Sulfur Fertilizer: A Future Constraint to the Sustainable Development
                        of China's Agriculture
                             By Feng Yuanqi
the former  Economic & Technical Commission  of  Ministry  of  Chemical
Industry
In the past 20 years 120 countries in the  world  have  been  found  in
short of sulfur fertilizers. Sulfur  shortage  not  only  affects  the
yield and  quality  of  agricultural  crops,   but  also  reduces  the
utilization rate of fertilizer nutrients. It has become  an  important
factor in maintaining the agricultural system and improving  the  soil
fertility.
1. Soil sulfur content and sulfur application tests in China
According to the report of FAO in 1995, the average     growth rate  of
the total grain output in China was 2.8% from 1974 to 1994,   but  the
unit yield dropped by 1.1% a year. It shows that  the  intensification
  of  agricultural  production  has  increased  the  burden   on   soil
productivity and fertility, and sulfur  shortage  in  soil  has  shown
itself. The rate of sulfur-lacking cultivated land in China  is  31  -
40% in Guangdong and Fujian, 20 - 30% in Guizhou,   Yunnan,   Sichuan,
Hunan and Hubei, 10 - 20% in Jiangsu, Zhejiang, Shandong,   Henan  and
Hebei, and 40 - 60% in Liaoning and Jilin. Many agricultural  research
institutes have therefore conducted a lot of tests  concerning  sulfur
application.
(1) Southwest Region
Kunming Ecological Research Institute of the Chinese Academy of Sciences,
the Entomological Research Institute of Yunnan Academy of Agricultural
Sciences and the Soil  &  Fertilizer  Research  Institute  of  Guizhou
Academy of Agricultural Sciences have made surveys to the soil  sulfur
content in Yunnan, Guizhou and Guangxi. Owing to  the  high  altitude,
great humidity and relatively low temperature in the  region,   it  is
easy for organisms to be formed but hard for them  to  be  decomposed.
The total sulfur amount in soil is therefore high but  the  amount  of
effective sulfur is still not enough. There is  a  universal  lack  of
sulfur in the region. The  study  of  sulfur  circulation  shows  that
sulfur outgoing is larger than sulfur incoming and a certain amount of
sulfur needs to be replenished. For example, 40.38 kg of sulfur  needs
to be applied to one hectare of rice/wheat field a year and 46. 21  kg
of sulfur needs to be applied to one hectare of rice/rice field a year
. Many effective measures worth dissemination were  summarized  in  the
tests.   Use  of  gypsum  can  increase  the  rice  yield  by  62. 8%.
Phosphogypsum was used in 300 000 hectares of farmlands in Yunnan  and
Guangdong from 1986 to 1996, and a total of 237 million yuan was reaped.
(2) North Region
Nanjing Soil Research Institute of the Chinese Academy of Sciences  has
made an analysis of soil effective sulfur content in 11  provinces  in
the region. The results show that there is sulfur shortage in 35.3% of
soil and the effective sulfur content is less than the critical figure
of 12 mg/l. Special attention should be  paid  to  sulfur  application
skills in sulfur-lacking areas and soil types.
(3) Reaches of the Yangtze River and the Huai River
Nanjing Soil Research Institute of the Chinese Academy of Sciences, the
  Ecological  Research  Institute  of  Hubei   University   and   Anhui
Agricultural University have conducted  sulfur  ( gypsum  and  sulfur)
application tests to different crops such as rape, peanut and  cabbage
in yellow cinnamon soil and red soil in the  reaches  of  the  Yangtze
River and the Huai River. The results prove that  use  of  sulfur  can
increase yield and improve quality,   but  different  soil  types  and
different crops have selectivity to sulfur fertilizers.
(4) Northwest Region
Surveys made by units including Northwest Agricultural University  show
that the sulfur content in loess soil of the region mainly comes  from
organic sulfur. However, the amount of effective sulfur is only 0.7 - 2.
2% of the total. Irrigation water with low-concentration sulfuric  acid
can increase the crop yield.
  Shaanxi is one of the major grain producing provinces in China. There
is sulfur shortage in 55.2% of the cultivated land  in  the  province.
The unit yield of the cultivated land in the province is only 63.5% of
the national average. There is a great potential  of  yield  increase,
and sulfur application will become an important measure for  promotion
of agricultural production in the province. There  are  mainly  yellow
cinnamon soil, loess soil and black loess soil in Gansu.   These  soil
types lack both effective sulfur amount and total sulfur amount,   and
there is sulfur shortage in 30 - 40% of the  cultivated  land  in  the
province.
2. Sulfur sources and application in China
(1) sulfur sources
Sulfur sources in soil: The average total sulfur  amount  in  different
soil types is 100 - 500 mg/kg in China. The sulfur content in soil  of
  South  China  and  East  China  mainly  comes  from  organic  sulfur,
accounting for 85 - 94% of the total. The sulfur content  in  soil  of
North China and Northeast China mainly comes  from  inorganic  sulfur,
accounting for 39.4 - 66.8% of the total. The soil types in East China
, South China and Southwest China are irrigated land, plantation,   dry
land and forest land in order of the average effective sulfur content.
  Sulfur sources in minerals: Sulfur sources in minerals in China mainly
include sulfur-containing coal, gypsum and pyrite. The sulfur  content
in coal in the highest.