Andrew N. Sharpley

This collection features four peer-reviewed reviews on phosphorus uptake and use in crops. The first chapter summarises the progress in research on root traits associated with phosphorus acquisition, including root morphology, architecture, biochemistry, colonisation by arbuscular mycorrhizal fungi, and fine root endophytes. The chapter also reviews the recent advances in breeding programmes to improve phosphorus acquisition efficiency. The second chapter discusses interactions between phosphorus management (phosphorus rate, source timing, and placement) and diverse cropping systems and climate and how these interactions are essential to efficient utilization of phosphorus resources. The third chapter assesses the key soil, root and microbial processes that influence phosphorus acquisition with a focus on factors that can be managed to ensure optimal use of fertiliser and development of root systems for improved phosphorus acquisition. A case study from Australia is used to demonstrate how phosphorus efficiency of grasslands can be improved. The final chapter reviews the environmental effects of phosphorus fertilisation in agriculture, primarily its impact on water quality. The chapter considers how future water quality issues can be mitigated and also examines the cycling, fate and transport of phosphorus in agriculture.

Since 1985, scientists have been documenting a hypoxic zone in the Gulf of Mexico each year. The hypoxic zone, an area of low dissolved oxygen that cannot s- port marine life, generally manifests itself in the spring. Since marine species either die or ee the hypoxic zone, the spread of hypoxia reduces the available habitat for marine species, which are important for the ecosystem as well as commercial and recreational shing in the Gulf. Since 2001, the hypoxic zone has averaged 2 1 16,500 km during its peak summer months , an area slightly larger than the state 2 2 of Connecticut, and ranged from a low of 8,500 km to a high of 22,000 km . To address the hypoxia problem, the Mississippi River/Gulf of Mexico Watershed Nutrient Task Force (or Task Force) was formed to bring together represen- tives from federal agencies, states, and tribes to consider options for responding to hypoxia. The Task Force asked the White House Of ce of Science and Technology Policy to conduct a scienti c assessment of the causes and consequences of Gulf hypoxia through its Committee on Environment and Natural Resources (CENR).

Since 1985, scientists have been documenting a hypoxic zone in the Gulf of Mexico each year. The hypoxic zone, an area of low dissolved oxygen that cannot s- port marine life, generally manifests itself in the spring. Since marine species either die or ee the hypoxic zone, the spread of hypoxia reduces the available habitat for marine species, which are important for the ecosystem as well as commercial and recreational shing in the Gulf. Since 2001, the hypoxic zone has averaged 2 1 16,500 km during its peak summer months , an area slightly larger than the state 2 2 of Connecticut, and ranged from a low of 8,500 km to a high of 22,000 km . To address the hypoxia problem, the Mississippi River/Gulf of Mexico Watershed Nutrient Task Force (or Task Force) was formed to bring together represen- tives from federal agencies, states, and tribes to consider options for responding to hypoxia. The Task Force asked the White House Of ce of Science and Technology Policy to conduct a scienti c assessment of the causes and consequences of Gulf hypoxia through its Committee on Environment and Natural Resources (CENR).