Agricultural practices strive to reduce STP while maintaining yield. Although reducing high STP can decrease Phosphorus loss without affecting yields, it is less likely to be the case at low STP. Careful management of the rate and timing of applied P, as well as P addition from residues as a secondary source, may make lower STP thresholds possible. MSc and PhD students are being recruited to examine how Water Use Efficiency, carbon allocation and drought tolerance are affected by residue management and P application rates and timing. Fields in Southern Ontario will be instrumented to monitor hydrometeorological conditions, carbon uptake (productivity) and water use at the field scale using eddy covariance. The effects of residue management will be examined through the quantification of canopy development, root activity and growth, and plant scale measurements of water use and productivity using leaf chamber gas exchange measurements (Plot/Leaf scale, LiCor 6800 Portable Photosynthesis System, Licor Inc., NE, USA) throughout the growing season at regular intervals. These positions at the University of Waterloo are fully funded.