The author wishes to acknowledge the private and public funding sources that supported his soil fertility research over the past 30 years. Private sources included several fertilizer companies with JR. Simplot and Agrium (currently Nutrien) being the two largest sources of support.  The major public sources have included the Arizona Iceberg Lettuce Research Council, the California Department of Food and Agriculture Fertilizer Research and Education Program, and the USDA Specialty Crop Block Grant (SCBG) program.  In addition to funding a large subset of the research that generated the guidelines in this report, the SCBG program specifically funded the construction of this webpage.

I express my gratitude to countless growers across Arizona and southern California that allowed the author access to their production fields as we scaled up soil fertility research efforts from small plots on University Experiment Farms into larger production units.

The author wishes to recognize the contribution of excellent technical support over the years. Key personnel involved in assisting the author in soil fertility research included Humberto Hernadez (1990s), Manual Peralta (2000s), Jay Subramani, Enrico Sanchez, and Lorena Alleman (2010 to 2025).

I am grateful to Jeff Silvertooth for discussions on the overall nutrient requirement of chile peppers, where the authors own data base was limited, and discussions on potassium (K) fertility and N plant testing in general, where he has faced the same challenges with these issues in Arizona cropping systems as the author. I am grateful to Michael Cahn for discussions concerning unique nuances concerning K fertility in tomato. I express my gratitude to Pedro Andrade, my co-investigator in our initial evaluations of variable rate fertilizer management.

The author also recognizes the large database for nitrogen management for vegetable crops generated by numerous researchers associated with the University of California, which was extremely helpful to his own efforts in Arizona. Although modifications for climate and cultural practices in Arizona were required, this database sometimes provided direction and sometimes independent corroboration of the authors results.

The author wishes to acknowledge the editorial support of Sonnet Nelson and Dawit Zerihun who scrutinized early drafts of this presentation. Sonnet Nelson is also responsible for a large subset of the photography. The author also wishes to recognize Craig Boesewetter of the University of Arizona Communication and Cyber Technologies for webpage design and construction.