Phosphorus loss by surface runoff from agricultural field plots with different cropping systems

Phosphorus (P) loss from agricultural fields through surface runoff may contribute to the eutrophication of surface waters. The objective of this study was to evaluate surface runoff and P transport from different cropping systems during 2007–2009. The treatments consisted of a control (wheat/fallow) and three double cropping systems: wheat/corn (Zea mays L.), wheat/cotton (Gossypium hirsutum L.), and wheat/soybean [Glycine max (L.) Merr.]. Wheat/fallow was not fertilized and had no crop planted during the summer crop growing season. The four treatments were randomly assigned to 12 plots of 5 × 2 m on a silt clay soil. Surface runoff from natural rainfall was sampled for P analysis during the 3 years. Double cropping systems, when compared with wheat/fallow, reduced runoff volume and losses of total dissolved P (TDP), particular P (PP), and total P (TP). Wheat/soybean was the most beneficial system reducing the 3-years mean runoff volume by 58%, TDP loss by 81%, PP loss by 89%, and TP loss by 85%, compared with wheat/fallow. The 3-years flow-weighted mean (FWM) concentrations of TDP, PP, and TP followed the order wheat/fallow > wheat/cotton > wheat/corn > wheat/soybean. The least temporal variations of the P concentrations and losses were observed from wheat/soybean. Therefore, selecting wheat/soybean as the main double cropping system appears to be a practical method for controlling runoff and associated P loss from farmland under similar weather and soil conditions.