System productivity and sustainable yield index (SYI)
System productivity was significantly (P≤0.05) differed among the cropping systems and NRCM practices in all the experimental years (Table 2). The RBcJ cropping system had significantly (P≤ 0.05) higher system productivity compared to remaining other cropping systems during all years. Among NCRM, productivity did not differ significantly in initial experimental year (2012-15), however, it was significantly higher in F2R1 compared to other practices during later year of experimentation (2016 to 2017). System productivity was significantly higher (19.33 Mg/ha) inJRBc over rest of the cropping systems. The pooled data for five years of system productivity indicated the significant (P≤ 0.05) variation among different cropping systems. The highest system productivity was recorded in RBcJ compared to all cropping system. The rest cropping systems had productivity as RVpJ(12.86 Mg/ha)>RMGgJ (11.98 Mg/ha) > RWJ (10.79 Mg/ha)> RR (8.79 Mg/ha). Among NRCM practices, F2R1 treatment had significantly higher system productivity (12.98 Mg/ha) than other practices. The highest sustainable yield index (SYI) in RGpJ cropping system (0.86) followed by RMMuJ (0.82)> RR (0.87)>RWJ(0.75) >RBcJ (0.72).
Table 2. System productivity and sustainable yield index (SYI) of different cropping systems under nutrient and crop residue management practices
|
2012-13
|
2013-14
|
2014-15
|
2015-16
|
2016-17
|
Pooled
|
SYI
|
Cropping system (CS)
|
|
RR
|
8.64
|
8.79
|
8.74
|
8.81
|
8.97
|
8.79D
|
0.77
|
RWJ
|
10.29
|
11.18
|
11.83
|
10.39
|
10.25
|
10.79C
|
0.75
|
RBcJ
|
22.28
|
19.26
|
17.74
|
21.84
|
15.52
|
19.33A
|
0.72
|
RVpJ
|
12.94
|
12.78
|
13.41
|
12.07
|
13.09
|
12.86B
|
0.86
|
RMGgJ
|
12.13
|
12.50
|
12.13
|
11.42
|
11.42
|
11.98B
|
0.82
|
SEm (±)
|
0.40
|
0.30
|
0.34
|
0.31
|
0.11
|
0.30
|
|
LSD (P <0.05)
|
1.16
|
0.86
|
0.98
|
0.90
|
0.31
|
0.94
|
|
Nutrients and crop residue management (NCRM) practices
|
F1R0
|
13.10
|
12.72
|
12.41
|
11.86
|
11.21
|
12.06
|
0.76
|
F1R1
|
13.41
|
12.78
|
12.67
|
12.30
|
11.39
|
12.51
|
0.80
|
F2R0
|
13.39
|
13.09
|
13.05
|
12.38
|
11.54
|
12.69
|
0.79
|
F2R1
|
13.12
|
13.01
|
12.95
|
12.77
|
12.04
|
12.98
|
0.84
|
SEm (±)
|
0.25
|
0.19
|
0.21
|
0.15
|
0.10
|
0.18
|
|
LSD (P <0.05))
|
NS
|
NS
|
NS
|
0.43
|
0.30
|
0.36
|
|
CS × NRCM
|
NS
|
NS
|
NS
|
NS
|
NS
|
|
|
R-Rice, J-Jute, W-Wheat, Bc-Baby corn; Vp; Vegetable pea; M-Mustard,Gg-Green gram; F1-75% NPK; F2-100% NPK; R0-No residue; R1-residue incorporation;
Soil C dynamics
Effect on soil carbon fractions:
Cropping system (CS) and nutrients and crop residue management (NCRM) practices significantly influenced (P<0.05) the different carbon fractions on upper soil surface (0-15 cm), however, at the lower depth of soil the influence of CS and NCRM practices was not significant (Table 3). Among different CS, RMGgJ recorded the significantly (P<0.05) higher very labile carbon (VLC) (1.39 g/kg) as compared to RR cropping system and it was almost equal with RVpJ, RBcJ cropping systems. Among NCRM practice, 100% NPK with crop residue incorporation (F2R1) recorded the significantly higher VLC compared to no residue either with 75% NPK (F1R0) or 100% NPK (F2R0). The labile carbon (LC) and less labile carbon (LLC) fraction in RMGgJ cropping system were significantly higher than RWJ and RR cropping systems however, these were non-significant with RVpJ and RBcJ cropping systems. Among NCRM practice, F2R1 had significantly higher LC and LLC fraction compared to remaining other practices. The non labile C fraction (NLC) did not vary significantly among different cropping systems, but NCRM practice i.e. F2R1 had significantly higher NLC compared to both F1R0 and F2R0 practices. The variation of carbon fractions among different cropping systems led to significant effect on total organic carbon (TOC) too. RMGgJ system significantly increased the TOC (7.60 g/kg) than all cropping systems, though it was at par with RVpJ (7.58 g/kg). Among NRCM practices, F2R1 had significantly increased the TOC (8.42 g/kg) as compared to remaining other practices. Though, all carbon fractions at 15-30 cm and 30-45 cm soil depth were almost equal among different cropping systems and NCRM practice, TOC was significantly higher at 15-30 cm depth in RMGgJ cropping system as compared to others cropping systems.
