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VI. Approaches to Solving the Problem

VI. Approaches to Solving the Problem

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359



RICE-BASED CROPPING SYSTEMS



-



Area



Yield



5.0



.



LO m

r

C



1.0



c

2



3.0 j--



973



1974



1975



1976



1977



1978



1979



1980



FIG.11. Area of double cropping of rice and provincial rice yield in Sichuan.



the fact that the cropping acreage had decreased 588,800 ha (16.1 %) as

compared with 1975.

Taoyuan County of Hunan Province provided another good example.

There were 20,000 ha of double rice located in the areas with high altitude

and with water and labor deficiency. By 1982, more than 10,000ha had been

transferred to wheat (or rapeseed, or green manure)-rice systems, resulting in

an increase of 10,496 tons of grain and a benefit of 4.8 million U.S. dollars.

According to the results of long-term cropping systems experiments

conducted by the Hubei, Hunan, and Jiangxi Academies of Agricultural

Sciences, the rotation systems (green manure-rice-rice followed by rapeseed-rice-rice, wheat-rice-rice, and board bean-rice-rice in four years)

showed a higher yielding potential, better nitrogen efficiency, and greater

Table 111

Comparison of Yields of Double-Cropping Rice

and Middle-Season Rice in the Sichuan Basin



Location



1st crop



2nd crop



Total



Yield of

middle rice

(tonha)



Western part

Central part

Southern part

Eastern part



4.52

3.79

3.95

3.58



2.18

1.73

1.64

1.82



6.70

5.52

5.59

5.40



5.41

4.38

4.59

4.28



Mean



3.96



1.84



5.80



4.67



Yield of double rice (ton/ha)



360



GUO YI XIAN AND FEI HUAI LIN



Table IV

Annual Grain Yield and Nitrogen Efficiency of Rotation

and Succession Cropping Systems

Nitrogen

applied in

rice (kg/ha)



Nitrogen

efficiency

(kg/kg)



System



Grain

yield

(kg/ha)



Rice

yield

(kg/ha)



Rotation"

Successionb

Increase (%)



12,534

11,256

11.4



11,099

11,256



304

331



36.5

34.0



- 1.39



- 8.88



7.35



Rotation: green manure-rice-rice-rapeseed-rice-rice-wheatrice-rice- broad-rice-rice.

* Succession: green manure-rice-rice.



economic benefits (Tables IV and V) as compared to the green manure-ricerice system conducted in succession.

The results also showed that soil physical properties under the rotation

system were improved. In Table VI, we see that the total porosity, particularly the noncapacity porosity of soil, increased under the rotation system.

Investigations carried out by the Hubei Academy of Agricultural Sciences

(1982) indicated that the rotation system resulted in nitrogen being released

earlier than with green manure-rice-rice in a succession system (Table VII).

At the maximum tillering stage, the first crop of rice after broad bean in the

rotation system had absorbed 79.4% of the total nitrogen absorbed in the

whole growing period, but the rice after green manure in the succession

system absorbed only 44.6%of the total amount of nitrogen. The retardation

of nitrogen release failed to meet the requirements of the first crop of rice, so

Table V

Economic Efficiency of Rotation and Succession Cropping Systems''



Location



Systems



Labor

cost

(U.S.$/ha)



Hubei



Rotation

Succession

Increase

Rotation

Succession

Increase



505

279

226

395

177

218



Hunan



'Data are for the period 1978-1981.



Material

cost

(U.S.$/ha)



Gross

return

(U.S.$/ha)



Net

return

(U.S.$/ha)



476

352

134

375

306

69



1775

1326

449

1860

1402

458



795

695

100

1090

919

171



361



RICE-BASED CROPPING SYSTEMS

Table VI

Soil Properties Under Rotation and Succession Systems

Volume

weight

(g/cm2)



System



Total

porosity



Noncapacity

porosity



Total

nitrogen



(%)



( %)



( %)



