Part 8
Recently a number of papers have been published dealing with the evaluation of black walnut varieties. In 1941 Kline and Chase(3) compiled the available published data and additional tests made by the Tennessee Valley Authority on nut weight and kernel percentage of black walnut selections. Two hundred and twelve clones and 335 tests are reported. As would be expected the samples of the same variety from different localities show variation in weight per nut and in total per cent kernel. For example, in 12 samples of the variety Ohio the weight per nut varies from 14.8 grams to 18.7 and the per cent kernel from 16.6 to 32.9. Twenty-one tests of Thomas show variations in single nut weight from 16.7 to 25.0 grams and in per cent kernel from 19.0 to 30.0. In general the samples grown in the north were made up of smaller nuts with less per cent kernel, indicating that the varieties were not suited to that latitude.
In 1942 Kline(4) worked out a somewhat technical method of evaluating walnut varieties on the basis of cash return per hour of labor spent in cracking with a hand operated cracker. A formula is proposed in which the variables of price and other factors may be substituted. The approach is on a commercial basis and the method is not intended for use in evaluating small samples. The paper represents many tests and establishes or affirms by statistically treated data several points of general interest in walnut testing, namely, (1) that a 25 nut sample is large enough to show varietal or other differences of a gram in total weight or 1 per cent of kernel weight, (2) that unless extreme accuracy is desired, moisture content may be ignored in making tests of 25 nut samples if the nuts have been hulled and air dried for about two months and (3) that the mean weight per nut and per cent kernel of nuts from the same tree may vary appreciably from year to year, for example a variation of 4.9 grams per nut and 3.3 per cent in kernel weight is reported for Snyder. Such variation is recognized and emphasizes the necessity of testing a variety in any locality for a number of years if correct valuation is to be made.
In Kline's paper earnings per hour for fifteen black walnut selections are given showing a maximum of $0.279 for the variety Norris, $0.245 for Ohio down to $0.12 for an unnamed seedling.
Lounsberry(5) published kernel cavity measurements for 64 clonal selections and related these to kernel weight per nut. Measurements of the thickness of the partition separating the halves of the kernel are also given. He does not relate these characters to scoring or cracking quality.
The purpose of the scoring system under discussion in this paper is to provide a realistic method of judging the relative merit of different clones of black walnuts that can be used mostly by members of the Northern Nut Growers Association or others having some skill in cracking technique. At the present time the Association has little reliable information either as to the performance of different varieties under different conditions in any one locality, from year to year on the same tree, or the suitability of any one variety growing in far different parts of the United States. It is important that such information be available and a workable basis of evaluation would be of the greatest value in obtaining it. Much of our information at the present time is from the many tests made by N. F. Drake(6, 7, 8) which are of great value in rating varieties. His schedule is an improvement over any previously proposed but fails to provide standard sampling and cracking procedure and includes the items of flavor and color which are in no way objective characters. The use of a point score based on the concept of a "perfect nut" is cumbersome and considered undesirable by the committee.
It is recognized that the value of a variety depends also upon the bearing habit of the tree, the nature of the husk, disease resistance and other characters.
It has been five years since the present schedule was proposed and enough tests have been made to give a basis for judgment as to the merits and weaknesses of the schedule. As stated in the original committee report it is generally agreed that the best measure of the value of a nut of any clone is the amount of usable or marketable kernels that can be obtained from a given weight of shucked nuts with the least labor. The characteristics of the nuts that contribute to this value are recognized as follows:
1. The size of the individual nut.
2. The per cent of kernel of total sample weight recovered without recracking and without the use of a pick.
3. The total per cent of kernel of total weight of sample.
4. The number of quarters.
5. The plumpness of the kernels.
6. The number of empty nuts or nuts with shrivelled kernels in the sample.
Flavor and color may be important but are so dependent upon personal preference and on the treatment of the samples before testing that they cannot be rated numerically.
In considering the value of any schedule the following questions are pertinent:
1. Is it possible for one operator testing one lot of nuts to obtain the same score with replicate random samples?
2. Is it possible for different operators to obtain approximately the same score on replicate samples?
3. Does the score give an accurate evaluation of the variation of a variety from year to year in one locality or in the same year in different localities? The latter is very important in determining the regions to which the variety is best adapted and the performance of the variety in any one locality.
4. What are the causes of variation in the scores obtained? Which of these reflect the inherent worth of the sample and which are related to technique, personal equation and methods of handling the sample?
5. What changes may be made in the schedule to weight the various factors to give a more realistic score of what changes in procedure will make the schedule more realistic?
