MSc

Rice is the most important food crop in the world and the staple food of more
than half of the world’s population including India. However, the productivity of rice in
Kerala is comparatively lower than other states. There is a requirement to develop
technologies that can increase the yield from the limited land resources. Paired row
planting is a modified planting geometry developed at the Regional Agricultural
Research Station, Pattambi which utilizes the border effect to enhance yield of rice and
this method is getting wide acceptance among the farmers. The intensity and spread of
diseases are greatly influenced by plant density, spacing and associated microclimatic
conditions. In this context, the present study was undertaken to assess the incidence of
diseases in new planting geometry, paired row planting.
A field experiment was conducted at the Regional Agricultural Research Station,
Pattambi over two seasons (rabi 2021 and kharif 2022). The experiment was laid out in
randomized block design with three treatments and seven replications using the rice
variety, Jyothi. The treatments were paired row planting (35-15 cm × 10 cm), normal
transplanting (15 cm × 10 cm) and direct sowing.
Disease incidence and severity were recorded at ten days interval from the first
notice of the symptom in the field. During the rabi season, the diseases observed were
bacterial blight, sheath blight, brown spot and false smut. In the kharif season, in
addition to these diseases, sheath rot was also observed. The incidence and severity of
diseases were significantly lower in paired row planting compared to normal
transplanting and direct sowing. The highest disease incidence and severity were noticed
in direct sowing. In addition to diseases, pest damage was also recorded at every ten
days interval. Infestation of case worm, leaf folder, yellow stem borer and rice bug were
noticed in the field. The damage due to the infestation of major pests, leaf folder, yellow
stem borer and rice bug was significantly lower in paired row planting when compared
to the other two systems. Like disease incidence, pest incidence was also significantly
higher in direct sowing, followed by normal transplanting. The difference in planting
geometry, plant population and associated microclimate can be considered as the
contributing factors responsible for the difference in diseases and pests incidence.
When the micrometeorological parameters viz., relative humidity and canopy
temperature were considered, it became evident that relative humidity was significantly
lower in paired row planting compared to normal transplanting and direct sowing. The
canopy temperature recorded in paired row planting was higher than the other two
systems. This might have added to its advantage in managing pest and disease
incidence. On the other hand, the significantly higher relative humidity and lower
canopy temperature observed in normal transplanting and direct sowing might have
acted as the contributing factor for the higher pest and disease incidence.
The influence of planting geometry on the rhizosphere microflora was analyzed
using serial dilution and plating technique. However, a significant difference between
the systems was not observed. The uniformity maintained with respect to soil properties,
nutrient and water management and variety used might be the reason behind this
observation.
The biometric parameters viz. number of tillers, number of leaves, plant height
and leaf area were recorded at every ten days interval. The results showed that the
number of tillers in paired row planting was significantly higher followed by direct
sowing and normal transplanting. Yield and yield attributes viz., number of hills per
metre square, number of panicles per hill, number of grains per panicle and number of
chaffy grains per panicle and thousand grain weight were also recorded. The number of
panicles per hill and grain yield recorded in paired row planting was significantly higher
than other two systems. The wider spacing in paired row planting might have reduced
the plant competition for resources and resulted in better growth and development of
plants that led to profused tillering and improved yield. The reduction in pest and
disease incidence might have also contributed significantly to the yield advantage.
The study also implies that the alterations in planting geometry can have a
significant influence on pest and disease incidence. From the results, we could infer that
in addition to the yield advantage, paired row planting also contributes significantly
towards disease and pest management and therefore it can be considered as a promising
planting geometry over the existing systems.