Abstract
The impacts of heat stress and management practices on growth and yield of wheat under the High Barind Tract environment were examined through executing five pot and field experiments at the FSRD site, Godagari, Rajshahi under OFRD of BARI, during three consecutive Rabi seasons of 2005-09. In first year (2006-07), the field performance of 100 wheat varieties/ines was evaluated at three sowing dates, and results revealed that sowing date had significant. impact on days to growth stages, growing degree days, grains spike, 1000-grain weight, grain yield, straw yield and harvest index The 14 and 30 December sowing dates curtailed the field duration of wheat by 4.70 and 11.56 days, respectively and exhibited 87.84 and 68.39% relative performance, respectively than that of 28 November sowing date. Among the 100 varieties/lines, the highest degree of heat tolerance index (1.13) was exhibited by BAW-1067 and LPSN-68, while LPNS-76 and Shatabdi showed slightly lower value (1.11). However, regarding the field performances of grain yield, heat tolerance index and heat susceptible index Shatabdi performed the highest and was identified as heat tolerant variety. Besides, Protival and Sonora-64 were evaluated as moderate heat tolerant and heat susceptible varieties, respectively. In pot experiment (2007-08), the applied ranges of temperature attributed significant impact on the grain yield, where normal temperature gave the highest yield (25.91g pat) but 7 day heat stress with Normal+5°C, and Normal+10°C declined the yield linearly. which exhibited 81.20 and 66.11% relative performance, respectively. In interaction, Shatabdi with normal temperature gave the highest yield (30.43g pot). However, 7 day heat stress at dough stage displayed slightly deteriorated yield (25.29g por) whereas continual heat stress during Booting Heading Flowering+Mik+Dough stages gave the poorest yield (15.77 g pat1). Heat stress for 3 day at flowering stage gave the yield of 23.01g pot, while 7 and 10 day heat stress declined the yield drastically (19.61 and 16.92g por, respectively). In field experiments (2007-09), Shatabdi produced the highest yields of grain (2.72 and 3.00 t he" in 2007-08 and 2008-09, respectively) due to the higher values of yield components (number of spikes m2, spikelets spike, grains spike" and 1000-grain weight) followed by Protiva (2.39 and 2.58 tha in 2007-08 and 2008-09, respectively). The management practices had significant impact on yield components and yields of wheat, where Recommended fertilizers (RF)+Boron (B)+Famyard manure (FYM)+Straw mulch exhibited the highest yields of grain in both years (2.68 and 2.75 t ha in 2007-08 and 2008-09, respectively). However, as an interaction, Shatabdi in combination with RF+B+FYM+Straw produced the largest yields (3.38 and 3.64 t ha in 2007-08 and 2008-09, respectively). The same interaction accounted for the highest gross margin (TK 28381 ha) in 2007-08, but Shatabdi along with RF+FYM+Straw exhibited the highest net return (Tk. 30779 ha) in 2008-09. Besides, RF alone contributed relatively lower margin (Tk 15155 and Tk. 18040 ha, respectively). Therefore, Shatabdi along with RF+8+FYM+Straw can be used for augmenting the grain yield as wel as economic retum of wheat under terminal heat stress condition (heat stress from heading to maturity stages) of the High Barind Tract in Bangladesh.