Table 1 gives data on replicate samples tested by the same operator. In the samples of Spear, numbers 1-6 the variation is as follows: weight of single nut 1.3 grams, per cent kernel first crack 2.9, total per cent kernel 2.6, number of quarters 3, penalties 4.5 points, score 9.2 points. In scores figured without penalty the variation is 5.4 points. Sample No. 7 was cracked November 4 before the nuts were dry and hence is not comparable with others.
Analysis of these differences indicates that the variation in nut weight is closely related to the number of shrunken and empty nuts in the sample. This is a difficult factor to evaluate in a practical way. At the time of the 1939 report it was suggested that the score should be figured on the basis of filled nuts. This cannot be arranged easily in testing because if the operator cracks the nuts before weighing there is almost sure to be loss of fragments of shell. Trying to correct the original weight in any way is necessarily inaccurate. Deciding whether or not the kernel of a nut is sufficiently shrivelled to deserve a penalty is a matter of judgment which is a personal matter.
The variation in per cent kernel first crack and total per cent kernel probably represents fairly the difference in the samples. The total per cent is a wholly objective value and varies practically as much as the per cent first crack. Uniformity in the number of quarters is striking. This large number is undoubtedly related to the fact that many of the kernels were shrunken enough to be penalized and others were perhaps shrunken enough so that they did not tightly fill the shell cavity. In general it may be said that the more tightly the kernels fill the shell the more difficult it is to extract large pieces. Thus having the kernels a little shrunken but not enough to seriously reduce their weight favors a higher score. Of course, in some varieties the kernels may he plump and still not fill the shell tight enough to make cracking difficult. This is a desirable condition.
Variability in penalties is more important (i. e. 4.5 points) than any other factor in influencing the final score. Without the penalties the scores of samples 1 to 6 would be 87.5, 84.0, 83.6, 83.7, 82.1 and 82.8 respectively which is fairly uniform. Statistically the presence of empty or shrivelled nuts in a lot from which samples are taken increases the number required to make a satisfactory sample by greatly increasing the individual variation of the single nut.
TABLE 1
Variation in the score of tests of duplicate samples made by the same operators. Twenty-five nut samples. Nuts grown at Ithaca, N.Y.
1942. Black Walnuts.
KEY: A: Wt. 1 nut grams B: % kernel 1st crack C: % kernel total D: Quarters number E: Penalty F: Score
----------------------------------------------------------------------------- Variety Treatment A B C D E F Remarks ----------------------------------------------------------------------------- Spear No. 1 S 18 hours 14.6 24.9 28.0 91 -3.5 84.0 1 empty, 5 shr. D 15 hours Spear No. 2 D 15 hours 15.7 24.0 26.8 94 -6.1 77.9 3 empty, 6 shr. Spear No. 3 D 15 hours 15.9 22.9 25.4 92 -3.5 80.1 1 empty, 5 shr. Spear No. 4 Dry 15.0 23.3 25.4 94 -5.0 78.7 1 empty, 8 shr. Spear No. 5 Dry 15.4 22.0 26.8 93 -4.5 77.6 1 empty, 7 shr., 20 bnd. qtrs. Spear No. 6 Dry 14.7 22.7 26.6 94 -8.0 74.8 4 empty, 8 shr., 16 bnd. qtrs. Spear No. 7 Nov. 4 16.7 27.9 28.8 98 96.7 only partly dried, 16 halves Snyder No. 1 Dry 16.8 23.1 26.0 87 -4.0 80.7 8 shr., 9 bnd. qtrs. Snyder No. 2 Dry 16.0 24.0 26.3 74 -3.5 81.0 1 empty, 5 shr., 13 bnd. qtrs. Snyder No. 3 Soaked 15.8 24.1 25.8 86 -4.0 77.5 1 empty, 6 shr., 8 bnd. qtrs. Snyder No. 4 Soaked 16.2 23.1 25.6 78 -7.5 75.5 3 empty, 9 shr., 8 bnd. qtrs. Snyder No. 5 Dry 18.2 19.9 26.4 90 -3.5 76.7 7 shr., bnd. Snyder No. 6 Nov. 4 21.2 27.6 29.8 95 100.8 qtrs. Eldridge Dry 20.8 19.3 23.1 98 80.7 13 halves, not Geneva, N.Y. well dried out " Dry 20.6 20.0 22.6 92 81.0 -----------------------------------------------------------------------------
With the variety Snyder a difference of 2.4 grams in weight per nut in samples 1 to 5 suggests poor sampling technique as this is an objective value. A difference of 4.2 per cent in first crack suggests carelessness on the part of the operator in cracking or difference in soaking as this is quite out of line with the variation of .8 per cent in per cent weight of total kernel. The difference of 16 quarters is considerable but represents only 1.6 score points. As with the Spear the variation in penalty of 4 points is greater than other factors except per cent first crack (i.e. 4.2% points). The difference in score of 5.5 points is obviously greater than desirable, but probably indicates the relative value of the samples. Without penalties the difference is 4.5 points.
