Abstract:
The disclosure is of a method for stimulating growth in a foliage plant. The method comprises potting the plant in a conventional potting medium to which there has been added a humate which was previously associated with a rutile sand deposit. The disclosure is also of improved potting mediums for foliage plants, which include rutile sand deposit derived humate.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a Division of U.S. Patent Application Ser. No. 109,794 filed on Jan. 7, 1980 and now issued as U.S. Pat. No. 4,274,860, and which in turn was a continuation-in-part of U.S. Patent Application Ser. No. 924,146 filed July 13, 1978 and now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to methods of stimulating plant growth and more particularly relates to potting mediums and their use to stimulate foliage plant growth. 
     2. Brief Description of the Prior Art 
     Humic acid containing materials such as peats, humates, lignites, leonardite and the like have been proposed heretofore for use as ingredients of plant fertilizer compositions. Conventional potting mediums for foliage plants have traditionally included, for example, peat as a component thereof. In spite of the fact that peat contains humic acid substances, we have found that the addition of a particular humate substance as an active ingredient of the potting media unexpectedly increases and stimulates the growth of foliage plants beyond the point that can be attributed to the peat. It is unexpected that the particular humate employed will affect foliage plants in this manner since humate is characterized by relatively high titanium and aluminum metal contents. These metals were generally heretofore considered to be toxic to foliage plants. Apparently at the levels found in the humate materials employed in the method of the invention, they are tolerable. In addition, the humate substance employed in the method of the present invention is of such a character that it would ordinarily be expected to reduce the water permeability of the potting medium. This, of course, is undesirable for the growth of foliage plants. However, the humate employed unexpectedly has no significant adverse effect on the water permeability of a potting media. 
     SUMMARY OF THE INVENTION 
     The invention comprises a method of stimulating the growth of foliage plants, which comprises; potting the plants in a foliage plant potting media which includes as an active ingredient a humate, said humate being one derived from an association with a rutile sand deposit. 
     The invention also comprises, in a conventional potting media for stimulating growth of foliage plants, the improvement which comprises the presence of from 0.1 percent to 10 percent by volume of a humate, said humate being one derived from an association with a rutile sand deposit. 
     The term &#34;foliage plant&#34; as used throughout the specification and claims means those plants grown primarily for their foliage and utilized for interior decoration and landscape purposes. While foliage plants may have flowers, these will be secondary to the foliage. The source of this definition is &#34;Using Florida Grown Foliage Plants&#34;, Bulletin 746, October, 1971, Florida Agricultural Experiment Station, University of Florida. Representative of foliage plants are those of the genus Calethea, Chamaedorea, Philodendron and the like. 
     The term &#34;conventional potting media&#34; as used throughout the specification and the claims means the known mixtures employed as a natural soil substitute to grow foliage plants described herein. Such mixtures are used extensively by plant growers to assist the plant to develop and maintain a functional root system of a quality which will enhance plant growth. The conventional potting media functions to support the plant, serve as a reservoir for water and nutrients and as an interface for gaseous exchange with the roots. The ingredients of a conventional potting media may include both organic and inorganic ingredients. Tree barks, ranging in size from coarse, chunky pieces to the size of fine to very fine sand particles can be used as the organic component. Peat and mosses can also be used as the organic component as well as shavings or chips of hard and soft-woods. Inorganic ingredients which may be used to make conventional potting media include for example sand, perlite, vermiculate, fine gravel and the like. 
     Conventional potting media also may contain nutrient materials such as mulches, natural soil, fertilizers and the like. All of the ingredients employed in admixture to obtain a &#34;conventional potting media&#34; are used in proportions which will yield a media porosity wherein about 50 percent of the pores present in the media will hold water and the remaining 50 percent will not, i.e.; are available for gases. A number of specific &#34;conventional potting media&#34; formulations have been suggested by the University of California (See Manual 23, Div. of Ag. Sciences, Univ. of Calif. &#34;The U.C. System for Producing Healthy Container-Grown Plants&#34; edited by Kenneth F. Baker, September 1957). 
     The term &#34;humate&#34; as used throughout the specification and claims refers to the product of natural flocculation or precipitation in sand deposits, of humic substances that were derived from natural leaching of the decayed plant and animal material (humus). The humate employed in the method and compositions of the invention are generally found in associate with rutile sand deposits and contain humic substances which may be active ingredients in stimulating growth of foliage plants. 
     The term &#34;humate derived from an association with rutile sand deposits&#34; as used throughout the specification and claims means a humate, initially found in association with rutile sand deposits and at least partially separated therefrom for use in the method of the present invention. 
     The term &#34;humic acid&#34; has been widely applied to acidic solids obtained from plant decompositions. More recently, humic acids have been regarded as the intermediate product or products which result in the conversion of lignin and other plant materials to hard coal. It is believed that in the decomposition of vegetable matter, that the portion of the cell wall material consisting largely of lignin is converted into humus. In time, the humus may be converted progressively to peat, brown coal, bituminous coal and finally into anthracite. More usually, &#34;humic substance&#34; is applied as a generic term for the organic acids derived from humus or the top layer of the soil, containing organic decomposition products of vegetation and animal organisms in admixture with inorganic compounds, sands, minerals, metal hydroxide bases etc. The chemical structure of the humic acids has not been established, but they are believed to be large condensed ring, polymer-like molecules containing pendant carboxylic and phenolic groups. Depending on their solubilities, humic substances are usually classified as humic acid, fulvic acid, hymatomelanic acid or humin. 
     DETAILED DESCRIPTION OF THE INVENTION 
     The humate compositions employed in the method of the invention are naturally occurring compositions of matter found in association with rutile sands. Rutile sand deposits are found in several places throughout the world. In the United States, rutile sand deposits are located in Florida, Georgia and South Carolina. The rutile sands are in a formation commonly referred to as &#34;hardpan&#34;. The hardpan comprises rutile sands bound together by a coating of humate. It is this humate which is employed in the present invention. 
     The desired humate may be separated from the rutile sand deposits by first breaking up the deposit formation of hardpan into a ground ore of a convenient size for handling. Much of the humate in the ground ore can be washed off with water to effect the desired separation. Additional humate can be obtained by washing the concentrated ore with aqueous sodium hydroxide. The aqueous mixture containing the free humates may then be treated with, for example, a strong mineral acid such as sulfuric acid or alum to regain the natural pH of the humate and facilitate settling out of the suspended humate. The separated humate may then be dried in the sunlight or by artifical means. The separated humate is unique, compositionally, and contains a high degree of oxygenated compounds. The average composition of rutile sand humate is as follows: 
     
