Soil evaporation under sole cropping and intercropping systems and the main driving factors

Several studies have shown that compared to sole cropping, well managed intercropping improves agricultural resources utilization efficiency, include radiation, nutrient, water and land. However, high productivity of traditional intercropping system has mainly depended on high input of agricultural resources. With severe water shortages in recent years (especially in mainland China), intercropping system of farming has continuously declined. The scientific challenge therefore is the determination of water consumption characteristics and systematic development of high-efficiency water-saving theories and technologies of intercropping system. In this study, a field experiment (comprising of wheat or maize sole cropping and wheat-maize intercropping systems under three different irrigation schemes) was conducted in 2008 in the Hexi Corridor oasis region. The study investigated soil evaporation characteristics and associated driving factors under the different cropping systems and treatments with the aim of laying the scientific basis for developing optimized irrigation techniques. The study showed that evapotranspiration (ET) under wheat-maize intercropping was 41.44%~47.15% higher than the average ET under wheat and maize sole cropping systems. Total soil evaporation (E) of intercropping system was significantly higher than that of sole cropping systems. However, daily E of intercropping system was significantly lower than that of maize sole cropping system. Also compared with sole cropping system of maize, wheat-maize intercropping system enhanced E/ET ratio. With increasing irrigation, total water consumption increased significantly under intercropping. However, the difference in water consumption between two adjacent irrigation treatments under sole cropping systems of wheat and maize was insignificant. The difference in E of sole cropping maize and intercropping wheat-maize was insignificant for different irrigation schemes. It then implied that high water consumption of intercropping system was mainly driven by high transpiration. Average daily E was positively correlated with water content in the 0~30 cm soil profile, temperature in the 0~25 cm soil profiles and average leaf area index of the crops. High E was driven by high water content in the 0~30 cm soil profile and temperature in the 0~25 cm soil profile of maize sole cropping system. On the average, wheat-maize intercropping not only reduced water consumption but also increased water and land use efficiency compared to sole cropping. This cut down wasteful crop transpiration, which was an effective means of water-saving irrigation.