Analysis of historical characteristics of phosphorus nutrient flow in food chain in Changchun area

Phosphorus is an important element of life, whose cycle and transformation are critical in the food chain. With statistical and literature data, the trends and characteristics of phosphorus flow in the food chain in Changchun area were investigated for the period 1993-2013 using the NUFER (Nutrient flows in Food chain, Environment and Resources use) model. The study determined the existing problems, put forward strategies and provided examples of optimal management of phosphorus in the food chain. The results showed that total input of phosphorus in the food chain system in Changchun area increased from 32.6 Gg in 1993 to 113.9 Gg in 2013. In food production, phosphorus flow in animal-derived food increased from 0.7 Gg in 1993 to 2.7 Gg in 2013, and that of plant-derived food dropped from 16.1 Gg in 1993 to 15.7 Gg in 2013. In food consumption, phosphorus flow rate in animal-derived food increased from 0.5 Gg in 1993 to 1.1 Gg in 2013, and phosphorus flow in plant-derived food dropped from 5.0 Gg in 1993 to 4.4 Gg in 2013. In the last two decades, phosphorus accumulation in the form of waste in the food chain increased by 15%, while phosphorus loss via runoff, leaching and erosion increased by 17.6 Gg. Up till 2013, the rate of phosphorus loss in the food chain was 20.2%. The trend in phosphorus use efficiency in various paths of the food chain decreased, in which the phosphorus utilization rate by animals/crops decreased from 94.2%/4.1% to 49.3%/3.8%, respectively. Phosphorus use efficiency in the whole food chain decreased by 20.3%. At the same time, the recycling efficiency of phosphorus gradually reduced. In the last two decades, phosphorus flow of food chain in Changchun area followed the path of "high input, high accumulation, high loss, low efficiency and low recycle". Therefore, it was important to control phosphorus input, reduce phosphorus loss, increase phosphorus recycling in waste and enhance the rate of phosphorus use efficiency in Changchun area.