Dairy processing wastewater treatment sludge (DPWTS) is applied to grassland to recycle valuable nutrients and organic matter. Until recently the chemical composition of the dominant DPWTS types (calcium, aluminium or iron rich) was unknown, but the latest study (Ashekuzzaman et al. in J Clean Prod 230:1266–1275, 2019) indicates that DPWTS has high nitrogen (N) and phosphorus (P) content and their inherent chemical properties may influence their availability and losses. Herein for the first time edge of field-losses and plant-available P changes are simulated in an agitator test 48 h after application. In terms of overall losses, metals are not of concern across treatment types, iron-rich DPWTS has the highest losses in terms of concentration of ammonium-N and carbon, whereas calcium-rich DPWTS has the highest dissolved reactive P (DRP) losses but lowest losses of ammonium-N and carbon. The loss of DRP was found to be strongly positively associated with the increase in water-extractable P, degree of P saturation, Morgan’s and Mehlich-3 extractable phosphorus (P_m, M3-P), respectively. Runoff concentrations presented here represent edge of field-losses and may not represent final concentrations entering a surface waterbody. In terms of plant-available P, there were no negative effects with P_m exhibiting a positive trend across DPWTS types and soils. In particular, a significant increase was found for the calcium-rich DPWTS across all soils (average increase in P_m by fivefold). As applying DPWTS to grassland is an understudied area, further field trials should focus on emissions to air and water and examine the fertilizer value from N and P perspectives. Thus a better management of DPWTS as fertiliser can be maintained from an agronomic and environmental context.

中文翻译：

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与乳品加工污泥施用相关的模拟径流中养分，碳和金属的潜在损失

乳制品废水处理污泥（DPWTS）用于草原，以回收宝贵的养分和有机物质。直到最近，尚不清楚主要的DPWTS类型（富含钙，铝或铁）的化学成分，但最新研究（Ashekuzzaman等人在J Clean Prod 230：1266–1275，2019）表明DPWTS具有高氮含量（N ）和磷（P）的含量及其固有的化学性质可能会影响其有效性和损失。在此，在施用后48小时，在搅拌器测试中首次模拟了田间损失和植物有效磷的变化。就总体损失而言，金属在所有处理类型中都不是问题，富铁的DPWTS在铵态氮和碳的浓度方面损失最大，而富含钙的DPWTS的溶解反应性P（DRP）损失最高，但铵态氮和碳的损失最低。发现DRP的损失与水萃取性P，P饱和度，Morgan's和Mehlich-3可萃取磷（P_m，M3-P）。此处提出的径流浓度代表田间损失的边缘，可能并不代表进入地表水体的最终浓度。就植物有效磷而言，没有不利影响，P _m在DPWTS类型和土壤上均表现出正趋势。特别是，发现在所有土壤中富含钙的DPWTS都有显着增加（P _m平均增加了五倍）。由于将DPWTS应用于草地是一个尚未充分研究的领域，因此进一步的田间试验应着眼于空气和水的排放，并从N和P角度检查化肥的价值。因此，从农艺和环境的角度来看，可以更好地管理DPWTS作为肥料。