Lability Index and Carbon management index
Lability Index: A significant difference in lability index (LI) was observed among different cropping systems and NCRM practices (Figure 3), however, it was only confined to upper surface of soil (0-15 cm). RMGgJ cropping system had significantly higher LI than other cropping systems except RVpJ system. Among NRCM practice, F2R1 significantly increased LI of carbon as compared to remaining other practices at 0-15 cm soil depth. Although, lability index was comparatively higher in lower soil surface (15-30 cm) than upper soil surface, neither cropping systems nor NCRM practices significantly influenced the LI at lower soil depth of 30-45 cm.
Table 3. Soil carbon pools/fractions under different Cropping system and Nutrients and crop residue managementpractices at different soil depth
|
0-15 cm soil depth
|
15-30 cm soil depth
|
30-45 cm soil depth
|
|
VLC
(g/kg)
|
LC
(g/kg
|
LLC
(g/kg
|
NLC (g/kg
|
TOC
(g/kg)
|
VLC
(g/kg)
|
LC
(g/kg
|
LLC
(g/kg
|
NLC (g/kg
|
TOC
(g/kg)
|
VLC
(g/kg)
|
LC
(g/kg
|
LLC
(g/kg
|
NLC (g/kg
|
TOC
(g/kg)
|
Cropping system (CS)
|
RR
|
1.02B
|
0.49B
|
0.59B
|
3.90A
|
6.17C
|
0.68CB
|
0.47A
|
0.57A
|
2.27A
|
4.02B
|
0.42A
|
0.38A
|
0.53A
|
2.30A
|
3.70A
|
RWJ
|
1.17AB
|
0.57B
|
0.69B
|
4.18A
|
6.57BC
|
0.68CB
|
0.55A
|
0.61A
|
2.90A
|
5.08A
|
0.47A
|
0.40A
|
0.57A
|
2.37A
|
3.87A
|
RBcJ
|
1.21A
|
0.70A
|
0.93A
|
4.10A
|
6.98B
|
0.69CB
|
0.65A
|
0.73A
|
2.99A
|
5.02A
|
0.49A
|
0.52A
|
0.62A
|
2.75A
|
4.40A
|
RVpJ
|
1.31A
|
0.82A
|
1.01A
|
4.34A
|
7.58A
|
0.81BA
|
0.67A
|
0.87A
|
3.17A
|
5.44A
|
0.48A
|
0.40A
|
0.74A
|
2.90A
|
4.49A
|
RMGgJ
|
1.39A
|
0.78A
|
1.08A
|
4.28A
|
7.60A
|
0.92A
|
0.78A
|
0.86A
|
3.32A
|
5.77A
|
0.58A
|
0.57A
|
0.74A
|
2.89A
|
4.74A
|
SEm (±)
|
0.08
|
0.08
|
0.08
|
0.16
|
0.21
|
0.10
|
0.11
|
0.15
|
0.37
|
0.27
|
0.13
|
0.06
|
0.20
|
0.30A
|
0.42
|
LSD (P <0.05))
|
0.23
|
0.24
|
0.23
|
0.46
|
0.58
|
0.28
|
NS
|
NS
|
NS
|
0.90
|
NS
|
NS
|
NS
|
NS
|
NS
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
F1R0
|
1.10b
|
0.50b
|
0.69b
|
3.81c
|
6.12c
|
0.68a
|
0.45a
|
0.46a
|
2.67a
|
4.78a
|
0.49a
|
0.42a
|
0.46a
|
2.38a
|
3.65a
|
F1R1
|
1.32a
|
0.61b
|
0.89b
|
4.20ba
|
7.22b
|
0.75a
|
0.55a
|
0.76a
|
2.99a
|
5.10a
|
0.55a
|
0.45a
|
0.65a
|
2.76a
|
4.42a
|
F2R0
|
1.20b
|
0.55b
|
0.74b
|
4.06cb
|
6.71bc
|
0.70a
|
0.48a
|
0.68a
|
2.78a
|
4.89a
|
0.52a
|
0.49a
|
0.63a
|
2.61a
|
4.05a
|
F2R1
|
1.40a
|
1.03a
|
1.22a
|
4.57a
|
8.32a
|
