Agriculture Reference
In-Depth Information
TABLE 9.10
Changes in Stocks of Soil Organic Carbon in 0-20 cm Layer during 42 Years
in Long-Term Field Experiment with Irrigation in Crop Rotation (Field No. 1)
Rainfed
With Irrigation
LSD
05
,
t/ha
Years
Indices
Unfertilized
Fertilized
Unfertilized
Fertilized
1968
Initial stocks of carbon,
70.1 Mg/ha
2010
Carbon stocks
62.6
64.1
62.6
66.2
2.8
Stock reduction
7.5
6.0
7.5
3.9
Percentage of initial
stocks
10.7
8.6
10.7
5.6
Rate of SOC loss,
Mg C/ha/year
0.18
0.14
0.18
0.09
Rate of SOC loss for 1-m depth
since 1968, Mg C/ha/year
0.59
0.28
0.58
0.45
Although the different systems of soil tillage in crop rotations had little effect on
crop yields, they had a larger effect on the retention of SOM (Table 9.12).
The greatest increase in stocks of SOM were observed in the crop rotation with a
mixture of alfalfa and perennial grasses for green biomass used with manure + NPK:
0.96 Mg/ha on the plots with minimum tillage and selective moldboard plowing, and
0.760 Mg/ha on the minimum-tillage plots.
The experimental data indicate synergy between three main components of the
farming system: use of perennial legumes and grasses in crop rotation, combina-
tion of minimum tillage with selective plowing, and integrated nutrient management
combining FYM with NPK. The legumes and grasses alone cannot maintain the
stocks of SOM under crop rotations on unfertilized plots. However, combination of
selective plowing and minimum tillage can reduce the losses of SOM under arable
land use systems. On the other hand, SOC stocks can be maintained or increased if
enough OM is added as FYM. A somewhat lesser benefit from the combination of
moldboard plowing and minimum tillage on fertilized plots with manure + NPK on
stocks of SOM was observed in crop rotation without perennial legumes and grasses.
This trend may be attributed to the quality of SOM under the influence of different
rotations, systems of soil tillage, and fertilization.
In general, plowing accelerates the oxidation of SOM. However, an optimal com-
bination of the moldboard plow and minimum tillage in crop rotation can be very
effective on heavy soils infested with perennial weeds. The danger of using mold-
board plowing in crop rotation comes mainly from the insufficiency of energy-rich
crop residues and manure, and in aggravating the risks of soil erosion.
The data from the multifactorial experiment were used to appraise the production
expenditures for winter wheat in crop rotation after maize silage and after alfalfa and
perennial grasses under both minimum tillage and selective use of moldboard plowing
with minimum tillage. The economic analyses were done by using a technological map
