Crop weather relationship in cauliflower (Brassica oleracea var.botrytis L.)
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Date
2012
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Department of Agricultural Meteorology, College of Horticulture, Vellanikkara
Abstract
A field experiment was conducted during 2010-11 and 2011-12 at the Department
of Agricultural Meteorology, College of Horticulture, Vellanikkara with the objectives to
study the effect of weather on growth and yield of cauliflower and to assess the suitability
of cauliflower under various crop growing environments. The study included five
planting times at an interval of 15 days (1st November, 15th November, 1st December, 15th
December and1st January) and two tropical hybrid varieties (Basant and Pusa Kartik
Sankar).
The different growth and yield characters like plant height, number of leaves, plant
biomass, duration of different growth stages and curd weight were recorded along with
monitoring of the incidence of various pests, diseases and physiological disorders. The
daily weather parameters like maximum and minimum temperatures, forenoon and
afternoon relative humidity, forenoon and afternoon vapour pressure, bright sunshine
hours, wind speed, rainfall and rainy days were collected and used in this study. Based on
these weather parameters, other important weather variables like mean temperature,
diurnal temperature range, forenoon and afternoon vapour pressure deficits and solar
radiation were determined. Various heat units like growing degree days, heliothermal
units and photothermal units were also worked out.
The maximum and mean temperature, diurnal temperature range, forenoon and
afternoon relative humidity, forenoon and afternoon vapour pressure deficits, bright
sunshine hours and solar radiation were found to be higher in 2010-11 as compared to
2011-12. Plant height, number of leaves and the duration of different growth stages were
found to be highly variable among the different planting times in both the years, but when
pooled over years, these characters became non-significant (except the duration from curd
initiation to harvest) with respect to the planting time as a result of the higher variability
between the two years for the different weather parameters.
The curd weight and the plant fresh and weights exhibited high significant
difference for the different planting times. Duration from transplanting to curd initiation
was found to be more critical for the curd yield. To determine the critical weather
elements affecting the crop growth, correlation analysis was done and it was observed
that the crop duration would increase with increase in the maximum temperature, bright
sunshine hours, solar radiation and afternoon vapour pressure deficit whereas, the
afternoon relative humidity showed a negative influence on crop duration. The curd yield
and plant weight were found to be decreasing with increase in the maximum temperature
and sunshine hours. The various heat units exhibited positive correlation with the duration
of different growth stages. Based on the weather parameters experienced by the crop
during the transplanting to curd initiation period, a regression equation with an R2 value
of 0.95 was developed to predict the curd weight.
The present study revealed that first fortnight of November is the optimum planting
time for tropical cauliflower in Thrissur District, since the maximum curd size was
obtained when planted on 1st November in 2011-12. The optimum weather for the
planting of tropical cauliflower was observed to be less than 31.2°C of maximum
temperature, less than 26.8°C of mean temperature, less than 8.8°C of diurnal temperature
range, less than 6.0 hrs of bright sunshine hours and less than 22.3 MJ m-2 of solar
radiation, with 22.5°C of minimum temperature. Intermittent rainfall and higher relative
humidity observed during the earlier planting times were found to be conducive for the
incidence of pests and diseases and the bacterial disease black rot was observed as a
serious threat to cauliflower cultivation in this region.
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173215