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Exploiting native soil phosphorus (P) and the large reservoirs of residual P accumulated over decades of cultivation, namely "legacy P", has great potential to overcome the high demand of P fertilisers in Brazilian cropping systems. Long-term field experiments have shown that a large proportion (> 70%) of the surplus P added via fertilisers remains in the soil, mainly in forms not readily available to crops. An important issue is if the amount of legacy P mobilized from soil is sufficient for the crop nutritional demand and over how long this stored soil P can be effectively 'mined' by crops in a profitable way. Here we mapped the spatial-temporal distribution of legacy P over the past 50 years, and discussed possible agricultural practices that could increase soil legacy P usage by plants in Brazil. Mineral fertiliser and manure applications have resulted in ~ 33.4 Tg of legacy P accumulated in the agricultural soils from 1967 to 2016, with a current annual surplus rate of 1.6 Tg. Following this same rate, soil legacy P may reach up to 106.5 Tg by 2050. Agricultural management practices to enhance soil legacy P usage by crops includes increasing soil pH by liming, crop rotation, double-cropping, inter-season cover crops, no-tillage system and use of modern fertilisers, in addition to more efficient crop varieties and inoculation with P solubilising microorganisms. The adoption of these practices could increase the use efficiency of P, substantially reducing the new input of fertilisers and thus save up to 31.8 Tg of P fertiliser use (US$ 20.8 billion) in the coming decades. Therefore, exploring soil legacy P is imperative to reduce the demand for mineral fertilisers while promoting long-term P sustainability in Brazil.

Devising policy instruments and interventions that can manage and mitigate the risks associated with microbial watercourse pollution is a significant concern of the contemporary environmental protection agenda. This paper reports on the work of a citizens’ jury that sought to elicit reasoned public judgments about the nature and acceptability of these risks as they relate to the role of livestock farming, and what might constitute socially acceptable and sustainable pathways to their management. By exploring this issue through a logical and sequential process of risk characterisation, risk assessment and risk management, the paper reveals how citizens’ juries can be used to contextualise and structure science-policy apprehensions of microbial watercourse pollution, and highlight where priorities for innovation and intervention might lie. Reactions and responses of participants to the jury process and its outputs, including issues of social and practical impact of the exercise, are also considered. The jury technique is argued to be useful in the way it cuts across disparate domains of responsibility and expertise for the governance of environmental risks, and therein challenges decision makers to think more broadly about the political, moral and economic framings of otherwise narrowly conceived science-policy problems.