Sample 7 of Spear and number 6 of Snyder were cracked November 4th when only partly cured and show the importance of curing in obtaining an accurate rating for a sample. The score of each variety was increased materially in all characteristics and no shrivelling was apparent. As a practical means of recovering the kernels in large pieces, cracking before the nuts are dried out is a decided advantage provided the kernels are cured before they are stored.
The duplicate samples of Eldridge check very closely and show no significant differences.
In Table 2 are given the results of ten tests on carefully replicated random samples of Snyder black walnuts. In making these samples the nuts were spread in a single layer on the floor and lots of 25 cut off the edges of this layer without selection of any kind. Even with such selection there is a variation of 1.2 grams in the average weight of single nuts from different samples. Per cent kernel first crack shows a minimum of 21.8 and a maximum of 26.9 in the ten samples. This difference is related mostly to the presence of 3 empty nuts in the low scoring sample as compared with none in the high scoring sample. The high score is also in part due to soaking. This variability is about the same as with total per cent kernel indicating that cracking technique was uniform. Comparing samples 1 and 2 in more detail it is found that the difference of 11.6 points in the score is caused by the presence of empty nuts in the sample. The average weight of kernels per single nut in sample 1 is 4.9 grams. The difference in the weights of the kernels of the two samples is 15 grams or about the weight of the kernels of 3 nuts. These empties also reduce the score by reducing the number of quarters recovered. Where empty nuts are involved, it is doubtful if random sampling will reduce variation unless the size of the sample is greatly increased, a practice which is not a practical solution in that a 25 nut sample is about as large as can be handled with any facility. It would seem that this difference in scores was a fair indication of the merit of the two samples. The scores of the other samples show a fair degree of uniformity. The high score of sample 4 is probably related to the soaking treatment though the scores of sample 3 also soaked is lower than that of sample 6 which was not soaked. It seems that when these conditions and with this variety stored in a fairly high humidity, soaking had little effect except to increase the number of halves recovered.
TABLE 2
Cracking tests by single operator with 10 random replicate samples of Snyder black walnuts. 1942 crop. 25 nut samples.
KEY: A: Wt. 1 nut grams B: % kernel 1st crack C: % kernel total D: Quarters number E: Penalty F: Score
Sample Treatment A B C D E F Remarks ----------------------------------------------------------------------------- 1 Dry as received 18.1 21.8 23.1 85 -9.0 72.7 3 empty, 12 shr. 2 Dry as received 18.5 24.0 25.8 99 -5.0 84.3 10 shr. 3 Soaked 9 hrs., dried 14 hrs. 18.6 25.7 28.0 94 -6.0 87.4 1 empty, 10 shr., 8 bnd. qtrs., 16 hvs. 4 Soaked as above 18.3 26.9 28.4 99 -4.5 91.7 9 shr., 5 bnd. qtrs., 19 hvs. 5 Held in cellar 4 days 18.0 24.4 25.7 90 -6.5 82.1 1 empty, 11 shr., (high humidity) 8 bnd. qtrs. 6 Held in cellar 7 days 19.0 25.6 27.2 99 -5.0 88.7 10 shr., 7 bnd. qtrs., 3 hvs. 7 Held in cellar 7 days 18.4 23.9 26.1 96 -6.5 82.3 1 empty, 11 shr., 9 bnd. qtrs. 8 Held in cellar 4 days 19.2 24.8 26.6 98 -5.5 86.4 11 shr., 4 bnd. qtrs. 9 Held in cellar 4 days 18.4 23.7 26.7 92 -7.5 81.6 2 black counted as empty, 11 shr., 12 bnd. qtrs. 10 Held in cellar 4 days 18.6 23.5 25.9 94 -5.5 83.4 1 empty, 9 shr., 10 bnd. qtrs. -----------------------------------------------------------------------------
Another lot of 24 random replicate 25 nut samples of Ohio black walnut from the original tree was made by scooping the nuts out of a bag with a quart berry box which held about 25 nuts. Care was used not to select the samples in any way. The lightest sample 3 weighed 385 grams, the heaviest 22 weighed 434 grams or a difference of 2 grams per nut. The score of these two samples was 85.0 and 85.4 respectively apparently because there were no empty nuts in either sample.
