Nitrogen fertilization and planting density effects on the physiological characteristics of stem, root bleeding sap and lodging resistance in spring maize

Abstract

In this study, three nitrogen (N) fertilization rates (100, 200 and 300 kg ha-1) and three planting densities (6.75, 8.25 and 9.75 million plants ha-1) were explored for their effects on maize cellulose, hemicellulose and lignin contents including lignin synthesis enzyme activity. The results showed that with increasing N fertilization and planting density, the content of cellulose and hemicellulose in maize stalks increased, and the activity of the cinnamyl-alcohol dehydrogenase (CAD) improved which was beneficial to the synthesis of stem lignin. The N application rates and planting densities in each treatment increased IAA (auxin), GA (gibberellin) and CTK (cytokinin) endogenous hormone levels and decreased ABA (abscisic acid) levels. Correlation analysis showed that the cellulose content of stems was significantly negatively correlated with the lodging rate, indicating that the higher the cellulose content, the lower the lodging rate of stem. Under the N fertilizer and planting density treatments, there was a significant positive correlation between IAA, cellulose and hemicellulose contents and a significant positive correlation with lignin content, indicating that endogenous hormones promoted the quality of stem fibre. CTK and GA were significantly positively correlated with yield, indicating that endogenous hormone regulation affects maize yield. The maximum yield 9321.21 kg ha-1 was obtained with the combination of 8.25 million plants ha-1 and 200 kg nitrogen ha-1(D2N2).