Effect of Sowing Times on Growth and Yield of Blackgram (Phaseolus Mungo L.)

Abstract

An experiment was conducted to study the effect of sowing times on growth and yield of blackgram (Phaseolus mungo L. ). Four varieties of blackgram viz., BARIMASH-1, BARIMASH-2, BARIMASH-3 and LOCAL VARIETY B-10 were used in the study. Seeds were sown on four different sowing times viz., 01 August (S1 ), 11 August (S2), 21 August (S3 ) and 31 August (S4) over two seasons during the kharif-2 monsoon under field conditions. The S3 (21 August) plants had the highest TDM than the other sowing and LOCAL VARIETY B-10 showed the highest TDM at all the sowings. Leaf area index (LAI) and leaf area duration (LAD) at most of the growth stages were found the highest in S1 (01 August) in both the years. Among the varieties, the highest LAI and LAD were observed in LOCAL VARIETY B-10 in both the years. CGR, RGR, RLGR, NAR, SLA and L WR at most of the stages were observed higher values in S3 plants (21 August sowing) whereas higher values in LAR was found in SI of all the sowings and varieties in both the years. The highest values of CGR, RGR, RLGR, LAR, SLA and L WR were found in LOCAL VARIETY B-10 whereas NAR showed better performance in BARIMASH-3 variety in both the years. Therefore, most of the growth attributes were higher in S3 (21 August sowing) and LOCAL VARIETY B-10 in both the years. Among the growth attributes, TDM, LAI, LAD and CGR increased with increasing plant age and then decreased gradually in both the years. Again, RGR, LAR, RLGR and L WR declined with increasing plant age. With few exceptions, NAR showed increasing tendency towards the later stages of growth. Only SLA showed increasing tendency at the middle stages of growth in both the years. At the early growing periods, mean air temperature (maximum and minimum) were higher and then declined upto the final harvest. So, S1 (01, August) had the highest air temperature and the lowest in S4 (31, August) than that of the middle growth stages in both the years. The lowest sunshine hours were observed during SI growing period and the highest in S4 in both the seasons. Significant sowing time and varietal effects were found for most of the phenological characters in both the years. Most of the phenological characters were observed higher values in S4 sowing (31 August) followed by the optimum sowing S3 (21 August) and showed their highest values in LOCAL VARIETY B-10. Days taken for attainment of most of the phenological stages were higher in S3 and LOCAL VARIETY B-10 required the highest number of days for attaining the different phenological stages. The requirement of heat units (GDD) at all the stages were significantly higher in S4 followed by S3 The LOCAL VARIETY B-10accumulated the highest heat unit (GDD) at most of the stages for all the sowings. The requirement of helio-thermal unit (HTU) at most of the stages were highest when the crops were sown in S4 (31 August) followed by S3 . HTU was observed higher values in LOCAL VARIETY B-10 of all the sowings at most of the stages. Pheno-thermal indices (PTI) during the different phenological stages were highest in S4 followed by S3 in both the years. At all the stages, PTI values were highest in BARIMASH-3. The plants of S3 used heat more efficiently than the other sowings and the highest HUE was observed in LOCAL VARIETY B-10 which was followed by BARIMASH-2 in both the years. Sowing time was always significant for chlorophyll a, b and total chlorophyll and chlorophyll a:b ratio and significant varietal effect was observed for chlorophyll b of matured green leaves. The SI plants ratio was observed for highest in S4 than the other sowmgs and BARIMASH-1 produced the highest chlorophyll a, b and total chlorophyll and LOCAL VARIETY B-10 produced be highest chlorophyll a: b ratio in both the years. The highest RLWC was recorded in S1 plants at 8.00 a.m. For all the sowings, it was higher at the morning (8.00 a.m.) and got reduced at 12.00 noon and showed some recovery at the afternoon (4.00 p.m.) in both the years. The highest RL WC was observed in BARIMASH-3 followed by LOCAL VARIETY B-10 at 8.00 a.m. and lowest in BARIMASH-2 for most of the cases in both the years. Among the yield and yield components, significant sowing time and varietal effects were observed at most of the characters in both the years. Most of the yield characters were found higher in S3 (21 August) sown crops in both the years. Among the varieties, most of the characters showed their higher values in LOCAL VARIETY B-10 followed by BARIMASH-3 in both the years respectively. Simple correlation co-efficient between yield and yield components indicated that grain yield of all the sowings was positively correlated with total dry matter (TDM) planf1, pod no. planf1, pod dry weight planr1, grain no. planf1 and grain weight planf1 except 3rd sowing whereas it was negatively associated with 100-seed weight and harvest index. It was suggested that for better growth and yield performances, seeds of blackgram should be sown on 3rd week of August (21 August) in the northern part of Bangladesh. LOCAL VARIETY B-10 may be considered as more widely adapted variety for this region.