PhD.

An investigation entitled “Acidity amelioration and nutrient management
practices for mitigating yield constraints of rice in Vaikom Kari” was carried out as
two field experiments in Vaikom Kari soils of Kuttanad during the period from 2014
to 2017 to standardize acidity amelioration and nutrient management practices for rice
to overcome yield constraints in Vaikom Kari and to work out the economics of
cultivation.
Experiment I entitled “Evaluation of acidity amelioration practices for rice in
Vaikom Kari” was conducted in farmer’s field in Kallara panchayat in Kottayam
district during November 2014 to March 2015. The experiment was laid out in RBD
with seven treatments in three replications with rice var. Uma. The treatments
included lime, dolomite and rice husk ash (RHA) applied as two splits- as basal + 30
DAS or as basal + one week before third dose of fertilizer application and a control
without ameliorants.
Lime, dolomite or RHA, irrespective of time of application, could produce
taller plants with higher LAI and tiller number at maximum tillering (MT), panicle
initiation (PI) and harvest stages. The same treatments recorded higher number of
panicles m-2 and 1000 grain weight and lower sterility percentage. Lime, dolomite or
RHA as basal + 30 DAS produced significantly higher grain yield over control. Grain
yield was significantly and positively correlated with LAI at MT and PI stages and
panicle number m-2. Higher straw yield was obtained with lime or dolomite as basal +
30 DAS and RHA treatments. Application of lime, dolomite or RHA as basal + 30
DAS resulted in higher dry matter production at harvest.
Soil ameliorants improved the uptake of macronutrients and micronutrients.
Uptake of N and K were significantly higher for lime, dolomite or RHA applied as
basal + 30 DAS while dolomite as basal + 30 DAS recorded the highest P uptake. The
highest uptake of Ca was found with lime as basal + 30 DAS and that of Mg and S
with dolomite as basal + 30 DAS. The highest uptake of Mn and Zn were observed


with lime as basal + 30 DAS, Cu with RHA as basal + 30 DAS and that of B with
lime, dolomite or RHA applied as basal + 30 DAS. The control treatment and RHA
applied as basal + one week before PI registered lower Na uptake and both RHA
treatments registered higher Al uptake. There was significant and positive correlation
of grain yield with uptake of nutrients except Fe, Zn and Al.
Lime and dolomite treatments were more effective in reducing soil acidity
and improving dehydrogenase activity and nutrient availability in the soil. The
ameliorated plots showed higher organic carbon status compared to control. Lime as
basal + one week before PI and dolomite treatments recorded higher soil available N
at seedling stage and at tillering and PI stages, any treatment except control could
register higher available N in the soil. Any liming material applied as basal + 30 DAS
improved soil available P status. No significant effect of treatments on available K
was observed. Lime or dolomite treatments resulted in higher availability of Ca while
dolomite treatments registered higher availability of Mg in the soil. At all stages
except harvest, the control plots recorded significantly higher status of available S and
Fe and lower status of Mn in the soil. Significant and positive correlation of pH with
available Ca and negative correlation with available Fe was observed at all stages of
crop growth. Soil available Cu status was the highest with control at PI stage and with
dolomite at harvest stage. Dolomite treatments recorded higher available B in the soil.
The highest Na content in the soil was registered by dolomite treatments at seedling
stage and by control at tillering stage. There was an increase in the availability of Na
at all stages of experimentation but the content was below the critical level of toxicity.
Soil exchangeable Al status was significantly higher in the control.
Lime, dolomite or RHA applied as basal + 30 DAS gave higher net income
and BCR while the control recorded the lowest net income and BCR.
Experiment II entitled “Standardization of nutrient management practices for
rice in Vaikom Kari” was conducted during August to December 2015 and 2016 in
farmers` fields in Thalayazham panchayat in Kottayam district. The experiment was
laid out in RBD with 16 treatments (formulated based on the results of the Experiment


