soils are mainly developed from red and yellow soils with high fertility and

water-holding capacities.



IV. REFORMATION A N D ACHIEVEMENTS

Large populations, limited arable land, and favorable natural conditions

generated the old traditional multiple-cropping systems in China. According

to ancient literature, as early as 221 B.C. relay cropping had been recorded

and rice-based double-cropping patterns had been noted. In the first century,

wheat-rice patterns were practiced in Nanyang county of Henan Province.

During the period of A.D. 200-900, frequent warfare forced a great number of

people to move from the north to the south, thereby promoting rice

production in the south. Common vetch was used as a green manure crop in

rice fields, and rice-rice, wheat-rice, and soybean-rice patterns were recorded

in the literature of this period. The necessity of rotation was first explained in

“Qi Min Yao Shu” (“The Major Measures for Feeding Peoples”), a wellknown ancient agricultural text (A.D. 540) in China.

After this, as the population grew, cropping systems were further developed. The triple-cropping systems of winter crops (such as wheat, rapeseed,

etc.)-rice-upland grain crops were generated, and the areas of rice-rice and

wheat-rice systems were expanded. By the fourteenth to sixteenth centuries

double-cropping rice systems (rice-rice) were common in the provinces of

Zhejiang, Fujian, and Guangdong and a green manure-rice-soybean system

was used in Hengnan County of Hunan Province. In the seventeenth to

eighteenth centuries, wheat-rice-rice systems were recorded.

For historical reasons and because of the farmers’ poor resources, however,

the cropping intensity was not very high in China. Even up to the early 1950s,

the cropping intensity still was only 110-120% in Hunan, Jiangxi, and

Sichuan Provinces, 160%in Zhejiang Province, 141.5% in Guangxi Province,



RICE-BASED CROPPING SYSTEMS



351



and 186% in Guangdong Province. In short, the region of the doublecropping rice system was confined to the southernmost parts of Zhejiang and

Jiangxi Provinces and to the south of the eastern part of Hunan Province, or,

in other words, to the south of 28”N. The wheat-rice system was the

predominant cropping system in the lower and middle reaches of the Yangtze

River Basin.

Since the founding of the People’s Republic of China, high priority has

been given to agrarian reform, building water conservancy facilities, and

restoring agricultural production. As the production conditions were improved, changes in cropping systems started and emphasis was placed on

raising cropping intensities. This was taken as one of the major approaches to

increasing national grain output. The course of reformation or change of

cropping systems can be divided into four stages as follows:

1. In the middle of the 1950s, the well-known “three changes,” i.e., to

change single-cropping rice into double-cropping rice, to change intercropping rice into sequential-cropping rice, and to change one crop a year into

two crops a year were widely recommended and cropping intensity was

increased.

2. In the 1960s, the emphasis of reformation of cropping systems resulted

in the expansion of the acreages of double cropping of rice and of green

manure crops before rice in the south and the expansion of the acreages of

wheat-rice and rapeseed-rice systems in the north. For instance, the area of

green manure-rice-rice increased from 3.6% to 61 % of the total area during

the period of 1955 to 1966 in Zhejiang Province.

3. In the 1970s, the new cropping systems known as double-cropping-ricebased triple-cropping systems (for short, double-rice three-crop systems),

such as barley-rice-rice, rapeseed-rice-rice, and wheat-rice-rice, were generated and expanded.

4. Since the end of the 1970s, as the national economic policies changed,

the rice-based cropping systems have entered a readjustment stage and have

been further improved to meet the needs of national economic development

and the new situation of agricultural production, transferring from selfsufficient production to commodity production.

As a result, after more than 30 years of effort, the rice-based cropping

systems in China have been changed markedly and have contributed greatly

to grain production in the country. The achievements can be summarized as

follows.

1. The double-cropping rice region has been pushed northward from 28”N

to about 32”N. Moreover, the area of double-cropping rice increased from 4

million ha to 11.4 million ha during the period from the early 1950s to 1977.

Double-rice three-crop systems have become the predominant local cropping



GUO YI XIAN AND FEI HUAI LIN



352



systems in the lower reaches of the Yangtze River Basin, the former doublecropping area of wheat-rice, rapeseed-rice, and green manure-rice. In 1976,

the area of double-rice three-crop systems accounted for 95% of the total rice

areas in Shanghai Municipality, and the annual grain yield averaged 11.2

ton/ha.

2. The wheat-rice cropping system region has extended from the original

Yangtze River Basin across the Huaihe and Yellow Rivers to the North

China Plain and has been established as a major cropping system there.

Taking Beijing as an example, the wheat-rice system had occupied 78% of the

municipal rice acreages by 1976.

