NPI enriched more down-regulation genes involved in starch and sucrose metabolism, phenylpropanoid biosynthesis, amino sugar and nucleotide sugar metabolism, glycolysis/gluconeogenesis pathway, leading to restricted root growth. Three GO terms including channel activity, water transport, and water channel activity caused a high degree of gene enrichment. Thirteen genes related to water absorption and transport such as ZM00001D003006, ZM00001D014285 et al. were highly up-regulated, which might be the key genes for the significant increase in water use efficiency of maize under negative pressure irrigation. Overall design: Monitoring of different genes under different irrigation methods