Research progress on cropland phosphorus balance in China

Although phosphorus is an essential element for plant growth, over surplus of phosphorus can also cause water environmental hazards such as eutrophication. Phosphorus balance (PB) is an indicator for phosphorus input and output extensively used in agricultural and environmental research. In this paper, PB in croplands in China was reviewed from four different aspects - calculation method, spatio-temporal variability analysis, crop type difference analysis and soil phosphorus content analysis. The study showed surplus PB in China's croplands and with increasing surplus levels. Regional variations in phosphorus surplus were significant, with farmland phosphorus deficiency in some areas which resulted in PB polarization. Due to differences in the calculation parameters or regional planning, vast differences were noted in different reports in terms of amounts of total surplus phosphorus, surplus phosphorus per hectare and spatial variation in surplus phosphorus. Irrespectively, the governing trends in temporal variations, effects of different planting on cropland PB and effects of PB on soil phosphorus content were basically identical. In order to control soil phosphorus polarization and to ensure a stable promotion of soil phosphorus pool in China, it was recommended that future research focused more on areas such as indicator evaluations, technical measurements, policy guides and public opinion propaganda.