The results of tests on 18 of these replicate samples of Ohio are given in Table 3. The nuts were apparently a uniform lot. The kernels while of good quality were in most cases not quite plump and did not fill the cavities of the shell tightly. This doubtless accounts for the large number of quarters recovered. The kernels on the whole were plumper than with the variety Snyder reported in Table 2 and there were fewer empty nuts. Of the samples that were not soaked the variation of 4.3 per cent in the per cent first crack is of the same order as variation of 3.6 per cent for total per cent kernel and indicates uniform cracking technique.
The data in Table 3 gives evidence of the effect of treatments before cracking. The first nine samples marked with an asterisk were held for several weeks in a damp cellar and have an average test score of 86.6. The last seven samples were held in a dry but unheated room for a week before cracking and show an average test score of 83.7. The average score for the two soaked samples was 93.9. Soaking also increased the number of halves and quarters recovered in the same way as shown with variety Snyder in Table 2. None of these samples was excessively dry. In this table the lowest score (sample 19) is directly related to the presence of 3 empty nuts in the sample. The low score of sample 21 is mostly related to low per cent first crack which is caused by large number of bound quarters and the high penalty related to empty nuts and shrivelled kernels. These scores seem to indicate the value of the samples but bring out the difficulty of obtaining equal scores from such replicate samples. The other scores in the table are probably as close to each other as can be expected with samples of this sort.
In this and the preceding tables the number of bound quarters is given as an indication of cracking technique. With the Hershey cracker the nuts of many varieties will split into four quarters without releasing the kernels. The number of such bound quarters is increased if the operator does not put sufficient pressure on the anvils to crush the shoulders of the nut and free the kernel. On the other hand if too much pressure is used and the anvils brought too close together the kernels will be crushed and the score affected adversely. With some varieties, for example, the Adams as shown in samples 1 and 2 in table 5, the nuts are so pointed at each end that the standard anvils do not strike the shoulders of the nut and many bound quarters result. With such varieties cracking with a hammer would probably give a better score. Anvils with deeper cavities in the ends would be an advantage for such nuts.
TABLE 3
Tests by the same operator of duplicate samples of Ohio black walnuts, treated in various ways before cracking. 25 nut samples. 1942 crop.
KEY: A: Wt. 1 nut grams B: % kernel 1st crack C: % kernel total D: Quarters number E: Penalty F: Score
