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ThesisItem Open Access Crop weather relationship in okra(Department of Agricultural Meteorology, College of Horticulture, Vellanikkara, 1999) Kavitha, S; KAU; Kesava Rao, A V RCROP WEATHER RELATIONSllP IN OKRA (Abelmoschus esculentus [L.} Moench), VARIETY 'ARKA ANAMIKA' The experiment was conducted during 1998-1999 at the College of Horticulture, Vellanikkara to find out the crop weather relationships of okra, 'Arka Anamika'. The experiment was laid out in randomised block design with three replications. The treatments consisted of twelve monthly sowing, starting from 21 st April 1998 to 21 st March 1999. Observations on morphological, phenological and yield attributes were recorded during the course of investigation. The daily values of weather elements viz., rainfall, number of rainy days, maximum and minimum surface air temperatures. bright sunshine, mormng and afternoon relative humidity, pan evaporation and wind speed were collected from the Principal Agricultural Meteorological Station, College of Horticulture, Vellanikkara, to work out the crop weather relationships of okra. March, April and September sown crops were significantly superior in terms of fruit yield per plant, number of harvests and crop duration. April sown crop was also superior in plant height, number of nodes on mainstem, and number of primary branches. The fruit yield was significantly associated with the plant height, number of nodes on main stem, number of primary branches, number of harvests and duration of the crop. A multiple regression equation was worked out for predicting fruit yield based on plant characters and it is as follows: Y = 3.08 XI + 11.15 X2 - 210.14 (R2 = 0.94) Where, XI is the duration of the erop in days, X2 is the number of harvests and Y is the yield per plant (g). Based on the association between weather elements and crop yield of okra, a multiple regression equation was worked out and given below: Y = 50.7 XI - 28.69 X2 + 16.11 X3 - 0.058 X4 - 456.29 (R2 = 0.76) Where, Y = yield per plant (g), X, - Minimum temperature (OC) during vegetative phase (6,h to 7th week after sowing), X2 - Maximum temperature (OC) during reproductive phase (6th to 9th week after sowing), X3 - Bright sunshine (h per day) during vegetative phase (4th to 6th week after sowing) and X.4 - Rainfall (mm) during vegetative phase (5th to 6th week after sowing).ThesisItem Open Access Crops weather relationship in rice(Department of Agricultural Meteorology, College of Horticulture,Vellanikkara, 2000) Sunil, K M; KAU; Kesava Rao, A V RAn experiment was conducted in the Agricultural research Station, Mannuthy during first, second and third crop seasons of 1998-99 to study the crop weather relationship in rice variety 'Kanchana'. The experiment was laid out in randomised block design with three replications. The treatment consisted of three dates of planting in each season i.e., 1 s\ i s" and 30th of June, 1 st 15th and 30th of October and 1 st, 15th and 30th of January. Observations on morphological and yield attributes were recorded during the course of investigation. The daily values of weather elements viz., maximum and minimum surface air temperature, bright sunshine, morning and afternoon relative humidity and wind speed were collected from the Principle Agro Meteorological Station, College of Horticulture, Vellanikkara, to work out the crop weather relationships in rice. . Crops transplanted on 1 st is" and 30tl) of October and 1 st 15th of June were significantly superior in terms of grain yield, panicle number, number of filled grains/panicle, number of leaves, plant biomass, number of tillers and leaf area index. The crop weather relationship studies showed that the wind speed, minimum temperature and mean temperature during flowering to maturity had a significant negative correlation with grain yield. But morning relative humidity and mean relative humidity during transplanting to panicle initiation stage had a significant positive influence on ultimate grain yield. The wind speed, mean temperature, temperature range, RH1-RH2 and solar radiation during vegetative stage were negatively correlated with the straw yield. Maximum temperature during beginning of grain filling to maturity stage also had a negative correlation. But increase in mimmum temperature, mean relative humidity, morning and afternoon relative humidities during transplanting to flowering stage was significantly increase the straw yield as there was a positive correlation. The regression equations developed in the study predicted the grain yield, straw yield, duration of vegetative phase and maximum leaf area index well and a close relation existed between observed and estimated yield. Based on the experimental data, minimum data set for the validation of rice model of the IBSNAT has been generated.ThesisItem Open Access Crop weather relationship studies in bitter gourd(Department of Agricultural Meteorology, College of Horticulture, Vellanikkara, 1996) Lincy Davis, P; KAU; Balakrishna Pillai, PAn experiment was conducted during 1995 – 96 at the College of Horticulture, Vellenikkara to find out the optimum date of sowing