Production of pecans is a large industry in the United States. Pecan trees (Carya illinoinensis) become huge trees, potentially 70 to 100 feet tall and 40 to 75 feet wide. For best growth these deciduous trees need a deep, fertile soil that never becomes soggy. Nut production is best in regions where the summers and long and warm. Grow pecans in U.S. Department of Agriculture hardiness zones 5 through 9.
Optimum Soil Characteristics
Since pecan trees develop a deep taproot, they must be planted on soils that have at least 4 to 7 feet of topsoil over a rock substrate or hard clay layer, according to the University of Arkansas. Pecans also appreciate a fertile soil, rich in nutrients. A loamy soil that is moist but well-drained across the growing season is best, but the trees are somewhat adaptable. Horticulturists at the university also comment that nitrogen and zinc are typically the two nutrients that pecan trees require that native soils may fail to provide.
Gerald Kidder and Sydney Park Brown write in "Your Florida Landscape" that sulfur is supplied to plants in decomposing organic matter, particles of gypsum and rainwater. Roots absorb sulfur in the form of sulfate ions. Sulfur deficiencies have not been reported for pecans in any area of the United States. Native soils contain ample sulfur amounts to support healthy tree growth, according to Esteban Herrara of New Mexico State University.
Conducting a soil analysis to determine nutrient composition of the topsoil in which pecan trees grow will indicate if supplemental sulfur is needed. Leaf analysis is the best way to determine fertilizer needs in pecans, according to the University of Arkansas and New Mexico State University. Little sulfur is needed by the trees, and by dry weight exists in pecan leaves between .2 and 2.5 percent by weight as noted by NMSU.
Since sulfur is usually abundant in soils due to parent materials, organic matter and rainwater, rarely is a sulfur-specific fertilizing warranted. Moreover, man-made nitrogen fertilizers typically contain fillers that already contain sulfur ions--such as any product that contains a "sulfate" ingredient. For example, when nitrogen is applied to pecan trees in the form of ammonium sulfate, sulfur is also applied in the process. Elemental sulfur applications (not sulfate or sulfide ingredients) cause soil pH to drop (become more acidic). If such a regimen is ever conducted, never apply more than 5 to 10 lbs. of sulfur per 1,000 square feet as advised by University of Florida experts in "Your Florida Landscape."
Herrara mentions that sulfur and any other nutrient in the soil can vary across an orchard as well as in different states or regions. Even though soil analysis or leaf analysis of one tree doesn't indicate a sulfur deficiency, another test nearby or from another tree could reveal different results. The alkaline soils of the American West when compared to the more acidic soils of the Southeast provide different results in pecan leaf analyses in different varieties, tree ages and times of year.