Browsing by Author "Prasada Rao, G S L H V"

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Changing global climatic scenario on environmental processes across India: its possible causes and impacts
(Academy of Climate Change Education and Research, Vellanikkara, 2016) Lekshmi Mudra, B; Prasada Rao, G S L H V
Climatic variability and small cardamom (Elettaria cardamomum Maton) production across the Westren Ghats
(Department of Agricultural Meteorology, College of Horticulture, Vellanikkara, 2004) Manikandan, N; Prasada Rao, G S L H V
A study was undertaken at the Department of Agricultural Meteorology, College of Horticulture, Kerala Agricultural University, Vellanikkara to analyse the variability of rainfall and surface air temperature over a period of time and its influence on the cardamom production and productivity across the Western Ghats for which the monthly data on rainfall, temperature (maximum and minimum) and nutritional status of soils were collected from six selected locations across the cardamom tract along with the data on area and production of small cardamom. The annual rainfall and rainfall during southwest monsoon (J une-Sep) increases from south to north across the cardamom tract and western parts (Kerala and Karnataka) of the Western Ghats receive better rainfall when compared to that of eastern parts (Tamil Nadu). The reverse trend was noticed during post monsoon (Oct- Nov) and winter (Dec-Feb) and eastern parts receive more rainfall than western parts. In summer (Mar-May), Kerala and Tamil Nadu receive relatively more rainfall than Karnataka. Trend analysis in rainfall revealed that a declining trend was noticed in annual rainfall at all the locations except Pampadumpara and Madikeri. Similar was the case during southwest monsoon except at Madikeri. In other seasons, no such uniform increasing or decreasing trend was noticed across the cardamom tract except at Thandikudi, where rainfall was declining in all seasons. The surface air temperature and its range were high (5.3 -15.9° C) over Karnataka, followed by Kerala (5.2 -11.7° C) and Tamil Nadu (6.9 -10.7 ° C). In majority of the locations, an increasing trend in annual maximum temperature was noticed. It was true in the case of southwest monsoon and post monsoon periods while a declining during winter and summer. Interestingly, an increasing trend was noticed in majority of the locations in the case of minimum temperature. It reflected on the temperature range also at fifty per cent of the locations (Pampadumpara, Madikeri and Thandikudi) during southwest and post monsoon seasons. It was reverse during winter and summer at all the locations except Saklespur and Mudigere. The study on the trends in moisture index (Im) showed that it declined at all the locations during southwest monsoon and annually except at Madikeri. During post monsoon and winter, an increasing trend in moisture index was noticed at all the locations except Thandikudi in post monsoon period. All the locations except at Pampadumpara, showed a declining trend in moisture index during summer. It was also noticed that the intensity of aridity was high towards north of cardamom tract. Studies on agroclimatic zonation of small cardamom revealed that the production potential of Zone I was relatively better (>200 kg / ha) when compared to that of Zone II and III across the Western Ghats, where the length of crop growing season was more than 300 days with annual Ima of more than 90 per cent. In addition, the annual temperature range was very low and optimum across the Zone 1. The production potential of small cardamom was low (100-150 kg / ha) over Zone III (Karnataka), where the length of crop growing season was less than 250 days with annual Ima of 70-75 per cent. The annual temperature range was also high, which may be detrimental to cardamom production in the Zone Ill. The Zone II fall under intermediary category (150-200 kg / ha), where the length of crop growing season was more than 250 days with annual Ima varied between 80 and 85 per cent. From the crop weather relationship studies, it was understood that the rainfall from December to May, annual temperature range and temperature range during southwest monsoon could explain up to 78 per cent variability in cardamom production. It was also noticed that cardamom production was high whenever the annual water deficit was low and vice-versa.
Climatic water balances of Kerala
(Kerala Agricultural University, 1982) Prasada Rao, G S L H V; Balakrishna Pillai, P
Crop weather relationship in cauliflower (Brassica oleracea var.botrytis L.)
(Department of Agricultural Meteorology, College of Horticulture, Vellanikkara, 2012) Karthika, V P; Prasada Rao, G S L H V
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.
Crop weather relationships of cocoa (Theobroma cacao L.)