Sample Treatment A B C D E F Remarks --------------------------------------------------------------------------- 9 *Dry 16.9 25.8 27.1 98 -0.5 91.3 1 shr., 5 bnd. qtrs., 7 halves 10 *Dry 16.8 23.8 25.2 95 -3.0 83.5 1 empty, 4 shr., 7 bnd. qtrs. 12 *Dry 16.2 24.5 26.5 97 -2.0 86.1 4 shr., 8 bnd. qtrs., 13 halves 24 *Dry 16.2 24.8 25.7 86 -3.0 84.2 2 empty, 2 shr., 4 bnd. qtrs., 8 halves 17 *Dry 17.3 24.8 27.3 97 -0.5 89.7 1 shr., 9 bnd. qtrs., 12 halves 21 *Dry 15.9 22.0 25.5 96 -4.0 78.2 1 empty, 6 shr., 14 bnd. qtrs., 17 halves 8 *Dry 16.6 25.2 26.9 99 -1.5 88.8 3 shr., 6 bnd. qtrs., 10 halves 15 *Dry 16.6 25.5 26.7 99 -1.5 89.8 3 shr., 5 bnd. qtrs., 12 halves 23 *Dry 16.4 25.2 26.2 96 -3.0 87.0 6 shr., 4 bnd. qtrs., 10 halves 11 Soaked 16.9 27.0 28.2 100 -1.5 93.5 Soaked 1 hr., moist 18, dried 12 hrs., 3 shr., 5 bnd. qtrs., 25 halves 16 Soaked 16.8 27.1 28.2 100 -0.8 94.3 Soaked as above, 1 shr., 5 bnd. qtrs., 16 halves 4 Dry 16.2 23.6 26.4 98 -3.5 82.9 7 shr., 10 bnd. qtrs., 15 halves 5 Dry 17.1 23.6 25.0 93 -3.0 83.1 1 empty, 6 shr., 5 bnd. qtrs., 10 halves 18 Dry 17.0 25.3 26.6 97 -2.0 88.6 4 shr., 6 bnd. qtrs., 8 halves 19 Dry 16.3 21.5 23.7 85 -4.5 75.1 3 empty, 3 shr., 9 bnd. qtrs., 8 halves 3 Dry 15.4 24.7 27.0 97 -3.0 85.0 6 shr., 8 bnd. qtrs., 5 halves 7 Dry 16.0 25.7 25.7 94 -3.5 86.1 7 shr., 6 halves, end reversed in cracking 22 Dry 17.4 24.1 25.8 94 -2.5 85.4 5 shr., 8 bnd. qtrs. ---------------------------------------------------------------------------
TABLE 4
Variation in score of replicate samples of 3 varieties of Black Walnuts tested by different operators and of same varieties from different sources
Wt. 1 % kernel % nut 1st kernel Quarters Variety Source grams crack total number Score ------------------------------------------------------------------------ Operator 1 Thomas--Weber, Ind. 20.4 20.8 24.2 75 81.6 Thomas--Jones, Pa. 14.6 28.8 30.3 95 96.8 Thomas--Baum, Pa. 14.3 25.6 27.0 100 89.0 Thomas--Worton, Md. 16.4 28.2 30.8 94 97.6 Average 16.4 25.8 28.1 91.0 91.2
Operator 2 Thomas--Weber, Ind. 22.0 22.2 23.8 47 83.0 Thomas--Jones, Pa. 17.5 26.7 31.4 55 92.1 Thomas--Baum, Pa. 17.0 24.0 26.5 72 85.5 Thomas--Worton, Md. 16.7 19.5 26.4 64 75.3 Average 18.3 23.1 27.0 59.5 83.9
Operator 3 Thomas--Jones, Pa. 18.1 16.2 27.1 52 69.2 Thomas--Baum, Pa. 16.1 19.1 26.6 68 74.4 Thomas--Worton, Md. 18.0 17.8 27.2 61 73.3 Average 17.4 17.7 27.0 60.3 72.3
Operator 1 Ten Eyck--Weber, Ind. 18.0 20.5 27.5 57 78.5 Ten Eyck--Jones, Pa. 15.4 21.1 23.2 99 79.1 Ten Eyck--Baum, Pa. 14.3 26.3 30.2 93 91.3 Ten Eyck--Worton, Md. 15.0 28.0 31.0 83 94.8 Average 15.7 24.0 28.0 83.0 85.9
Operator 2 Ten Eyck--Weber, Ind. 19.1 24.4 26.5 38 84.8 Ten Eyck--Jones, Pa. 16.4 24.6 24.6 64 84.3 Ten Eyck--Baum, Pa. 15.8 25.7 26.5 54 86.0 Ten Eyck--Worton, Md. 15.4 25.5 28.7 55 86.2 Average 16.7 25.0 26.6 52.7 85.3
Operator 3 Ten Eyck--Weber, Ind. 16.8 17.3 24.6 57 69.4 Ten Eyck--Jones, Pa. 15.2 21.1 23.3 84 77.4 Ten Eyck--Baum, Pa. 15.0 18.3 19.7 69 68.4 Ten Eyck--Worton, Md. 15.7 25.2 30.1 76 88.5 Average 15.7 20.5 24.4 71.5 75.9
Operator 1 Ohio--Weber, Ind. 17.2 28.5 29.7 89 98.0 Ohio--Jones, Pa. 16.4 28.7 29.9 96 99.2 Ohio--Baum, Pa. 14.2 31.1 31.1 99 101.9 Ohio--Worton, Md. 13.7 30.8 30.8 88 99.5 Average 15.4 29.8 30.4 93.0 99.6
Operator 2 Ohio--Weber, Ind. 19.1 25.1 28.3 59 89.3 Ohio--Jones, Pa. 17.2 27.3 27.5 64 91.9 Ohio--Baum, Pa. 15.0 27.4 28.1 63 90.1 Ohio--Worton, Md. 14.9 26.1 29.1 58 87.4 Average 16.5 26.5 28.2 61.0 89.7
Operator 3 Ohio--Weber, Ind. 17.7 21.4 27.7 65 80.8 Ohio--Jones, Pa. 17.2 22.9 28.2 74 84.5 Ohio--Baum, Pa. 15.0 24.9 29.3 81 87.5 Ohio--Worton, Md. 14.6 22.4 28.7 66 80.3 Average 16.1 22.9 28.5 71.5 83.3 ------------------------------------------------------------------------