Purpose

Being the most widespread soil in the Chengdu Plain in Sichuan Basin, China, paddy soil has a great importance in agriculture and ecology. Anthropogenic activities alter the concentrations and stoichiometric ratios (C:N, C:P, and N:P) of carbon (C), nitrogen (N), and phosphorus (P) in paddy soil. This study aims to investigate whether the cycling of C, N, and P in paddy soil is influenced by cropping system and pedogenic process (the subtype of paddy soil).

Materials and methods

In this study, we collected 1080 soil samples at 0–20 cm from five cropping systems (rice monoculture (RM), vegetable monoculture (VM), rice and vegetable rotation (RVR), rice and wheat rotation (RWR), rice and oilseed rape rotation (ROR)) and six subtypes (bleached paddy soil (BPS), gleyed paddy soil (GPS), percogenic paddy soil (PPS), degleyed paddy soil (DPS), submergienc paddy soil (SPS), and hydromorphic paddy soil (HPS)) of paddy soil in Chengdu. Soil organic carbon (SOC), soil total nitrogen (TN), and soil total phosphorus (TP) concentrations were determined to calculate the stoichiometric ratios.

Results and discussion

Our results indicated that the concentrations of SOC, TN, and TP of paddy soil were higher than those of cropland on a global scale. There are similar stoichiometric ratios between paddy soil in Chengdu Plain and the cropland in the global scale. The cropping system and subtype significantly altered the soil nutrient concentrations and stoichiometric ratios. The concentrations of soil TN under rotation systems (RV, RW, and RO) were significantly higher than those of VM. The soil with the subtypes of BPS and GPS were related to low TP concentration.

Conclusions

The cropping system of VM showed soil N consumption compared with the traditional cropping system (rotation systems, such as RV, RW, and RO). In addition, subtype also significantly influenced the element balance in paddy soil. The balance of soil C, N, and P is mainly affected by fertilizer application of N and P.