Technical Abstract: Pecan trees are remarkably capable of maintaining a satisfactory internal balance among essential macro-, micro- and beneficial nutrients; however, this balance is potentially disrupted when trees are sufficiently stressed. Stress can be due to many factors, but is most typically linked to either excessive fertilization, dry soils, disrupted or poor soil microflora, or soils possessing unique soil chemistry or chemical composition. These interactions are complex, and are often difficult to predict or diagnose, thus easily misleading orchard manages or extension specialists to attribute tree maladies to a particular element where in reality it is being caused by one or more different and interacting elements. This interaction is usually apparent in situations where one element is exceedingly high and another element is exceedingly low. Adverse nutrient interactions are most typical in intensely managed orchards on sites differing greatly from the river bottom soils in which the species evolved. This presentation addresses only two-way interactions; yet, in reality, three-, four-, or even five-way element interactions potentially cause orchard maladies. A basic understanding of how elements interact in both the soil solution and within the tree itself is necessary for sufficiently understanding what is happening within trees and orchards. This complexity highlights the importance of avoiding repetitive annual applications of fertilizers without proper chemical analysis of soil and tree foliage, and at least a basic understanding of the consequences on the uptake or bioavailability of other nutrients. It is a basic principle in ecosystems that when one factor is altered, it usually has unanticipated consequences on many other factors. The same principle applies to pecan nutrition management. Orchard managers must therefore be cautious about routine long-term application of nutrient elements, sewage, or waste and recognize that too much of a good thing can lead to unanticipated consequences that can be difficult and expensive to correct. Careful evaluation of annual foliar nutrient analysis and an occasional soil analysis (with separate analysis of the soil zones) are therefore important to ensuring long-term optimization of nut productivity of orchard enterprises. This presentation presents information about a multitude of antagonistic and synergistic interactions. The most important antagonistic interactions in most pecan orchards are those involving zinc.