Long-term fertilisation causes excess supply and loss of phosphorus in purple paddy soil

Diffusive Gradients in Thin Films as a Reference Method for Assessing Soil Phosphorus by Visual and Near-Infrared Spectroscopy

Phosphorus (P) deficiency is a severe challenge in many agricultural areas around the globe, while at the same time, aquatic environments are threatened by leaching and runoff of excess P in other areas. Accurate, cheap, and rapid assessment of crop P needs and risk of P loss is therefore necessary to optimize the use of P fertilizer worldwide. The purpose of this study was to develop a method to predict soil P concentrations by visual and near-infrared spectroscopy using reference P concentrations determined by diffusive gradients in thin films (DGT); Olsen P results were included for comparison. The study was conducted on paddy soils from six main rice-producing ( L.) provinces in southern China. Using DGT P as a reference resulted in a better visual and near-infrared calibration to predict soil P concentrations, as compared with using Olsen P.

Potential of Controlled Irrigation and Drainage for Reducing Nitrogen Emission from Rice Paddies in Southern China

The effect of controlled irrigation and drainage (CID) at different growth stages of rice on nitrogen (N) from rice paddy was studied. Submergence at different stages was imposed in specially designed experimental tanks in 2009 and 2010 based on alternate wetting and drying technology (AWD, the control, CK). Treatments include CID treatment at tiller stage (T1), jointing-booting stage (T2), panicle initiation stage (T3), and milky stage (T4). Results showed that fertilization could significantly increase the concentration ofNH4+-N and TN in surface water but had a little influence onNO3--N. The concentrations ofNH4+-N andNO3--N in surface water increased at first and then decreased after fertilization, while the concentrations ofNH4+-N and TN in groundwater kept on being relatively stable. Compared to CK, CID significantly increased the concentration ofNH4+-N in surface water at four stages. However, it reduced the concentration ofNO3--N. Consistent with the reduction of drainage, CID at four stages could significantly decrease the amount ofNH4+-N andNO3--N losses by runoff in relation to CK.