Total

phosphorus

~~~



( %)



Total

organic

matter (%)



~



Rotation

Succession



1.078

1.040



61.1

56.8



14.7

5.46



0.175

0.167



0.149

0.139



3.054

2.591



Increase



0.038



4.3



9.24



0.008



0.010



0.104



a



Data are for 3 years from 1978-1981.



that an extra nitrogen fertilizer had to be applied. During the duration of

these experiments, the green manure area diminished in these three provinces

and the rapeseed area increased. For instance, in Hubei Province, the green

manure area declined from 808,000 ha to 558,000 ha from 1977 to 1981 and

rapeseed area increased from 59,000 ha to 118,000 ha. Consequently, rotation

systems are recommended.



B. DEVELOPING

NEWRICE-BASEDCROPPING

SYSTEMS

1. Developing Rice-Based Cropping Systems Involving Soybeans,

Maize, Potatoes, and Vegetables in the South



It was recognized that the utilization of soybeans, maize, potatoes, and

vegetables in rice-based cropping systems would bring benefits through the

Table VII

Nitrogen-Absorbed Pattern of First Crop in Rotation and Succession Systems"



Sampling

date



Growing

stage



Rotation

Succession

Increase



June 16

May 30



Peak tiller

Peak tiller



Rotation

Succession

Increase



July 26

July 20



Ripening

Ripening



System



I5N absorbed

@%/Pot)



Rate of N

fertilizer

utilized



89 1

359

532



36.5

15.5

20.7



49.1

21.3

27.8



1123

808

315



38.5

22.4

16.1



51.7

32.1

19.6



Total N

absorbed

(mdpot)



From Hubei Academy of Agricultural Sciences (1982).



GUO YI XIAN AND FEI HUAI LIN



362



Table VIII

Annual Grain Yield in New Experimental Cropping Systems"



System

Soybean-rice

Soybean + maize-rice

Maize-rice

Green manure-rice-rice

Rapeseed - rice- rice



First

crop



Second

crop



1687

1231

4400



6413



1189



Third

crop



Total

8100



1855



6153



6160

5739

5354



5339

5636



9239

10,560

11,075

10,986



a From Hunan Soil and Fertilizer Institute (1983). Data are

measured in kilograms per hectare.



lowering of the peak labor demands at field turnaround times and would also

improve soil properties and the quality of the agricultural products.

Results of new cropping system experiments conducted from 1980 to 1982

by the Soil and Fertilizer Institute of the Hunan Academy of Agricultural

Sciences (1983) showed that green manure-rice-rice and rapeseed-rice-rice

systems had the highest grain productivity, followed by maize-rice and

soybean + maize-rice. The soybean-rice system gave the lowest productivity

(Table VIII). However, the soybean-rice system performed best in terms of

protein yield, while the green manure-rice-rice system was the worst. In spite

of the fact that rapeseed-rice-rice and green manure-rice-rice systems

provided the highest gross and net return, their labor benefit was lowest due

to their high labor requirement (Table IX).

The soil properties were obviously improved in the soybean-rice system

(Table X). As the proportion of air in the soil was increased, the content of

Table IX

Economic Benefits of Different Systems in New Cropping Systems Experiment"



System

Soybean-rice

Soybean + maize-rice

Maize-rice

Green manure-rice-rice

Rapeseed-rice-rice



Gross

Material

Net

return

cost

return

Labor

(U.S.%/ha) (U.S.%/ha) (U.S.%/ha) (man-day/ha)

708

746

733

798

1024



198

225

24 1

253

314



' From Hunan Soil and Fertilizer Institute (1983).



510

521

492

545

710



165

315

330

338

525



Net

return per

man-day

(U.S.$)

3.09

1.65

1.49

1.62

1.35



363



RICE-BASED CROPPING SYSTEMS

Table X

The Properties of Soil Under Different Systems in

New Cropping Systems Experiment"

Phase proportion



(%)



Redox

potential

Eh(mV)



Total reducing

matter

(MEQPWg)



11.2

4.5



363.2

113.3



2.69

4.92



Solid



Liquid



Gas



System



(%I



(%)



Soybean-rice

Green manure-rice-rice



44.7

47.7



43.1

47.7



From Hunan Soil and Fertilizer Institute (1983).



reducing matter decreased and the redox potential of the paddy soil was

raised. These advantages promoted the release of some soil nutrients and

made the fertilizer utilization more efficient (Tables XI and XII). The output/

input ratio of nitrogen and phosphorus was higher in the systems involving

soybean and maize.

The return of nitrogen and phosphorus in the residues was higher in the

rapeseed-rice-rice and green manure-rice-rice systems than in the maizerice system.

The new systems of soybean-rice and soybean + maize-rice have been

recommended in Hunan Province, where the acreage had increased to

13,200 ha by 1982. The yield from these systems, according to the typical