0.77a
|
0.60a
|
0.88a
|
2.95a
|
5.18a
|
0.58a
|
0.56a
|
0.64a
|
2.86a
|
4.55a
|
SEm (±)
|
0.07
|
0.07
|
0.11
|
0.14
|
0.19
|
0.08
|
0.099
|
0.096
|
0.18
|
0.18
|
0.06
|
0.06
|
0.08
|
0.21
|
0.23
|
LSD (P <0.05)
|
0.20
|
0.21
|
0.30
|
0.40
|
0.55
|
NS
|
NS
|
NS
|
NS
|
NS
|
NS
|
NS
|
NS
|
NS
|
NS
|
CS × NRCM
|
NS
|
NS
|
NS
|
NS
|
NS
|
NS
|
NS
|
NS
|
NS
|
NS
|
NS
|
NS
|
NS
|
NS
|
NS
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
R-Rice, J-Jute, W-Wheat, Bc-Baby corn; Vp; Vegetable pea; M-Mustard,Gg-Green gram; F1-75% NPK; F2-100% NPK; R0-No residue; R1-residue incorporation; TOC-total organic C; SOC- Soil Oxidisable C by Walkley–Black ; VLC- very labile C; LC- labile C; LLC- less labile C; NLC- non-labile C. Means data with different alphabets letters (Uppercase for main plot and lower case for sub-plot comparison) within a column are significantly differ at P < 0.05 according to Duncan’s Multiple Range Test (DMRT) test.
Carbon management index (CMI):
CMI significantly influenced by cropping systems and NCRM practices (Figure 4). The highest CMI was recorded with RMGgJ (61.2) and 100% NPK with crop residue incorporation in soil (63.0), the reference soil had the maximum CMI i.e. 100. At 0-15 cm soil depth RMGgJ cropping system had the highest CMI (61.2), though; it was non-significant with RVpJ cropping system (57.5). The similar trend was followed among cropping systems at 15-30 cm depth but CMI did differ significantly at 30-45 cm depth. NRCM practices also could not significantly influence the CMI at both 15-30 and 30-45 soil depth.
C sequestration (Cseq) rate:
The significant effect of cropping systems and NCRM practices on Cseq rate (varied from 0.31 to 0.56 Mg/ha/year) was observed, however, it was mostly confined to the upper surface of soil i.e. at 0-15 and 15-30 cm of soil depth (Figure 5). At lower soil depth i.e. (30-45 cm), the Cseq rate was not significantly affected either of cropping systems and NCRM practices. At 0-15 cm soil depth, RMGgJ system significantly increased the Cseq rate (0.56 Mg/ha/year) than remaining other cropping systems, however, it was at par with RVpJ cropping system. While, at 15-30 cm soil depth only RMGgJ system recorded significantly higher Cseq rate than all other cropping systems. Among NCRM practice, F2R1 significantly increased the Cseq rate than other practices at both 0-15 cm and 15-30 cm. But at lower depth (30-45 cm) Cseq rate in all NCRM practice was almost equal.
