PhD

Conservation agriculture (CA) is an approach to manage agro-ecosystems for
improved and sustained productivity, increased profits and food security while
preserving and enhancing the resource base, which emphasize minimum soil
disturbance, permanent soil cover and diversified crop rotation. In India and Kerala,
there is dearth of information on resource-conserving techniques, for productivity,
profitability and soil health. Hence the present study entitled “Conservation agriculture
practices for upland rice based cropping system” was carried out at Agronomy Farm,
College of Agriculture, Vellanikkara from May 2019 to March 2021 to develop a
conservation agricultural practices for upland rice-okra-green manure cropping system.
Rice–okra-green manure cropping system with conservation practices were
compared with rice–okra-green manure cropping system without conservation
practices. The experiment was laid out in RBD with 10 treatments replicated thrice and
was repeated for two years keeping the same layout. The treatments consisted of
Direct seeding rice (DSR) in flat bed (FB) + brown manuring (BM)- okra+ green
manuring (GM)-cowpea, DSR in FB+ BM- okra + crop residue mulch (CRM)-
cowpea, DSR in FB+ GM- okra + GM-cowpea, DSR in FB+ GM- okra + CRMcowpea, DSR in raised bed(RB) + BM- okra + GM-cowpea, DSR in RB+ BM-okra+
CRM-cowpea, DSR in RB+ GM- okra + GM-cowpea, DSR in RB+ GM- okra+ CRMcowpea, DSR in FB – okra-fallow, DSR in RB- okra-fallow.
Conservation treatments had significant influence on growth, yield parameters
and yield of rice. Growth and yield attributes were highest in direct seeding rice in flat
bed + green manuring which had an yield increment of 49 % compared to control ie.,
direct seeding rice in flat bed without any conservation agriculture practice. Raising
rice crop in raised bed without cowpea intercropping also resulted in 23 % higher rice
yield compared to rice grown alone in flat bed. Conservation treatments had significant
influence on weed suppression. Growing of cowpea as an intercrop in rice and its
incorporation at 25 DAS either by cutting it and spreading as mulch (green manuring)
or decomposing it using 2-4-D application (brown manuring) either in flat bed and
raised bed resulted in 58-73% reduction of weeds in upland situation. Physiological
parameters like leaf area index, crop growth rate, relative growth rate and net
assimilation rate were found higher in direct seeding rice in flat bed+green manuring.
Significantly higher values of nutrient uptake, resource use efficiencies such as water
use efficiency, partial factor productivity of NPK, net returns and B:C ratio in direct
seeding rice in flat bed + green manuring proved the superiority of this conservation
practice in rice over conventional DSR-okra-cowpea.
Okra crop was raised in sequence with rice in the same field keeping the layout
undisturbed. Field was made weed free before sowing with minimum soil
disturbance using brush cutter after harvest of rice. Conservation agriculture practices
applied to both rice and okra had significant influence in the growth and yield
performance of okra. From the results it was observed that growth and yield
parameters were higher when okra was raised on flat bed with the application of
previous crops residue as mulch. DSR in FB+GM–okra+ CRM recorded the highest
okra yield of 16.47 t/ha with 71-83 % reduction in weeds compared to control ie
DSR in flat bed - okra. Physiological parameters like leaf area index, crop growth
rate, relative growth rate and net assimilation rate were found higher in conservation
treatments compared to non-conservation treatments. The highest NPK uptake,
resource use efficiencies such as water use efficiency, partial factor productivity of
NPK and high B:C ratio were recorded in DSR in FB +GM –okra + CRM.
Cowpea was raised after okra by keeping the same layout in all conservation
treatments and the field was kept as fallow in non-conservation agriculture
treatments. The highest biomass yield of 1920.22 kg/ha was recorded in DSR in FB
+GM –okra + CRM -cowpea at 45 DAS. While assessing the whole cropping system,
conservation treatments recorded 72.60 % land use efficiency and 300 % multiple
cropping index but whereas non conservation treatments recorded 60.27 % land use
efficiency and 200 % multiple cropping index. Among the different conservation
agriculture practices applied to rice –okra-green manure cropping system, DSR in
FB +GM –okra + CRM –cowpea recorded the highest cropping system resource use
efficiency, net profit and and a B:C ratio.
Soil physical, chemical and biological properties were improved due to the
effect of conservation treatments over non conservation treatments. Water holding
capacity was increased by 31.96 %, porosity by 16.66 % and the soil moisture by
39.83 % in DSR in FB +GM–okra + CRM–cowpea over the non conservation
method.The highest soil carbon stock and sequestration at 0-15 and 15-30 cm soil
depth were recorded in DSR in FB +GM –okra + CRM–cowpea. At 45 cm only a
meagre storage was recorded in DSR in FB +BM –okra + CRM –cowpea. The
treatments without conservation agriculture practices ie DSR in FB–okra-fallow
showed a negative value for sequestration. It indicates the loss of carbon in
conventional method. A slow increase in sequestration after each crops clearly
indicated that conservation agriculture practices for a long run will sequester the
carbon to entire soil profile.
The result of the present two years study indicated that in a rice-okra-green
manure cropping system in upland, direct seeding rice in flat bed with green
manuring followed by okra with crop residue mulch of previous crop followed by
cowpea as green manure can be recommended as a cost effective and sustainable
conservation agriculture practice as it resulted in higher system yield, better weed
control, sustained the soil health and higher B:C ratio.