survey, averaged 7541 kg/ha for soybean-rice (of which soybean contributed

1643 kg, rice 5898 kg) and 7792 kg/ha for soybean + maize-rice (soybean

1575 kg, maize 749 kg, rice 5470 kg).

Table XI

Output/Input Ratio of Nitrogen of Different Systems

In New Experimental Cropping Systems"



System



Output

(kg/ha)



Input

(kg/ha)



Output/

Input



Residue

returned

(kg/ha)



Soybean-rice

Soybean + maize-rice

Maize-rice

Green manure-rice-rice

Rapeseed-rice-rice



275.5

290.4

209.7

314.7

345.2



153.5

223.5

301.7

280.2

402.5



1.80

1.30

0.70

1.12

0.86



29.3

29.0

3.9

99.1

78.1



a



From Hunan Soil and Fertilizer Institute (1983).



364



GUO YI XIAN A N D FEI HUAI LIN



Month



FIG.12. Monthly rainfall distribution in Beijing, Changsha, and Hangzhou.



Table XI1

Output and Input of Phosphorus of Dilferent Systems

In New Experimental Cropping Systems"

~



System



Output

Wha)



Input

@/ha)



Output/

Input



Residue

returned

(kg/ha)



Soybean-rice

Soybean + maize-rice

Maize-rice

Green manure-rice-rice

Rapeseed-rice-rice



96.6

107.8

126.7

121.4

158.5



83.9

85.2

107.0

125.4

199.4



1.15

1.26

1.18

0.97

0.79



6.78

7.28

4.95

17.03

29.00



a



From Hunan Soil and Fertilizer Institute (1983).



RICE-BASED CROPPING SYSTEMS



365



2. Developing Rice-Based Cropping Systems Involving Dry-Seeded

Rice in the North

Because of the low and unstable rainfall, inadequate water is the main

restraint on rice production in the northern parts of China. The rainfall

patterns of Beijing (North China), Hangzhou (East China), and Changsha

(Central China) (Fig. 12) show that the annual rainfall in Beijing is the lowest.

However, the monthly rainfall in July and August is somewhat higher in

Beijing than in Hangzhou and Changsha. This is very favorable for dryland

rice production. The technology of dry-seeded (DS) rice avoids serious spring

droughts and reduces the need for irrigation water by two-thirds to threefourths as compared with transplanted rice. The yields of dry-seeded rice in

Beijing Municipality are about 6 ton/ha for commercial varieties and 7.5 ton/

ha for the hybrid rice cultivators.

New cropping systems such as fallow-rice (DS), wheat-rice (DS), and

rapeseed-rice (DS) are being generated and recommended. The acreage of

dry-seeded rice in North China had extended to 90,000 ha in 1984 and will

likely extend further in coming years.

c.



USING THE



VARIETIES WITH



PROPER



MATURITY



Using the varieties with proper maturity is a key feature for getting high

and stable yields in the high-cropping-intensity areas. Early varieties ensure

that the crop ripens early and avoids the low-temperature damage of late

autumn. However, late varieties make full use of the growing season and get

higher yields. Farmers used to prefer late varieties rather than early ones.

As a result, a considerable area of second-crop rice was transplanted after

early August (the critical date in Suzhou District), so that yields of these fields

were low in years with normal weather and even suffered a greater loss in

years with cold weather. It was reported that 6.6% of the first crop of rice and

8% of the second crop of rice were transplanted after the critical date in 1976

in Zhejiang Province.

Which maturity class of varieties would be suitable in multiple-cropping

systems? The answers vary within different localities. In the southern part of

Jiangsu Province, the border region of double cropping of rice, early

maturing varieties were recommended for all the three crops in double-rice

three-crop systems. In Zhejiang Province, south of Jiangsu, early maturing

varieties were recommended only for the first (winter) crop, and late varieties

were recommended for the second and third crops. Actually, varieties with

different maturities were always used in a proper combination.

Investigations in high-yielding areas (annual grain yield more than 12 ton/

ha) in Zhejiang indicated that early varieties occupied 62.1% of the fields



366



GUO YI XIAN AND FEI HUAI LIN



under the first crop, and late varieties occupied 51.5 and 55.0% of the fields

under the second and third crops, respectively. Recently, in order to advance

the ripening date of the medium and late varieties, heat preservation nurseries

for the first crop of rice were widely used and the rice benefited from timely

transplanting. It was reported that the rice area transplanted after the critical

date in Zhejiang was reduced to only 0.3-0.5%of the total rice fields in 1981.



D. IMPROVING

THE COMPONENT

TECHNIQUES

Yields of certain cropping systems are high or low depending not only on

