Estimating water needs of maize (Zea mays L.) using the dual crop coefficient method in the arid region of northwestern China

Abstract

Understanding crop water needs is essential for irrigation scheduling and water saving measures in an
arid region because of its limited water supply. This study was performed using the dual crop
coefficient method to predict seasonal changes in evapotranspiration (ETc) for maize fields in
northwestern China in 2004. The reference crop evapotranspiration ET0, an important parameter in
simulating the actual crop evapotranspiration (ETc), was estimated using FAO Penman–Monteith
equation. The values suggested by FAO-56 were used for the basal crop coefficients (Kcb) after
adjustment for the specific climatic condition in the study area. The soil evaporation coefficients (Ke)
were determined for the climate, the soil, the maize growing stages, and the irrigation method. Some
missing climatic parameters were calculated. The results showed that the ETc values were very low
(average value of 1.09 mm day- 1) except during irrigation events in the initial stage of crop growth. The
ETc value increased during the crop development stage (average value of 3.67 mm day- 1) and reached
its peak during the mid- season stage (average value of 5.49 mm day-1), then the ETc value declined
rapidly during the last crop growth stage (average value of 3.33 mm day-1). In general, the
evapotranspiration (ETc) ranged from 0.54 to 7.69 mm day-1 and the total actual ETc was 611.5 mm at
the experimental site in the growing season of 2004.