Transpiration of female and male parents of seed maize in northwest China

Drip irrigation under mulch (DM) has been widely promoted and applied in arid regions. The process of crop growth and surface water and energy transfer will change significantly under the dual control of mulch and drip irrigation compared with those under the traditional border irrigation under mulch (BM) method, which will further affect the regional eco-hydrology process. The Hexi Corridor has become the largest seed maize production base in China due to its abundant solar radiation, and heat resources and large diurnal temperature difference. Unlike grain maize, seed maize can be divided into female and male parent plants. The growth conditions of the parent plants differ; male plants are planted 7-14 d later than female plants to produce preferable fertilization conditions, which distinctly influences the energy transfer process between the different parent plants and the soil and ultimately leads to significantly different plant water consumption in the maize field. To determine the difference in the transpiration rate between a BM field and a DM field and to reveal the difference in water consumption characteristics between female and male plants, eddy covariance system (EC) measurements, a thermal balance sap flow system and micro-lysimeters were applied to conduct continuous, fixed-location comparison measurements of the total evapotranspiration from 2014 to 2016. The total evapotranspiration (ET), transpiration rates of the female (T-f) and male plants (T-m) and the soil evaporation (E-s) in seed maize fields were separately analysed in both the BM field and DM fields. Results indicated that T-f/ET, T-m/ET and E-s/ET dynamically varied with the crop growth during the whole growth period. Transpiration rates under the DM treatment were 2-8% higher than those under the BM treatment under the local agricultural management conditions. Besides, the female plant transpiration rate exceeded the male plant transpiration rate by 9-20% in the BM treatment and by 14-32% in the DM treatment field during the whole growth stages. However, male plant transpiration produced after the pollination of female plants is useless to final seed production. It is more practical to decrease the planting ratio of male to female plants to the appropriate level and remove the male plants earlier to increase the water use efficiency in seed maize fields. Moreover, the seed maize field in this study had a smaller proportion of soil evaporation than those in other grain maize field studies conducted around the world, which was probably due to the mulching effect and higher plant density.