         ______________________________________COMPOSITION OF RUTILE SAND HUMATE______________________________________ElementalComposition            Composition, Wt. Percent(Dry Basis) (%)         &#34;As Is&#34;  Ash       AshC    H     O      N   S   Moisture                            (&#34;As Is&#34;)                                    (Dry Basis)______________________________________36.7 2.3   23.7   0.6 0.3 9.8    30.9    34.3______________________________________Functional GroupContents (Dry Basis)meq/g*Total  Carboxylic          Ratios, Wt./Wt. (Dry Basis)Acidity  Acid                C:H      C:O______________________________________6.0    2.1                 16.0:1   1.5:1______________________________________            Metal Contents (Dry Basis)            (%)            AL    Ti     Fe      Ca______________________________________            6     1      1       0.1______________________________________ *Methods for the functional group analysis may be found in M. Schnitzer and S. U. Khan, &#34;Humic Substances in the Environment,&#34; Marcel Dekker, Inc., New York, New York, 1972, pp. 39-41. The barium hydroxide method fo total acidity and calcium acetate method for carboxylic acid groups described in the citation were used. 
    
     It will be appreciated that the above analysis is for a specific material and the compositional make-up of rutile sand humate may vary somewhat for different materials within the same sand body. In general, the humate compositions employed in the method of the invention have compositional make-ups which provide a carbon to hydrogen ratio (weight to weight) of from 9.5-17.5:1.0; a carbon to oxygen ratio of 1.0-2.0:1.0; an aluminum content of 2.8 to 8.4 percent by weight; a titanium content of 0.5 to 1.5 percent by weight and a calcium content of less than 0.5 percent by weight. 
     It will also be appreciated from the above analysis that rutile sand associated humates contain substantially large proportions of some metals, particularly aluminum and titanium as well as a lower calcium content than is generally found in humates obtained from other sources. For example, leonardite is a humate substance closely related in composition. A commercially available leonardite has the following composition: 
     
