Recovery growth and water use of intercropped maize following wheat harvest in wheat/maize relay strip intercropping

Recovery growth is common in relay intercropping systems and is a feasible practice for increasing total productivity of these systems. Previous studies have focused on the description of recovery growth, but the physiological changes and water use assessment during the recovery growth period remain unclear. A field experiment was conducted in Yangling, Shaanxi province, China during the 2014-2015 and 2015-2016 growing seasons to investigate maize physiological characteristics, root morphology, and transpiration efficiency during the recovery growth period. Three cropping systems (sole wheat, sole maize, wheat/maize intercropping) and two water treatments (supplementary irrigation and rainfed) were evaluated. Wheat was more competitive than maize during the intercropping co-growth period. During the co-growth period, the aboveground dry matter of intercropped wheat was 20.1 %-37.8 % greater than for sole wheat and water consumption was 14.9 %-15.9 greater than for sole wheat. However, plant height and aboveground dry matter of intercropped maize during the co-growth period were less than for sole maize. Total root length of intercropped maize under supplementary irrigation initially exhibited rapid growth after wheat harvest, especially in the border rows. Subsequently, aboveground dry matter showed recovery growth, with final aboveground dry matter (2-yr average) of border rows and inner rows being 1 % and 4.5 %, respectively, greater than sole maize dry matter. Relative chlorophyll content and photosynthetic rate of intercropped maize were 4.3 %-19.2 % and 1.7 %-15.9 %, respectively, higher than observed for sole maize under irrigated conditions. Transpiration efficiency of intercropped maize during the recovery period was 10 % and 50.9 % greater than observed for sole maize under irrigated conditions in 2015 and 2016, respectively. Some recovery growth did occur under rainfed conditions, but it did not completely compensate for the growth reduction that occurred during the co-growth period. Supplementary irrigation promoted recovery growth of intercropped maize. Recovery growth improves intercropped maize grain yield and efficient use of water resources.