Molecular Speciation of Phosphorus in Long-term Located Fertilization by
Liquid-state Nuclear Magnetic Resonance Spectroscopy
Abstract
The long-term substitution of mineral phosphorus (P) fertilizers by
manure fertilizers combined with nitrogen (N) fertilizer can effectively
reduce water pollution and slow down the consumption of P rock
resources. Knowledge is needed about how those affect soil P forms to
understand soil P cycling and plant P uptake. However, these mechanisms
have not been fully elucidated. Therefore, we studied the effects of
long-term fertilization on soil P forms in different soil depths. The
results of the 40 years field experiments showed that fertilization can
significantly improve the P extraction efficiency using NaOH-EDTA in
different soil depths. The majority of P was in the form of
orthophosphate for all the treatments, which constituted 14.9-483.6
mg/kg (0-20 cm), 24.1-224.4 mg/kg (20-40 cm), and 23.7-59.5 mg/kg (40-60
cm). The proportion of organic P forms was significantly increased by
long-term fertilization in 20-40 cm soil layer. The concentrations of
all P compounds in topsoil increased significantly under the treatment
of the combination of manure fertilizer and mineral fertilizers (N and
P). The addition of manure fertilizer extremely increased the
stereoisomers of IHP (myo-IHP, scyllo-IHP, neo-IHP, and D-chiro-IHP) and
the proportion and concentration of corrected diesters. Fertilization
year had no significant difference in IHP stereoisomers and phosphate
diester. The results indicate that in the long-term, different
fertilization treatments and different soil depths had the best overall
effect, which could significantly increase yield and the content of
orthophosphate directly absorbed by crops and IHP stereoisomers that
could be used by plants in the long run.