3.2. Variability in yield and meteorological conditions during 24 h before tapping
During the period under study, 200 tappings were undertaken. The mean yield was 51.1 g/tree/tap and the range is between 19.1 and 90.5 g/tree/tap. A summary of the prevailing meteorological conditions during the 24-h period before tapping is given in Table 1. Rainfall was less than 5 mm for about 72% of the days and during 10% of the days it was more than 20 mm/day. The Tx varied between 30°C and 35°C, during 74% of the days. The day-to-day variability in Tn, prior to tapping was 7%. An inverse relationship between Tn and yields were observed. For about 78% of the days, the Tn recorded prior to tapping was between 22°C and 25°C.
The mean values for Tx and Tn are 31.5°C and 22.8°C, respectively. The mean daily sunshine duration was 7 h, with 85 days (42.5%) recorded between 9 and 11 h. Very low values of Vf observed at the time of tapping, which is favourable to high initial flow rate. Mean Ep during the period under study was 3.9 mm/day. In about 86% of the days, it varied between 2 and 6 mm/day, with 111 days recording between 3 and 5 mm/day. The mean VPD in the morning was 3.0 mb where as in the afternoon it was 18.2 mb. The range in the Va (1.5–40.2 mb) indicate moist as well as dry atmospheric conditions in the afternoon prevailed prior to when the trees are tapped.
The correlation coefficients between latex yield and different meteorological conditions are shown in Table 2. Significant negative correlation between yield of rubber trees and Tx, S, Ep and positive association with rainfall was observed. The multiple regression equation between yield and previous day weather conditions is obtained as follows:
equation(1)
equation(2)
where R1 is the 24 h accumulated rainfall; Tx1 and Va1 are the maximum temperature and afternoon vapour pressure deficit observed before tapping. Inclusion of R1 and Va1 has not improved the R2 value ( Eq. (2)). The rainfall influences the variability in other weather conditions, except Tn ( Table 2). Similarly, Tx influences Ep and Va and S influences Ep and Va. Thus the mutual correlations between meteorological variables used in the regression analysis showed little improvement over the maximum temperature. Further, total rainfall in a day could not reflect the effective component of rainfall utilised in regulating soil moisture status as well as water relations of the trees.
3.2. Variability in yield and meteorological conditions during 24 h before tappingDuring the period under study, 200 tappings were undertaken. The mean yield was 51.1 g/tree/tap and the range is between 19.1 and 90.5 g/tree/tap. A summary of the prevailing meteorological conditions during the 24-h period before tapping is given in Table 1. Rainfall was less than 5 mm for about 72% of the days and during 10% of the days it was more than 20 mm/day. The Tx varied between 30°C and 35°C, during 74% of the days. The day-to-day variability in Tn, prior to tapping was 7%. An inverse relationship between Tn and yields were observed. For about 78% of the days, the Tn recorded prior to tapping was between 22°C and 25°C.The mean values for Tx and Tn are 31.5°C and 22.8°C, respectively. The mean daily sunshine duration was 7 h, with 85 days (42.5%) recorded between 9 and 11 h. Very low values of Vf observed at the time of tapping, which is favourable to high initial flow rate. Mean Ep during the period under study was 3.9 mm/day. In about 86% of the days, it varied between 2 and 6 mm/day, with 111 days recording between 3 and 5 mm/day. The mean VPD in the morning was 3.0 mb where as in the afternoon it was 18.2 mb. The range in the Va (1.5–40.2 mb) indicate moist as well as dry atmospheric conditions in the afternoon prevailed prior to when the trees are tapped.The correlation coefficients between latex yield and different meteorological conditions are shown in Table 2. Significant negative correlation between yield of rubber trees and Tx, S, Ep and positive association with rainfall was observed. The multiple regression equation between yield and previous day weather conditions is obtained as follows:
equation(1)
equation(2)
where R1 is the 24 h accumulated rainfall; Tx1 and Va1 are the maximum temperature and afternoon vapour pressure deficit observed before tapping. Inclusion of R1 and Va1 has not improved the R2 value ( Eq. (2)). The rainfall influences the variability in other weather conditions, except Tn ( Table 2). Similarly, Tx influences Ep and Va and S influences Ep and Va. Thus the mutual correlations between meteorological variables used in the regression analysis showed little improvement over the maximum temperature. Further, total rainfall in a day could not reflect the effective component of rainfall utilised in regulating soil moisture status as well as water relations of the trees.
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