         ______________________________________COMPOSITION OF A LEONARDITE______________________________________                     Composition,Elemental Composition     Wt. Percent(Dry Basis) (%)  &#34;As Is&#34;  Ash      AshC     H       O       S    Moisture                             (&#34;As Is&#34;)                                    (Dry Basis)______________________________________50.61 2.80    19.83   1.15 15.50  16.87  19.96______________________________________Functional Group Contents(Dry Basis) meq/gTotal    Carboxylic           Ratios, Wt./Wt.Acidity  Acid                 C:H     C:O______________________________________5.3      1.8                  18.1:1  2.6:1______________________________________Metal Contents (Dry Basis) %AL    Ti      Fe      Ca______________________________________0.8   0.06    1.1     2.4______________________________________ 
    
     It will be appreciated from a comparison of the analysis for the commercial leonardite that humates associated with rutile sand deposits generally have lower carbon to hydrogen and carbon to oxygen ratios. It is believed that these compositional differences of rutile associated humates accounts for the functional advantages associated with their use as plant growth stimulators. I believe that the humate could have a beneficial effect on the transfer of micronutrients to the plants or directly affect their growth through a plant growth regulator effect. It is well known that small amounts of certain organic compounds can have a remarkable effect on the growth of plants; see &#34;Humic Substances in the Environment&#34;, supra., pp. 298-301. 
     The method of the invention is carried out by first providing the above described humate, separated from its previous association with rutile sand deposits. The rutile sand derived humate is employed in the method of the invention by simple admixture with conventional potting medias employed to initiate growth in foliage plants. In general, the proportion of humate employed is within the range of about 0.1 to about 10 percent by volume of the potting media. In the case of the Chamadorea, a proportion of 0.1 to 5 percent is most advantageous and in the case of the Calathea, a proportion of 1.0 to 10.0 percent is preferred. 
    
    
     The following examples describe the manner and process of making and using the invention and set forth the best mode contemplated by the inventor of carrying out the invention but are not to be construed as limiting. 
     EXAMPLE 1 
     A total of 90 pot type containers (5&#34; diameter) suitable for potting Calathea makoyana (peacock plant) was provided with 90 clumps (3-7 plants/clump) for potting, in the containers. The pots and plants were divided into three series of 30 each, identified by the sequential letters A-C. Each series was further divided into six groups of 5 pots (giving 5 replications) identified by the sequential numbers 1-6, inclusive. The plants were potted in an assigned pot within the groups 1-6, employing a different potting medium for each of the groups 1-6. The potting mediums differ by relative proportions of humate derived from association with rutile sands and having the specific composition and analysis set forth above and Florida peat component. Representative portions of each potting media were subjected to chemical and physical analysis. The analysis was as follows: 
     
         __________________________________________________________________________Potting Media.sup.1 pH       Soluble Salts (ppm)Rutile                    Satu-    Satu-                                  CEC*  WHC**                                             Pore Space (%)   Sand Florida       Pine          Cypress               Water:Soil.sup.2                     rated                        Water:Soil.sup.2                              rated                                  by volume                                        % by Capil-                                                 Non-No.   Humate   Peat       Bark          Shavings               2:1   Paste                        2:1   Paste                                  meq/cc                                        volume                                             lary                                                 Capillary                                                      Total__________________________________________________________________________1  0    50.0       25 25   5.2   5.0                        1293.6                              2951.2                                  6.7   60.2 60.3                                                 13.9 74.22  .1   49.9       25 25   5.2   5.1                        1170.4                              2738.4                                  5.8   65.6 65.6                                                 13.4 79.03  5    45.0       25 25   5.1   4.9                        1545.6                              2805.6                                  14.4  55.5 56.1                                                 17.1 73.24  10   40.0       25 25   5.0   5.0                        1310.4                              2892.4                                  15.6  51.3 54.3                                                 15.7 70.05  25   25.0       25 25   4.6   4.2                        1066.8                              2027.2                                  6.4   49.4 49.4                                                 13.6 63.06  50   --  25 25   4.8   4.5                        1061.2                              1694.0                                  14.7  52.9 52.9                                                 18.4 71.3__________________________________________________________________________ .sup.1 Percent of each by volume. .sup.2 2 parts water to 1 part potting media by volume  *CEC = Cation Exchange Capacity **WHC = Water Holding Capacity 
    
     After potting, the potted plants were held for about 156 days under the following growing conditions. 
     
