Plant availability of recycled P -fertilizers - pot experiment

Following P fertilisers were tested: Triple superphosphate (TSP) = highly water soluble mineral fertiliser; bone char (BC) = non-soluble high P containing, clean P resource; surface-modified bone char (BCplus) = predicted higher P solubility than BC through surface modification; thermo-chemically treated sewage sludge ash (SSA); and struvite from municipal waste water treatment (MAP). Fertiliser effects were evaluated in a pot experiment planted with annual rye grass. In each pot 280 mg of P were added into 6 kg (DM) of an acidic (pH 5.2) sandy silt soil with initially low amounts of available P (24.2 mg kg-1 PCAL). Zero and TSP fertilisation served as control in the completely randomized block experiment with four replicates. An incubation period of between 0 days and 8 weeks in fortnightly steps was implemented. The P uptake of annual rye grass was only slightly influenced by the incubation time of the fertilisers in soil. The relative agronomic efficiency (RAE) shows that MAP performed equally or better than TSP (RAE = 100 %). BCplus had an average RAE of 87 %, with a high variation between the incubation times. The RAE of SSA seemed to decrease constantly with incubation time. SSA, BCplus and MAP seemed all to perform best when applied directly prior to seeding.

本试验测试了以下几种磷肥：重过磷酸钙（Triple superphosphate, TSP）——高水溶性矿物肥料；骨炭（bone char, BC）——不溶性高磷含量清洁磷资源；表面改性骨炭（surface-modified bone char, BCplus）——经表面改性后预测磷溶解度高于BC的材料；热化学处理污泥灰（thermo-chemically treated sewage sludge ash, SSA）；以及市政污水处理产生的鸟粪石（struvite from municipal waste water treatment, MAP）。
采用盆栽试验（pot experiment）评估各磷肥的肥效，供试作物为一年生黑麦草（annual rye grass）。每盆向6 kg干物质（dry matter, DM）的酸性砂质粉壤土（初始pH为5.2，初始有效磷含量较低，为24.2 mg·kg⁻¹ PCAL）中施加280 mg磷素。本完全随机区组试验（completely randomized block experiment）设置4次重复（replicates），以不施磷处理与TSP施磷处理作为对照。试验设置0 d至8周的土壤培养期（incubation period），以两周为间隔开展阶段性取样。
土壤中磷肥的培养时长对一年生黑麦草的磷素吸收量（P uptake）影响微弱。相对农艺效率（relative agronomic efficiency, RAE）结果显示，MAP的肥效与TSP相当甚至更优（RAE=100%）；BCplus的平均RAE为87%，且不同培养时长下的RAE波动较大；SSA的RAE似乎随培养时长延长持续降低。SSA、BCplus与MAP均在播种前即刻施用时肥效最佳。