Design and experiment of scheduling irrigation device based on pan evaporation for drip-irrigated cotton under plastic mulch

A simple visual device for scheduling irrigation based on pan evaporation for drip-irrigated cotton under plastic mulch was designed, and an irrigation scheduling model based on field water budget was established. The most suitable plant-pan coefficient for drip-irrigated cotton under plastic mulch and the indicators to schedule irrigation were determined in field conditions, while a revision method for the indicators was proposed under rainfall conditions. The field test proved that it was an effective way to program drip-irrigated cotton irrigation, once marked, there was no need for human intervention beyond checking the position of the water level in relation to the irrigation control marks. The suitable irrigation intervals based on pan evaporation at 140, 75, 50 and 120 mm and irrigation water amount of 0.15, 0.4, 0.7 and 0.25 times of accumulated pan evaporation for seedling stage, bud stage, flowering and bolling stage, and boll opening stage, respectively, could be recommended for drip-irrigation cotton under plastic mulch in the north of Xinjiang area, China.