         ______________________________________Temperature        70° F.-95° F.Percent Shade:     Approximately 90.Light (foot candles):              1,200 to 1,500.Water frequency.   Three times a week______________________________________ 
    
     During the growth period, fertilizer (19-6-12 Osmocote) was applied at the start and after about 90 days. The rate of fertilizer application was varied between the series A-C as follows: 
     
         ______________________________________RATE OF FERTILIZER APPLICATIONSeries A     Series B       Series C______________________________________600 lbs. nitrogen        1200 lbs. nitrogen                       1800 lbs. nitrogenper acre per year        per acre per year                       per acre per year______________________________________ 
    
     During growth period, pesticides (Kelthane, Pentac or Sevin) were applied uniformly on occasion to each plant. 
     At the termination of the growth period, each plant was evaluated for its growth during the period. The results of the evaluation are shown in Table 1 below together with the composition of the potting media used for each plant. The reported figures are averages for all of the plants in each potting mixture. 
     
                       TABLE 1______________________________________Potting Mixture Results with Calathea MakoyanaPotting Media.sup.1    Average  AverageRutile Sand          Florida Pine Cypress                              Number PlantNo.  Humate    Peat    Bark Shavings                              Leaves Grade.sup.2______________________________________1    0         50.0    25   25     28.2    3.3 a.sup.32    .1        49.9    25   25     23.2   3.3 a3    5         45.0    25   25     25.7   4.1 b4    10        40.0    25   25     27.1   4.2 b5    25        25.0    25   25     27.3   3.8 b6    50        --      25   25     25.5   3.8 b______________________________________ .sup.1 Percent of each by volume. .sup.2 1 = poor quality, 3 = good, salable, 5 = excellent quality .sup.3 Mean separation between columns as determined by Duncan&#39;s multiple range, 1% level. [D. B. Duncan, Biometrics, 11, 1 (1955)]. 
    
     It will be observed from the Table 1 that the average plant grade was significantly improved when 5 percent or more by volume of the rutile sand derived humate was an active ingredient in the potting media. 
     In the above example, the plant evaluation of each of the three series, according to the rate of fertilizer application, showed that the level (rate) of fertilizer application provided no interaction with the humate presence. The average number of leaves and the plant grade average according to each of the series A-C is shown in Table 2, below. 
     
                       TABLE 2______________________________________Fertilizer Results with Calathea Makoyana  Fertilizer Rate               Average No. Average PlantSeries lbs. N/A/hr  Leaves      Grade.sup.2______________________________________A       600          23.3 a.sup.3                           3.2 aB      1200         27.6 b      4.0 bC      1800         27.6 b      4.0 b______________________________________ .sup.2 1 = poor quality, 3 = good, salable, 5 = excellent quality. .sup.3 Mean separation between columns as determined by Duncan&#39;s multiple range, 1% level. 
    
     EXAMPLE 2 
     The procedure of Example 1, supra, was repeated except that the plant Calethea makoyana as used therein was replaced with three Chamaedorea elegans (parlor palm) plants. The plant growth evaluations (average) are shown in Table 3 below, together with the composition of the potting medias used for the plants. 
     
                                           TABLE 3__________________________________________________________________________Results with Chamaedorea ElegansPotting Media.sup.1    Application Rate                           Average                                  AverageRutile Sand      Florida          Pine             Cypress                  Fertilizer                           Top wt.                                  PlantNo.  Humate      Peat          Bark             Shavings                  lbs N/A/yr                           (gms)  Grade.sup.3__________________________________________________________________________Series A 1   0     50.0          25 25    600     6.4                              abc.sup.4                                  2.6                                    abc 2   .1    49.9          25 25    600     9.7                              bcde                                  3.3                                    bcdef 3   5     45.0          25 25    600     10.5                              de  3.7                                    cdefg 4   10    40.0          25 25    600     6.2                              ab  2.9                                    bcde 5   25    25.0          25 25    600     5.3                              a   3.3                                    ab 6   50    --  25 25    600     6.9                              abc 3.3                                    bcdefSeries B 7   0     50.0          25 25   1200     12.2                              ef  4.0                                    efg 8   .1    49.9          25 25   1200     14.4                              f   4.2                                    fg 9   5     45.0          25 25   1200     9.7                              bcde                                  3.8                                    defg10   10    40.0          25 25   1200     7.5                              abcde                                  3.2                                    bcdef11   25    25.0          25 25   1200     6.7                              abc 2.9                                    bcde12   50    --  25 25   1200     6.4                              abc 2.9                                    bcdeSeries C13   0     50.0          25 25   1800     5.9                              a   2.5                                    ab14   .1    49.9          25 25   1800     12.2                              ef  4.2                                    fg15   5     45.0          25 25   1800     12.6                              ef  4.5                                    g16   10    40.0          25 25   1800     10.0                              cde 3.8                                    defg17   25    25.0          25 25   1800     6.8                              abc 2.7                                    abcd18   50    --  25 25   1800     4.0                              a   1.9                                    a__________________________________________________________________________ .sup.1 Percent of each by volume. .sup.3 1 = poor quality, 3 = good, salable, 5 = excellent quality. .sup.4 Mean separation between columns as determined by Duncan&#39;s multiple range, 1% level. (D. B. Duncan, loc. cit.) 
    
