Effect of High Temperature and Mulching on Growth and Yield of Wheat (Triticum aestivum L.)

Abstract

An experiment was conducted to study the effect of high temperature and mulching on growth and yield of wheat (Triticum aestivum L.) during two consecutive seasons (2008-09 and 2009-10). The experiment comprised of four sowing dates, viz., 17 November (S1 ), 2 December (S2), 17 December (S3) and 1 January (S4), two varieties namely, Bijoy (V1 ) and Gourab (V2) and four mulching treatments, no mulching (M1 ), water hyacinth mulching (M2), rice straw mulching (M3) and black polythene mulching (Mi). The experiment was laid out in a split-split plot design assigning the sowing date to the main plot, variety to the sub-plots and mulching to the sub-sub plots. The treatments were replicated three times. The experimental results revealed that the highest total dry matter (TDM), leaf area index (LAI) and crop growth rate (CGR) were obtained from 17 November (S1 ) sowing and the lowest were obtained from I January (S4) sowing in both the years. With some exceptions, numerically the highest relative growth rate (RGR), relative leaf growth rate (RLGR) and leaf weight ratio (L WR) were obtained from S1 sowing and the lowest were obtained from S4 sowing in both the years at all the harvests. Numerically the highest leaf area ratio (LAR) values were observed at S4 sowing at the early stages of growth and at the later stages S1 sowing showed the highest value in 2008-09. In 2009-10 growing season, numerically the highest LAR values were observed at S2 sowing at all the harvests. Other growth attributes such as net assimilation rate (NAR), specific leaf area (SLA) did not show any clear cut pattern among the sowing dates in both the years. Between the two varieties, Bijoy showed higher TDM, LAI and CGR values at all the harvests as compared to Gourab. No clear cut superiority was observed between the varieties for RGR, RLGR, NAR, SLA and L WR. The highest TDM, LAI and CGR were obtained from black polythene mulching (M4) and the lowest were obtained from control treatment (M1 ) in both the years at all the harvests. No clear cut pattern of mulching on RGR and RLGR was observed in both the years. With some exceptions, the highest NAR values were obtained from M4 mulching and the lowest values were obtained from control in both the years. The number of days for attaining different phenological stages was higher for early sowing condition. 17 November sowing (S1 ) required the maximum days for crown root initiation, tillering, booting, heading, anthesis, grain filling and maturity. The S4 (1 January sowing) plants required the lowest days to attain these stages in both the years. The highest heat units (GDD) were required in S1 plants followed by S2, S3 and S4 plants at all the phenological stages in both the years. It was also observed that the requirement of heat units for all the phenological stages decreased with delay in sowing. The S1 plants had the highest HTU and S3 plants had the lowest HTU at all the phenological stages in the first year. In the second year, the SI plants had the highest HTU at all the phenological stages except atgrain filling and maturity stages. Requirements of higher heat units, helio-thermal units (HTU) were observed in Bijoy (V 1) than Gourab (V2) at all the phenological stages in both the growing seasons. lt was found that the highest heat units were required in M4 crops and was successively followed by M3, M2 and M1 . Moisture retention capacity (MRC) and relative leaf water content (RL WC) of the flag leaves were higher in the early-sown crops and lower the in late-sown crops. The highest MRC and RL WC were observed in M4 crops and the lowest were observed in M1 (control) at each time of the day. The S1 (17 November sowing) and M4 plants (black polythene mulching) contained the highest amount of chlorophyll a, chlorophyll b and total chlorophyll (a+b) than the other sowings. The S4 and M1 (control) plants contained the lowest amount of chlorophyll a, chlorophyll b and total chlorophyll (a+b). All the yield and yield contributing characters i.e., plant height, number of total tillers planr 1 , number of effective tillers planr1 , spike length, extrusion length, number of spikelets spike·1 , number of fertile spikelets spike· 1, 1000-grain weight, grain yield, straw yield, biological yield and harvest index were highest in 17 November sowing (S 1) and the lowest values were found in I January sowing (S4) plants in both the years. Between the two varieties, Bijoy produced higher plant height, number of total tillers planr1 , number of effective tillers planr1 , spike length, extrusion length, number of spikelets spike· 1, number of fertile spikelets spike·1, I 000-grain weight, grain yield, straw yield, biological yield and harvest index than Gourab. All the yield and yield contributing characters showed highest value in black polythene mulching (M4) and the minimum values were observed in M1 (control) in both the years.