2. Material and methods
A relatively drought tolerant clone RRII 105, evolved by the Rubber Research Institute of India (RRII) and recommended as category I for large scale commercial planting, was planted during 1982 at the Experimental Station of RRII, Kottayam (Latitude: 9°32′N, Longitude: 76°36′E and Altitude: 73 m). The study area represents the traditional rubber growing tracts of India. Also, about 90% of the cultivable areas in and around the experimental field are occupied by rubber plantations. A total of 30 trees, having uniform girth were selected for this study. The system of tapping adopted was a half-spiral cut in the bark of the tree with alternate daily harvest (1/2S d/2 system).
In general, tapping begins at 0730 h (IST) and latex is collected at around 1100 h. Experimental tapping started on 11 July 1989 and continued up to 31 December 1990. The method of yield recording was cup coagulation and latex was collected on all tapping days. Yield was determined by coagulating the latex from individual trees in collecting cups by adding a few drops of 1% formic acid. After drying the coagulate in a smoke house, the yield (weight of dry rubber) is obtained from individual tree and then the average yield on each tapping day was obtained.
Daily meteorological data viz., rainfall (R), maximum (Tx) and minimum (Tn) temperature, sunshine duration (S), forenoon and afternoon relative humidity and pan evaporation (Ep) from a well maintained Agromet observatory, 200 m away from the plantation, were recorded. From temperature and humidity values, the VPD in the forenoon (Vf) and afternoon (Va) were calculated. The statistical analysis of frequency distribution, mean, standard deviation (SD) and coefficient of variation (CV) of different weather elements were undertaken.
The Pearson correlation coefficients and step-wise multiple regression relationships between the latex yield and meteorological parameters at different lead periods (windows) were also analysed to quantify the yield–weather relations. The weather and climate associated with above average yields are identified.
2. Material and methodsA relatively drought tolerant clone RRII 105, evolved by the Rubber Research Institute of India (RRII) and recommended as category I for large scale commercial planting, was planted during 1982 at the Experimental Station of RRII, Kottayam (Latitude: 9°32′N, Longitude: 76°36′E and Altitude: 73 m). The study area represents the traditional rubber growing tracts of India. Also, about 90% of the cultivable areas in and around the experimental field are occupied by rubber plantations. A total of 30 trees, having uniform girth were selected for this study. The system of tapping adopted was a half-spiral cut in the bark of the tree with alternate daily harvest (1/2S d/2 system).In general, tapping begins at 0730 h (IST) and latex is collected at around 1100 h. Experimental tapping started on 11 July 1989 and continued up to 31 December 1990. The method of yield recording was cup coagulation and latex was collected on all tapping days. Yield was determined by coagulating the latex from individual trees in collecting cups by adding a few drops of 1% formic acid. After drying the coagulate in a smoke house, the yield (weight of dry rubber) is obtained from individual tree and then the average yield on each tapping day was obtained.Daily meteorological data viz., rainfall (R), maximum (Tx) and minimum (Tn) temperature, sunshine duration (S), forenoon and afternoon relative humidity and pan evaporation (Ep) from a well maintained Agromet observatory, 200 m away from the plantation, were recorded. From temperature and humidity values, the VPD in the forenoon (Vf) and afternoon (Va) were calculated. The statistical analysis of frequency distribution, mean, standard deviation (SD) and coefficient of variation (CV) of different weather elements were undertaken.
The Pearson correlation coefficients and step-wise multiple regression relationships between the latex yield and meteorological parameters at different lead periods (windows) were also analysed to quantify the yield–weather relations. The weather and climate associated with above average yields are identified.
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