BSc-MSc (Integrated)

The present study entitled “Carbon sequestration and crop weather relations in
long term fertilizer experiment was formulated with the objectives of studying the
effect of long term application of fertilizers and manures on soil carbon
sequestration pattern and crop weather relations under long term fertilizer
experiments with rice-rice cropping sequence maintained at Pattambi. The
objectives were set out to study the carbon sequestration pattern in long term
fertilizer experiment (LTFE), estimation of the SOC sequestration efficiency of
different organic manures and to analyze and establish crop weather relations in
LTFE.
The LTFE consist of 12 treatments viz. T1:50 percent NPK, T2: 100 per
cent NPK, T3:150 per cent NPK, T4: 100 per cent NPK + lime CaCO3 @ 600 kg
ha-1, T5: 100 per cent NPK, T6: 100 per cent NP, T7: 100 per cent N, T8: 100
percent NPK + FYM @ 5 t ha-1 (to Virippu crop only), T9: 50 percent NPK +
FYM @ 5 t ha -1 (to Virippu crop only), T10: 100 percent NPK + in situ growing
of Sesbania aculeata (for Virippu crop only) ,T11: 50 percent NPK + in situ
growing of Sesbania aculeata (for Virippu crop only), T12: Absolute control (No
fertilizers/ manures). The grain yield, straw yield, stubbles left after harvest and
unincorporated weed biomass were quantified for calculating the carbon inputs
into soil. The soil organic carbon distribution pattern was analysed in different
depths. The total carbon inputs and soil organic carbon sequestration rate were
plotted to establish the relationship. Crop weather relations were studied through
correlation studies and DSSAT modelling.
Integrated nutrient management practice T8 (100 Per cent NPK + FYM)
recorded higher values for grain yield and growth related parameters followed by
T10 (100 per cent NPK + in situ growing of Sesbania aculeata) and T3 (150 per
cent NPK).The soil which received 100 per cent NPK+FYM (T8) had higher mass
of total organic carbon in top soil followed by T10. A significant positive linear
relationship exists between carbon inputs and rate of carbon sequestration. The
mean carbon sequestration efficiency was 8.4% in top soil. The average
sequestration efficiency for FYM and daincha were 12.18 and 8.58% respectively.
The decrease in dose of fertilizers incorporated along with organic manures
decreased the carbon sequestration efficiency of the organic amendments.
Therefore application of FYM seems to be a preferred strategy for enhancing SOC
sequestration in lateritic soils due to its higher carbon sequestration efficiency.
Maximum temperature had a positive impact on grain yield in both
seasons Virippu and Mundakan, while the effect of minimum temperature was not
significant. In general the rainfall and wind speed had negative impact on grain
yield.
Furthermore, crop weather relations in rice are established by using
available long term data using DSSAT. There is perfect concurrence between
observed and predicted grain yield of the experiment. So this study will help in
planning better and judicious carbon management strategies and recommendations
for these soils for sustainable health and crop production.