Phosphorus in China's Intensive Vegetable Production Systems: Overfertilization, Soil Enrichment, and Environmental Implications

China's vegetable production has experienced a rapid growth in recent years. Total production amounted to 522.7 million Mg (1 Mg = 10(6) g) in 2009, which was more than nine times that in 1980 and represented >50% of the world production. Meanwhile, excessive use of animal manures and chemical fertilizers in vegetable fields has brought various production and environmental challenges, including excessive accumulation of nutrients in soils and accelerated water pollution problems. In this study, we have evaluated the current status of phosphorus (P) in China's intensive vegetable production systems based on data summarized from nearly 100 publications plus results from our recent experiments. Gross overfertilization occurred in greenhouse (571 kg P ha(-1)) and open-field (117 kg P ha(-1)) vegetable systems compared with P removal in harvested crops (44 and 25 kg P ha(-1)) per season. Excess P input led to soil enrichment of labile P, measured as Olsen-P, averaging 179 (greenhouses) and 100 mg P kg(-1) (open fields) in the 0- to 20-cm soil depth, and in some cases led to P leaching, as evidenced by increases in Olsen-P and CaCl2 - P at the 40- to 60-cm soil depth. The vast majority of vegetable soils had Olsen-P exceeding the critical level (46.0-58.0 mg P kg(-1)) for optimum vegetable yield. Innovative policies and strategies are urgently needed to implement science-based nutrient management practices to attain sustainable vegetable production while protecting natural and environmental resources.