Agriculture Reference
In-Depth Information
7.3.4 Change in SOC Pool under Different Fertilizer Managements
over Long-Term Experiments ........................................................... 177
7.4 Conclusions ................................................................................................... 180
Acknowledgments .................................................................................................. 181
References .............................................................................................................. 181
7.1 INTRODUCTION
The Huang-Huai-Hai plains (HHH) is the principal wheat (
Triticum aestivum
)-
maize (
Zea mays
) production area in China and is characterized by high chemical
fertilizer inputs since the 1980s. Data from eight long-term experiments for monitor-
ing soil organic carbon (SOC) changes under different fertilizer managements over
time were collated to study the trends in SOC for the following six treatments: (i) con-
trol without inorganic or organic fertilizers (CK); (ii) chemical fertilizers used as N,
P, and K without organic manure (UF); (iii) combined application of NPK without
organic manure (CF); (iv) retention of wheat and maize straw along with the use
of animal manure (O); (v) combined use of chemical fertilizers and organic manure
(FO); and (vi) combined application of chemical fertilizers N, P, or K separately and
organic fertilizers (UFO). The data indicated the following: (i) The mean SOC pool at
0-20 cm depth was 18.9 ± 1.8, 19.7 ± 1.7, 20.8 ± 2.1, 20.3 ± 2.5, 23.4 ± 7.2, and 24.3 ±
6.6 Mg ha
−1
for CK, UF, CF, O, UFO, and CFO managements, respectively, and was
in the order of CFO > UFO > O > CF > UF > CK. (ii) In comparison with CK, the
SOC pool increased with all fertilizer management treatments, and the mean absolute
SOC pool change (ΔSOC over this period) was −0.5, 0.8,
1.9, 1.6, 4.8, and 5.4 Mg ha
−1
for CK, UF, CF, O, UFO, and CFO treatments, respectively. (iii) The highest rate of
increase in SOC pool was measured in CFO, and the maximum rate (MR) of increase
ranged from 224.4 to 1969.7 kg ha
−1
year
−1
, and the 23 years average rate (AR) ranged
from 74.0 to 1529.6 kg ha
−1
year
−1
. (iv) The trend line for UFO and CFO within all the
experimental sites indicated an increasing trend, which maintained a constant/stable
SOC pool for CK, UF, CF, and O fertilizer managements. (v) There was a threshold
for CFO and UFO fertilizer managements; the maximum SOC pools for the XinjiA,
XinjiB, and Xuzhou sites were 42.1, 34.2, and 26.4 Mg ha
−1
, and the experimental
durations to achieve these rates were 21.0, 41.9, and 15.7 years, respectively. (vi) The
maximum SOC pools under UFO for the XinjiA, XinjiB, and Xuzhou sites were 42.8,
26.4, and 34.2 Mg ha
−1
, and the experimental durations to achieve those SOC pools
were 23.0, 20.0, and 15.8 years, respectively. The SOC concentration/pool in the root
zone were strongly affected by the fertilizers and management.
Soils are important to the moderation of numerous ecosystem services such as net
primary productivity, food and fiber production, water storage and quality, and biodi-
versity (Lal 2010a). SOC is an important determinant of soil quality and sustainable
agriculture, and its quality and quantity influence soil fertility and crop production.
The SOC pool in the root zone is influenced by soil fertility management. Most soils
in managed ecosystems contain a lower SOC concentration/pool than those under
natural environments because of the higher rates of mineralization accelerated by
changes in soil temperature and moisture regimes, lower input of biomass C, and
higher losses caused by accelerated erosion and leaching (Lal 2004). The SOC pool
