Agriculture Reference
In-Depth Information
7.3.2 SOC p
OOl
C
hAngeS
under
d
ifferent
f
fertilizer
m
AnAgementS
C
OmpAred
with
CK
The data in Table 7.4 show changes in SOC pool for different fertilizer and manage-
ment treatments compared with CK, and that of CK compared with the antecedent
SOC pool of arable land. In general, the mean SOC pool increased by 3.0 Mg ha
−1
,
with the maximum and minimum change from 37.3 to −3.8 Mg ha
−1
, respectively.
Of the total of 1113 observations, 1013 (90%) indicated an increase and 110 (10%) a
decrease in the SOC pool.
The magnitude of change in different fertilizer managements vis-à-vis CK dif-
fered widely. All fertilizer managements contained significantly more SOC pool
compared with that of CK. Furthermore, significant differences in the magnitude
of increase in SOC pool were observed for UFO, CFO, and also for O, UF, and CF
fertilizer management treatments. However, no significant difference in SOC pool
occurred between CFO and UFO, and among O, UF, and CF treatments. The mean
ΔSOC were −0.5, 0.8, 1.8, 1.6, 4.8, and 5.4 Mg ha
−1
for CK, UF, CF, O, UFO, and
CFO, respectively. The highest SOC sequestration was observed for CFO, and its
magnitude was in the order of CFO > UFO > CF > O > UF > CK.
The trend line was computed to estimate the SOC sequestration potential for dif-
ferent fertilizer managements in the HHH region between 1978 and 2003. The rates
of SOC sequestration estimated in this region differ from those reported by Pan et al.
(2010) and Wu and Cai (2007), and are discussed below for each treatment.
7. 3 . 2 .1 C K
The change in SOC pool with reference to the initial level was −0.5 Mg ha
−1
. Of the
110 measurements in CK, the maximum and minimum change in SOC pool was
3.8 and −3.8 Mg ha
−1
, respectively. These results of ΔSOC pool in CK are similar to
those reported by Wu and Cai (2007). The baseline of SOC pool in arable land was
18.9 ± 1.8 Mg ha
−1
in the HHH. Of all the experimental sites, the SOC pool increased
only in the XinjiA and ZhengzouB sites, and decreased in all other experimental
sites. Therefore, the SOC pool without fertilizer inputs in the HHH remained at a
low level between 1978 and 2003. These trends in the SOC pool in cropland soils in
the HHH ecosystem are similar to those of cultivated soils of South Asia and sub-
Saharan Africa where the attendant decline in soil quality is among the important
causes of low and declining agronomic production (Lal 2010b). The trend of SOC
pool for CK fertilizer management is suboptimal and good neither for achieving food
security nor mitigating the climate change or improving the environment.
7.3.2.2 O
The mean increase in SOC pool is 1.6 Mg ha
−1
. This result is similar to an increase of
2.1-2.9 g kg
−1
reported by Ma et al. (2010). The mean range of increase in SOC pool
was lower than those for CFO and UFO. The magnitude of increase in SOC pool
with the use of organic manure was less than that for the combined use of inorganic
fertilizer and organic manure. The maximum and minimum increases were 6.5 and
2.3 Mg ha
−1
, respectively. The maximum increase of 2.4 Mg ha
−1
was observed in
HenshuiB. The results show that the application of organic manures has similar