and to study the crop – weather relationship in bitter gourd, variety mc –84. The experiment was laid out in randomised black design with 3 replications. The treatments consisted of twelve dates of sowing starting from April 15th, 1995 and ending in March, 15th, 1996. For each and every treatment one control plot was maintained. The biometric observations of the crop growth characters, flowering and yield attributes were taken at different stages of development of the crop. The observations on the incidence of pests and diseases were recorded from the control plots. The observations on weather elements were recorded daily. October sowing was significantly superior to others with regard to number of female flower production, number of fruits, fruit set, fruit length girth, weight and yield. The crop weather relationship studies showed that the temperature range during 45 to 65 DAS and sunshine hours during 40-60 DAS were positively correlated with both total yield and number of female flowers per plant while minimum temperature during 45-60 DAS and mean relative humidity during 45-70 DAS were negatively correlated with both total yield and number of female flowers per plant. Crop sown during September, October and November were free from the attack of Bactrocera cucurbitae (Coq.). While Eudioptes indica (Saund.) occurred throughout the year. Mosaic disease incidence was severe in crops sown during June. But September sown crop was free from diseases.ThesisItem Open Access Crops weather relationship in tomato(Department of Agricultural Meteorology, College of Horticulture, Vellanikkara, 1998) Ajithkumar, B; KAU; Lalitha Bai, E KAn experiment was conducted during 1997-98 at the College of Horticulture, vellanikkara to study to influence of date of sowing and levels of nitrogen on the growth and yield of tomato ((Lycopersicon esculentum Mill.) The experiment was laid out in split plot design with three replications. The treatment consisted of nine dates of planting starting from June 15th to February 15th in the main plot and two levels of nitrogen (125 kg N ha-1 and 75 kg N ha-1) in the subplot. Observations on morphological and yield attributes were recorded during the course of investigation. The daily values of various weather elements recorded at the Agromet observatory, college of Horticulture, Vellanikkara were collected to work out the crop weather relationship. February planted crop took less number of days for first flowering, 50 per cent flowering, and had the shortest crop duration. While June planting took maximum number of days for first and 50 per cent flowering. Where as maximum duration of the crop was recorded by planting in October. December planting was significantly superior to other treatments with regard to yield characters. The maximum number of fruits per plant was obtained for December planting followed by October and November planting. Application of 125 kg N ha-1 significantly improved the yield and yield characters as compared to that in 75 kg N ha-1. Higher dose of nitrogen favoured the earlier fruit set, maximum duration of the crop, increase in the number of fruits per plant and thus resulted in enhanced fruit yield. The crop weather relationship studies showed that the morning relative humidity and afternoon relative humidity during the 1st-2nd weeks after planting had a positive effect on the days to first flowering. The minimum temperature (7th-8th week) and morning relative humidity (6th-7th week) were negatively correlated with yield. Days to first flowering showed a negative correlationship with maximum temperature, minimum temperature, temperature range and hours of bright sunshine during the 1st-2nd weeks after planting. The maximum temperature of (31.60C-32.10C) and minimum temperature of 24.10C-24.30C) found to be optimum for early flowering. Wheras minimum temparature of (22.10C-23.30C) and relative humidity during morning hours (70-74%) during 6th and 8th week after planting are optimum for the increase yield. Under Vellanikkara condition, maximum temparature of 30.60C-33.70C, minimum temperature of 22.10C-24.30C, bright sunshine hours of 5.2-10.0, morning relative humidity of 70-86 per cent, afternoon relative humidity of 45-59 per cent is required for optimum crop growth. Based on the experimental data, minimum data set for the validation of tomato model of the IBSNAT has been generated. Result of the present experiment indicate that at Vellanikkara surrdounding tomato can be successfully raised if seedlings are planted in the middle of December. Weather during October and November are also congenial for getting higher yield. The higher dose of nitrogen (125 kg/ha) gave better yield than the recommended dose of nitrogen.ThesisItem Open Access Agroclimatology in crop planning for central zone of Kerala(Department of Agricultural Meteorology, College of Horticulture, Vellanikkara, 1999) Ajith, K; KAU; Kesava Ravo, A V RA study was undertaken to determine weekly index of moisture adequacy (I MA) and water availabi I ity periods for various locations in the central zone of Kerala and to examine the viability of important crops. Daily rainfall data for the period 1978-97 were collected