Metabolomic Analysis of Rhizosphere Soil Fertility in Maize (Zea mays) at Milking Stage

Abstract

In this study rhizosphere soil of corn at a milk stage was collected to investigate characteristic metabolites and their potential functions. Total nitrogen, organic matters, ammonium nitrogen, pH values, available phosphorus and potassium were determined by semimicro-Kjeldahl method, potassium dichromate (external heating) method, indophenol blue colorimetric method, potentiometry, NaHCO3 leaching-molybdenum-antimony colorimetric method and NH4OAc leaching-flame spectrometry, respectively. In addition, UPLC-Q/TOF-MS was adopted for non-targeted metabolomic analysis. As revealed by results, the total nitrogen contents in soils collected from Dongchuang (i.e., DCMRS for short) 0.67 ± 0.14 mg/kg lower than from Fumin (i.e., FMMRS for short); moreover, both DCMRS and FMMRS were acid soils. DCMRS contains higher levels of AN (Ammonium nitrogen), SOC (Soil organic carbon), and AP (Available phosphorus) than FMMRS. The amount of TN (Total nitrogen) contained in FMMRS soil was 2.410 ± 0.422 mg/kg, which is higher than DCMRS. All data derived from UPLC-Q/TOF-MS met the corresponding requirements for further analysis. Metabolites such as 2-methyl-1-propylamine, gamma-butyrolactone and 3-methyl-1-butylamine were detected in DCMRS and FMMRS samples. Several pathways were included, such as lipid metabolism, xenobiotics biodegradation and metabolism, terpenoids and polyketides, and amino acid metabolism. Through comparison of FMMRS and DCMRS, metabolic pathways associated with nitrogen, carbon, and antibiotic metabolism including iron transport were significantly different between them. Taken together, FMMRS is more fertile, less acidic, and higher in nitrogen than DCMRS.