the system itself but also on the agronomic techniques used. Improving the

component techniques related to the multiple-cropping systems plays an

important role in solving the problems in high-cropping-intensity areas.

Raising properly aged and strong seedlings is among the major improved

component techniques. According to local environmental conditions, various

techniques have been developed for different systems, and different maturing

classes of crop varieties have been used. Examples of improved means of

handling rice seedlings are (1) thick sowing of early maturing varieties to save

land and costs and to obtain young and vigorous seedlings; (2) thinner

sowing for late varieties to get big and strong seedlings; and (3) “deposite

seedling techniques,” which utilize double transplanting. The latter involves

sowing in the primary nursery, and after about 30 days the rice seedlings are

transplanted into a “deposite (interval) nursery.” After another half-month,

the seedlings are retransplanted into paddy fields. This system is used for

hybrid rice to get seedlings which are not only strong but which bear many

tillers and have high-yielding potential.

In the southeast region of Sichuan Province, the high summer temperature

region, deposite nursery techniques have been adopted to sow rice earlier and

to ensure earlier heading of hybrid rice, thereby avoiding high-temperature

damage which occurs in late July and early August.

In addition to these systems, techniques of undersowing, intercropping,

relay cropping, and zero tillage are widely used in order to fully utilize the

growing season.

Close spacing of crops is commonly practiced in high-cropping-intensity

areas with relatively short growing seasons. An example is that of the second

crop of rice in Shanghai Muncipality and the southern part of Jiangsu

Province, where the rice plant density may be as high as 60 hills per square

meter. We do not consider this density to be rational, but we recognize that

high plant density is one of the characteristics of some multiple-cropping

systems.

Applying large amounts of pig manure and composts plays an important

role in maintaining soil fertility and high yields in multiple-cropping systems.



367



RICE-BASED CROPPING SYSTEMS

Table XI11

Relation Between Annual Amount of Pig Manure Applied

and Nutrient Contents in Soil"



Treatment

45 tonha



22.5 tonlha



Organic

matter



Total

nitrogen



Available

phosphorus



( %)



( %)



( %)



1974

1979



3.25

3.84



0.222

0.263



120

165



Increase



0.61



0.041



45



1974

1979

Increase



3.24

3.62

0.38



0.228

0.250

0.022



113

106



Year



-7



Zhejiang, 1974-1979.



Research of the Soil and Fertilizer Institute of the Zhejiang Academy of

Agricultural Sciences showed that high manure applications in wheat-ricerice system plots (Table XIII) resulted in higher organic matter, total

nitrogen, and available phosphorus contents in soil during the experimental

period of 1974 to 1979. Heavy top-dressing of nitrogen chemical fertilizers is

recommended to promote vigorous growth in very short vegetative growing

stages of crops.

E. DEVELOPING

LIVESTOCK

TOGETHER

WITH CROPPRODUCTION



Although high cropping intensity lowers the economic efficiency of material and labor inputs, the inclusion of livestock in the system not only meets

market demands but also improves the economic returns from crop production, since by-products and crop residues can be used as feed for livestock.

Reports from the Animal Husbandry and Veterinary Sciences Institute of the

Jiangsu Academy of Agricultural Sciences indicate that feeding swine with

mixtures of wheat, soybean, and rice shortened the feeding duration by

17.6-26.0 days. It also provided an increase of 9.4-15.0 kg of body weight

over cases in which the animal feeds contained only rice or wheat.

Also, the development of agricultural mechanization is an important

approach to relieving the labor stress in areas of high crop intensity. It is

expected that, as national economic development progresses, agricultural

mechanization will be further extended.

Finally, there still remain many problems in high-cropping-intensity areas,

such as the shortage of early maturing and disease resistant varieties of wheat,

soybeans, and maize suitable for lowland conditions. The yield of soybeans



368



GUO YI XIAN AND FEI HUAI LIN



after or before rice is still low and unstable. The cropping systems in low- and

medium-yieldingareas are far from satisfactory,especially in view of the fact

that the grain problem has been at least temporarily solved in China. Ricebased cropping systems are deserving of further research and improvement.

