BSc-MSc (Integrated)

A field experiment entitled “Crop weather modelling of cocoa production in humid tropics under the purview of climate change (Theobroma cacao L.)” was conducted at Academy of climate change education and research, Vellanikkara from2017-18. The location is situated at 10°31’ N and 76 °13’ 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 area is benefited both by the Southwest and Northeast monsoons, but a maximum share (68-72%) from southwest monsoon. The maximum precipitation (735.5mm) is received during June, followed by July. December to April form the dry months with scattered downpour. February, March and April are the hottest months with a mean maximum temperature of 35.4°C. Unusual and pre-monsoon showers are expected from March to May. Heavy rainfall from June-September, followed by a prolonged dry spell from November. The daily weather parameters viz., maximum and minimum temperatures, rainfall, morning and afternoon relative humidity, wind speed and Bright sunshine hours recorded at Agro-meteorological observatory, College of Horticulture, Vellanikkara were used for the study. The general climate of the location has studied for 35 years (1983-2017). The highest monthly temperature recorded during the months of February, March and April. December and January are considered as the coldest months. Maximum morning Relative humidity was more than 90% during the months from June to October and the lowest morning Relative humidity was recorded in the months of December and January. The afternoon Relative humidity also followed the same trend. Highest monthly average wind speed was recorded in the months of December and January. The period from June to October is considered as the rainy season which contributed more than 85% of the total annual rainfall. The average annual evaporation is 1394.7 mm and the average monthly evaporation is 116 mm. The pods harvested during November (post monsoon season) was superior in pod weight. In contrast, the pods harvested during monsoon were inferior in pod weight. The seasonal variations were found significant. In the case of wet weight, it can be observed that seasonal impact of weather was insignificant. The wet weight of pods was superior in year 2014 followed by 2012 and then 2013. Similar trend was observed in the case of pod length, pod breadth and husk weight. The yield and biometric parameters recorded at Cocoa Research Station, Vellanikkara was used for estimating various model parameters. Simulations in SUCROS-Cocoa was carried out for cacao trees of 1–11-year-old. Furthermore, the densities of model trees is bounded to 700–2500 ha-1. Climatic limitations of the model are an average day temperature between 10 and 40°C, and an annual precipitation of at least 1250 mm per year. The leaf area index (LAI) of shade trees should not exceed 3, and soil depth should be >1.5 m. Simple linear correlations between important morphological, yield attributes and mean weekly weather parameters like maximum temperature, minimum temperature, mean temperature and temperature range, relative humidity (morning, afternoon, mean and difference between morning and afternoon relative humidity), wind speed, bright sunshine, were carried out. Pod weight had a significant positive correlation with morning relative humidity, afternoon relative humidity and rainfall, whereas maximum temperature, sunshine hours and evaporation showed a significant negative correlation. The minimum temperature showed positive correlation the beginning of pod formation and it was negatively influenced the pod weight during the final stages of pod development. Soil temperature at different depths were also negatively influenced the pod development. There was significant negative correlation with maximum temperature, solar radiation, soil temperature and evaporation during the initial stages of pod development but during the final stages of pod development these weather parameters had significant positive correlation. The influence of relative humidity, rainfall, rainy days and wind speed just opposite compared to temperature and evaporation. They had a positive correlation in the initial stages of pod development and negative correlation during the final stages. Increase in minimum temperature during the initial as well as final stages of pod development were detrimental number of beans per pod where as it has a positive influence during the middle stages.