Pecan trees grow well or poorly, depending on the soil type. Soils have quite different water-holding and -releasing capacity, which is important to pecan tree growth and nut production. Pecans require huge volumes of water to produce nuts, so they naturally establish and develop on the deeper soil types, especially where there is a stable water table.
When choosing a soil site for nonirrigated pecan production, look for a deep well-drained soil with a stable water table at six to eight feet so the roots can feed from the capillary water. If those soil types are unavailable, consider where the water will come from. Where adequate natural water is available or the soil is correct, nut size and production potential may not be as important as on more marginal soil types.
Where irrigation is possible, there are more variables to consider, including your marketing goals and the value of pecans. When looking at growing pecans on droughty soils, we are limited to varieties that are smaller and more easily filled. The larger varieties are going to be much more difficult to fill because of stress and competition. Where trees would receive insufficient water, consider using varieties that produce smaller nuts, and maybe even consider using them on soils that have good water relationships. The varieties that I'm referring to are 'Kanza', 'Caddo', and 'Sioux'. 'Kanza' produces about seventy to eighty small nuts per pound, and under stress, it may take as many as ninety nuts to produce a pound. On a soil that exhibits good water relationships, nut size could increase so that 'Kanza' produces sixty-five nuts per pound. Nut size is similar for 'Caddo' and 'Sioux'. The three are good varieties for southern Oklahoma and northern Texas: although small, they exhibit great nutmeat characteristics. 'Caddo' has such a high nut yield potential that it may be a questionable one for the marginal soil types.
I also consider these varieties good selections for introducing into a native orchard where the management wants to start new trees. They should actually complement the native pecans when not harvested separately. If the grower wants to keep them separate to sell them, they are a premium product that can be merchandised for a better price. Large varieties such as 'Choctaw', 'Mohawk', 'Meramac', and 'Kiowa' are in demand for retail trade but are more susceptible to marginal soil conditions. Because of their size and requirement for optimal conditions to properly fill, they have developed a reputation as being a poor variety choice, even though soil type, water relationships, and sites were sometimes to blame.
'Pawnee' is a tough variety that certainly should be considered for pecan production in Oklahoma. It should not be put on a really marginal site but would be able to produce better on a more marginal site than those large varieties I mentioned.
One of the old varieties that seems to always come up in a varietal discussion is 'Stuart'. It has proven over time to produce quite well on good soil sites. In years with good rainfall, it produces well on marginal soils. It's one that is not considered a good quality nut, which may be part of the reason it continues to perform. If a grower were looking for a variety with very low maintenance and decent quality, I would recommend 'Stuart'.
When selecting that perfect variety, you need to look farther than just the characteristics that are appealing when you eat pecans. Large, plump, well-filled meats that are easy to shell is the characteristic that most people find appealing. As the person making a decision about varieties, you should look past the most appealing characteristics to the management structure: it may require a compromise. Are management and water adequate for the varieties that you selected?
You should consider other variety characteristics associated with pecan production, such as scab susceptibility and possible resistance to aphids (such as 'Pawnee' has). Don't forget the significant impact of soils and their ability to supply water and nutrients to that variety. Pick the variety that would be most likely to perform where you place it. Consider all factors in selecting that perfect variety rather than just the one that really fits your palate.
For additional information, visit the Oklahoma Pecan Management Web site at http://www.hortla.okstate.edu/pecan.