Ridge-furrow with plastic film mulching system decreases the lodging risk for summer maize plants under different nitrogen fertilization rates and varieties in dry semi-humid areas

As a water-saving cultivation technique, the ridge-furrow with plastic film mulching (RF) system has been a popular planting strategy and has been generally promoted to raise crop yields. However, the effect of the RF system on the susceptibility of maize to lodging is inconclusive. A two-year field experiment, with three planting practices (FP: rain-fed flat planting, TI: traditional irrigation planting and RF) in coupled with two nitrogen (N) application rates (225 and 75 kg N ha-1) and two maize (Zea mays L.) cultivars (Zhengnong9 and Zhengdan958), was established to evaluate the risk of lodging under RF and identify how the RF system affects maize lodging. The results revealed that lodging susceptibility had a significantly positive relationship with grain yield (r (coefficient of correlation between lodging rate and grain yield) = 0.36* and 0.79** in 2013 and 2014, respectively), and our previous studies have showed that the maize yield of RF system was significantly higher than the FP practice, suggesting that the RF system increased the lodging risk of maize compared to the FP practice. However, compared with TI, RF decreased plant height, length and centre of gravity height of the basal third internode and improved the stalk bending resistance strength of the basal third internode, leading to significantly increase in the stalk lodging resistance index and reductions in the lodging rate with a simlar grain yield. In summary, RF strategy can be as a hopeful system for summer maize cuiltivation in dry semi-humid areas. High N application rates decreased lodging rate regardless of the plant pattern or cultivar in two years. The lodging rate of Zhengdan958 was significantly higher than that of Zhengnong9. The redundancy analysis showed that plant height, length and stalk bending resistance strength of the basal third internode and centre of gravity height were the vital factors that affected maize lodging, explaining more than 70 % of the total variation in the lodging rate. The plant height, length of the basal third internode and centre of gravity height revealed remarkable positive corrlations with the lodging rate; in addition, the stalk bending resistance strength of the basal third internode revealed remarkable negative corrlation with the lodging rate over the two years. These relationships suggest that increasing stalk strength and decreasing centre of gravity height and plant height result in higher lodging resistance and should be considered in future maize breeding programmes.