Agriculture Reference
In-Depth Information
By a statistical integration of SOM contents of croplands, Pan et al. (2009)
reported  linear response of provincial mean cereal productivity to the aver-
age SOM content of croplands of China, though varying in incremental response
depending upon climatic conditions and socioeconomical and technological factors
( Figure  18.1 ). The mean provincial cereal yields of the major crop production prov-
inces of North China (solid triangles) from 1950 to 1999 are strongly related to their
mean topsoil SOM contents. However, such a relationship is weak for the provinces
in southeast China, and there was no response in other provinces such as Jiangsu and
Shanghai. The linear correlations suggest an approximate productivity of 8 Mg/ha
for rainfed uplands and 6 Mg/ha for rice paddies corresponding to a SOM content of
10 g/kg (Figure 18.1).
Furthermore, data from long-term monitoring and field experiments with differ-
ent management practices revealed also significant SOM control on crop productiv-
ity and sustainability (Table 18.1). In general, a change in SOM content of 0.1% could
reduce the variability by 1% to 2%. However, the overall changes in soil organic
carbon (SOC storage under agricultural development for the last decades and the
future sequestration capacity of the croplands have experienced a large C debt since
the early twenty-first century. The SOC storage has been a major issue in relation
to the highly variable crop production since the end of the last century (Table 18.1).
In addition, there was also evidence that SOM had prominent impacts on rural eco-
nomic development, even though it was not entirely based on agriculture. A regression
analysis of data compiled from the second Chinese soil survey showed that the mean
agriculture production of a municipality in Jiangsu in the early 1980s at the time of
the survey was correlated with the mean SOM score (a ranking value of croplands
determined by the proportion of cropland area with high SOM category, correspond-
ing to a relative SOM abundance in croplands) ( Figure 18.2 ).
TABLE 18.1
Temporal Variability in Crop Yield of Long-Term Experiments in Relation to
SOC Contents across China
Agro/Ecoregion
Crop
Yield Variability (%)
Topsoil SOC (g/kg)
Central China plain
Wheat-maize
30-45
7-8
Tai Lake plain
Rice
8-30
16-20
Northern Zhejiang plain
Rice
12-30
15-17
Rolling area of red soils in
Hunan
Winter wheat
30-40
9-11
Purple basin of Sichuan
Winter wheat
15-30
15-18
Summer rice
13-20
Rolling area of red soil,
Jiangxi
Double rice
8-17
13-20
Source: Yield and SOC data from the long-term experiment sites between the late 1980s and early 2000s,
courtesy of Dr. Xu Mingang.
 
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