REFERENCES

Bureau of Agriculture, Zhejiang Province. 1982. Suggestion on re-adjustment of cropping

systems in Zhejiang Province. “Material of Provincial Workshop on Techniques of Grain

Production,” pp. 23-28 (in Chinese).

Chinese Association of Agricultural Sciences Societies and Jiangsu Association of Agricultural

Sciences Societies. 198 1. Investigation on development of double rice 3-crop systems in

Suzhou Prefecture. Lett. News Crop. Syst. Res. 5, 22-28 (in Chinese).

Ding Ying. 1963. “Rice in China,” pp. 167-180. Agricultural Publ. House (in Chinese).

Ding Xian-Zhe, and Fang Xian-Zhang. 1981. Reformation and tendency of rice-based cropping

systems in Zhejiang Province. “ A Collection of Cropping Systems Research Reports,” pp.

149-162 (in Chinese).

Fei Huai Lin. 1984. The achievements and problems of rice-based cropping systems in China.

Rep. Crop. Syst. Work. Group Meet., 14th, IRRI pp. 83-104.

Guo Yi-Xian. 1982. The rice-based cropping systems and their developments in China. Rep.

Workshop Crop. Syst. Res. Asia, IRRI pp, 331-344.

Guo Yi Xian. 1984. Problems in rice-based multiple cropping systems and the solving

approaches. Proc. Int. Crop Sci. Symp., Japan. Oct. 17-20, pp. 55-68.

Hubei Academy of Agricultural Sciences. 1982. Report of collaborative research on double rice

3-crop systems experiment in Hubei. Hunan and Jiangxi Provinces. A Certification of

Achievements of Rice-based Triple Cropping Systems Research (in Chinese).

Hunan Soil and Fertilizer Institute. 1983. A summary report of long-term rice-based cropping

systems research (in Chinese).

Jiangsu Agricultural Modernization Institute. 1982. Report of pre-production experiment on

wheat + maize-rice system in Taihu Lake District. “Selections of the Research Reports of

Taihu Lake Site,” pp. 73-76 (in Chinese).

Tu Zheng Wen. 1984. Rice insect pest control in high cropping intensity areas. Rep. Crop. Sysr.

Work. Group Meet., 14th, IRRI pp. 105-117.

Wang Chu Yun, Liang Dun Fu, and Xian Min Yue. 1980. A review and prospect of cropping

systems reformation in Sichuan Province. Nut. Crop. Syst. Workshop (in Chinese).

Zhu Bin Hai. 1962. “Climate in China.” Beijing Science Press (in Chinese).



Index

A



Cations

exchangeable, and clay and aggregate bonding, 108-110

reaction with variable-charge soils, 183-228

four-layer model, 195-207

quantitative modeling of, 221-226

single-layer model, 191-193

three-layer model, 193-195

Charge, development on variable-charge surfaces, 185-186

China, rice-based cropping systems, 339-368

belts of, 345-350

component techniques, improvement of,

366-367

day length and, 342-343

development of new systems, 361-363

growing season stress, 354

labor utilization for, 356

and livestock development, 367-368

multiple-cropping systems, problems with,

353-358

net income of fanners, 356-357

pest problems, 355

population and, 344-345

precipitation effects, 341-342

reformation and achievements, 350-353

soil variability and, 343-344

solutions to problems of, 358-368

temperature effects, 340-341

use of varieties with proper maturity, 365366

Clay minerals

application of first-order kinetics to, 240-



Adsorption, on variable-charge surfaces, 186207

description of, 186- 190

four-layer model, 195-202

rates, 207-21 1

single-layer model, 191-193

three-layer model, 193- 195

Aeration, and root growth impedance, 136140

Africa, weed composition in upland rice, 288

Agricultural soils

clay and aggregate bonding in, 108-112

exchangeable cations and electrolyte effects, 108-110

temporary dispersion effects, field expression, 110- 112

water flow in, 114-127

infiltration, 114-122

redistribution within root zone, 112- 127

Algae, blue-green (cyanobacteria), nitrogen

fixation, 274-276

Anions, reaction with variable-charge soils,

183-228

four-layer model, 195-207

quantitative modeling of, 221-226

single-layer model, 191-193

three-layer model, 193-195

Asia, weed flora in upland rice, 285-286

Autocorrelation, and spatial dependence analysis, 56-57



B

Bonding

aggregate, in agricultural soils, 108-1 12

clay, in agricultural soils, 108- I12

organic matter, in agricultural topsoils, 113114



C

Carbon dioxide, atmospheric, effect on gaseous hydrocarbons in soil, 174



245



ionic exchange in, kinetics, 258-260

ionic reactions

kinetics, 231-263

rate-limiting steps, 250-255

Clays, micaceous, ionic exchange rate on,

259-260

Cropping systems, rice-based, in China

component techniques, improvement of,

366-367

day length and, 342

development of new systems, 361-363

369



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