Analysing water productivity response to sowing window, irrigation levels and mulching using CERES-wheat model

Abstract

Field experiments were carried out during rabi seasons of 2015-16 and 2016-17 at the Research Farm, Punjab Agricultural University, Ludhiana. Wheat variety PBW 621 was sown on three dates (D1: 4th week of October, D2: 2nd week of November and D3: 4th week of November) with two irrigation levels (I1: IW/ CPE = 0.9, I2: At CRI, 5-6 weeks after 1st irrigation, 3-4/5-6 weeks after 2nd irrigation, 2/4 weeks after 3rd irrigation as per dates of sowing) and mulch application (M1: without mulch, M2: straw mulch @ 5 t ha-1). Earlier sown mulch applied crop with four post-sowing irrigations produced highest (5312.5 kg ha-1) and late sown without mulch application crop with irrigation @IW/CPE = 0.9 produced lowest grain yield (3900.5 kg ha-1). Simulation results depicted -1.1 to 16.8 per cent deviation in crop yield, -1.4 to -21.0 per cent in water use and 12.7 to 45.5 per cent in water productivity. Increase in temperature from 1oC to 3oC decreased wheat yield by 6.3 to 27.0 per cent under D1 and 3.3 to 17.6 per cent under D2, however, it increased from 8.1 to 16.2 per cent under D3, indicating D3 as most appropriate under future warming scenarios. Increase in CO2 concentration decreased water use and increased yield and water productivity.