PhD

The study entitled “Productivity and soil health of rice based cropping systems
under organic management” was conducted in the Department of Agronomy, College
of Horticulture, Vellanikkara during 2015-2017 to find out the suitable rice based
cropping system under organic management.
The experiment was laid out in randomized block design with three
replications. Rice was grown under four different cropping systems for two
consecutive years with and without foliar spray of liquid organic manures (LOMs).
The rotations followed were rice-rice-njavara rice, rice-rice-salad cucumber, rice-rice-
vegetable cowpea, rice-rice-amaranthus and rice-rice-fallow. The management
practices were followed as per the Package of practices recommendations: (Ad hoc)
for organic farming: Crops of the Kerala Agricultural University. Jeevamrurtham,
Panchagavyam, green leaf extract and fish amino acid were the liquid organic
manures sprayed at 15 days intervals after transplanting.
The growth and yield parameters of all the crops were found to be better with
the application of liquid organic manures. All the crops performed well in the second
year due to the significant effect of crop diversification, residual effect of manures
applied for the preceding crop and the improvement in soil health. There was
significant reduction in the number of weeds, pests and diseases associated with rice
due to crop rotation under organic management.
Rice-rice-salad cucumber with and without LOMs produced significantly higher
rice equivalent yield (29.58 and 24.67 t ha-1 respectively) and system productivity
(81.03 and 67.58 kg ha-1 day-1 respectively) than rest of the sequences. Better
sustainability yield index was recorded in rice-rice-vegetable cowpea with LOMs
(0.26) followed by the same system without LOMs (0.20).
With 300% cropping intensity, rice-rice-salad cucumber with and without LOMs
recorded higher gross return (11,20,180/ 9,57,423 ₹ ha-1 respectively) and net return
237
(7,25,126/ 5,74,416 ₹ ha-1 respectively) compared to rice-rice-fallow with 200%
cropping intensity (3,27,039 ₹ ha-1 gross return and 1,72,539 ₹ ha-1 net return). Among
the sequences, the B:C ratio was found to be the highest in rice-rice-vegetable cowpea
with and without LOMs (2.99 and 2.76 respectively).
The soil characters were also significantly influenced by the treatments. The
decreasing trend in bulk density is an indication of improvement in porosity and water
holding capacity of the soil in the long run. Rice-rice-vegetable cowpea with LOMs
recorded the highest organic carbon (1.46%), available N and P content (192.04 and
71.11 kg ha-1 respectively) while rice-rice-salad cucumber with LOMs had the highest
available K content (332.78 kg ha-1). Total microbial biomass (bacteria, fungi and
actinomycetes) and dehydrogenase activity were found to be the highest with rice-rice-
vegetable cowpea with and without LOMs followed by rice-rice-salad cucumber with
and without LOMs. The highest soil health index was registered by rice-rice-vegetable
cowpea with and without LOMs (3.34 and 3.00 respectively) followed by rice-rice-
amaranthus.
The study revealed that foliar application of liquid organic manures enhanced the
soil health and productivity of rice as well as other crops grown in rotation. Rice-rice-
salad cucumber was found to be the best rice based cropping system with maximum
net return, whereas rice-rice-vegetable cowpea system improved the soil physical,
chemical and biological properties and thus sustained the soil health.