I) in three replications with rice var. Uma. The treatments were dolomite, lime +
MgSO4 or RHA + MgSO4 along with 100% POP alone or with 100% POP + foliar
spray of 13:0:45 (1%) or borax (0.5%) or 13:0:45 + borax at PI stage. Lime + MgSO4
+ 75% POP + 13:0:45 + borax as well as lime without MgSO4 + 100% POP combined
with 13:0:45 or borax or both were also included as treatments.
The treatments involving dolomite and lime with or without MgSO4 produced
taller plants, higher tiller number m-2 and higher LAI during both the years. Dolomite
+ POP + 13:0:45 produced the highest number of panicles m-2. Higher test weight and
lower sterility percentage were observed with dolomite + POP + 13:0:45 and dolomite
+ POP + 13:0:45 + borax. Higher grain yield of 5.42 and 5.57 t ha-1 during 2015 and
2016 respectively were produced by dolomite + POP + 13:0:45 followed by dolomite
+ POP + 13:0:45 + borax and lime + MgSO4 POP + 13:0:45. Grain yield was
significantly and positively correlated with LAI at MT and PI stages and with panicle
number m-2. Pooled analysis also proved the significance of the above treatments in
producing higher grain yield. Lower yields were produced by the treatments involving
RHA and 75% POP during both the years and in the pooled data. In general, higher
straw yields were noticed with the treatments involving dolomite or lime along with
foliar spray of 13:0:45 or 13:0:45 + borax. Higher dry matter production was noticed
with dolomite + POP along with 13:0:45 or borax during first year and with dolomite
+ POP or lime + MgSO4 + POP along with 13:0:45 or 13:0:45 + borax during second
year.
In general, higher uptake of macronutrients and micronutrients was observed
with dolomite or lime + MgSO4 treatments along with 100% POP during both the
years. Uptake of Na was the highest with RHA + MgSO4 + POP + 13:0:45 during first
year and with dolomite treatments during second year. Higher Al uptake was
observed with lime + POP + 13:0:45 with or without MgSO4. Significant and positive
correlation of grain yield with uptake of P, K, Ca, Mg, S, Mn, Zn, Cu and B and
negative correlation with Fe was observed during first year. During second year, the
yield was significantly and positively correlated with uptake of nutrients except Na
and Al.


The treatments involving dolomite, lime with or without MgSO4 performed
better in ameliorating soil acidity than RHA treatments during both the years. The
treatments involving RHA showed higher EC values. All the treatments except those
involving RHA helped in improving dehydrogenase enzyme activity in the soil during
the cropping period. The initial soil organic carbon status was maintained during the
cropping period due to nutrient management practices. Availability of N in the soil
improved due to treatments involving dolomite + POP during seedling stage and due
to those involving lime + POP without MgSO4 at other stages. The treatments
involving dolomite + POP and lime + POP with or without MgSO4 recorded higher
available P during all crop stages. In general, higher status of available K was
registered by the treatments involving RHA or lime without MgSO4. All treatments
involving lime or dolomite registered higher soil available Ca and those involving
dolomite or lime + MgSO4 showed higher availability of Mg in the soil. In general,
available S in the soil decreased from initial status during the cropping period. The
treatments involving dolomite registered lower status of soil available Fe and higher
status of available Mn and B. Higher status of available Zn was registered by the
treatments involving dolomite or lime + MgSO4. The treatments involving dolomite,
lime + MgSO4 or RHA + MgSO4 along with POP registered higher available Cu in
the soil. Dolomite treatments recorded lower status of Na and exchangeable Al in the
soil. Soil pH was significantly and positively correlated with available P and
significantly and negatively correlated with available Fe and exchangeable Al in the
soil.
The economics of cultivation in terms of net income and BCR were the
highest with dolomite + POP + 13:0:45 during both the years which was closely
followed by dolomite + POP + 13:0:45 + borax. The treatments involving RHA and
75% POP registered lower net income and BCR.
The results of the study revealed the superiority of dolomite for ameliorating
soil acidity in Vaikom Kari soil compared to lime or rice husk ash. Split application of
dolomite as basal dose and at 30 DAS proved more effective than application as basal
dose and one week prior to fertilizer application at panicle initiation stage. Soil acidity


amelioration with dolomite @ 500 kg ha-1 (300 kg as basal dose and 200 kg ha-1 at 30
DAS) and soil application of 90:45:45 kg NPK ha-1 (full P as basal and N and K in
three equal splits at 20 DAS, 35 DAS and PI stage) along with foliar spray of 13:0:45
(1%) or combined spray of 13:0:45 (1%) and borax (0.5%) at panicle initiation stage
resulted in higher productivity and profitability from rice cultivation in Vaikom Kari
soil.