Carbon sequestration/build up
Significant variation was recorded in carbon stocks after five years of continuous cultivation of different cropping systems and NCRM practices (table 4). The upper soil surface (0-15 cm) had higher C accumulation (1.55 to 3.32 Mg/ha) than lower soil depth of 15-30 (0.79 to 2.71 Mg/ha) and 30-45cm (1.55 to 3.32 Mg/ha), irrespective of cropping systems and NCRM practices. Significantly higher C buildup was observed in RMGgJ system than other cropping systems; however, it was at par with RVpJ system. The RBcJ, RWJ and RR cropping systems had almost equal C build in upper surface of soil. Among NCRM practices, F2R1 had significantly higher C sequestration than other practices. at 15-30 cm soil depth only RMGgJ cropping system could significantly increase the C sequestration compared to all cropping systems, remaining other cropping system recorded almost equal C sequestration at this soil depth. Among NCRM practice, 100% NPK applied with crop residue had higher C accumulation than other practices at upper soil surface (0-15 cm). At 30-45 cm soil depth, neither cropping systems nor NCRM practices significantly influenced the C accumulation in soil. The C accumulation trend in greater depth i.e. 0-30 and 0-45 had similar trend of than 0- 15 cm soil depth.
Stratification ratio (SR) of SOC
Stratifications ratio (SR) of SOC which is the indicator of soil quality was lower (1.16 to 1.24) at 0-15/15-30 depth ratio as compared to 0-15/30-45 depth ratio (1.27 to 1.38) irrespective of cropping systems and NCRM practices (Figure 6). Among cropping systems, RMGgJ recorded significantly higher SR compared to RR and RWJ under both the depth ratio, however, it was similar with RVpJ and RBcJ cropping systems. Among NCRM practice, F2R1 recorded significantly higher SR than F1R0 and F2R0 but that was similar F1R1 at both depths.
Table: 4 soil carbon build up/sequestration under different Cropping system and nutrients and crop residue management (NCRM) practices at different soil depth
|
SOC accumulation (Mg/ha)
|
|
0-15 cm
|
15-30 cm
|
30-45
|
0-30 cm
|
0-45 cm
|
Cropping system (CS)
|
RR
|
1.55C
|
0.79B
|
0.72A
|
2.01C
|
3.12B
|
RWJ
|
1.85BC
|
0.96B
|
0.92A
|
2.67BC
|
3.53B
|
RBcJ
|
1.87BC
|
1.18B
|
0.81A
|
2.95BC
|
3.67B
|
RVpJ
|
2.49BA
|
1.29B
|
1.03A
|
3.93BA
|
5.08BA
|
RMGgJ
|
3.32A
|
2.31A
|
1.51A
|
5.45A
|
6.88A
|
SEm (±)
|
0.30
|
0.23
|
0.25
|
0.56
|
0.70
|
LSD (P <0.05))
|
0.89
|
0.68
|
NS
|
1.62
|
2.02
|
Nutrients and crop residue management (NCRM) practices
|
F1R0
|
1.95b
|
0.69c
|
0.8a
|
2.53b
|
3.34c
|
F1R1
|
2.16b
|
1.59ba
|
1.04a
|
3.90ab
|
4.92ba
|
F2R0
|
2.05b
|
1.15bca
|
0.91a
|
2.93b
|
3.81c
|
F2R1
|
2.76a
|
1.84a
|
1.21a
|
4.07a
|
5.76a
|
SEm (±)
|
0.21
|
0.26
|
0.26
|
0.39
|
0.57
|
LSD (P <0.05))
|
0.56
|
0.76
|
NS
|
1.12
|
1.2
|
CS × NRCM
|
NS
|
NS
|
NS
|
NS
|
NS
|
R-Rice, J-Jute, W-wheat, Bc-Baby corn; Vp; Vegetable pea; M-mustard,Gg-Green gram; F1-75% NPK; F2-100% NPK; R0-No residue; R1-residue incorporation;) TOC, total organic C; SOC, : Soil Oxidisable Carbon by Walkley–Black ; VLC, very labile C; LC, labile C; LLC, less labile C; NLC, non-labile C, Means followed by similar letters (Capital letter for main plot and small for sub-plot comparison) within a column are not significantly different at P < 0.05 according to Duncan’s Multiple Range Test (DMRT) test.
