Tillage practices affect biomass and grain yield through regulating root growth, root-bleeding sap and nutrients uptake in summer maize

No tillage (NT) of summer maize (Zea mays L.) is the dominant agricultural practice in the annual double-cropping system of winter wheat–summer maize in the North China Plain, and the long-term NT is often unfavorable for the growth of maize roots. The aim of this study was to evaluate the effect of 2-year-old rotary tillage (RT) and plowing tillage (PT) based at NT soil on root growth, spatial distribution, nutrients uptake and grain yield in Wuqiao of the North China Plain. PT and RT significantly increased root biomass across 0–40cm soil profile in the whole growth stage. Lower bulk density under PT and RT was compared to under NT in the 0–20cm soil profile, and penetration resistance under NT was significantly higher than under PT and RT in the 0–30cm soil profile. Root length density (RLD) in the uppermost soil profile (0–10cm) had no evident differences among tillage practices at silking stage, but RLD under PT and RT was significantly greater than under NT at maturity. Moreover, RLD and root surface density (RSD) were significantly higher under PT than under NT in the topmost layer, 10–50cm soil profile, but there were no differences in RLD and RSD among tillage practices at the deeper soil profile below 60cm. PT and RT markedly improved the root-bleeding sap rate in the whole growth stages in 2011 and most growth stages in 2012. In addition, NH4+ and NO3− delivery rate under PT were significantly higher than those under RT and NT in 2011 and 2012, and under RT were significantly higher than under NT in 2012. The delivery rate of P, K, Ca, Mg, Fe and Zn in bleeding sap under PT was significantly higher than those under NT at different growing stages across the two years. Our results suggested that short-term PT and RT could increase root biomass, improve root spatial and temporal distribution, and enhance nutrients uptake, which resulted in higher biomass and grain yield of summer maize in the North China Plain.