Climate warming and management impact on the change of phenology of the rice-wheat cropping system in Punjab, Pakistan.

Highlights • Observed data from ten districts were used to simulate the impact of historical climate warming on the rice-wheat cropping in Punjab, Pakistan. • Reductions in rice and wheat phenological phases were observed due to climate warming. • Cultivars with higher thermal time and high temperature tolerance are recommended for an adaptation to climate warming for the rice-wheat system. Abstract The phenological changes of a long-term observed rice-wheat system (RWS) were used to determine the relationships among management practices, climate change, and crop phenology to devise adaptation strategies for RWS for mitigating the potential impact of climate change. The study comprised of 10 sites of observed and simulated rice-wheat system phenological data for the historical period from 1980 to 2014 in Punjab, Pakistan. The observed climate warming from sowing or/transplanting to maturity ranged from 0.50 to 1.20 °C decade−1 for rice and 0.77 to 1.07 °C decade−1 for wheat. The observed rice phenological stages were advanced by an average of 7.90 (sowing (S)), 6.60 (transplanting (T)), 4.30 (panicle initiation (PI)), 5.00 (anthesis (A)) and 6.40 (maturity (M)) days decade−1, while rice phenological phases were reduced by an average of 1.4 (S-T), 6.40 (T-M), 3.00 (PI-A), 4.70 (PI-M) and 4.10 (A-M) days decade−1. For wheat, sowing (S) and emergence (E) dates were delayed by an average of 9.50 and 1.30 days decade−1, while anthesis (A) (5.30 days decade−1) and maturity (M) (5.40 days decade−1) dates were advanced. The duration of wheat phenological phases was reduced by an average of 5.50 (S-A), 5.70 (S-M) and 4.60 (A-M) days decade−1. The S and E dates were positively correlated with increasing temperature and the A and M dates and phases (S-A, A-M, and S-A) were negatively correlated with increasing temperature for all study locations. Using the CSM-CERES-Rice and CSM-CERES-Wheat models for standard, field-tested cultivars of rice and wheat for all locations for the 35-year period showed that the simulated phenology stages were earlier with climate warming compared to the observed phenology stages. A significant portion of the negative impact of warming on rice (35%) and wheat (21%) was offset by growing new cultivars that had higher thermal time requirements. Thus, to mitigate climate change impacts, new cultivars for RWS should be introduced that require higher growing degree days and have a high temperature tolerance. [ABSTRACT FROM AUTHOR]