Nitrogen dynamics in soil
Nitrogen fractions
The cropping systems and NCRM practices significantly influenced the ammonia-N (NH4-N) and nitrate N (NO3-N) content particularly at upper soil surface i.e. up to 30 cm soil depth (table 5). RMGgJ cropping system recorded the higher NH4-N (13.6 mg/kg of soil) compared to other cropping systems, though, it was at par with and RVpJ (13.0 mg/kg) cropping system. Among NCRM practices, 100% NPK with residue incorporation (F2R1) significantly increased the NH4-N (14.0 mg/kg) content than all other practices. Application of 75% NPK with residue incorporation (F1R1) recoded the higher NH4-N than that of 100%NPK without residue (F2R0) at 0-15 cm soil depth. The variation among cropping systems for NO3-N content followed the same trend as NH4-N, however, it was non-significant between RVpJ and RBcJ. At 15-30 cm soil depth, again RMGgJ system recorded the higher NH4-N and NO3-N compared to all cropping systems except RVpJ where it was statistically at par. Among NCRM practices, significantly higher NH4-N and NO3-N content in F2R1 practice (6.05 mg/kg) than remaining other practices. At deeper soil (30-45 cm) layer, neither of cropping systems and NCRM practices significantly affected the N fractions. The variation in available N (KMnO4extractable) among different cropping systems was also noticed. RMGgJ system recorded significantly higher available N (116 mg/kg) than RWJ (108 mg/kg) and RR (105 mg/kg) cropping systems at 0-15 cm soil depth. Among NCRM practices, F2R1 practices significantly enhanced the available N compared to 100% NPK without crop residue incorporation. Although, total N did not differ significantly among different cropping systems, it was higher in RMGgJ (1146 mg/kg). Among NCRM practices, the F2R1 practices significantly enhanced the total N compared to remaining NCRM practices at 0-15 cm soil depth.
Table 5. Soil nitrogen pools/fractions under different Cropping system and Nutrients and crop residue management (NCRM) practices at different soil depth
|
0-15 cm soil depth
|
15-30 cm soil depth
|
30-45 cm soil depth
|
|
NH4-N (mg/kg)
|
NO3 -N mg/kg
|
Av.-N
(mg/kg)
|
Total N (mg/kg)
|
NH4 -N (mg/kg)
|
NO3 -N mg/kg
|
AvN
(mg/kg)
|
Total N (mg/kg)
|
NH4 -N (mg/kg)
|
NO3 -N (mg/kg)
|
AvN
(mg/kg)
|
Total N (mg/kg)
|
Cropping system (CS)
|
RR
|
11.1B
|
4.13D
|
105.7CB
|
1094.5A
|
9.12B
|
3.52B
|
92.0B
|
929.5A
|
6.63A
|
2.02A
|
72.3A
|
766.8A
|
RWJ
|
11.8B
|
4.95CD
|
108.5CB
|
1091.0A
|
9.75B
|
3.87B
|
94.6B
|
957.6A
|
6.77A
|
2.36A
|
74.1A
|
795.4A
|
RBcJ
|
11.7B
|
5.17CB
|
110.7BA
|
1123.0A
|
9.48B
|
4.18AB
|
93.4B
|
994.5A
|
7.24A
|
2.72A
|
79.2A
|
850.1A
|
RVpJ
|
13.0A
|
5.75BA
|
112.7BA
|
1118.7A
|
11.04A
|
4.52A
|
96.1BA
|
1019.2A
|
7.02A
|
3.02A
|
81.7A
|
867.6A
|
RMGgJ
|
13.6A
|
6.15A
|
116.2A
|
1146.8A
|
11.14A
|
4.84A
|
97.7A
|
1021.0A
|
7.54A
|
3.11A
|
84.2A
|
868.7A
|
SEm (±)
|
0.38
|
0.31
|
3.28
|
