Xiaoxin Li

Methane, Carbon Dioxide and Nitrous Oxide Fluxes in Soil Profile under a Winter Wheat-Summer Maize Rotation in the North China Plain

The production and consumption of the greenhouse gases (GHGs) methane (CH4), carbon dioxide (CO2) and nitrous oxide (N2O) in soil profile are poorly understood. This work sought to quantify the GHG production and consumption at seven depths (0–30, 30–60, 60–90, 90–150, 150–200, 200–250 and 250–300 cm) in a long-term field experiment with a winter wheat-summer maize rotation system, and four N application rates (0; 200; 400 and 600 kg N ha−1 year−1) in the North China Plain. The gas samples were taken twice a week and analyzed by gas chromatography. GHG production and consumption in soil layers were inferred using Fick’s law. Results showed nitrogen application significantly increased N2O fluxes in soil down to 90 cm but did not affect CH4 and CO2 fluxes. Soil moisture played an important role in soil profile GHG fluxes; both CH4 consumption and CO2 fluxes in and from soil tended to decrease with increasing soil water filled pore space (WFPS). The top 0–60 cm of soil was a sink of atmospheric CH4, and a source of both CO2 and N2O, more than 90% of the annual cumulative GHG fluxes originated at depths shallower than 90 cm; the subsoil (>90 cm) was not a major source or sink of GHG, rather it acted as a ‘reservoir’. This study provides quantitative evidence for the production and consumption of CH4, CO2 and N2O in the soil profile.

Tillage Effects on Intracellular and Extracellular Soil Urease Activities Determined by an Improved Chloroform Fumigation Method

The intracellular urease activity in soils determined by the chloroform fumigation method is underestimated because of urease degradation by soil protease and denaturation by chloroform. The objectives of this study were to correct this underestimation and to investigate the responses of intracellular, extracellular, and total urease activities to no-tillage, reduced tillage, and moldboard plowing treatments. Surface layer soils (0-20 cm) after 8-year different tillage treatments were collected. First, the soil samples were fumigated with ethanol-free chloroform in the presence of a protease inhibitor. Subsequently, a urease addition experiment was conducted to determine what percentage of soil urease was denatured during the fumigation procedure. Our results showed that the corrected intracellular urease activities in soils under no-tillage, reduced tillage, and moldboard plowing accounted for 58.2%, 62.3%, and 51.7% of the total urease activity, respectively. Both no-tillage and reduced tillage significantly increased the intracellular, extracellular, and total urease activities compared with moldboard plowing. The ratio between intracellular and extracellular urease activities was not significantly different between no-tillage and reduced tillage probably because the soil ammonia content was similar under these treatments. The three urease activity pools were significantly correlated with soil organic C, microbial biomass C and N, and available P. These results indicate that both the intracellular and extracellular urease activities were sensitive indicators for monitoring soil quality under different tillage practices.

Livestock housing and manure storage need to be improved in China

China Zhaohai Bai,† Xiaoxin Li,† Jie Lu,† Xuan Wang,† Gerard L. Velthof,‡ David Chadwick, Jiafa Luo, Stewart Ledgard, Zhiguo Wu, Shuqin Jin, Oene Oenema,‡ Lin Ma,*,† and Chunsheng Hu*,† †Key Laboratory of Agricultural Water Resources, Center for Agricultural Resources Research, Institute of Genetic and Developmental Biology, The Chinese Academy of Sciences, 286 Huaizhong Road, Shijiazhuang 050021, Hebei, China ‡Wageningen Research, Environmental Research P.O. Box 47, 6700 AA, Wageningen, The Netherlands School of Environment, Natural Resources and Geography, Bangor University, Bangor, LL57 2UW, U.K. AgResearch Limited, Ruakura Research Centre, Private Bag 3123, Hamilton, New Zealand University of Pennsylvania, School of Veterinary Medicine, 3800 Spruce Street, Philadelphia, Pennsylvania 19104, United States Research Center for Rural Economy Ministry of Agriculture, No. 56, Xisizhuanta Hutong, Beijing 100810, China