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aestivum ), mustard ( Brasicca compestriss ), sunflower ( Carthamus tinctorius )] than
in a fallow-based (rainy-season fallow followed by other post-rainy season crops)
system and was in the following order: groundnut-groundnut > groundnut-chickpea
> groundnut-wheat > groundnut-mustard > groundnut-sunflower, though SYI was
the highest in the groundnut-groundnut system in Vertisols (Typic Haplustert).
16.13.2.2 Finger Millet-Based Production System
In the case of groundnut-finger millet rotations, the SYI was in accord with the SOC
pool, and there existed a significant correlation between the annual input of CRs ( r =
0.98-0.99, R 2 = 0.97, P < 0.05), total cumulative C input ( r = 0.85-0.94, R 2 = 0.73 -
0.88, P < 0.05), C buildup ( r = 0.96-0.98, R 2 = 0.93-0.97, P < 0.05), profile SOC
( r = 0.96-0.98, R 2 = 0.93-0.97, P < 0.05), and C sequestrated ( r = 0.96-0.98, R 2 =
0.93-0.97, P < 0.05) ( Table 16.17 ). In case of finger millet monocropping, a significant
relationship was observed between SYI and annual CR C inputs ( r = 0.97, R 2 = 0.94,
P < 0.05), total cumulative C input ( r = 0.93, R 2 = 0.87, P < 0.05), C buildup ( r = 0.95,
R 2 = 0.90, P < 0.05), profile SOC ( r = 0.95, R 2 = 0.90, P < 0.05), and C sequestrated
( r = 0.95, R 2 = 0.90, P < 0.05) ( Table 16.18 ). Application of chemical fertilizers alone
could not sustain productivity of either a cereal- or legume-based system on a long-
term basis. Manna et al. (2005) reported similar positive yield trends in the NPK and
NPK + FYM treatments in soybean-wheat systems on Alfisols at Ranchi, Bihar.
16.13.2.3 Winter Sorghum-Based Production System
The SYI was also in accord with the SOC stock, and a significant correlation existed
between SYI and the total C input ( r = 0.87* [one asterisk means significant at P ≤ 0.05
level], R 2 = 0.76, P < 0.05), % SOC sequestration ( r = 0.90*, R 2 = 0.81, P < 0.05), profile
SOC stock ( r = 0.90*, R 2 = 0.81, P < 0.05), and SOC sequestered ( r = 0.90*, R 2 = 0.81,
P  < 0.05) ( Table 16.19 ). However, the correlation of SYI with the annual input of CR
was weak ( R 2 = 0.31). A beneficial effect of application of organic materials as a source
of N on sorghum grain yield has been reported earlier by Bellakki and Badanur (2000).
16.13.2.4 Pearl Millet-Based Production System
In general, there exists a strong relationship between SOC concentration/stock and
grain yield (Bronson et al. 1998; Yadav et al. 2000; Regmi et al. 2002; Singh et al.
2004). There also exists a linear relationship between the SYI and SOC fractions
(Srinivasarao et al. 2011e). These trends indicate the importance of SOC fractions on
crop yield through improvement in soil quality (Srinivasarao et al. 2011b). A signifi-
cant relationship was also observed between SYI and total C inputs ( r = 0.67-0.75,
R 2 = 0.45-0.56, P < 0.05) and the profile SOC stock ( r = 0.78-0.88, R 2 = 0.61-0.77,
P  < 0.05) ( Table 16.20 ). Thus, the maintenance of SOC stock through regular addi-
tion of organics determines the sustainability of rainfed conditions involving pearl
millet-based production systems (Srinivasarao et al. 2011e).
16.13.2.5 Safflower- and Soybean-Based Production System
The SYI of safflower is in accord with the SOC concentration and stock, and a signifi-
cant correlation exists between SYI and the total C input ( R 2 = 0.53* [one asterisk means
significant at p ≤ 0.05 level], P < 0.05), % SOC sequestration ( R 2 = 0.63*,  P  < 0.05),
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