31.9
|
0.37
|
0.25
|
2.32
|
25.2
|
0.25
|
0.23
|
2.6
|
23.8
|
LSD (P <0.05))
|
1.10
|
0.91
|
8.78
|
NS
|
1.07
|
0.72
|
NS
|
NS
|
NS
|
NS
|
NS
|
NS
|
Nutrients and crop residue management (NCRM) practices
|
F1R0
|
11.1c
|
4.13c
|
105.9b
|
1045.4b
|
9.01b
|
3.65c
|
91.9b
|
949.9a
|
6.89a
|
2.18a
|
77.0a
|
798.9a
|
F1R1
|
12.4b
|
5.52b
|
111.3b
|
1116.1b
|
10.59a
|
4.28b
|
93.2b
|
965.5a
|
6.73a
|
2.29a
|
78.2a
|
806.7a
|
F2R0
|
11.9c
|
5.33cb
|
108.9b
|
1102.9b
|
9.64b
|
3.79c
|
94.0ba
|
976.6a
|
7.39a
|
2.83a
|
78.4a
|
837.2a
|
F2R1
|
14.0a
|
6.05a
|
118.5a
|
1195.4a
|
11.21a
|
5.06a
|
101.0a
|
1048.0a
|
7.50a
|
3.29a
|
81.0a
|
878.1a
|
SEm (±)
|
0.23
|
0.19
|
2.03
|
25.5
|
0.19
|
0.17
|
2.43
|
21.13
|
0.87
|
0.16
|
1.61
|
18.5
|
LSD (P <0.05))
|
0.67
|
0.56
|
5.87
|
73.6
|
0.57
|
0.49
|
NS
|
NS
|
NS
|
NS
|
NS
|
NS
|
CS × NRCM
|
NS
|
NS
|
NS
|
NS
|
NS
|
NS
|
NS
|
NS
|
NS
|
NS
|
NS
|
NS
|
R-Rice, J-Jute, W-wheat, Bc-Baby corn; Vp; Vegetable pea; M-mustard,Gg-Green gram; F1-75% NPK; F2-100% NPK; R0-No residue; Av. N is KMnO4 extractable N, , Means followed by similar letters (Capital letter for main plot and small for sub-plot comparison) within a column are not significantly different at P < 0.05 according to Duncan’s Multiple Range Test (DMRT) test.
Lability Index (LI) and Nitrogen management Index (NMI)
Lability Index (LI) : LI of N did not differ significantly either by cropping systems and NCRM practices at any soil depth (Figure 7). However, numerically higher LI was obtained in RMGgJ (1.10) followed by RVpJ (1.06)>RBgJ(1.03)> RWJ (1.01)> RR (0.99). Among NRCM practices, the LI followed the order as F2R1 (1.10)> F2R0 (1.06)> F1R1 (1.03)> F1R0 (1.01).
Nitrogen management Index (NMI): Cropping systems and NCRM practices significantly influence the NMI in 0-15 cm soil depth (Figure 8). The RMGgJ cropping system significantly increased the NMI as compared to remaining cropping systems except RVpJ system, where NMI was almost equal with RMGgJ. Among NCRM practice, F2R1 significantly increased the NMI than remaining other practices. At lower depth neither of these practices could significantly improve the NMI.
Nitrogen stocks:
Cropping systems and NCRM practices significantly improved the N stock (1.98 to 2.27 Mg/ha) on the upper soil surface (0-15 cm and 15-30 cm) after six years of continuous cropping (Table 6). Among different cropping systems, RMGgJ system recorded the higher N stocks compared to all other systems except RVpJ. Among NCRM practice, F2R1 had significantly higher N stock than F1R0 (75%NPK without crop residue) other practice. If we compared N stock at greater depth i.e. 0-30 cm then RMGgJ, RVpJ and RBcJ cropping systems had almost equal N stocks but that was comparatively higher than RR cropping system. Among NCRM practices, F2R1 (100% NPK with crop residue) recorded the higher N stock than both 75% NPK with and without crop residues practices.
