This book features five peer-reviewed reviews on improving nitrogen-use efficiency (NUE). The first chapter provides an overview of the recent advances in optimising NUE in crop production, focussing on broadacre cereals and oilseeds. The chapter also addresses the impact of underfertilisation and overfertilisation on crop yield, grain quality and profit. The second chapter outlines recent advances in understanding nitrogen (N) cycling in soil, as well as the main issues researchers and farmers are presented with when attempting to optimise productivity while minimising environmental impacts. The third chapter considers the ways in which molecular interventions can be used to optimise crop NUE in rice and how these interventions can contribute towards producing rice genotypes with high yields at low N-inputs. The fourth chapter reviews the principal mechanisms of N-uptake and efficient capture by crop root systems. The chapter also details the impact of abiotic stress factors on N-uptake and proliferation, such as soil structure and overall health. The final chapter reviews the role of traits related to N-uptake, N-assimilation and N-remobilisation in breeding more efficient varieties of wheat. The chapter also discusses future major research trends, such as high-throughput phenotyping.