Groundwater irrigation is critical for adapting wheat systems to warming temperatures in the Eastern Indo-Gangetic Plains in India

Warming temperatures are reducing wheat yields in India, and one way to reduce negative impacts is to sow wheat earlier. Yet farmers in Northeast India commonly sow wheat past the optimum time window. Previous studies have suggested this delay is driven by delays in the preceding rice growing season, which have cascading impacts on wheat sow date. It, however, remains unclear which specific rice management decisions are the most consequential for wheat sow date and what potential strategies may help advance the overall crop calendar. We used household survey data from 356 farmers in Bihar, India and structural equation modeling to identify the specific time points in the rice growing season that most impact wheat sow date. Our results suggest that late rice nursery establishment and rice harvest were associated with subsequent delays in the crop calendar. We also found that increasing groundwater irrigation access prior to the start of monsoon rains may be the most effective way to advance rice and wheat sowing. Our results provide insights into the specific time points in the crop calendar when interventions may be the most consequential, which is critical for developing interventions to help farmers adapt wheat systems to warming temperatures.