Table 6. Total nitrogen stock under different cropping system and nutrients and crop residue management (NCRM) practices at different soil depth
Treatments
|
TN pool/stock (Mg/ha)
|
0-15 cm
|
15-30
|
30-45
|
0-30
|
0-45
|
Cropping system (CS)
|
RR
|
1.98B
|
1.82B
|
1.8A
|
3.91B
|
5.65B
|
RWJ
|
2.12AB
|
1.91B
|
1.95A
|
4.04AB
|
5.93A
|
RBcJ
|
2.13AB
|
2.02AB
|
2.08A
|
4.18A
|
6.18A
|
RVpJ
|
2.17A
|
2.05AB
|
2.10A
|
4.24A
|
6.20A
|
RMGgJ
|
2.29A
|
2.11A
|
2.14A
|
4.36A
|
6.25A
|
SEm (±)
|
0.07
|
0.056
|
0.062
|
0.11
|
0.16
|
LSD (P <0.05))
|
0.18
|
0.15
|
NS
|
0.33
|
0.49
|
Nutrients and crop residue management (NCRM) practices
|
F1R0
|
2.02b
|
1.89b
|
1.91b
|
3.91b
|
5.76b
|
F1R1
|
2.15ba
|
1.93b
|
1.99b
|
4.07b
|
5.97b
|
F2R0
|
2.18ba
|
1.95ab
|
2.02ba
|
4.13ba
|
6.06ba
|
F2R1
|
2.27a
|
2.10a
|
2.16a
|
4.37a
|
6.45a
|
SEm (±)
|
0.058
|
0.04
|
0.050
|
0.10
|
0.14
|
LSD (P <0.05))
|
0.17
|
0.14
|
0.15
|
0.29
|
0.42
|
CS × NRCM
|
NS
|
NS
|
NS
|
NS
|
NS
|
R-Rice, J-Jute, W-wheat, Bc-Baby corn; Vp; Vegetable pea; M-mustard,Gg-Green gram; F1-75% NPK; F2-100% NPK; R0-No residue; R1-residue incorporation;) TN, total nitrogen; Means followed by similar letters (Capital letter for main plot and small for sub-plot comparison) within a column are not significantly different at P < 0.05 according to Duncan’s Multiple Range Test (DMRT) test.
N sequestration (Nseq) rate:
Cropping systems and NCRM practices significantly affected the Nseq rate (varied from 39 to 62 kg/ha/year), but it was mostly confined to upper soil surface (0-15 and 15-30 cm soil depth) (Figure 9). Among cropping systems, RMGgJ system recorded significantly higher Nseq rate (62 kg/ha/year) than that of remaining other cropping systems, however, it was at par with RVpJ cropping system at 0-15 cm. Among NCRM practice, F2R1 significantly increased the Nseq rate than other practices at both 0-15 cm and 15-30 cm soil depth. While, at lower depth 30-45 cm neither cropping systems nor NCRM practices significantly influenced the Nseq rate. When we calculated Nseq rate with depth of soil 0-30 and 0-45 cm, RMGgJ cropping systems had significantly higher Nseq rate than all cropping systems except RVpJ. Remaining four cropping systems recorded the almost similar Nseq rate. Among NCRM practices, F2R1 recorded significantly higher Nseq rate than F2R0 and F1R0 but it was at par with F1R1.
Stratification ratio (SR) of N
The similar trend of SR of N (Figure 10) was recorded as SR of SOC, however, the value ranged from 1.10 to 1.24 and 1.28-1.42 at 0-15/15-30 and 0-15/30-45 cm depth, respectively. The RMGgJ cropping system recoded the significantly higher SR of N than remaining other cropping systems, however, it was at par with RVpJ cropping system. The SR of N in remaining other cropping systems was non-significant. Among NCRM practice, F2R1 recorded significantly higher SR than F1R0 and F2R0 , although, that was similar to F1R1practice at both depths.