(Department of Agricultural Meteorology, College of Horticulture, Vellanikkara, 2009) Manikandan, N; Prasada Rao, G S L H V
Effect of date of planting on the duration and grain yield of rice cultivar allikkannan
(Kerala Agricultural University, 1994) Prasada Rao, G S L H V
Impact of climate change on water availability across western ghats
(Academy of Climate Change Education and Research, Vellanikkara, 2015) Anjali Nair, B; Prasada Rao, G S L H V
The present study entitled “Impact of climate change on water availability across Western Ghats” was taken up at the Energy and Wetlands Research Group, Indian Institute of Science, Bangalore during 2014-‘15 with the objectives of analyzing the changes in surface air temperature and rainfall across the Western Ghats along the Coast, Ghat and Plain regions and visualizing the likely scenario in land use and water availability in two selected basins viz., Karamana Basin (Thiruvananthapuram, Kerala and Sita Basin, Udupi, Karnataka) under the projected climate change scenario. The data required for the study were obtained from the Directorate of Economics and Statistics, Government of Karnataka, website of NOAA, website of Hydrology Department, University of Princeton and from the publications of the Central Government Department and the concerned State Departments. The study revealed that the rainfall over the Western Ghats as a whole doesn’t reveal any trend from 1901-2010 while it is not so at the regional level. However, the maximum and minimum temperatures along the Western Ghats showed an increasing trend from 1948- 2010. The trend was similar at regional level except in the plains of the Northern Western Ghats which showed a marginal decrease in the mean maximum temperature. Both the representative river basins viz., Karamana in Thiruvananthapuram district and Sita in Udupi district have undergone changes in the land use pattern which altered the water balance of the basin along with the change in population since last two decades from 1990 to 2010. The Karamana Basin suffered a deficit in the available water owing to the low rainfall received in the basin in comparison to the huge demand of water and the situation tend to aggravate with an increase in water demand and decrease in rainfall over the basin. But, Sita basin receives abundant rainfall which caters to the needs of the basin which rules out the water deficit in the basin unless in case of occurrence of moderate to severe drought.
Leaf and spadix phenology of coconut (Cocos nucifera L.)
(Department of Agricultural Meteorology, College of Horticulture, Vellanikkara, 2004) Shajeesh Jan, P; Prasada Rao, G S L H V
The field experiment entitled "Leaf and spadix phenology of coconut (Cocos nucifera L.) was conducted at Department of Agricultural Meteorology, College of Horticulture, Vellanikkara, during the period from February 2002 - June 2003. The investigations were undertaken with the following objectives such as to understand the seasonal influence on leaf and spadix production and their interval on different cultivars of coconut namely Tiptur Tall, Kuttiadi (WCT), Kasargod (WCT) and Komadan (WCT) including the duration of spadix emergence and on leaf and spadix phenology of coconut. All the four coconut cultivars behaved uniformly with respect to seasons in terms of functional leaves, spathe and female flower production. Nevertheless, they responded differently to different weather variables. However, Tiptur Tall was tolerant to weather aberrations and superior in terms of its floral and yield characters. The study indicated that favourable weather conditions during post monsoon season might have resulted in maximum absorption and translocation of food material during the same season in which maximum number of functional leaves were noticed whereas the rise in temperature, vapour pressure deficit coupled with low rainfall and bright' sunshine hours led to higher leaf shedding during summer. The favourable weather conditions such as optimum soil moisture, maximum temperature and bright sunshine hours during the primordium initiation (29 months prior to the spathe emergence) resulted in maximum spathe emergence during post monsoon. The unfavourable weather conditions such as low rainfall, less rainy days and high maximum temperature coupled with bright sunshine during the primordia initiation stage would have played a major role in low emergence of spathes during the southwest monsoon. The study also indicated that low minimum temperature, and optimum temperature range, wind speed, vapour pressure deficit, evaporation and sunshine hours resulted in maximum spathe duration during winter. The reasons for maximum spadix emergence during summer season can be attributed to the maximum number of spathes present on the crown during winter in which the duration from spathe to spadix was also more. When coconut spathes were exposed to a range of higher atmospheric temperature it may cause for early spadix emergence. In contrast, the number of spathes present on the crown was less during the southwest monsoon and hence the opening of spathe during the ensuing post monsoon was less. The high female flower production during summer can be attributed to the favourable weather prevailed during primordia initiation (32 months prior to the spadix emergence) and ovary development (6-7 months before the spadix emergence,). High maximum temperature, temperature range, sun shine hours and high vapour pressure deficit and prolonged dry spell during the above critical stages caused to the low female flower production during post monsoon season. The number of female flowers produced could be explained up to 99 percent due to weather prevailed during the above two critical stages in the case of Kuttiadi and Kasargod. The relationship between the female flower production and button shedding revealed that when female flower production was high button shedding was also high, while not in the case of Tiptur Tall. It also revealed that button shedding was more in summer 2003 when compared to that of summer 2002. It was attributed to the occurrence of prolonged dry spell from November 2002 to 8th June 2003 when compared to that of summer 2002. In addition to the prolonged dry spell during the above season, the occasional intermittent rains in the form of cloud burst/ summer showers might have caused imbalance in nut setting resulting in immediate fall of buttons. The spathe duration and button shedding in coconut responded positively to the growing degree days. It revealed that that both the above phenological events may respond to thermal regime. Future line of work Such studies, if undertaken for at least five years, will be quite useful in understanding the response of biotic events to weather variations. In addition, the information can be used in crop improvement programmes of coconut.
Phytoclimate of paddy
(Kerala Agricultural University, 1983) Prasada Rao, G S L H V
Proceedings of the WTO workshop: impact of climate change on the agricultural sector in tropical countries
(Kerala Agricultural University, Vellanikkara, 2007) Prasada Rao, G S L H V