Computation and validation of different agroclimatic indices for wheat
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Date
2023
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Punjab Agricultural University, Ludhiana
Abstract
The field experiment was conducted at the Research Farm, Department of Climate Change and Agricultural Meteorology, Punjab Agricultural University, Ludhiana during rabi season of 2021-22. The wheat varieties viz., PBW 1 Zn, PBW 725, Unnat PBW 343 and PBW 752 were sown on October 26, November 8, November 16 and November 23. The crop was sown in Randomised complete block design with four replications. The recommended Package of Practices by PAU were followed for raising the crop. The micrometeorological parameters viz. photosynthetically active radiation (PAR), canopy temperature and relative humidity within canopy were recorded at periodic intervals. Biometric observations such as leaf area index (LAI) and dry matter accumulation (DMA) were recorded periodically. The yield and yield contributing characteristics were recorded at the time of harvesting. The wheat yield data of Ludhiana district from 2000-2001 to 2021-22 were collected and corresponding meteorological data on different parameters were obtained from Agrometeorological Observatory. Different agroclimatic indices viz., growing degree days, heliothermal units, photo-thermal units, pheno-thermal index, hygro-thermal units and relative temperature disparity were computed at different phenological stages. Heat use efficiency, helio-thermal use efficiency, photo-thermal use efficiency and radiation use efficiency were computed during rabi 2021-22. The results indicates that growing degree days, photo-thermal units, hygro-thermal units and relative temperature disparity were higher in October 26 sowing as compared to November 23 sowing. Whereas, helio-thermal units were higher in November 23 sowing. Heat use efficiency, helio-thermal use efficiency and photo-thermal use efficiency were higher in October 26 sown crop as compared to November 23 sown crop for total biomass and grain yield.The results showed that crop sown on November 23 experienced higher canopy temperature at reproductive stages as compared to October 26 sown crop. The grain yield was significantly higher in October 26 sowing (44.3 q ha-1) as compared to November 23 (39.2q ha-1) for variety Unnat PBW 343. Historical data on wheat yield and meteorological parameters were analysed from 2002-03 to 2021-22. The extreme heat wave years (2003-04, 2008-09 and 2021-22) indicates that maximum and minimum temperatures were higher than normal by 4 to 5°C during reproductive stage and no rainfall due to absence of western disturbances in the month of February and March was responsible for yield reduction. Temperature condition index was lower at reproductive phase and positively correlated with grain yield. Lower the values of temperature condition index, higher was the stress condition in the wheat crop and viceversa. The crop remained under stress in October 26 and November 8 sowing for 45 days whereas for November 16 and November 23 remained for 60 days. It means that late sown crop (November 16 and November 23) faced stress at heading stage and remained under stress for longer period as compared to early sowing (October 26 and November 8) which faced the moderate stress at anthesis stage.
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Manpreet Kaur (2023). Computation and validation of different agroclimatic indices for wheat (Unpublished M.Sc. thesis). Punjab Agricultural University, Ludhiana, Punjab, India.