Variations in eco-enzymatic stoichiometric and microbial characteristics in paddy soil as affected by long-term integrated organic-inorganic fertilization

<div><p>To investigate the effects of different nutrient management regimes on the soil chemical, eco-enzymatic stoichiometric and microbial characteristics, soil samples were collected from a 30-year, long-term field experiment with six plots growing rice. The results showed that as integrated fertilization increased, so did the concentrations of soil total or available nutrients and microbial biomass carbon (MBC). Our results also found enhanced soil basal respiration and cumulative carbon mineralization compared to chemical fertilization alone at the same nutrient doses. The activities of soil protease (Pro), β-glucosidase (βG), N-acetyl-glucosaminidase (NAG) and acid phosphatase (AP) from the integrated fertilization treatments were significantly higher than those of the treatments without organic manure, so did the activities of soil leucyl aminopeptidase (LAP) and urease (Ure) from the treatment with organic manure in addition to farmer practise fertilization (NPKM2). The stoichiometric ratios, expressed as lnβG/ln(NAG+LAP)/lnPro/lnUre/lnAP, ranged from 1:0.94:1.04:0.67:1.01 to 1:0.98:1.10:0.78:1.25, indicating that the acquisition of C, N and P changed consistently and synchronously under different nutrient management strategies. Integrated fertilization was more beneficial to the acquisition and utilization of soil organic carbon compared to low-molecular-weight organic nitrogen. We concluded that protease and urease should be considered in eco-enzymatic stoichiometric assessments for the hydrolysis of proteins, amino acids, carbohydrates and phosphomonoesters in soil, and integrated fertilization with chemical fertilizers and organic manure should be recommended as a preferable nutrient management system for intensive rice cultivation.</p></div

Soil enzyme activities of different fertilization treatments.

<p>Vertical bars represent the SE (n = 3) and lowercase letters indicate significant differences among fertilizer treatments at the <i>p <</i> 0.05 level.</p

Pearson correlation coefficients between soil enzymes, MBC, SBR, C_min and TN, TP, SOC, Ah-N, Olsen-P, pH.

<p>Pearson correlation coefficients between soil enzymes, MBC, SBR, C_min and TN, TP, SOC, Ah-N, Olsen-P, pH.</p

Correlation matrix with soil microbial and biochemical parameters.

<p>Correlation matrix with soil microbial and biochemical parameters.</p

Molar ratios of soil SOC, soil TN and TP after long-term different fertilization.

<p>Molar ratios of soil SOC, soil TN and TP after long-term different fertilization.</p

Nutrient doses of different treatments.

<p>Nutrient doses of different treatments.</p

Soil enzymatic stoichiometric characteristics of different treatments.

<p>Soil enzymatic stoichiometric characteristics of different treatments.</p

Soil nutrient concentrations and pH values after long-term different fertilization.

<p>Soil nutrient concentrations and pH values after long-term different fertilization.</p

Soil MBC, SBR and C_min under different fertilization treatments.

<p>Vertical bars represent the SE (n = 3) and lowercase letters indicate significant differences among fertilizer treatments at the <i>p <</i> 0.05 level.</p