Completely devoted to applicati on of models to opti mize the use of limited water and nutrients in various climates, this collecti on will inspire confi dence in the capacity of modeling to tackle the biggest threats to secure agriculture. To obtain the most producti on from available water while maintaining natural resources, we need whole system-based quanti tati ve knowledge and tools to help select appropriate crops and manage water and associated inputs on a site-specifi c basis under changing climate. Site-specifi c experimental results are available for limited locati ons, limited periods of ti me, and limited management opti ons. Well-tested process models of cropping systems can extend fi eld research results to long-term weather conditi ons, as well as other climates and soils, allowing us to explore new management opti ons. The case studies in this volume are promising examples of these kinds of soluti ons.

Dr. Laj Ahuja is a retired soil scientist at USDA in Fort Collins, CO.

Dr. Liwang Ma is a research soil scientist at the USDA-ARS Rangeland Resources and Systems Research Unit at Fort Collins. Dr. Ma's research interests include the use of system ecological and biophysical models to quantify agricultural production and environmental impacts at multiple spatiotemporal scales in rangelands and croplands.

Dr. Robert Lascano is a GS-15 Soil Scientist and Research Leader of the Wind Erosion & Water Conservation (WEWC) Research Unit of the Cropping Systems Research Laboratory at Lubbock.