The productivity of any cultivar is, of course, of prime importance. We generally measure productivity in average kernel yield produced each year. We determine kernel yield by multiplying the tree nut yield by the percent kernel determined from a 50 nut subsample of each tree. In Table 1 below, we list the average kernel yield for each cultivar in the Ponder Farm Test for years 1-10 and years 11-20. The average for years 1-10 will give a good estimate of a cultivar's precocity, or quickness of bearing. For example, 'Cape Fear' and 'Candy', two very precocious cultivars, have about three times the average yield of 'Melrose', a non-precocious cultivar, in years 1-10. These cultivars would thus give a much quicker return on your investment. However, as mature trees, they do not maintain this yield advantage and have a similar average yield to most other cultivars in years 11-20. Selecting a highly precocious cultivar makes sense if the tree is going to be a temporary tree. However, for a permanent tree it is probably more important to choose varieties with stable production and high quality.
Determining productivity is very difficult to accomplish. Most of these cultivar yields are averages from 3-5 trees. If one or more trees is damaged, or lies on the orchard edge, yields may be higher or lower and this will influence the cultivar average. We try to eliminate obviously flawed trees, but we can't control everything. Having a higher replicate number would alleviate this problem, but would decrease the number of cultivars we could trial. Another problem is that this test is in a single orchard, a different location might give a different ranking of the same cultivars. Given these flaws, I would suggest that these numbers be considered generalizations only. You will probably want to avoid cultivars that rank at the bottom, but, for example, I would not plant 'Sumner' over 'Sioux' just because this test indicates that 'Sioux' is more productive.
Where are Desirable and Stuart?
Unfortunately, 'Desirable' and 'Stuart' and most of the older cultivars were not included in the Ponder Variety Test in the first plantings. We have yield data for these cultivars from the Old and Young Variety Tests, but these were started so long ago and in another location and they aren't really comparable to data in Table 1. In the more recent plantings of the Ponder Variety Test, both 'Desirable' and 'Stuart' have been included as check cultivars so that we will have this data in the future.
Table 1. Kernel yield* rankings (pounds/tree) for trees planted 1979-2003 in the Ponder Variety Trial.
|Variety||Years 1-10||Variety||Years 11-20|
*Kernel yield was determined by multiplying total yield by percent kernel for each year. Values were then summed for the time period.