     The averages for the three series A-C are collated in Table 4, below. 
     
                                           TABLE 4__________________________________________________________________________Effect of Potting Mixture on Chamaedorea ElegansPotting Media.sup.1  Average Growth   Rutile Sand    Florida        Pine           Cypress                Height                     Top wt.                          Root wt.                                PlantNo.   Humate    Peat        Bark           Shavings                 (cm)                     (gms)                          (gms) Grade.sup.2__________________________________________________________________________1  0     50.0        25 25   22.6 cd.sup.3                     8.2 b.sup.3                          3.0 bc.sup.3                                3.0 ab.sup.32  .1    49.9        25 25   23.5 d                     12.1 c                          4.3 d 3.9 c3  5     45.0        25 25   22.9 cd                     10.9 c                          4.1 d 4.0 c4  10    40.0        25 25   21.5 c                     7.9 b                          3.2 c 3.4 b5  25    25.0        25 25   19.7 b                     6.3 ab                          2.2 b 2.7 a6  50    --  25 25   17.6 a                     5.8 a                          1.3 a 2.7 a__________________________________________________________________________ .sup.1 Percent of each by volume. .sup.2 1 = poor quality, 3 = good, salable, 5 = excellent quality. .sup.3 Mean separation between columns as determined by Duncan&#39;s multiple range, 1% level. (D. B. Duncan, loc. cit.) 
    
     As may be seen in Tables 3 and 4, the best height, top weight, root weight and plant grade growth indicators occurred when 0.1 percent by volume of the rutile sand humate was incorporated in the potting medium. However, a 5 percent level of the same humate also provided excellent growth increases. In this example, the 1200 or 1800 lb. nitrogen level fertilizer rate generally provided the best growth as shown in Table 5, below. 
     
                       TABLE 5______________________________________Effect of Fertilizer Level on Chamaedorea ElegansFertilizer   Average Growth Rate       Height   Root wt.                            Top wt. PlantSeries lbs N/A/yr (cm)     (gms)  (gms)   Grade.sup.2______________________________________A      600       20.6 a.sup.3                     2.9    7.5 a.sup.4                                    3.0B     1200       22.3 b   3.3    9.5 b   3.5C     1800       20.9 a   2.8    8.6 ab  3.3______________________________________ .sup.2 1 = poor quality, 3 = good, salable, 5 = excellent quality. .sup.3 Mean separation between columns as determined by Duncan&#39;s multiple range, 1% level. (D. B. Duncan, loc. cit.) .sup.4 Mean separation between columns as determined by Duncan&#39;s multiple range, 5% level. (D. B. Duncan, loc. cit.) 
    
     EXAMPLE 3 
     The procedure of Example 1, supra, was repeated except that the clumps of Calathea makoyana as used therein was replaced with three Philodendron scandens oxycardium (heart leaved philodendron) plants and the rate of fertilizer application was as follows: 
     
         ______________________________________RATE (LBS. NITROGEN PER ACRE PER YEAR)Series A    Series B       Series C______________________________________750         1500           2250______________________________________ 
    
     The plant growth evaluations by measurement of the average vine length at the end of the growth period are shown in Table 6, below, together with the compositional make-up of the potting medium. The reported figures are averages for the indicated series and groups. 
     
