Integrating soil testing phosphorus into environmentally based manure management in pen-urban regions: A case study in the Beijing area

Rapid growth in intensive pen-urban livestock farming has led to excessive manure phosphorus (P) loads in some regions of China, with an increasing risk of eutrophication of watercourses. There is an urgent need to assess the potential regional landbank available to receiVe these manures to both satisfy crop demand and reduce environmental pollution. In this case study, we assessed the potential distribution of manure P applications to arable land in the Beijing area, based on the exclusion of land above a critical value of soil Olsen-P, with a slope >25 degrees, and land designated as water protection zones. The effects of different cropping area structures and contrasting P application strategies on changes in soil P status were assessed using scenario analysis. Results show that current manure generation (2011) has resulted in high P surpluses, with an average manure P loading rate to arable land of 53 kg P ha(-1). We estimate that 11% of arable land is unsuitable for continuous P applications due to high soil P levels, which exceed the P environmental risk threshold. Under the traditional P management scenario, the Olsen-P in vegetable and orchard land will be saturated (more than soil P environmental threshold) before 2030, whilst the Olsen-P of cereal land will be close to the soil P environmental threshold in 2030. Scenario analysis results suggested that increasing the proportion of manure applied to cereal fields reduced the annual P surplus, which in turn alleviated the over-accumulation of P in orchards and vegetable fields. The annual total manure P excretion is expected to increase from 21.3 Gg in 2011 to 30.8 Gg in 2030, and the predicted soil Olsen-P levels for 2030 are estimated to increase to 55, 106 and 132 mg kg in cereal, orchard and vegetable land, respectively. However, a balanced P management strategy could maintain much lower soil Olsen-P levels, i.e., 24,22 and 27 mg kg(-1) in cereal, orchard and vegetable land, respectively. Applying manure to cereal fields with relatively low Olsen-P levels, and exporting surplus manure out of the peri-urban regions of Beijing are regarded as the key strategies to minimize environmental P risk. (C) 2015 Elsevier B.V. All rights reserved.