Evapotranspiration and water dynamics of lucerne and following crops in the northwest Loess Plateau

The formation of a dried soil layer after the long-term cultivation of lucerne (Medicago sativa) in the northwest Loess Plateau, China, could seriously affect the growth of subsequent crops. A field study was conducted to investigate the evapotranspiration and water dynamics of crops cultivated after lucerne production. This study involved the following six treatments: lucerne-lucerne (L–L), lucerne-fallow (L–F), lucerne-wheat (Triticum aestivum, L–W), lucerne-corn (Zea mays, L–C), lucerne-potato (Solanum tuberosum, L–P), and lucerne-millet (Setaria italica, L–M). Average water use efficiency (WUE) was greater in the L–P treatment, followed by the L–C treatment, and was the lowest with the L–W treatment after 3 years of continuous production, indicating that 9-year-old lucerne rotated with potato and corn resulted in higher crop WUE than the other treatments. The L–C treatment had the highest water consumption during the crop growing period; however, it had the lowest evaporation among the different treatments, which decreased the percentage of evaporation of crop total water consumption to 17.0%, which promoted transpiration in the corn crop. Average field water content was increased by 18.4% to 34.9% compared to continuous lucerne in the 0 to 300 cm soil layer depth. The L–F treatment was the best for water restoration among the six treatments, followed by the L–P treatment. Based on the WUE and soil water characteristics, potato and corn are optimal crops for cultivation after lucerne in the northwest Loess Plateau, China. Therefore, optimising land-use management can mitigate the formation of a dried soil layer and assist the development on the northwest Loess Plateau.