from 26 stations in the central zone. Daily data on maximum and minimum temperature, wind speed, maximum and minimum relative humidity and bright sunshine hours for Kochi, Palakkad, Pattambi and Vellanikkara were collected. Soil data and crop data were also collected for the zone. Mean weekly, monthly, seasonal & annual rainfall and coefficient of variation for all stations were worked out. Spatial variation of mean rainfall and coefficient of variation during the different seasons were studied. Monthly , dependable rainfall at 75 per cent and 90 per cent ' •• vere calculated using the ranking method suggested by Frere and Papov, and its spatial variation over the zone was studied. Initial and conditional probabilities of receiving 30 mm or more rainfall per week following Markov chain model for all the rain gauge stations were worked out and discussed. Water balance elements were computed for the 26 stations following book- keeping method of Thornthwaite. PET was computed following the modified Penman method as suggested by Doorenbos and Pruitt. Annually, the actual evapotranspiration (AET) varied from <400 mm in the eastern region of the zone to >700 mm in the southern part of the zone. The lowest AET ,. of 311 mm was observed at Parambikulam and a highest of 779 mm at Piravom. A I gradual increase of AET can be observed from northern part to southern part. The midland and of the central part of the zone had higher values of water deficit (WD) \ 1 '~L t '. compared to the northern and southern parts i.e., more than 1300 mm. Parambikulam had highest value for WD i.e., 1606 mm. Almost all the coastal region and midland of the northern and southern parts were found to have lesser WD value « 1300 mm.) Water surplus (WS) was high in the midland and coastal areas of the zone. The highest value of WS, 913 mm was observed at Wadakkancherry followed by Kunnamkulam (614 mm) both in the coastal region. Almost all stations in the coastal region were found to have higher values ofWS, i.e., more than 400 mm except a small patch around Kochi. Water availability periods were identified comparing the AET and PET. It was found that water availability periods followed the same pattern for most of the stations in the central zone. It was characterised by a 1 st sub humid period followed by a humid period and a 2nd subhumid period. The highest number of moist days was recorded at Piravom (203) followed by Aluva and Perumbavoor(188). At this station the humid period extended for 170 days which is also the highest value compared to all other stations. The least number of moist days was observed at Parambikulam (82). At this station there is a break in the humid period which gave way to a sub humid period. Most of the stations have total number of moist days more than 150. Generally, the water availability period starts in the 2nd week of June and extends up to 3rd week of November. " The cropping system of the central zone of Kerala was analysed and it was found that the cropping patterns fall under three major categories (1) mainly paddy (2) mainly coconut and (3) plantations other than coconut. The viability of these cropping patterns based on water availability periods and soil information are discussed.ThesisItem Open Access Crop weather relationships of cocoa (Theobroma cacao L.)(College of Horticulture, Vellanikkara, 2009) Manikandan, N; KAU; Prasada, Rao G S L H VA field experiment entitled “Crop weather relationships of cocoa (Theobroma cacao L.)” was conducted at the Department of Agricultural Meteorology, College of Horticulture, Vellanikkara from April 2007 to March 2008. The location is situated at 10o31’ N and 76 o13’ E at an elevation of 25 m above the mean sea level in the central zone of Kerala. The experimental site is attached to the farm of Cadbury – KAU Co-operative Cocoa Research Project, Vellanikkara. The experimental cocoa trees were 20-year-old. A total number of 30 cocoa trees were selected, out of which 15 each were grown under shade and open conditions. The trees in shade were classified as plants giving yield of <15, 15-30 and more than 30 pods per tree per year and the plants in open were classified as plants giving yield of <60, 60-90 and more than 90 pods per tree per year. The biotic events viz., flowering and fruiting characters were recorded once in a week during the study period of one year. Daily meteorological data on maximum and minimum temperatures, relative humidity (morning and evening), rainfall and rainy days, bright sunshine hours, evaporation and cloud amount were collected from the Department of Agricultural meteorology, College of Horticulture, Vellanikkara. The investigations were undertaken with the objectives such as to study the seasonal influence on flowering and fruiting behaviour of cocoa, to find out the relationship between weather elements and biotic events of cocoa and to understand the impact of climate variability on cocoa production and productivity across the State of Kerala. The biotic events viz., flowering, pod set and cherelle production in cocoa were seen throughout the year though weekly variations were significant and almost no biotic events were recorded in August. The