Source-sink relationship and yield stability of two maize cultivars in response to water and fertilizer inputs in northwest China

Increasing the capacity of plants to assimilate carbon (source), or to tap into the internal carbon reservoir (sink), has the potential of realizing high and stable yield under a more variable climate. A three-year field experiment was conducted to explore the source-sink relationships of two maize (Zea mays L.) cultivars in response to various water and fertilizer inputs, and evaluate the yield sustainability in northwest China. There were two fertilization rates (unfertilized, F0; fertilized, F1), two irrigation strategies (rainfed, RF; supplemental drip irrigation, DI) and two maize cultivars (ZD958 and QL14). The results showed that the newly released maize cultivar (QL14) had higher leaf chlorophyll content at the silking and grain-filling stages than the old one (ZD958); meanwhile, QL14 had higher root dry matter at maturity than ZD958 under DIF1. The aboveground and root dry matter increased with the amount of water and fertilizer, while the root-shoot ratio decreased. Cultivar significantly affected the vegetative organ dry matter partitioning, especially under severe drought at the silking stage. QL14 had stronger root system and larger leaf dry matter than ZD958, and was more drought-resistant under serious water-stressed conditions. Dry matter translocation (DMT) was crucial for grain yield formation under limited nutrients con-ditions, and ~55% of total dry matter at maturity was accumulated at the grain-filling stage under adequate water and fertilizer conditions. DIF1 had higher sustainable yield index (SYI) than RFF1. There was no significant difference in grain yield between the two maize cultivars under DIF1, but the average SYI of QL14 (0.94) was greater than that of ZD958 (0.89). The present study indicates that the newly released maize cultivar (QL14) with stronger root system and stay-green characteristics is beneficial for increasing drought resistance and keeping yield stable in the semi-humid and drought-prone region of northwest China.