Impacts of Irrigation Time and Well Depths on Farmers' Costs and Benefits in Maize Production

In the North China Plain, drought usually occurs during the interval between wheat harvest and maize sowing in normal and dry years. The first irrigation for maize plays a critical role in guaranteeing seed germination and grain yields. Using experimental data from Xinxiang in 2019 and survey data of 641 farmers from the North China Plain in 2020, this study adopts a cost-benefit analysis method to investigate the impacts of irrigation time and well depths on farmers' costs and benefits in maize production. The results showed that farms with well depth > 120 m accounted for 49% of total farms, especially in Hebei Province, and 38% wells had low water yield < 2.7 m(3) kW(-1)h(-1). Delaying the time of the first irrigation made maize yields decline by up to 307 kg ha(-1) day(-1). Well depths increased irrigation costs and total maize production cost in an exponential manner, causing farmers' benefits to decrease exponentially with well depths. With well depth > 180 m, the proportion of irrigation cost to total cost rose to 14%, whereas well depth > 230 m directly caused the farmers' profits negative. A critical well depth of 230 m was put forward as the upper limit for farmers adopting maize planting in the NCP. The concept of 'rotational irrigation strategy' and suggestions of adopting drip irrigation, sprinkler irrigation, or hose-reel sprinkler irrigation were recommended to advance 6-8 days for the first irrigation period, compared with traditional flood irrigation.