                       TABLE 6______________________________________Results with Philodendron Scandens Oxycardium                           AveragePotting Media.sup.1   Fertilizer                           Vine  Hu-    Florida Pine Cypress                             Rate    lengthNo.    mate   Peat    Bark Shavings                             lbs N/A/yr                                     (cm)______________________________________Series A 1     0      50.0    25   25      750    32.4 bc.sup.3 2     .1     49.9    25   25      750    46.1 d 3     5      45.0    25   25      750    36.5 cd 4     10     40.0    25   25      750    28.8 bc 5     25     25.0    25   25      750    27.4 abc 6     50     --      25   25      750    29.9 bcSeries B 7     0      50.0    25   25     1500    22.8 ab 8     .1     49.9    25   25     1500    36.7 cd 9     5      45.0    25   25     1500    20.7 ab10     10     40.0    25   25     1500    31.1 bc11     25     25.0    25   25     1500    34.6 bcd12     50     --      25   25     1500    22.7 abSeries C13     0      50.0    25   25     2250    32.0 bc14     .1     49.9    25   25     2250    29.0 bc15     5      45.0    25   25     2250    33.8 bcd16     10     40.0    25   25     2250    29.2 bc17     25     25.0    25   25     2250    32.6 bc18     50     --      25   25     2250    17.2 a______________________________________ .sup.1 Percent of each by volume. .sup.3 Mean separation between columns as determined by Duncan&#39;s multiple range, 1% level. (D. B. Duncan, loc. cit.) 
    
     A collation of the vine length figures with a plant evaluation by leaf size, top weight, root weight and plant grade is shown in Table 7, below. The figures given in Table 7 are averages for all plants in the different potting compositions. 
     
                                           TABLE 7__________________________________________________________________________Effect of Potting Mixture on Philodendron Scandens OxycardiumPotting Media.sup.1 Averages   Rutile           Leaf.sup.2                        Vine   Sand Florida       Pine          Cypress               Size                   Top wt.                        Length                              Root wt.                                   PlantNo.   Humate   Peat       Bark          Shavings               (cm)                   (gms)                        (cm)  (gms)                                   Grade.sup.3__________________________________________________________________________1  0    50.0       25 25   6.7 33.4 b.sup.4                        29.0 ab.sup.4                              2.8 b.sup.4                                   2.8 ab.sup.42  .1   49.9       25 25   6.7 40.8 b                        37.3 c                              5.0 d                                   3.8 c3  5    45.0       25 25   6.8 37.8 b                        30.3 abc                              4.0 c                                   3.3 bc4  10   40.0       25 25   6.6 35.3 b                        29.7 ab                              3.9 c                                   3.2 bc5  25   25.0       25 25   6.6 35.4 b                        31.5 bc                              3.6 bc                                   3.1 abc6  50   --  25 25   6.5 24.4 a                        23.2 a                              1.3 a                                   2.5 a__________________________________________________________________________ .sup.1 Percent of each by volume. .sup.2 Two leaves, length plus width/4. .sup.3 1 = poor quality, 3 = good, salable, 5 = excellent quality.  .sup.4 Mean separation between columns as determined by Duncan&#39;s multipl range, 1% level. (D. B. Duncan loc. cit.) 
    
     As may be observed from the Table 7, changing the potting medium had no effect on average leaf size and average top weights were similar except at the highest level of rutile sand humate presence. At that level of presence, these growth indicators were significantly lower. Vine length, root weight and plant grade growth averages were greatest when 0.1 percent by volume of rutile sand humate was incorporated into the potting medium. The 5 and 10 percent rutile sand humate levels also gave growth as good or better than occurred with the controls. Although growth varied with the rate of fertilizer application, the lowest rate was generally best in this example as may be observed from the growth averages as given in Table 8, below. 
     
                       TABLE 8______________________________________Effect of Fertilizer Level on Philodendron Scandens Oxycardium     Average Fertilizer           Leaf    Top   Vine Rate      Size.sup.2                   wt.   Length                               Root wt.                                      PlantSeries lbs N/A/yr           (cm)    (gms) (cm)  (gms)  Grade.sup.3______________________________________A      750       6.4 a.sup.4                   37.6  33.5 b.sup.5                               113.7  3.3B     1500      6.7 b   32.7  28.1 a                               107.7  3.0C     2250      6.9 c   33.3  29.0 ab                                86.6  3.0______________________________________ .sup.2 Two leaves, length plus width/4. .sup.3 1 = poor quality, 3 = good, salable, 5 = excellent quality. .sup.4 Mean separation between columns as determined by Duncan&#39;s multiple range, 5% level. (D. B. Duncan, loc. cit.)  .sup.5 Mean separation between columns as determined by Duncan&#39;s multipl range, 1% level. (D. B. Duncan, loc. cit.)