Relationship CMI, NMI and Yield with different fraction of soil C and N
The Pearson correlation matrix data indicated that CMI was highly significant (P<0.01) correlated with SOC (r=0.88), and all C fractions (Table 7), however, it was negative correlated with BD. All labile, less labile, non-labile carbon had significant and strong correlation with TOC and among them. NMI was significantly positive correlated with Av N (r=0.85), NH4-N (r=0.44) and NO3-N (r=0.45) but it was negative correlated with BD, though, that was non-significant. A significant correlation was also observed between yield and LLC (r=0.40), yield with NH4-N (r=0.41) and NO3-N (r=0.39). CMI and NMI as indicator of soil quality were related (r=0.39) and both had significant correlation with yield (r=0.33) and (r=0.35), respectively.
Table: 7Correlation between different carbon and nitrogen fraction
|
TOC
|
SOC
|
VLC
|
LC
|
LLC
|
NLC
|
CMI
|
BD
|
TN
|
Av.N
|
NH4-N
|
NO3-N
|
NMI
|
YD
|
TOC
|
1
|
0.39**
|
0.67**
|
0.76**
|
0.51**
|
0.78**
|
0.88**
|
-0.17
|
0.33*
|
0.41**
|
0.49**
|
0.51**
|
0.36**
|
0.05
|
SOC
|
|
1
|
0.32*
|
0.12
|
0.16
|
0.62**
|
0.41**
|
0.18
|
0.32*
|
0.57**
|
0.26*
|
0.28*
|
0.10
|
0.26*
|
VLC
|
|
|
1
|
0.41**
|
-0.11
|
0.45**
|
0.82**
|
0.23
|
0.15
|
0.29*
|
0.43**
|
0.44**
|
0.27*
|
0.21
|
LC
|
|
|
|
1
|
0.35**
|
0.41**
|
0.81**
|
-0.262*
|
0.18
|
0.35**
|
0.32*
|
0.36**
|
0.30*
|
0.21
|
LLC
|
|
|
|
|
1
|
0.04
|
0.48**
|
-0.23
|
0.17
|
0.38**
|
0.16
|
0.13
|
0.35**
|
0.40**
|
NLC
|
|
|
|
|
|
1
|
0.47**
|
0.04
|
0.12
|
0.17
|
0.47**
|
0.48**
|
0.15
|
0.28*
|
CMI
|
|
|
|
|
|
|
1
|
-0.04
|
0.24
|
0.44**
|
0.44**
|
0.45**
|
0.39**
|
0.35*
|
BD
|
|
|
|
|
|
|
|
1
|
0.21
|
-0.10
|
-0.02
|
0.05
|
-0.07
|
-0.13
|
TN
|
|
|
|
|
|
|
|
|
1
|
0.21
|
0.30*
|
0.29*
|
0.41**
|
0.05
|
Av,N
|
|
|
|
|
|
|
|
|
|
1
|
0.21
|
0.42**
|
0.85**
|
0.32*
|
NH4-N
|
|
|
|
|
|
|
|
|
|
|
1
|
0.88**
|
0.44**
|
0.41**
|
NO3-N
|
|
|
|
|
|
|
|
|
|
|
|
1
|
0.45**
|
0.39**
|
NMI
|
|
|
|
|
|
|
|
|
|
|
|
|
1
|
0.33*
|
YD
|
|
|
|
|
|
|
|
|
|
|
|
|
|
1
|
**.Correlation is significant at the P< 0.01 level;*. Correlation is significant at the P< 0.05 level ) TOC: total organic C; SOC : Soil oxidisable Carbon by Walkley–Black ; VLC, very labile C; LC, labile C; LLC, less labile C; NLC, non-labile C, CMI: Carbon management index; BD; bulk density; Av,-N: Avialble N; TN: total nitrogen; NMI: Nitrogen management index, YD; system productivity