pattern of biotic events in cocoa under open and shade were also similar. All the yield groups showed identical trend in flowering, pods set and cherelle production of cocoa irrespective of open and shade. However, the average number of flowers, pod set and cherelle was always lower in shade conditions when compared to the cocoa grown under open conditions. It is observed that the light availability on an average over cocoa under rubber (shade) was only 45 per cent, varying from 39 % (October) to 56 % (April). The overall percentage contribution of number of flowers, pod set and cherelle during summer was high when compared to that of the other seasons. The flowering appears to be very low during the heavy wet spell due to mechanical damage as well as low bright sunshine available to the crop. It reveals that the light availability is very important for better performance of cocoa in terms of flowers, pod set and cherelle production. The correlations between rainfall and flowering indicated that rainfall had negative (-0.464) relationship with flowering, as no significant flowering was seen during the heavy rainfall period from June-October. Nevertheless, the summer rains (February-May) two weeks before flowering influenced the flowering favourably. The positive relationship of cocoa flowering with maximum temperature was only due to flowering pattern of cocoa but not due to high maximum temperature (35-37°C) that prevailed during the summer. There was a positive trend between the helio-thermal units (HTU) and biotic events such as flowering, pods set and cherelle production in cocoa and significant at 0.01 level. The helio-thermal units depend on growing degree days, which is a function of temperature [(Max+Min/2)-10oC] and number of daily sunshine hours. The number of pods harvested was more in October and November, followed by summer (February-April) in contrast to the mean trend where the mean yield was more during summer followed by post monsoon season. The pattern of pod harvest was different between the habitats (open and shade) as the peak harvest in shade appeared during February – March while October – November in open. The coefficient of variation was very high (48.9-124.3 %) in monthly pod yield of cocoa while it was less (23 %) in the case of annual yield of cocoa. It indicated that the monthly cocoa yield is very sensitive to extreme weather conditions. The study also revealed that there was a sharp decline in cocoa area while increase in production and productivity due to technological interventions. However, the inter-annual variations in cocoa yield could be related to weather aberrations and it had no biennial bearing tendency. The pods harvested during November (post monsoon season) was superior in pod weight (562g), pod length (17.03 cm) and bean weight (1.28). The pods harvested during September (rainy season) and January (winter) showed intermediary, having the pod weight of 555 g/pod in September and 524 g/pod in January. The pods harvested during summer recorded 44 and 29 per cent less in pod weight and bean weight, respectively when compared to post monsoon season. Hence, a harvest of five pods during the post and southwest monsoon seasons equals to nine pods harvested during summer season, 5.4 pods during winter while 5.1 pods in south west monsoon. The study reveals that the low pod and bean weights during summer were due to high number of pods produced, moderate to severe soil moisture stress and high maximum temperature including temperature range. The maximum temperature from January to March had a profound influence on annual cocoa yield. The relationship between growing degree days (GDD) and yield also indicated similar trend as in the case of maximum temperature. The mean maximum temperature during summer was high in poor yield years while less in good yield years. There was an inverse trend between the annual rainfall and cocoa yield. It was found that the difference in cocoa yield during rainy months was very significant followed by post monsoon between good and bad yield years and thus the adverse influence of heavy rain on cocoa yield. On an average, the decline in yield was 45 per cent in bad yield years when compared to the mean yield while 45 per cent increase in good yield years during the southwest monsoon. The percentage increase in yield during good years when compared to that of bad years was 72 and 58 per cent during southwest monsoon and post monsoon, respectively. On examination through step wise regression, it was understood that the model explained 43 per cent variation in pod yield of cocoa due to maximum temperature alone. It revealed that high maximum temperature during summer with heavy rainfall during rainy season is likely to affect the annual cocoa yield adversely up to 40-50 per cent. Similar results were obtained when the secondary data on annual cocoa yield at the State level was subjected to crop weather analysis. From the above, it is clearly understood that high maximum temperature during summer, high rainfall and low light availability during the rainy season are the main factors limiting the cocoa production and productivity over the humid tropics.