3. Overall cropping intensity was considerably increased. According to the

statistics, during the period from 1952 to 1979, the cropping intensity of grain

crop fields in the southern 13 provinces, the major rice-growing provinces,

raised from 153% to 203% (green manure excluded). In Guangdong Province, the cropping intensity increased from 186% to 205% in 1966 and to

230% in 1977. And in North China, the cropping intensity also increased. In

Beijing, all the paddy fields had been single cropped in past. Following the

adaption of the wheat-rice system, the cropping intensity of paddy fields

reached the peak of more than 178% in 1976.

4. Rice-cropping acreages were increased in the north, northeast, and

northwest rice belts by 660,000 ha, or one-third of the original rice-cropping

acreage. In Beijing, the rice-cropping acreage was only 3867 ha in 1949. It

increased to 64,500 ha in 1971, a 16.7-fold increase.

5. Increased cropping intensity contributed to increases in grain production. According to the statistics during the period of 1949 to 1981, the

national rice acreage increased from 25.7 to 33.3 million ha, the yield

increased from 1890 to 4320 kg/ha, and the total production increased from



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1961



1965



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1973



1977



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FIG.9. Cropping intensity and provincial yield in Zhejiang.



1981



353



RICE-BASED CROPPING SYSTEMS



48.6 to 144.0 million tons. Increase in cropping intensity has played an

important role in increasing grain production in the past more than 30 years.

It has been estimated that cropping intensity contributed 43% of the total

increase in rice production. Taking Zhejiang Province as an example (Fig. 9),

in 1949 the cropping intensity was 160% and the annual grain yield per

hectare was 2.25 ton; it increased to 173%and 4.1 ton in 1955, 196%and 6.6

ton in 1966, 222% and 7.5 ton in 1972, and 232% and 9.42 ton in 1978,

respectively. This showed the significant correlation between cropping intensity and annual grain yield per hectare.



V. PROBLEMS N MULTIPLE-CROPPING SYSTEMS

Although the reformal 3n of rice-based cropping sytems has made considerable contributions to agricultural production, recently people are much

concerned with the stagnant unstable yields and the high costs of some highcropping-intensity regions. In Wuxi County of Jiangsu Province, where

double-rice three-crop systems had covered almost all the paddy fields, the

increase of grain production averaged 3.9%each year in the period from 1965

to 1976. It declined to 2.3% in the period from 1976 to 1979. The major

problems that constrained the yield are summarized below.



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Rice



Wheat

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FIG.10. Growing period of some major systems in Suzhou and Beijing.



354



GUO YI XIAN AND FEI HUAI LIN



A. GROWING

SEASON

STRESS

In expanding triple-cropping systems in original double-cropping regions,

particularly in the border area, or expanding double-cropping systems in

original single-cropping regions, the first problem met was the stress of the

growing season. The total growing duration for double-rice three-crop

systems was 420-460 days a year in Zhejiang Province and the Suzhou

Prefecture of Jiangsu Province (of which green manure occupied 180 days,

rapeseed 220, barley 190, and double rice 250 days). There was a deficit of 55

to 100 days a year. In Beijing Municipality, the total duration of the

wheat-rice cropping system amounted to 410 days (of which wheat needed

250 days and rice 160 days), resulting in a deficit of 45 days a year. Even if

seedlings were raised in a nursery, or green manure was undersowed

(Astragalus and common vetch) before harvest of the rice, the growing season

was still not long enough. Harvesting the previous crop and planting the next

one must be done within 5-10 days (Fig. 10). As Fig. 10 shows, in Suzhou

Prefecture the first crop of rice does not ripen until the beginning of August,

and the second crop of rice must be transplanted not later than August 10-12.

Any delay would be bound to cause a sharp yield reduction or even the loss of

harvest in cold years.



B. DETERIORATION

OF SOIL PHYSICAL AND CHEMICAL PROPERTIES

Studies by the Shanghai, Zhejiang, and Guangdong Academies of Agricultural Sciences of cropping systems and soil fertility showed that the contents

of organic matter, total nitrogen, and total phosphoros in soil under doublerice three-crop systems were higher than that under double-cropping systems

before they were changed. Similar results (Table I) were obtained by the

Guangdong Academy of Agricultural Sciences in experimental plots. Contents of organic matter, total nitrogen, and total phosphorus in soil under a

wheat-rice-rice system for 3 years were higher than those under a rice-ricefallow system. These results illustrate the effects of greater organic and

chemical fertilizer applications in triple-crossing systems.

However, because the waterlogging period of the fields under double-rice

three-crop systems is about 40 days longer than those under wheat-rice

systems, and also because of successive plowing and harrowing in the wet

conditions each year, the tillage layer of the soil is shallower and the plow pan

is thicker. Investigations in the Suzhou Prefecture of Jiangsu Province by the

Nanjiang Soil Institute of the Chinese Academy of Sciences indicated that

double-rice three-crop systems obviously reduced the contents of microaggregates and the total soil porosity, resulting in low permeability and low



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